Inhibition of Bmp signaling affects growth and differentiation in the anagen hair follicle

Growth and differentiation of postnatal hair follicles are controlled by re ciprocal interactions between the dermal papilla and the surrounding epider mal hair precursors. The molecular nature of these interactions is largely unknown, but they are likely to involve several families of signaling molec ules, including Fgfs, Wnts and Bmps, To analyze the function of Bmp signali ng in postnatal hair development, we have generated transgenic mice express ing the Bmp inhibitor, Noggin, under the control of the proximal Msx2 promo ter, which drives expression in proliferating hair matrix cells and differe ntiating hair precursor cells. Differentiation of the hair shaft but not th e inner root sheath is severely impaired in Msx2-Noggin transgenic mice. In addition to hair keratins, the expression of several transcription factors implicated in hair development, including Foxn1 and Hoxc13, is severely re duced in the transgenic hair follicles, Proliferating cells, which are norm ally restricted to the hair matrix surrounding the dermal papilla, are foun d in the precortex and hair shaft region. These results identify Bmps as ke y regulators of the genetic program controlling hair shaft differentiation in postnatal hair follicles.