Learning about the role of the three loci (referred to as LYST, 17q25.3, and TTC3/DSCR9) has added to a more comprehensive and concise understanding of the genetic basis of human eye colour. With the new knowledge generated by the team, we now know more than half of the attributes in eye colour variance. Although the LYST gene had previously been acknowledged as a pigmentation gene in mice and cattle, no association with pigmentation had ever been made to the other two genes prior to this study.
Summarising the results in their published paper, the scientists write: 'Our quantitative prediction model explained over 50% of eye colour variance, representing the highest accuracy achieved so far in genomic prediction of human complex and quantitative traits, with relevance for future forensic applications.'
The genome-wide study involving almost 6 000 Dutch Europeans (and a further 3 500 individuals from Australia and the UK for study replication) was the first ever to be conducted on quantitative human eye colour. Their novel approach was to measure hue and saturation values of eye colour from high-resolution digital, full-eye photographs.
The approach was so effective that the researchers recommend fine phenotyping as a useful strategy for finding genes involved in human complex traits, highlighting the method as being extremely cost effective, portable and time efficient.
Indeed, it was due to the fine phenotyping approach that the scientists found that variation in human eye colour is a constant (unbroken) grading from the lightest shade of blue to the darkest shade of brown or black. For the team, human eye colour varies in more ways than the one represented by the blue, green and brown categories studied in the past.
Dr Manfred Kayser of the Erasmus University Medical Center referenced the remarkable potential of the research results in helping with criminal and forensic investigations, 'where appearance prediction from biological material found at crime scenes may provide investigative leads to trace unknown persons'.
In addition to researchers from several departments within Erasmus University Medical Center, the project included teams from the University of Cologne in Germany, King’s College London in the UK, and Australia's Queensland Institute of Medical Research and University of Western Australia.
The research was supported by the GEFOS ('Genetic factors for osteoporosis') and ENGAGE ('European network for genetic and genomic epidemiology') projects, which received a total of EUR 15 million in funding under the Health Theme of the EU's Seventh Framework Programme (FP7).
The MY EUROPIA ('European training in myopia research') Marie Curie Research Training Network, which received EUR 3.17 million under the EU's Sixth Framework Programme (FP6), and the GENOMEUTWIN ('Studies of European volunteer twins to identify genes underlying common diseases') project, supported under the 'Quality of Life and Management of the Living Resources' programme of the EU's Fifth Framework Programme (FP5) also contributed to the study.