. Interestingly, manipulation of other genes in the NF-kB pathway does not result in this striking epidermal phenotype, suggesting a novel function for IKKa in epidermal differentiation 1 . IKKa 2/2 mice are born sheathed by a thickened, un- differentiated epidermis and die shortly after birth. The development of hair follicles is also retarded. The limbs and snout of the mice are shortened and blunt, although the axial skeleton is largely intact, as if the thickened epi- dermis restricts outgrowth during development 3 . These