Friday, April 30, 2021

Was North America Populated by 'Stepping Stone' Migration across Bering Sea?

  

Image: Glacial Isostatic Adjustment (GIA) reconstructions of Beringia at 30,000 BP (as early as ice history data go), 20,500 BP (Last Glacial Maximum), 10,500 BP (just before the Bering Strait opened) and 8000 BP (shortly before inundation was complete). Potential kelp habitat is highlighted in bright red at depths of 3 to 20 m, which are suitable for bull kelp wherever rocky bottom may occur. 





Credit: Jerome Dobson, et al.

For thousands of years during the last ice age, generations of maritime migrants paddled skin boats eastward across shallow ocean waters from Asia to present-day Alaska. They voyaged from island to island and ultimately to shore, surviving on bountiful seaweeds, fish, shellfish, birds and game harvested from coastal and nearshore biomes. Their island-rich route was possible due to a shifting archipelago that stretched almost 900 miles from one continent to the other.


A new study from the University of Kansas in partnership with universities in Bologna and Urbino, Italy, documents the newly named Bering Transitory Archipelago and then points to how, when and where the first Americans may have crossed. The authors’ stepping-stones hypothesis depends on scores of islands that emerged during the last ice age as sea level fell when ocean waters were locked in glaciers and later rose when ice sheets melted. The two-part study, just published in the open-access journal Comptes Rendus Geoscience, may answer what writer Fen Montaigne calls “one of the greatest mysteries of our time . . . when humans made the first bold journey to the Americas.”

The “stepping-stones” idea hinges on retrospective mapping of sea levels while accounting for isostacy — deformation of the Earth’s crust due to the changing depth and weight of ice and water, reaching its greatest extreme during the Last Glacial Maximum about 20,500 years ago.

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Credit: KU

“We digitally discovered a geographic feature of considerable size that had never been properly documented in scientific literature,” said principal author Jerome Dobson, professor emeritus of geography at KU. “We named it the Bering Transitory Archipelago; it existed from about 30,000 years ago through 8,000 years ago. When we saw it, we immediately thought, ‘Wow, maybe that's how the first Americans came across.’ And, in fact, everything we’ve tested seems to bear that out — it does seem to be true.”

For more than a decade, researchers have pondered a mystery within a mystery. Mitochondrial DNA indicates that migrants were isolated somewhere for up to 15,000 years on their way over from Asia to North America. The Beringian Standstill Hypothesis arises from the fact that today Native American DNA is quite different from Asian DNA, a clear indication of genetic drift of such magnitude that it can only have happened over long periods of time in nearly complete isolation from the Asian source population. The Bering Transitory Archipelago provides a suitable refugium with internal connectivity and outward isolation.

Dobson said people crossing the Bering Sea probably didn’t have sails but could have been experienced in paddling skin boats like the kayaks and umiaks that Inuits use today.

“They probably traveled in small groups,” he said, “either from Asia or islands off the coast of Asia. Some maritime people are known to have existed 27,000 years ago on northern Japanese islands. They probably were maritime people — not just living on islands, but actually practicing maritime culture, economy and travel.”

Dobson recently received the American Geographical Society’s Cullum Geographical Medal (the same gold medal that Neil Armstrong won for flying to the moon and Rachel Carson won for writing “Silent Spring”). He named and continuously champions “aquaterra” — all lands that were exposed and inundated repeatedly during the Late Pleistocene ice ages — thus creating a zone of archeological promise scattered offshore from all coastal regions around the globe.

Recently, Dobson and co-authors Giorgio Spada of the University of Bologna and Gaia Galassi of Urbino University “Carlo Bo” applied an improved Glacial Isostatic Adjustment model to nine global choke points, meaning isthmuses and straits that have funneled transport and trade throughout history. Significant human migrations are known to have occurred across some of them, including “Beringia”— all portions of the Bering Sea that were exposed before, during and after the Last Glacial Maximum.

“These Italian ocean scientists read my ‘Aquaterra’ paper and took it upon themselves to refine the boundaries of aquaterra for the whole world at coarse resolution and for Beringia itself at fine resolution,” Dobson said. “Later we agreed to join forces and tackle those nine global choke points. At the end of that study, we suddenly spotted these islands in the Bering Sea, and that became our focus. This had an immediate potential because it could be a real game-changer in terms of all sciences understanding how migration worked in the past. We found startling results in certain other choke points and have begun analyzing them as well.”

In Beringia, the three investigators contend, this action produced a “conveyor belt” of islands that rose from the sea and fell back again, pushing bands of people eastward. “The first islands to appear were just off the coast of Siberia,” the KU researcher said. “Then islands appeared ever eastward. Most likely migrants kept expanding eastward, too, generally to islands within view and an easy paddle away.”

By 10,500 years ago, when the Bering Strait itself first appeared, almost all islands in the west had submerged. Only three islands remained, and paddling distances had increased accordingly. Thus, occupants were forced to evacuate, and they faced a clear choice: return to Asia, which they knew to be populated and may even have left due to population pressures and resource constraints, or paddle east to less known territory, perhaps less populated islands with ample resources.

To fully confirm the idea set forth in the new paper, Dobson said researchers from many fields will need to collaborate as one geographer and two ocean scientists have done here.

“We ourselves are at a stage where we definitely need underwater confirmation,” he said. “No doubt underwater archaeologists by title will prevail in that quest, but other disciplines, specialties and fields are essential. Working together plus scouring diverse literature, we presented a fundamentally new physical geography for scientists to contemplate. That should entice every relevant discipline to question conventional theory and explore new ideas regarding how, when and where people came to North America. More broadly, aquaterra can serve as a unifying theme for understanding human migrations, demic expansions, evolutionary biology, culture, settlement and endless other topics.”







Contacts and sources:
Brendan M. Lynch
The University of Kansas  



Publication:

How Long Is a Day on Venus? Scientists Crack Mysteries of Our Closest Neighbor

Venus is an enigma. It’s the planet next door and yet reveals little about itself. An opaque blanket of clouds smothers a harsh landscape pelted by acid rain and baked at temperatures that can liquify lead.

Now, new observations from the safety of Earth are lifting the veil on some of Venus’ most basic properties. By repeatedly bouncing radar off the planet’s surface over the last 15 years, a UCLA-led team has pinned down the precise length of a day on Venus, the tilt of its axis and the size of its core. The findings are published today in the journal Nature Astronomy.

Fundamentals such as how many hours are in a Venusian day provide critical data for understanding the divergent histories of Venus and Earth, UCLA researchers say.
Venus
NASA/JPL-Caltech

“Venus is our sister planet, and yet these fundamental properties have remained unknown,” said Jean-Luc Margot, a UCLA professor of Earth, planetary and space sciences who led the research.

Earth and Venus have a lot in common: Both rocky planets have nearly the same size, mass and density. And yet they evolved along wildly different paths. Fundamentals such as how many hours are in a Venusian day provide critical data for understanding the divergent histories of these neighboring worlds.

Changes in Venus’ spin and orientation reveal how mass is spread out within. Knowledge of its internal structure, in turn, fuels insight into the planet’s formation, its volcanic history and how time has altered the surface. Plus, without precise data on how the planet moves, any future landing attempts could be off by as much as 30 kilometers.

“Without these measurements,” said Margot, “we’re essentially flying blind.”

The new radar measurements show that an average day on Venus lasts 243.0226 Earth days — roughly two-thirds of an Earth year. What's more, the rotation rate of Venus is always changing: A value measured at one time will be a bit larger or smaller than a previous value. The team estimated the length of a day from each of the individual measurements, and they observed differences of at least 20 minutes.

“That probably explains why previous estimates didn’t agree with one another,” Margot said.

Venus’ heavy atmosphere is likely to blame for the variation. As it sloshes around the planet, it exchanges a lot of momentum with the solid ground, speeding up and slowing down its rotation. This happens on Earth too, but the exchange adds or subtracts just one millisecond from each day. The effect is much more dramatic on Venus because the atmosphere is roughly 93 times as massive as Earth’s, and so it has a lot more momentum to trade.

The UCLA-led team also reports that Venus tips to one side by precisely 2.6392 degrees (Earth is tilted by about 23 degrees), an improvement on the precision of previous estimates by a factor of 10. The repeated radar measurements further revealed the glacial rate at which the orientation of Venus’ spin axis changes, much like a spinning child’s top. On Earth, this “precession” takes about 26,000 years to cycle around once. Venus needs a little longer: about 29,000 years.

With these exacting measurements of how Venus spins, the team calculated that the planet’s core is about 3,500 kilometers across — quite similar to Earth — though they cannot yet deduce whether it’s liquid or solid.

Venus as a giant disco ball

On 21 separate occasions from 2006 to 2020, Margot and his colleagues aimed radio waves at Venus from the 70-meter–wide Goldstone antenna in California’s Mojave Desert. Several minutes later, those radio waves bounced off Venus and came back to Earth. The radio echo was picked up at Goldstone and at the Green Bank Observatory in West Virginia.

