IKKα Is a p63 Transcriptional Target Involved in the Pathogenesis of Ectodermal Dysplasias

The transcription factor p63 plays a pivotal role in the development and differentiation of the epidermis and epithelial appendages. Indeed, mutations in p63 are associated with a group of ectodermal dysplasias characterized by skin, limb, and craniofacial defects. It was hypothesized that p63 exerts its functions by activating specific genes during epidermal development, which in turn regulate epidermal stratification and differentiation. We have identified I-kappaB kinase alpha (IKKα) as a direct transcriptional target of p63 that is induced at early phases of terminal differentiation of primary keratinocytes. We show that the ΔNp63 isoform is required for IKKα expression in differentiating keratinocytes and that mutant p63 proteins expressed in ectodermal dysplasia patients exhibit defects in inducing IKKα. Furthermore, we observed reduced IKKα expression in the epidermis of an ankyloblepharon ectodermal dysplasia clefting patient. Our data demonstrate that a failure to properly express IKKα may play a role in the development of ectodermal dysplasias.