Background

The face is a biological display of our identity and controlled in the most part by genes.1-3 There is consistent facial concordance between identical twins,4 identifiable facial features within families,5 geographic populations,6 and the sexes,7 and finally distinctive facial features associated with particular genetic conditions.8,9 This suggests that inter-individual variation in craniofacial morphology is primarily determined by genetic variation.

Studies of craniofacial heritability are performed on twin and parent-offspring databases and provide insight in the relative contribution of genetic and environmental effects on craniofacial parameters.4,5,10,11 Heritability studies allow the focus on those facial parameters displaying a strong genetic component as well as acknowledging possible environmental influences. Most if not all studies on craniofacial heritability start from sparse descriptions of facial shape using a limited set of manually indicated landmarks. Variation in these landmarks is then comprised using principal component analysis or by measuring geometric features such as distances, curvature, ratios and/or angles. Subsequently, for each principal component or geometric feature separately a heritability score is computed using correlations between parent and offspring or between twins. However, sparse representations typically overlook salient features of facial shape. Furthermore, heritability studies today do not investigate co-inheritance between different geometric features. Doing so would allow subdivision of facial shape into modules (multiple landmarks and measurements grouped together) of co-inheritance, that when analyzed as groups could reveal higher levels of inheritance.

Research Aim

The aim of this proposal is to perform a spatially-dense analysis of facial heritability and co-heritability starting with Fathers and offspring data available within ALSPAC. The study outcome is two-fold. In a first instance a spatially dense view on facial heritability per landmark will be provided. In a second instance, a subdivision of facial shape into modules of co-inheritance will be provided. Subsequently, the benefit of such a modularization will be tested in a limited association study between facial shape and known craniofacial genes based on BRIM.12