“We use Venus as a giant disco ball,” said Margot, with the radio dish acting like a flashlight and the planet’s landscape like millions of tiny reflectors. “We illuminate it with an extremely powerful flashlight — about 100,000 times brighter than your typical flashlight. And if we track the reflections from the disco ball, we can infer properties about the spin [state].”

Spin axis of Venus

Credit: Jean-Luc Margot/UCLA and NASA

The complex reflections erratically brighten and dim the return signal, which sweeps across Earth. The Goldstone antenna sees the echo first, then Green Bank sees it roughly 20 seconds later. The exact delay between receipt at the two facilities provides a snapshot of how quickly Venus is spinning, while the particular window of time in which the echoes are most similar reveals the planet’s tilt.

The observations required exquisite timing to ensure that Venus and Earth were properly positioned. And both observatories had to be working perfectly — which wasn’t always the case. “We found that it’s actually challenging to get everything to work just right in a 30-second period,” Margot said. “Most of the time, we get some data. But it’s unusual that we get all the data that we’re hoping to get.”

Despite the challenges, the team is forging ahead and has turned its sights on Jupiter’s moons Europa and Ganymede. Many researchers strongly suspect that Europa, in particular, hides a liquid water ocean beneath a thick shell of ice. Ground-based radar measurements could fortify the case for an ocean and reveal the thickness of the ice shell.

And the team will continue bouncing radar off of Venus. With each radio echo, the veil over Venus lifts a little bit more, bringing our sister planet into ever sharper view.

This research was supported by NASA, the Jet Propulsion Laboratory and the National Science Foundation.

Other researchers who contributed to the study are Donald Campbell of Cornell University; Jon Giorgini, Joseph Jao and Lawrence Snedeker of the Jet Propulsion Laboratory; and Frank Ghigo and Amber Bonsall of the National Radio Astronomy Observatory in West Virginia.


Contacts and sources:
Stuart Wolpert
UCLA



Publication:




Oldest Evidence of Human Activity in African Desert Cave Unveiled



Few sites in the world preserve a continuous archaeological record spanning millions of years. Wonderwerk Cave, located in South Africa's Kalahari Desert, is one of those rare sites. Meaning "miracle" in Afrikaans, Wonderwerk Cave has been identified as potentially the earliest cave occupation in the world and the site of some of the earliest indications of fire use and tool making among prehistoric humans.

Entrance to Wonderwerk Cave
Credit:  Michael Chazan

New research, published in Quaternary Science Reviews, led by a team of geologists and archaeologists from the Hebrew University of Jerusalem (HU) and the University of Toronto, confirms the record-breaking date of this spectacular site. "We can now say with confidence that our human ancestors were making simple Oldowan stone tools inside the Wonderwerk Cave 1.8 million years ago. Wonderwerk is unique among ancient Oldowan sites, a tool-type first found 2.6 million years ago in East Africa, precisely because it is a cave and not an open-air occurrence," explained lead author Professor Ron Shaar at HU's Institute of Earth Sciences.

The team were able to successfully establish the shift from Oldowan tools (mainly sharp flakes and chopping tools) to early handaxes over 1 million years ago, and to date the deliberate use of fire by our prehistoric ancestors to 1 million years ago, in a layer deep inside the cave. The latter is a particularly significant because other examples of early fire use come from open-air sites where the possible role of wildfires cannot be excluded. Moreover, Wonderwerk contained a full array of fire remnants: burnt bone, sediment and tools as well as the presence of ash.

Dating cave deposits is one of the greatest challenges in paleo-anthropology, aka the study of human evolution. To overcome this challenge, the team analyzed a 2.5-meter thick sedimentary layer that contained stone tools, animal remains and fire remnants using two methods: paleomagnetism and burial dating. "We carefully removed hundreds of tiny sediment samples from the cave walls and measured their magnetic signal," described Shaar.

Magnetization occurred when clay particles, that entered the cave from outside, settled on the prehistoric cave floor, thereby preserving the direction of the earth's magnetic field at that time. "Our lab analysis showed that some of the samples were magnetized to the south instead of the north, which is the direction of today's magnetic field. Since the exact timing of these magnetic "reversals" is globally recognized, it gave us clues to the antiquity of the entire sequence of layers in the cave," added Shaar.

Prof. Ari Matmon, Director of HU's the Institute of Earth Sciences, relied on a secondary dating method to further confirm when the earliest "humans" may have occupied the site. "Quartz particles in sand have a built-in geological clock that starts ticking when they enter a cave. In our lab, we are able to measure the concentrations of specific isotopes in those particles and deduce how much time had passed since those grains of sand entered the cave," he explained.

The dating of prehistoric human activity at Wonderwerk Cave has far-reaching implications. The co-directors of the Wonderwerk Cave project, Prof. Michael Chazan at the University of Toronto and Liora Kolska Horwitz at HU's National Natural History Collections, explained that the findings at Wonderwerk "are an important step towards understanding the tempo of human evolution across the African continent. With a timescale firmly established for Wonderwerk Cave, we can continue studying the connection between human evolution and climate change, and the evolution of our early human ancestors' way of life."

On the southern edge of the Kalahari Desert, Wonderwerk Cave is also a place of great spiritual significance to local communities, attesting to the cave's cultural importance for both past and present peoples. The Wonderwerk Cave Research Project is committed to protecting the site and to working with neighboring towns to develop the educational and cultural potential of this unique place.


Contacts and sources:
Tali Aronsky
 Hebrew University of Jerusalem (HU)


Publication:
Magnetostratigraphy and cosmogenic dating of Wonderwerk Cave: New constraints for the chronology of the South African Earlier Stone Age
RonShaar et al. http://dx.doi.org/10.1016/j.quascirev.2021.106907

International Research Teams Explore Genetic Effects of Chernobyl Radiation

Researchers have used DNA sequencing technology to explore scientific questions about the effects of radiation from the Chernobyl nuclear disaster on human health.
Silhouettes of adults and children and DNA code over a photo of the Chernobyl nuclear power plant.

Credit: National Cancer Institute | iStock

In two landmark studies, researchers have used cutting-edge genomic tools to investigate the potential health effects of exposure to ionizing radiation, a known carcinogen, from the 1986 accident at the Chernobyl nuclear power plant in northern Ukraine. One study found no evidence that radiation exposure to parents resulted in new genetic changes being passed from parent to child. The second study documented the genetic changes in the tumors of people who developed thyroid cancer after being exposed as children or fetuses to the radiation released by the accident.

The findings, published around the 35th anniversary of the disaster, are from international teams of investigators led by researchers at the National Cancer Institute (NCI), part of the National Institutes of Health. The studies were published online in Science on April 22.

"Scientific questions about the effects of radiation on human health have been investigated since the atomic bombings of Hiroshima and Nagasaki and have been raised again by Chernobyl and by the nuclear accident that followed the tsunami in Fukushima, Japan," said Stephen J. Chanock, M.D., director of NCI’s Division of Cancer Epidemiology and Genetics (DCEG). "In recent years, advances in DNA sequencing technology have enabled us to begin to address some of the important questions, in part through comprehensive genomic analyses carried out in well-designed epidemiological studies."

The Chernobyl accident exposed millions of people in the surrounding region to radioactive contaminants. Studies have provided much of today’s knowledge about cancers caused by radiation exposures from nuclear power plant accidents. The new research builds on this foundation using next-generation DNA sequencing and other genomic characterization tools to analyze biospecimens from people in Ukraine who were affected by the disaster.

The first study investigated the long-standing question of whether radiation exposure results in genetic changes that can be passed from parent to offspring, as has been suggested by some studies in animals. To answer this question, Dr. Chanock and his colleagues analyzed the complete genomes of 130 people born between 1987 and 2002 and their 105 mother-father pairs.

One or both of the parents had been workers who helped clean up from the accident or had been evacuated because they lived in close proximity to the accident site. Each parent was evaluated for protracted exposure to ionizing radiation, which may have occurred through the consumption of contaminated milk (that is, milk from cows that grazed on pastures that had been contaminated by radioactive fallout). The mothers and fathers experienced a range of radiation doses.

The researchers analyzed the genomes of adult children for an increase in a particular type of inherited genetic change known as de novo mutations. De novo mutations are genetic changes that arise randomly in a person’s gametes (sperm and eggs) and can be transmitted to their offspring but are not observed in the parents.

For the range of radiation exposures experienced by the parents in the study, there was no evidence from the whole-genome sequencing data of an increase in the number or types of de novo mutations in their children born between 46 weeks and 15 years after the accident. The number of de novo mutations observed in these children were highly similar to those of the general population with comparable characteristics. As a result, the findings suggest that the ionizing radiation exposure from the accident had a minimal, if any, impact on the health of the subsequent generation.

