The genetics of human physical appearance

Despite its great biological and social importance the genetic basis of variation in human physical appearance is poorly understood. Identical twins share all of their genes and show striking physical resemblance, while more distant relatives tend to look less alike the less closely related they are. This variation in degree of family resemblance suggests that many genes influence physical appearance. However, few of the genes have been identified. The aim of this proposal is to identify genetic variants influencing a selection of such features: body size and shape, pigmentation (of hair, skin and eyes), facial features, type of hair, baldness and hair greying. To facilitate this task we propose to study Latin American populations which represent a mixture of different continental populations (Europeans, Native Amerindians and Africans). These continental populations have quite differentiated physical features and provide us with higher statistical power for detecting genetic effects. With independent funding we are recruiting over 7,500 Latin American research volunteers (from Mexico, Colombia, Peru, Chile and Brazil) and we are characterizing their physical appearance. We record face features using photographs and specialized imaging processing techniques, skin using an instrument allowing colour measurement and the other features through physical examination. Here we request funding for the genetic analysis of this sample. Initially we propose to examine the entire human genome in 3000 individuals using about ~300,000 genetic markers. This information will be used (together with the human genome sequence) to identify regions showing association with the physical characteristics of the individuals. The regions showing association will then be examined in the rest of the Latin American cohort (an additional 4,500 individuals) and in European cohorts being studied by collaborators (comprising over 20,000 individuals). In this way we will confirm our findings. We will then use statistical techniques to evaluate if these variants can predict the physical characteristics of unknown individuals based only on a DNA sample. Identification of genes involved in physical appearance has a number of important consequences for basic biological research, such as examining the evolution of this traits and optimize their use in studies on human origins and diversification. This work will also have important biomedical implications as the genes identified could be involved in human disorders (of development pigmentation, aging and skin cancer). This work will also lay the foundation for the development of an entire new field of forensic genetics: the reconstruction of an individual's physical appearance based on a DNA sample. Finally, our proposal will inform the public about aspects of the relationship between genetics, ethnic identity and race.

Here we propose to identify genes responsible for variation at a range of visible phenotypes in humans: height, facial features, pigmentation (of hair, skin and eyes), hair morphology, greying and baldness. We propose to examine populations from Latin America of mixed ancestry. These populations will allow us to explore a wider range of phenotypic and genetic diversity than hitherto attempted. They will also allow us to apply novel methods of genomic mapping based on combining the signals of association and admixture. Collection of a study sample of ~7,500 individuals is funded independently. We propose to perform chip genotyping in 3,000 of these individuals. Association tests will exploit imputation based on whole genome sequence data we are generating independently. The top hits from this phase will be followed-up through genotyping 386 SNPs in the entire cohort of 7,500 individuals. Follow-up will include meta-analyses with European cohorts of over 20,000 individuals being characterized by collaborators as well as other publicly available data. Finally, we will evaluate the efficacy of SNP data in predicting phenotypes by use of mixed regression models. This work will lay the ground for analyses on the evolution of traits differing between human populations and inform their use in physical anthropology. Investigating the genetics of these phenotypes is of interest for developmental biology and for research on aging. Genes influencing variation of visible traits constitute candidates for disease causation, particularly in developmental, aging and pigmentation disorders and skin cancer. This work is of high social impact because of its potential forensic applications, particularly the inference of aspects of an individual physical appearance based on a DNA sample. Public interest in this project will be strong given its relevance to debates about identity and racism, and their relation to genetics research.

There is great interest amongst the forensics community in the development of methods to predict the physical appearance of an individual based on DNA information, sometimes called 'DNA forensic phenotyping'. The aim is to develop this methodology as an investigative tool, a kind of 'genetic eyewitness'. There are two fundamental research problems that need to be solved in order to develop this field. First we need to identify genetic variants associated with specific phenotypic features across human populations and second we need to establish the value of these variants in phenotypic prediction. Both questions are addressed in this proposal. Developing these novel forensic genetic tools is potentially of great economic importance. At the moment the forensic DNA industry is almost entirely focused on products for DNA fingerprinting analysis. Developing products for forensic DNA phenotyping would open an entirely new market sector. A key element in our strategy to maximise the forensic impact of our research proposal is our collaboration within the VISIGEN consortium which brings together researchers from the UK, the Netherlands, Australia and Italy with whom we have signed a collaboration agreement to serve as framework for data sharing, publication and definition of IP terms. VISIGEN aims to foster research into the genetics of visible traits and promote its industrial exploitation. The consortium has initiated negotiations licence agreement with IDENTITAS a company interested in the development of a DNA chip (and accompanying algorithms) for forensic phenotyping in world populations. We anticipate that this license agreement will be signed while this proposal is being implemented. Independent of VISIGEN the Co-PI DJB will use his extensive contacts in the forensic science world both to inform the direction of forensic applications of the project, and as a route to dissemination of our results. DJB sits on the External Advisory Group of the Forensic Science Service and is a member of the UK Forensic Regulator's DNA Specialist Group. He is also on the steering committee of the new UCL Centre for Forensic Science which will be a focus for interdisciplinary research on aspects of forensic science impacting the criminal justice system. Research on human physical appearance and its relationship to genetics is of great interest to the public. There is also great public sensitivity towards this kind of research, as it can easily be perceived as reinforcing racial stereotypes and racism. To address these issues our ongoing work involves an important social research. For this we have the support of two social anthropologists with extensive expertise the social science implications of contemporary genomics research, Prof. Peter Wade (U. Manchester) and Dr. Sahra Gibbon (UCL). To maximise the public visibility of this aspect of our work we will interact closely with the UCL media office. This work has attracted the attention of several television producers and an editor from Princeton University Press and we will explore options for producing a TV documentary and a book on 'The genetics of human appearance'. We also plan to organise public engagement activities including open lectures/debates at UCL led by Prof. Steve Jones (UCL), an internationally recognized figure in the public understanding of science who often lectures on the topic of genetics research and racism. In organizing these activities we will also be supported by UCL's Public Engagement Unit one of the six national Beacons for Public Engagement funded by the Research Councils.