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Le secret des vraies blondes

(et des vrais blonds)

à lire sur Nature :

The secret of a natural blond   pp660 - 661
Hopi Hoekstra

Elucidating the molecular mechanisms responsible for changes in gene expression is important for understanding the evolution of morphological traits. A new study identifies the molecular basis of the association between KITLG and blond hair color, presenting an intriguing example of how a single DNA base-pair change in an upstream regulatory element can cause relatively large and specific downstream changes in phenotype.

A molecular basis for classic blond hair color in Europeans

Nature Genetics 46, 748–752 (2014) doi:10.1038/ng.2991

Received 30 November 2013 Accepted 01 May 2014 Published online 01 June 2014

Hair color differences are among the most obvious examples of phenotypic variation in humans. Although genome-wide association studies (GWAS) have implicated multiple loci in human pigment variation, the causative base-pair changes are still largely unknown1. Here we dissect a regulatory region of the KITLG gene (encoding KIT ligand) that is significantly associated with common blond hair color in northern Europeans2. Functional tests demonstrate that the region contains a regulatory enhancer that drives expression in developing hair follicles. This enhancer contains a common SNP (rs12821256) that alters a binding site for the lymphoid enhancer-binding factor 1 (LEF1) transcription factor, reducing LEF1 responsiveness and enhancer activity in cultured human keratinocytes. Mice carrying ancestral or derived variants of the human KITLG enhancer exhibit significant differences in hair pigmentation, confirming that altered regulation of an essential growth factor contributes to the classic blond hair phenotype found in northern Europeans.

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