"We view these results as very reassuring for people who were living in Fukushima at the time of the accident in 2011," said Dr. Chanock. "The radiation doses in Japan are known to have been lower than those recorded at Chernobyl."

In the second study, researchers used next-generation sequencing to profile the genetic changes in thyroid cancers that developed in 359 people exposed as children or in utero to ionizing radiation from radioactive iodine (I-131) released by the Chernobyl nuclear accident and in 81 unexposed individuals born more than nine months after the accident. Increased risk of thyroid cancer has been one of the most important adverse health effects observed after the accident.

The energy from ionizing radiation breaks the chemical bonds in DNA, resulting in a number of different types of damage. The new study highlights the importance of a particular kind of DNA damage that involves breaks in both DNA strands in the thyroid tumors. The association between DNA double-strand breaks and radiation exposure was stronger for children exposed at younger ages.

Next, the researchers identified the candidate "drivers" of the cancer in each tumor — the key genes in which alterations enabled the cancers to grow and survive. They identified the drivers in more than 95% of the tumors. Nearly all the alterations involved genes in the same signaling pathway, called the mitogen-activated protein kinase (MAPK) pathway, including the genes BRAF, RAS, and RET.

The set of affected genes is similar to what has been reported in previous studies of thyroid cancer. However, the researchers observed a shift in the distribution of the types of mutations in the genes. Specifically, in the Chernobyl study, thyroid cancers that occurred in people exposed to higher radiation doses as children were more likely to result from gene fusions (when both strands of DNA are broken and then the wrong pieces are joined back together), whereas those in unexposed people or those exposed to low levels of radiation were more likely to result from point mutations (single base-pair changes in a key part of a gene).

The results suggest that DNA double-strand breaks may be an early genetic change following exposure to radiation in the environment that subsequently enables the growth of thyroid cancers. Their findings provide a foundation for further studies of radiation-induced cancers, particularly those that involve differences in risk as a function of both dose and age, the researchers added.

"An exciting aspect of this research was the opportunity to link the genomic characteristics of the tumor with information about the radiation dose — the risk factor that potentially caused the cancer," said Lindsay M. Morton, Ph.D., deputy chief of the Radiation Epidemiology Branch in DCEG, who led the study.

"The Cancer Genome Atlas set the standard for how to comprehensively profile tumor characteristics," Dr. Morton continued. "We extended that approach to complete the first large genomic landscape study in which the potential carcinogenic exposure was well-characterized, enabling us to investigate the relationship between specific tumor characteristics and radiation dose."

She noted that the study was made possible by the creation of the Chernobyl Tissue Bank about two decades ago — long before the technology had been developed to conduct the kind of genomic and molecular studies that are common today.

"These studies represent the first time our group has done molecular studies using the biospecimens that were collected by our colleagues in Ukraine," Dr. Morton said. "The tissue bank was set up by visionary scientists to collect tumor samples from residents in highly contaminated regions who developed thyroid cancer. These scientists recognized that there would be substantial advances in technology in the future, and the research community is now benefiting from their foresight."

About the National Cancer Institute (NCI): NCI leads the National Cancer Program and NIH’s efforts to dramatically reduce the prevalence of cancer and improve the lives of cancer patients and their families, through research into prevention and cancer biology, the development of new interventions, and the training and mentoring of new researchers. For more information about cancer, please visit the NCI website at cancer.gov or call NCI’s contact center, the Cancer Information Service, at 1-800-4-CANCER (1-800-422-6237).In two landmark studies, researchers have used cutting-edge genomic tools to investigate the potential health effects of exposure to ionizing radiation, a known carcinogen, from the 1986 accident at the Chernobyl nuclear power plant in northern Ukraine. One study found no evidence that radiation exposure to parents resulted in new genetic changes being passed from parent to child. The second study documented the genetic changes in the tumors of people who developed thyroid cancer after being exposed as children or fetuses to the radiation released by the accident.

The findings, published around the 35th anniversary of the disaster, are from international teams of investigators led by researchers at the National Cancer Institute (NCI), part of the National Institutes of Health. The studies were published online in Science on April 22.

"Scientific questions about the effects of radiation on human health have been investigated since the atomic bombings of Hiroshima and Nagasaki and have been raised again by Chernobyl and by the nuclear accident that followed the tsunami in Fukushima, Japan," said Stephen J. Chanock, M.D., director of NCI’s Division of Cancer Epidemiology and Genetics (DCEG). "In recent years, advances in DNA sequencing technology have enabled us to begin to address some of the important questions, in part through comprehensive genomic analyses carried out in well-designed epidemiological studies."

The Chernobyl accident exposed millions of people in the surrounding region to radioactive contaminants. Studies have provided much of today’s knowledge about cancers caused by radiation exposures from nuclear power plant accidents. The new research builds on this foundation using next-generation DNA sequencing and other genomic characterization tools to analyze biospecimens from people in Ukraine who were affected by the disaster.

The first study investigated the long-standing question of whether radiation exposure results in genetic changes that can be passed from parent to offspring, as has been suggested by some studies in animals. To answer this question, Dr. Chanock and his colleagues analyzed the complete genomes of 130 people born between 1987 and 2002 and their 105 mother-father pairs.

One or both of the parents had been workers who helped clean up from the accident or had been evacuated because they lived in close proximity to the accident site. Each parent was evaluated for protracted exposure to ionizing radiation, which may have occurred through the consumption of contaminated milk (that is, milk from cows that grazed on pastures that had been contaminated by radioactive fallout). The mothers and fathers experienced a range of radiation doses.

The researchers analyzed the genomes of adult children for an increase in a particular type of inherited genetic change known as de novo mutations. De novo mutations are genetic changes that arise randomly in a person’s gametes (sperm and eggs) and can be transmitted to their offspring but are not observed in the parents.

For the range of radiation exposures experienced by the parents in the study, there was no evidence from the whole-genome sequencing data of an increase in the number or types of de novo mutations in their children born between 46 weeks and 15 years after the accident. The number of de novo mutations observed in these children were highly similar to those of the general population with comparable characteristics. As a result, the findings suggest that the ionizing radiation exposure from the accident had a minimal, if any, impact on the health of the subsequent generation.

"We view these results as very reassuring for people who were living in Fukushima at the time of the accident in 2011," said Dr. Chanock. "The radiation doses in Japan are known to have been lower than those recorded at Chernobyl."

In the second study, researchers used next-generation sequencing to profile the genetic changes in thyroid cancers that developed in 359 people exposed as children or in utero to ionizing radiation from radioactive iodine (I-131) released by the Chernobyl nuclear accident and in 81 unexposed individuals born more than nine months after the accident. Increased risk of thyroid cancer has been one of the most important adverse health effects observed after the accident.

The energy from ionizing radiation breaks the chemical bonds in DNA, resulting in a number of different types of damage. The new study highlights the importance of a particular kind of DNA damage that involves breaks in both DNA strands in the thyroid tumors. The association between DNA double-strand breaks and radiation exposure was stronger for children exposed at younger ages.

Next, the researchers identified the candidate "drivers" of the cancer in each tumor — the key genes in which alterations enabled the cancers to grow and survive. They identified the drivers in more than 95% of the tumors. Nearly all the alterations involved genes in the same signaling pathway, called the mitogen-activated protein kinase (MAPK) pathway, including the genes BRAF, RAS, and RET.

The set of affected genes is similar to what has been reported in previous studies of thyroid cancer. However, the researchers observed a shift in the distribution of the types of mutations in the genes. Specifically, in the Chernobyl study, thyroid cancers that occurred in people exposed to higher radiation doses as children were more likely to result from gene fusions (when both strands of DNA are broken and then the wrong pieces are joined back together), whereas those in unexposed people or those exposed to low levels of radiation were more likely to result from point mutations (single base-pair changes in a key part of a gene).

The results suggest that DNA double-strand breaks may be an early genetic change following exposure to radiation in the environment that subsequently enables the growth of thyroid cancers. Their findings provide a foundation for further studies of radiation-induced cancers, particularly those that involve differences in risk as a function of both dose and age, the researchers added.

"An exciting aspect of this research was the opportunity to link the genomic characteristics of the tumor with information about the radiation dose — the risk factor that potentially caused the cancer," said Lindsay M. Morton, Ph.D., deputy chief of the Radiation Epidemiology Branch in DCEG, who led the study.

"The Cancer Genome Atlas set the standard for how to comprehensively profile tumor characteristics," Dr. Morton continued. "We extended that approach to complete the first large genomic landscape study in which the potential carcinogenic exposure was well-characterized, enabling us to investigate the relationship between specific tumor characteristics and radiation dose."

She noted that the study was made possible by the creation of the Chernobyl Tissue Bank about two decades ago — long before the technology had been developed to conduct the kind of genomic and molecular studies that are common today.

