Hair defects in Hoxc13 mutant mice.

Hox genes encode transcription factors that are important during normal embryonic development of diverse organisms including vertebrates. In mammals, Hox genes are responsible for conferring regional identity in embryonic tissues, including the limb bud, the neural tube, the presomitic mesoderm and the intestinal tract. Recent studies have demonstrated expression of Hox genes in skin and hair follicles, suggesting potential functions for these genes in epidermal appendages. These studies are reviewed here with emphasis on Hoxc13, as Hoxc13 mutants are the first Hox mutants to demonstrate overt hair defects. In addition, because Hoxc13 does not show regionally restricted expression in the skin, as demonstrated for other Hox genes, the potentially different roles of Hoxc13 versus other Hox genes in the skin are discussed.