BMP-FGF Signaling Axis Mediates Wnt-Induced Epidermal Stratification in Developing Mammalian Skin

The study demonstrated that while Wnt signaling from proliferative basal cells was not necessary for their differentiation, it was crucial for forming the spinous layer in mammalian skin through a BMP-FGF signaling cascade in the dermis. Disruption of Wnt secretion led to spinous layer defects, which could be corrected by transgenically expressed Bmp4. BMP4, acting non-cell autonomously, activated FGF7 and FGF10 signaling, increasing the proliferative basal cell population. This research identified a critical BMP-FGF signaling axis in the dermis that responded to epidermal Wnts and regulated basal progenitors during epidermal stratification.