"These studies represent the first time our group has done molecular studies using the biospecimens that were collected by our colleagues in Ukraine," Dr. Morton said. "The tissue bank was set up by visionary scientists to collect tumor samples from residents in highly contaminated regions who developed thyroid cancer. These scientists recognized that there would be substantial advances in technology in the future, and the research community is now benefiting from their foresight."

About the National Cancer Institute (NCI): NCI leads the National Cancer Program and NIH’s efforts to dramatically reduce the prevalence of cancer and improve the lives of cancer patients and their families, through research into prevention and cancer biology, the development of new interventions, and the training and mentoring of new researchers. For more information about cancer, please visit the NCI website at cancer.gov or call NCI’s contact center, the Cancer Information Service, at 1-800-4-CANCER (1-800-422-6237).Contacts and sources:
NIH/National Cancer Institute




Publications: 

Lack of transgenerational effects of ionizing radiation exposure from the Chernobyl accident.
Meredith Yeager, Mitchell J. Machiela, Prachi Kothiyal, Michael Dean, Clara Bodelon, Shalabh Suman, Mingyi Wang, Lisa Mirabello, Chase W. Nelson, Weiyin Zhou, Cameron Palmer, Bari Ballew, Leandro M. Colli, Neal D. Freedman, Casey Dagnall, Amy Hutchinson, Vibha Vij, Yosi Maruvka, Maureen Hatch, Iryna Illienko, Yuri Belayev, Nori Nakamura, Vadim Chumak, Elena Bakhanova, David Belyi, Victor Kryuchkov, Ivan Golovanov, Natalia Gudzenko, Elizabeth K. Cahoon, Paul Albert, Vladimir Drozdovitch, Mark P. Little, Kiyohiko Mabuchi, Chip Stewart, Gad Getz, Dimitry Bazyka, Amy Berrington de Gonzalez, Stephen J. Chanock.Science, 2021; eabg2365 DOI: 10.1126/science.abg2365


Radiation-related genomic profile of papillary thyroid cancer after the Chernobyl accident.
Lindsay M. Morton, Danielle M. Karyadi, Chip Stewart, Tetiana I. Bogdanova, Eric T. Dawson, Mia K. Steinberg, Jieqiong Dai, Stephen W. Hartley, Sara J. Schonfeld, Joshua N. Sampson, Yosi Maruvka, Vidushi Kapoor, Dale A. Ramsden, Juan Carvajal-Garcia, Charles M. Perou, Joel S. Parker, Marko Krznaric, Meredith Yeager, Joseph F. Boland, Amy Hutchinson, Belynda D. Hicks, Casey L. Dagnall, Julie M. Gastier-Foster, Jay Bowen, Olivia Lee, Mitchell J. Machiela, Elizabeth K. Cahoon, Alina V. Brenner, Kiyohiko Mabuchi, Vladimir Drozdovitch, Sergii Masiuk, Mykola Chepurny, Liudmyla Yu. Zurnadzhy, Maureen Hatch, Amy Berrington de Gonzalez, Gerry A. Thomas, Mykola D. Tronko, Gad Getz, Stephen J. Chanock. Science, 2021; eabg2538 DOI: 10.1126/science.abg2538


Hubble Watches How a Giant Planet Grows

NASA’s Hubble Space Telescope is giving astronomers a rare look at a Jupiter-sized, still-forming planet that is feeding off material surrounding a young star.

“We just don’t know very much about how giant planets grow,” said Brendan Bowler of the University of Texas at Austin. “This planetary system gives us the first opportunity to witness material falling onto a planet. Our results open up a new area for this research.”

This illustration of the newly forming exoplanet PDS 70b shows how material may be falling onto the giant world as it builds up mass. By employing Hubble’s ultraviolet light (UV) sensitivity, researchers got a unique look at radiation from extremely hot gas falling onto the planet, allowing them to directly measure the planet’s mass growth rate for the first time. The planet PDS 70b is encircled by its own gas-and-dust disk that’s siphoning material from the vastly larger circumstellar disk in this solar system. The researchers hypothesize that magnetic field lines extend from its circumplanetary disk down to the exoplanet’s atmosphere and are funneling material onto the planet’s surface. The illustration shows one possible magnetospheric accretion configuration, but the magnetic field’s detailed geometry requires future work to probe. The remote world has already bulked up to five times the mass of Jupiter over a period of about five million years, but is anticipated to be in the tail end of its formation process. PDS 70b orbits the orange dwarf star PDS 70 approximately 370 light-years from Earth in the constellation Centaurus.


Credits: NASA, ESA, STScI, Joseph Olmsted (STScI)


Though over 4,000 exoplanets have been cataloged so far, only about 15 have been directly imaged to date by telescopes. And the planets are so far away and small, they are simply dots in the best photos. The team’s fresh technique for using Hubble to directly image this planet paves a new route for further exoplanet research, especially during a planet’s formative years.

This huge exoplanet, designated PDS 70b, orbits the orange dwarf star PDS 70, which is already known to have two actively forming planets inside a huge disk of dust and gas encircling the star. The system is located 370 light-years from Earth in the constellation Centaurus.

“This system is so exciting because we can witness the formation of a planet,” said Yifan Zhou, also of the University of Texas at Austin. “This is the youngest bona fide planet Hubble has ever directly imaged.” At a youthful five million years, the planet is still gathering material and building up mass.

Hubble’s ultraviolet light (UV) sensitivity offers a unique look at radiation from extremely hot gas falling onto the planet. “Hubble’s observations allowed us to estimate how fast the planet is gaining mass,” added Zhou.


The European Southern Observatory’s Very Large Telescope caught the first clear image of a forming planet, PDS 70b, around a dwarf star in 2018. The planet stands out as a bright point to the right of the center of the image, which is blacked out by the coronagraph mask used to block the light of the central star.


Credits: ESO, VLT, André B. Müller (ESO)


The UV observations, which add to the body of research about this planet, allowed the team to directly measure the planet’s mass growth rate for the first time. The remote world has already bulked up to five times the mass of Jupiter over a period of about five million years. The present measured accretion rate has dwindled to the point where, if the rate remained steady for another million years, the planet would only increase by approximately an additional 1/100th of a Jupiter-mass.

Zhou and Bowler emphasize that these observations are a single snapshot in time – more data are required to determine if the rate at which the planet is adding mass is increasing or decreasing. “Our measurements suggest that the planet is in the tail end of its formation process.”

The youthful PDS 70 system is filled with a primordial gas-and-dust disk that provides fuel to feed the growth of planets throughout the entire system. The planet PDS 70b is encircled by its own gas-and-dust disk that’s siphoning material from the vastly larger circumstellar disk. The researchers hypothesize that magnetic field lines extend from its circumplanetary disk down to the exoplanet’s atmosphere and are funneling material onto the planet’s surface.

“If this material follows columns from the disk onto the planet, it would cause local hot spots,” Zhou explained. “These hot spots could be at least 10 times hotter than the temperature of the planet.” These hot patches were found to glow fiercely in UV light.

Hubble observations pinpoint planet PDS 70b. A coronagraph on Hubble’s camera blocks out the glare of the central star for the planet to be directly observed. Though over 4,000 exoplanets have been cataloged so far, only about 15 have been directly imaged to date by telescopes. The team’s fresh technique for using Hubble to directly image this planet paves a new route for further exoplanet research, especially during a planet’s formative years.  

Credits: Joseph DePasquale (STScI)

These observations offer insights into how gas giant planets formed around our Sun 4.6 billion years ago. Jupiter may have bulked up on a surrounding disk of infalling material. Its major moons would have also formed from leftovers in that disk.

A challenge to the team was overcoming the glare of the parent star. PDS 70b orbits at approximately the same distance as Uranus does from the Sun, but its star is more than 3,000 times brighter than the planet at UV wavelengths. As Zhou processed the images, he very carefully removed the star’s glare to leave behind only light emitted by the planet. In doing so, he improved the limit of how close a planet can be to its star in Hubble observations by a factor of five.

“Thirty-one years after launch, we’re still finding new ways to use Hubble,” Bowler added. “Yifan’s observing strategy and post-processing technique will open new windows into studying similar systems, or even the same system, repeatedly with Hubble. With future observations, we could potentially discover when the majority of the gas and dust falls onto their planets and if it does so at a constant rate.”

The researchers' results were published in April 2021 in The Astronomical Journal.

The Hubble Space Telescope is a project of international cooperation between NASA and ESA (European Space Agency). NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy in Washington, D.C.


Contacts and sources:
Claire Andreoli
NASA's Goddard Space Flight Center,





Future Drones Likely to Resemble 300-Million-Year-Old Flying Machine

University of South Australia researchers have drawn inspiration from a 300-million-year-old superior flying machine – the dragonfly – to show why future flapping wing drones will probably resemble the insect in shape, wings and gearing.

