Characterization of Wnt gene expression in developing and postnatal hair follicles and identification of Wnt5a as a target of Sonic hedgehog in hair follicle morphogenesis

Mutations in WNT effector genes perturb hair follicle morphogenesis, sugges ting key roles for WNT proteins in this process. We show that expression of Wnts 10b and 10a is upregulated in placodes at the onset of follicle morph ogenesis and in postnatal hair follicles beginning a new cycle of hair grow th. The expression of additional Wnt genes is observed in follicles at late r stages of differentiation. Among these, we find that Wnt5a is expressed i n the developing dermal condensate of wild type but not Sonic hedgehog (Shh )-null embryos, indicating that Wnt5a is a target of SHH in hair follicle m orphogenesis. These results identify candidates for several key follicular signals and suggest that WNT and SHH signaling pathways interact to regulat e hair follicle morphogenesis. (C) 2001 Elsevier Science Ireland Ltd. All r ights reserved.