Saturday, September 05, 2009

EDAR & the shovel-shaped incisor   posted by Razib @ 9/05/2009 07:23:00 PM

Dienekes is posting more ASHG abstracts. This one is interesting:
A nonsynonymous SNP in EDAR is associated with tooth shoveling

Teeth display variations among individuals in the size and the shape of cusps, ridges, grooves, and roots. In addition, there are certain dental characteristics which are predominant in certain human groups, such as tooth shoveling of upper incisors that is major in Asian populations but rare or absent in African and European populations...Human genome diversity data have revealed that the derived allele of a nonsynonymous single nucleotide polymorphism (SNP), rs3827760 that is also called EDAR T1540C, is predominant in East Asian populations but absent in populations of African and European origins. It has recently been reported that the 1540C allele is associated with Asian-specific hair thickness. The aim of this study is to clarify whether the nonsynonymous polymorphism in EDAR is also associated with dental morphology in humans or not. For this purpose, we measured crown diameters and tooth shoveling grades, genotyped EDAR T1540C, and analyzed the correlations between them in Japanese populations. To comprehend individual patterns of dental morphology, we applied a principal component analysis (PCA) to individual-level metric data, the result of which implies that multiple types of factors affect the tooth size. This study clearly demonstrated that the number of the Asian-specific EDAR 1540C allele is strongly correlated with the tooth shoveling grade.

We've posted on EDAR. Interesting that it seems it is related to another classic "Mongoloid" physical trait, the shovel-shaped incisor, which loomed large back in the day when bones and teeth were the way you identified remains. Of course, other ancient populations had shovel-shaped incisors, so it isn't as if this is totally unique to the peoples of East Asia and the Americas. In any case, this shouldn't be too surprising, EDAR does a lot of things, as evident by the summary in GeneCards:
This gene encodes a member of the tumor necrosis factor receptor family. The encoded transmembrane protein is a receptor for the soluble ligand ectodysplasin A, and can activate the nuclear factor-kappaB, JNK, and caspase-independent cell death pathways. It is required for the development of hair, teeth, and other ectodermal derivatives. Mutations in this gene result in autosomal dominant and recessive forms of hypohidrotic ectodermal dysplasia.