A team of PhD students led by UniSA Professor of Sensor Systems, Javaan Chahl, spent part of the 2020 COVID-19 lockdown designing and testing key parts of a dragonfly-inspired drone that might match the insect’s extraordinary skills in hovering, cruising and aerobatics.

Flapping wing mechanism made using a 3D printer in a student's home laboratory.

Credit: University of South Australia (UniSA)


The UniSA students worked remotely on the project, solving mathematical formulas at home on whiteboards, digitising stereo photographs of insect wings into 3D models, and using spare rooms as rapid prototyping workshops to test parts of the flapping wing drone.

Their findings have been published in the journal Drones.

Describing the dragonfly as the “apex insect flyer,” Prof Chahl says numerous engineering lessons can be learned from its mastery in the air.

“Dragonflies are supremely efficient in all areas of flying. They need to be. After emerging from under water until their death (up to six months), male dragonflies are involved in perpetual, dangerous combat against male rivals. Mating requires an aerial pursuit of females and they are constantly avoiding predators. Their flying abilities have evolved over millions of years to ensure they survive,” Prof Chahl says. 

UniSA researchers modelled the dragonfly's unique body shape and aerodynamic properties.


Credit: University of South Australia (UniSA)


“They can turn quickly at high speeds and take off while carrying more than three times their own body weight. They are also one of nature’s most effective predators, targeting, chasing and capturing their prey with a 95 per cent success rate.”

The use of drones has exploded in recent years – for security, military, delivery, law enforcement, filming, and more recently health screening purposes – but in comparison to the dragonfly and other flying insects they are crude and guzzle energy.

The UniSA team modelled the dragonfly’s unique body shape and aerodynamic properties to understand why they remain the ultimate flying machine.

Because intact dragonflies are notoriously difficult to capture, the researchers developed an optical technique to photograph the wing geometry of 75 different dragonfly (Odonata) species from glass display cases in museum collections.

In a world first experiment, they reconstructed 3D images of the wings, comparing differences between the species.

“Dragonfly wings are long, light and rigid with a high lift-to-drag ratio which gives them superior aerodynamic performance.

“Their long abdomen, which makes up about 35 per cent of their body weight, has also evolved to serve many purposes. It houses the digestive tract, is involved in reproduction, and it helps with balance, stability and manoeuvrability. The abdomen plays a crucial role in their flying ability.”

The researchers believe a dragonfly lookalike drone could do many jobs, including collecting and delivering awkward, unbalanced loads, safely operating near people, exploring delicate natural environments and executing long surveillance missions.
  
Prof Javaan Chahl has a joint appointment with the Defence Science and Technology Group. The other researchers involved in the project included UniSA PhD students Nasim Chitsaz, Blake McIvor and Titilayo Ogunwa; UniSA engineer Timothy McIntyre; Jia-Ming Kok (DST Group) and Dr Ermira Abdullah (University Putra Malaysia)
 


Contacts and sources:
Candy Gibson
University of South Australia




Publication: Biomimetic Drones Inspired by Dragonflies Will Require a Systems Based Approach and Insights from Biology
Javaan Chahl, Nasim Chitsaz, Blake McIvor, Titilayo Ogunwa, Jia-Ming Kok, Timothy McIntyre, Ermira Abdullah. . Drones, 2021; 5 (2): 24 DOI: 10.3390/drones5020024


Mapping ‘Superhighways’ Travelled by First Australians

‘Superhighways’ used by a population of up to 6.5 million Indigenous Australians to navigate the continent tens of thousands of years ago have been revealed by new research using sophisticated modelling of past people and landscapes.

The new insights into how people not only survived, but thrived, in harsh environments provide further evidence of the capacity and resilience of the ancestors of Indigenous people, and help paint a picture of large, well-organised groups navigating tough terrain.

The ‘peopling’ of Sahul — the combined mega continent that joined Australia with New Guinea when sea levels were lower than today — could have taken as little as 5,000 years as people moved from the far northwest, all the way to Tasmania in the southeast.

Credit: Flinders University


Models also predict that the total population of Sahul could have reached as much as 6.5 million people, according to the studies led by researchers from the Australian Research Council Centre of Excellence for Australian Biodiversity and Heritage (CABAH).

Many Aboriginal cultures believe people have always been here, while others have strong oral histories of ancestral beings arriving from the north.

While there are many hypotheses about where, how and when Indigenous Australians first settled in Sahul, archaeological evidence is scarce.

Now, a group of multidisciplinary experts have collaborated to investigate these questions using state-of-the-art modelling techniques, with the findings published in two companion papers in Nature Communications and Nature Human Behaviour.

Real-world data about long-distance dispersal of people, human survival, fertility rates and the chance of natural disasters were used in combination with principles of human ecology and behaviour and with anthropological, ecological and environmental data to model the peopling of Sahul, in the Nature Communications study led by Professor Corey Bradshaw, CABAH Chief Investigator at Flinders University.

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Data for the 10 million km2 super-continent were used to develop a simulation model and run more than 120 scenarios to predict population size and growth rate. Strongest support was found for the arrival of people 50,000 or 75,000 years ago, with the average establishment rate of 1 km per year emerging from the model giving rise to a maximum population of up to 6.5 million people.

“Guided by Indigenous knowledge, we are coming to appreciate the complexity, prowess, capacity and resilience of the ancestors of Indigenous people in Australia,” Professor Bradshaw said. “The more we look into the deep past, the more we understand that many people have long underestimated the ingenuity of these extraordinary cultures.”

To investigate travel pathways across Sahul, an international team of archaeologists, anthropologists, geographers, ecologists, geneticists, geologists, and computer scientists built the most complete digital elevation model ever constructed for the continent, including areas now underwater.

The model featured in the sister paper in Nature Human Behaviour allowed researchers to understand what early people would have seen — particularly prominent land features within a relatively flat landscape. Other factors, including the physiological capacity of people, difficulty of the terrain, and availability of water were also included.



“If it’s a new landscape and we don’t have a map, we’re going to want to know how to move efficiently throughout a space, where to find water, and where to camp — and we’ll orient ourselves based on high points around the lands,” said superhighways lead author, archaeologist and computational social scientist Stefani Crabtree, a CABAH Associate Investigator, Fellow at the Santa Fe Institute, and Professor at Utah State University.

The scientists identified and tested more than 125 billion possible pathways using rigorous computational analysis in the largest movement-simulation project ever attempted, with the pathways compared with the oldest known archaeological sites to help to distinguish the most likely routes.

Map of what Australia looked like for most of the human history of the continent when sea levels were lower than today.
 Image: Author provided

The patterns that emerged formed distinct ‘superhighways’ across the continent, as well as secondary routes. Several of the identified superhighways echo well-documented Aboriginal trade routes criss-crossing the country — including the trade of pituri native tobacco from Cape York to South Australia via Birdsville, and the trade of Kimberley baler shell into central Australia.

“Australia’s not only the driest, but also the flattest populated continent on Earth,” explained CABAH Deputy Director, Distinguished Professor Sean Ulm from James Cook University. “Our research shows that prominent landscape features and water sources were critical for people to navigate and survive on the continent.

“In many Aboriginal societies, landscape features are believed to have been created by ancestral beings during the Dreaming. Every ridgeline, hill, river, beach and water source is named, storied and inscribed into the very fabric of societies, emphasising the intimate relationship between people and place. The landscape is literally woven into peoples’ lives and their histories. It seems that these relationships between people and Country probably date back to the earliest peopling of the continent.”

Professor Lynette Russell, CABAH Deputy Director and Co-Chair of its Indigenous Advisory Committee, said: “This modelling established the infrastructure for detailed local and regional studies to engage respectfully with Indigenous knowledges, ethnographies, historical records, oral histories and archives.”

The results of these new studies suggest that there are fundamental rules people follow as they move into new landscapes, and that these same approaches could shed light on other major migrations in human history, such as the first waves of migration out of Africa at least 120,000 years ago.

Future work could inform the search for undiscovered archaeological sites, or even apply the techniques to forecast the movements of human migration in the near future, as populations flee drowning coastlines and climate disruptions.


Contacts and sources:
Flinders University



Publication: Stochastic models support rapid peopling of Late Pleistocene Sahul.
Corey J. A. Bradshaw, Kasih Norman, Sean Ulm, Alan N. Williams, Chris Clarkson, Joël Chadœuf, Sam C. Lin, Zenobia Jacobs, Richard G. Roberts, Michael I. Bird, Laura S. Weyrich, Simon G. Haberle, Sue O’Connor, Bastien Llamas, Tim J. Cohen, Tobias Friedrich, Peter Veth, Matthew Leavesley, Frédérik Saltré.Nature Communications, 2021; 12 (1) DOI: 10.1038/s41467-021-21551-3


COVID-19 Survivors Evidence an Increased Risk of Death, Serious Illness

A major study details numerous long-term effects of COVID-19, pointing to massive health burden.

The new study from Washington University School of Medicine in St. Louis shows that even mild cases of COVID-19 increase the risk of death in the six months following diagnosis and that this risk increases with disease severity. The comprehensive study also catalogues the wide-ranging and long-term health problems often triggered by the infection, even among those not hospitalized.

Credit: Sara Moser


As the COVID-19 pandemic has progressed, it has become clear that many survivors — even those who had mild cases — continue to manage a variety of health problems long after the initial infection should have resolved. In what is believed to be the largest comprehensive study of long COVID-19 to date, researchers at Washington University School of Medicine in St. Louis showed that COVID-19 survivors — including those not sick enough to be hospitalized — have an increased risk of death in the six months following diagnosis with the virus.

The researchers also have catalogued the numerous diseases associated with COVID-19, providing a big-picture overview of the long-term complications of COVID-19 and revealing the massive burden this disease is likely to place on the world’s population in the coming years.

The study, involving more than 87,000 COVID-19 patients and nearly 5 million control patients in a federal database, appears online April 22 in the journal Nature.

“Our study demonstrates that up to six months after diagnosis, the risk of death following even a mild case of COVID-19 is not trivial and increases with disease severity,” said senior author Ziyad Al-Aly, MD, an assistant professor of medicine. “It is not an exaggeration to say that long COVID-19 — the long-term health consequences of COVID-19 — is America’s next big health crisis. Given that more than 30 million Americans have been infected with this virus, and given that the burden of long COVID-19 is substantial, the lingering effects of this disease will reverberate for many years and even decades. Physicians must be vigilant in evaluating people who have had COVID-19. These patients will need integrated, multidisciplinary care.”

In the new study, the researchers were able to calculate the potential scale of the problems first glimpsed from anecdotal accounts and smaller studies that hinted at the wide-ranging side effects of surviving COVID-19, from breathing problems and irregular heart rhythms to mental health issues and hair loss.

“This study differs from others that have looked at long COVID-19 because, rather than focusing on just the neurologic or cardiovascular complications, for example, we took a broad view and used the vast databases of the Veterans Health Administration (VHA) to comprehensively catalog all diseases that may be attributable to COVID-19,” said Al-Aly, also director of the Clinical Epidemiology Center and chief of the Research and Education Service at the Veterans Affairs St. Louis Health Care System.

The investigators showed that, after surviving the initial infection (beyond the first 30 days of illness), COVID-19 survivors had an almost 60% increased risk of death over the following six months compared with the general population. At the six-month mark, excess deaths among all COVID-19 survivors were estimated at eight people per 1,000 patients. Among patients who were ill enough to be hospitalized with COVID-19 and who survived beyond the first 30 days of illness, there were 29 excess deaths per 1,000 patients over the following six months.

“These later deaths due to long-term complications of the infection are not necessarily recorded as deaths due to COVID-19,” Al-Aly said. “As far as total pandemic death toll, these numbers suggest that the deaths we’re counting due to the immediate viral infection are only the tip of the iceberg.”

The researchers analyzed data from the national health-care databases of the U.S. Department of Veterans Affairs. The dataset included 73,435 VHA patients with confirmed COVID-19 but who were not hospitalized and, for comparison, almost 5 million VHA patients who did not have a COVID-19 diagnosis and were not hospitalized during this time frame. The veterans in the study were primarily men (almost 88%), but the large sample size meant that the study still included 8,880 women with confirmed cases.

To help understand the long-term effects of more severe COVID-19, the researchers harnessed VHA data to conduct a separate analysis of 13,654 patients hospitalized with COVID-19 compared with 13,997 patients hospitalized with seasonal flu. All patients survived at least 30 days after hospital admission, and the analysis included six months of follow-up data.

The researchers confirmed that, despite being initially a respiratory virus, long COVID-19 can affect nearly every organ system in the body. Evaluating 379 diagnoses of diseases possibly related to COVID-19, 380 classes of medications prescribed and 62 laboratory tests administered, the researchers identified newly diagnosed major health issues that persisted in COVID-19 patients over at least six months and that affected nearly every organ and regulatory system in the body, including:
  • Respiratory system: persistent cough, shortness of breath and low oxygen levels in the blood.
  • Nervous system: stroke, headaches, memory problems and problems with senses of taste and smell.
  • Mental health: anxiety, depression, sleep problems and substance abuse.
  • Metabolism: new onset of diabetes, obesity and high cholesterol.
  • Cardiovascular system: acute coronary disease, heart failure, heart palpitations and irregular heart rhythms.
  • Gastrointestinal system: constipation, diarrhea and acid reflux.
  • Kidney: acute kidney injury and chronic kidney disease that can, in severe cases, require dialysis.
  • Coagulation regulation: blood clots in the legs and lungs.
  • Skin: rash and hair loss.
  • Musculoskeletal system: joint pain and muscle weakness.
  • General health: malaise, fatigue and anemia.

While no survivor suffered from all of these problems, many developed a cluster of several issues that have a significant impact on health and quality of life.

Among hospitalized patients, those who had COVID-19 fared considerably worse than those who had influenza, according to the analysis. COVID-19 survivors had a 50% increased risk of death compared with flu survivors, with about 29 excess deaths per 1,000 patients at six months. Survivors of COVID-19 also had a substantially higher risk of long-term medical problems.

“Compared with flu, COVID-19 showed remarkably higher burden of disease, both in the magnitude of risk and the breadth of organ system involvement,” Al-Aly said. “Long COVID-19 is more than a typical postviral syndrome. The size of the risk of disease and death and the extent of organ system involvement is far higher than what we see with other respiratory viruses, such as influenza.”

In addition, the researchers found that the health risks from surviving COVID-19 increased with the severity of disease, with hospitalized patients who required intensive care being at highest risk of long COVID-19 complications and death.

“Some of these problems may improve with time — for example, shortness of breath and cough may get better — and some problems may get worse,” Al-Aly added. “We will continue following these patients to help us understand the ongoing impacts of the virus beyond the first six months after infection. We’re only a little over a year into this pandemic, so there may be consequences of long COVID-19 that are not yet visible.”

In future analyses of these same datasets, Al-Aly and his colleagues also plan to look at whether patients fared differently based on age, race and gender to gain a deeper understanding of the risk of death in people with long COVID-19.Credit: Sara Moser
 




Contacts and sources:
Julia Evangelou
Washington University School of Medicine



Publication: High-dimensional characterization of post-acute sequalae of COVID-19.
Ziyad Al-Aly, Yan Xie, Benjamin Bowe. Nature, 2021; DOI: 10.1038/s41586-021-03553-9



New All-Sky Map of Milky Way's Outer Reaches Released

The highlight of the new chart is a wake of stars, stirred up by a small galaxy set to collide with the Milky Way. The map could also offer a new test of dark matter theories.

Images of the Milky Way and the Large Magellanic Cloud (LMC) are overlaid on a map of the surrounding galactic halo. The smaller structure is a wake created by the LMC’s motion through this region. The larger light-blue feature corresponds to a high density of stars observed in the northern hemisphere of our galaxy.


Credit: NASA/ESA/JPL-Caltech/Conroy et. al. 2021 Full Image Details


Astronomers using data from NASA and ESA (European Space Agency) telescopes have released a new all-sky map of the outermost region of our galaxy. Known as the galactic halo, this area lies outside the swirling spiral arms that form the Milky Way’s recognizable central disk and is sparsely populated with stars. Though the halo may appear mostly empty, it is also predicted to contain a massive reservoir of dark matter, a mysterious and invisible substance thought to make up the bulk of all the mass in the universe.

The data for the new map comes from ESA’s Gaia mission and NASA’s Near Earth Object Wide Field Infrared Survey Explorer, or NEOWISE, which operated from 2009 to 2013 under the moniker WISE. The study makes use of data collected by the spacecraft between 2009 and 2018.

The new map reveals how a small galaxy called the Large Magellanic Cloud (LMC) – so named because it is the larger of two dwarf galaxies orbiting the Milky Way – has sailed through the Milky Way’s galactic halo like a ship through water, its gravity creating a wake in the stars behind it. The LMC is located about 160,000 light-years from Earth and is less than one-quarter the mass of the Milky Way.

A simulation of dark matter surrounding the Milky Way galaxy (small ring at center) and the Large Magellanic Cloud (LMC) reveals two areas of high density: the smaller of the two light blue areas is a wake created by the LMC’s motion through this region. The larger corresponds to an excess of stars in the Milky Way’s northern hemisphere. ]
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Credit: NASA/JPL-Caltech/NSF/R. Hurt/N. Garavito-Camargo & G. Besla

Though the inner portions of the halo have been mapped with a high level of accuracy, this is the first map to provide a similar picture of the halo’s outer regions, where the wake is found – about 200,000 light-years to 325,000 light-years from the galactic center. Previous studies have hinted at the wake’s existence, but the all-sky map confirms its presence and offers a detailed view of its shape, size, and location.

This disturbance in the halo also provides astronomers with an opportunity to study something they can’t observe directly: dark matter. While it doesn’t emit, reflect, or absorb light, the gravitational influence of dark matter has been observed across the universe. It is thought to create a scaffolding on which galaxies are built, such that without it, galaxies would fly apart as they spin. Dark matter is estimated to be five times more common in the universe than all the matter that emits and/or interacts with light, from stars to planets to gas clouds. 

Although there are multiple theories about the nature of dark matter, all of them indicate that it should be present in the Milky Way’s halo. If that’s the case, then as the LMC sails through this region, it should leave a wake in the dark matter as well. The wake observed in the new star map is thought to be the outline of this dark matter wake; the stars are like leaves on the surface of this invisible ocean, their position shifting with the dark matter.

The interaction between the dark matter and the Large Magellanic Cloud has big implications for our galaxy. As the LMC orbits the Milky Way, the dark matter’s gravity drags on the LMC and slows it down. This will cause the dwarf galaxy’s orbit to get smaller and smaller, until the galaxy finally collides with the Milky Way in about 2 billion years. These types of mergers might be a key driver in the growth of massive galaxies across the universe. In fact, astronomers think the Milky Way merged with another small galaxy about 10 billion years ago.

“This robbing of a smaller galaxy’s energy is not only why the LMC is merging with the Milky Way, but also why all galaxy mergers happen,” said Rohan Naidu, a doctoral student in astronomy at Harvard University and a co-author of the new paper. “The wake in our map is a really neat confirmation that our basic picture for how galaxies merge is on point!”

A Rare Opportunity

The authors of the paper also think the new map – along with additional data and theoretical analyses – may provide a test for different theories about the nature of dark matter, such as whether it consists of particles, like regular matter, and what the properties of those particles are.

“You can imagine that the wake behind a boat will be different if the boat is sailing through water or through honey,” said Charlie Conroy, a professor at Harvard University and an astronomer at the Center for Astrophysics | Harvard & Smithsonian, who coauthored the study. “In this case, the properties of the wake are determined by which dark matter theory we apply.”

Conroy led the team that mapped the positions of over 1,300 stars in the halo. The challenge arose in trying to measure the exact distance from Earth to a large portion of those stars: It’s often impossible to figure out whether a star is faint and close by or bright and far away. The team used data from ESA’s Gaia mission, which provides the location of many stars in the sky but cannot measure distances to the stars in the Milky Way’s outer regions.

After identifying stars most likely located in the halo (because they were not obviously inside our galaxy or the LMC), the team looked for stars belonging to a class of giant stars with a specific light “signature” detectable by NEOWISE. Knowing the basic properties of the selected stars enabled the team to figure out their distance from Earth and create the new map. It charts a region starting about 200,000 light-years from the Milky Way’s center, or about where the LMC’s wake was predicted to begin, and extends about 125,000 light-years beyond that.

Conroy and his colleagues were inspired to hunt for LMC’s wake after learning about a team of astrophysicists at the University of Arizona in Tucson that makes computer models predicting what dark matter in the galactic halo should look like. The two groups worked together on the new study.

One model by the Arizona team, included in the new study, predicted the general structure and specific location of the star wake revealed in the new map. Once the data had confirmed that the model was correct, the team could confirm what other investigations have also hinted at: that the LMC is likely on its first orbit around the Milky Way. If the smaller galaxy had already made multiple orbits, the shape and location of the wake would be significantly different from what has been observed. Astronomers think the LMC formed in the same environment as the Milky Way and another nearby galaxy, M31, and that it is close to completing a long first orbit around our galaxy (about 13 billion years). Its next orbit will be much shorter due to its interaction with the Milky Way.

“Confirming our theoretical prediction with observational data tells us that our understanding of the interaction between these two galaxies, including the dark matter, is on the right track,” said University of Arizona doctoral student in astronomy Nicolás Garavito-Camargo, who led work on the model used in the paper.

The new map also provides astronomers with a rare opportunity to test the properties of the dark matter (the notional water or honey) in our own galaxy. In the new study, Garavito-Camargo and colleagues used a popular dark matter theory called cold dark matter that fits the observed star map relatively well. Now the University of Arizona team is running simulations that use different dark matter theories to see which one best matches the wake observed in the stars.

“It’s a really special set of circumstances that came together to create this scenario that lets us test our dark matter theories,” said Gurtina Besla, a co-author of the study and an associate professor at the University of Arizona. “But we can only realize that test with the combination of this new map and the dark matter simulations that we built.”

Launched in 2009, the WISE spacecraft was placed into hibernation in 2011 after completing its primary mission. In September 2013, NASA reactivated the spacecraft with the primary goal of scanning for near-Earth objects, or NEOs, and the mission and spacecraft were renamed NEOWISE. NASA’s Jet Propulsion Laboratory in Southern California managed and operated WISE for NASA’s Science Mission Directorate. The mission was selected competitively under NASA’s Explorers Program managed by the agency’s Goddard Space Flight Center in Greenbelt, Maryland. NEOWISE is a project of JPL, a division of Caltech, and the University of Arizona, supported by NASA’s Planetary Defense Coordination Office.
 





Contacts and sources:
Calla Cofield
NASA/Jet Propulsion Laboratory




Publication: All-sky dynamical response of the Galactic halo to the Large Magellanic Cloud.
Charlie Conroy, Rohan P. Naidu, Nicolás Garavito-Camargo, Gurtina Besla, Dennis Zaritsky, Ana Bonaca, Benjamin D. Johnson. Nature, 2021; 592 (7855): 534 DOI: 10.1038/s41586-021-03385-7



Eastern and Western House Mice Took Parallel Evolutionary Paths

A house mouse from a southern population (left) is much smaller than a house mouse from a northern population (right), even when raised in the same environment, showing that the body size difference is the result of genetic variation caused by adaptation, presumably to cold temperatures. 


Credit: UC Berkeley photos by Katya Mack 

The European house mouse has invaded nearly every corner of the Americas since it was introduced by colonizers a few hundred years ago, and now lives practically everywhere humans store their food.

Yet in that relatively short time span — 400 to 600 mouse generations — populations on the East and West Coasts have changed their body size and nest building behavior in nearly identical ways to adapt to similar environmental conditions, according to a new study by biologists at the University of California, Berkeley.

To make these adaptations — at least in the case of body size — mice in the Western United States evolved many of the same genetic changes as their cousins in the East, showing that evolution often works on the same genes in different populations when those populations are confronted with similar environmental conditions.

The study represents one of the first times scientists have tracked down the genetic changes underlying a complex adaptive trait in mammals, though similar studies have been conducted with laboratory insects, such as fruit flies, and in fish.

“The big take-home message from this paper is that there is some predictability to evolution, both at the organismal level and at the genetic level,” said study leader Michael Nachman, UC Berkeley professor of integrative biology and director of the campus’s Museum of Vertebrate Zoology. “We have shown that the same genes have been recruited independently in two different areas, all over very short evolutionary time. This is a good example of rapid evolutionary change over short times for a complex adaptive trait.”

The findings also have implications for mammals other than rodent pests.

“The mice we are studying are a reasonable model for thinking about human evolution as well, since humans have been in the Americas about as many generations as house mice,” Nachman said. “We found genes involved in mouse body size that had previously been implicated in metabolism and things like obesity in humans, so there also are parallels between humans and mice.”

House mice (Mus musculus domesticus) were introduced to America by colonizers from Europe, and have since spread throughout the Western Hemisphere. Originally from around the Mediterranean Sea, they have invaded habitats as diverse as the Arizona desert, the slopes of 10,000-foot peaks in the Andes and the frigid Alberta plains. 

UC Berkeley photo by Katya Mack

Nachman and his colleagues were able to prove that these traits have a genetic cause — they resulted from nature, not nurture — by raising mice from different environments in the lab under the same environmental conditions. House mice from New York and Alberta, Canada, always produced bigger nests than mice from Florida and Arizona, even when nesting at the same temperature, while the northern mice were always bigger than the southern mice, despite being raised in similar conditions.

“We and many other people have studied natural populations for a long time and you can document differences among natural populations,” he said. “But in this case, we went one step further and took those animals into the lab and reared them for multiple generations so we could ask whether the differences we see in nature are due to the environment or due to genetics. By having a combination of animals in the wild and animals in the lab, we can tease out the genetic component to the traits that we are studying.”

The study appeared today in the journal PLOS Genetics.
Canadian mice vs. Arizona mice

Nachman and his team have been studying house mice in North and South America for several years to determine how they have adapted to different environments — physiologically and genetically — since arriving as stowaways aboard ships from Europe. His goal has been to link changes in physiology and instinctual behavior to changes in specific genes, to understand how multiple genes interact to create changes in complicated adaptations.


Sites in North America from which the researchers collected house mice, with average annual temperature shown in color. The scale on left is in degrees Celsius. Latitude is shown on the vertical axis, longitude on the horizontal axis. 

Graphic courtesy of Michael Nachman

To date, most studies linking genetic change — genotype — to physiological change — phenotype — have involved relatively simple characteristics, such as changes in fur color with environment, or development of insecticide resistance.

House mice — Mus musculus domesticus, the ancestor of all laboratory mice used today — seemed a good subject since they exist in a wide variety of habitats throughout the Americas, including in the Andes at elevations above 4,000 meters (13,000 feet). Over the years, Nachman and his colleagues have collected hundreds of individual mice from Tierra del Fuego at the tip of South America to southern Canada and upstate New York, and from different elevations in Ecuador and Bolivia, and sequenced all the genes in their genomes.

Nachman said that he couldn’t help but notice that in the wild, northern mice — from Edmonton, Alberta, and Saratoga Springs, New York — tended to be larger than southern mice from Tucson, Arizona, and Gainesville, Florida, though it wasn’t always clear given that the mice differed in age, diet and health. Larger body size is a well-known adaptation to colder weather, referred to as Bergmann’s rule after the 19th century German biologist Carl Bergmann.

“Mice from 45 degrees north latitude are about 50% bigger than mice from the equator,” Nachman said. “A mouse from the equator is about 12 grams; a mouse from upstate New York is about 18 grams. That is a big difference. If we were talking about humans, that would be a 100-pound versus 150-pound person, on average.”

Northern mice also build bigger nests: about twice the size of southern mice.

To determine the genetic relationships among these mouse populations, his team collected 10 mice from 5 different sites in the West, about equally spaced from Tucson to Edmonton, sequenced their genes and compared them to the genes of mice his team had collected earlier along the East Coast from Gainesville to Saratoga Springs. He found that, though Northeastern mice and Northwestern mice had both developed larger bodies and built larger nests, they were not closely related. New York mice were more closely related to other Eastern mice than to Alberta mice, while Alberta mice were more closely related to other Western mice than to New York mice.

The researchers raised southern mice (left) in the lab under the same environmental conditions as northern mice (right), providing cotton for 24 hours so that they could build a nest. Northern mice tended to fill their cages with cotton.

 Photos by Katya Mack

If Eastern and Western mice are two distinct populations that independently adapted to cold weather using the same strategy — larger size and larger nests — did their genes also change?

To find out, he and his colleagues established lab colonies with 41 individual mice from the extreme areas sampled: Edmonton (EDM) in the north and Tucson (TUC) in the south. Raising them in identical indoor conditions, the northern mice over five generations retained their larger body size and larger nest building behavior, showing that the behavioral and physiological changes were in fact encoded in their genetics. Three years ago, Nachman conducted similar experiments with mice from Saratoga Springs (SAR) and Gainesville (GAI), and found similar results from these Eastern populations.

“By bringing them into the common lab environment and keeping them there at a comfy room temperature for a few generations, we can conclude that any differences we see have a genetic basis,” he said.

They then conducted a genome-wide association study to identify which variant or allele of each gene in the genome had changed frequency along with the change in body mass. They’re still tracking the genetic causes of nest building.
Finding the genetic basis for Bergmann’s Rule

The researchers identified eight mutations in five genes associated with increased body size in the Edmonton mice.

“We found that of all those genes that we identified for body size, four of the five genes show strong signatures of natural selection in both the East and West,” he said. “That suggests that we found some genes that are contributing to this pattern, known as Bergmann’s Rule, which is actually one of the most widespread geographic patterns in the evolution of warm-blooded animals. We are starting to get at its genetic basis in this study.”

A house mouse nestled in cotton. By raising mice through many generations, UC Berkeley researchers were able to tease out which behaviors and physiological traits are controlled by genes. 

UC Berkeley photo by Katya Mack

Combining these data with the results from Nachman’s previous study of house mice in New York and Florida, the researchers found a total of 16 genes that showed parallel evolution along the north-south gradient on both coasts, many of which are involved in regulating body temperature. For example, the gene Trpm2, which causes mice to avoid very high temperatures, showed genetic changes in southern populations.

While mice in the East and West exhibited evidence of independent evolution in many of the same genes, each region also harbored genetic adaptations not seen in the other region. In the West, for example, fur color varied with soil color: northern mice were a darker shade, consistent with trying to blend in on damper, darker soil. Eastern mice did not show such variation.

Nachman is continuing to study house mouse variation, and hopes eventually to employ CRISPR genome editing to alter genes in his mouse populations to confirm their involvement in traits such as body size.

“We’d like to edit some of these genes and see if we can take a mouse from Canada and turn it into a mouse that looks like a Tucson mouse, or vice versa,” he said.

The work was funded by the National Institutes of Health (RO1 GM074245, R01 GM127468). The NIH and The Jackson Laboratory also support Nachman’s development of new house mouse strains — SAR, GAI, EDM, TUC and a fifth strain, MAN, from Manaus, Brazil — that researchers can use in place of the inbred lab mouse — the most popular strain is called C57BL/6 — if they want greater genetic variation in their mouse studies.

Co-authors of the paper are former postdoctoral fellows Kathleen Ferris, Andreas Chavez, Megan Phifer-Rixey and Ke Bi, former doctoral student Taichi Suzuki and current postdoc Elizabeth Beckman. Ferris, Chavez, and Phifer-Rixey are now on the faculty at Tulane University, The Ohio State University and Monmouth University, respectively.


Contacts and sources:
Robert Sanders
University of California - Berkeley





Publication: The genomics of rapid climatic adaptation and parallel evolution in North American house mice (PLOS Genetics)



Research Uncovers High Risk to Pregnant Women from COVID-19

A study of more than 2,100 pregnant women across 18 countries worldwide has revealed that COVID-19 is associated with a higher risk of severe maternal and newborn complications than previously recognized.

The researchers, from the Nuffield Dept of Women's & Reproductive Health at the University of Oxford, report the findings of the INTERCOVID Study in the journal JAMA Pediatrics, providing, for the first time, detailed comparative information about the effects of COVID-19 in pregnancy.

In the paper, published today, they conclude the risk to mothers and babies is greater than acknowledged at the beginning of the pandemic, and that health priority measures should include pregnant women.

Aris Papageorghiou, Professor of Fetal Medicine at the University of Oxford, who co-led INTERCOVID, said, ‘Women with COVID-19 during pregnancy were over 50% more likely to experience pregnancy complications (such as premature birth, pre-eclampsia, admission to intensive care and death) compared to pregnant women unaffected by COVID-19.

'Newborns of infected women were also nearly three times more at risk of severe medical complications, such as admission to a Neonatal Intensive Care Unit – mostly due to premature birth. The good news, however, is that the risks in symptomless infected women and non-infected women were similar.’



Credit: Shutterstock

The researchers sought to understand the effects of COVID-19 in pregnancy by collecting robust data on pregnant women with and without a diagnosis of COVID-19, an important step to ensure that families understand the risks involved, mothers and babies receive the best possible care, and health resources, such as vaccines, are appropriately allocated. However, until now, the quality of the available information has been limited.

The paper describes the work of over 100 researchers that recently completed the INTERCOVID Study involving over 2,100 pregnant women from 43 maternity hospitals in 18 low, middle and high-income countries worldwide.

The study is unique because each woman affected by COVID-19 was compared to two non-infected pregnant women giving birth at the same time in the same hospital.

Professor Papageorghiou, continued: ‘Fortunately, there were very few maternal deaths; nevertheless, the risk of dying during pregnancy and in the postnatal period was 22 times higher in women with COVID-19 than in the non-infected pregnant women.'

The study also highlighted that close to 10% of newborns from mothers that were test-positive for the virus also tested positive for the virus during the first few postnatal days.

José Villar, Professor of Perinatal Medicine at the University of Oxford, who co-led the study, said, ‘Importantly, breastfeeding does not seem to be related to this increase. Delivery by Caesarean section, however, may be associated with an increased risk of having an infected newborn.’

The study demonstrates the importance of collecting large-scale multinational data quickly during a health crisis, as researchers were able to complete the study in only 9 months, using infrastructure that was already in place from Oxford’s multicentre INTERGROWTH-21st Project.

Professor Villar continued: ‘The existing INTERGROWTH-21st infrastructure was critical in enabling researchers worldwide to implement this urgent initiative in record time, and their commitment to the study was remarkable. Examining the long-term effects on mothers and children is the next challenge’.

Stephen Kennedy, Professor of Reproductive Medicine at the University of Oxford, who co-led the study, concluded, ‘We now know that the risks to mothers and babies are greater than we assumed at the start of the pandemic and that known health measures when implemented must include pregnant women. The information should help families, as the need to do all one can to avoid becoming infected is now clear. It also strengthens the case for offering vaccination to all pregnant women.’


Contacts and sources:





Publication: