Katherine Hixon, Lindsey Rhea, Jennifer Standley, Frank J. Canady, John W. Canady, Martine Dunnwald

Interferon Regulatory Factor 6 (IRF6) is critical for craniofacial development, epidermal differentiation, and tissue repair. IRF6 mutations cause Van der Woude Syndrome (VWS) and Popliteal Pterygium Syndrome. Individuals with VWS exhibit craniofacial anomalies, including cleft lip and palate and lip pits. Furthermore, they have an increased risk for wound-healing complications following surgical repair when compared with patients with nonsyndromic cleft lip and palate (NSCLP). However, nothing is known about the skin of these patients. The objective was to characterize the skin of patients with VWS. We hypothesize that IRF6 is required for proper skin homeostasis in humans. Discarded tissue from a hip was collected during surgical alveolar bone graft. Samples from children with VWS harboring IRF6 mutations (n = 2) were compared with samples from children with NSCLP (n = 7). Histology was assessed following hematoxylin and eosin staining. The expressions of Proliferating Cell Nuclear Antigen, IRF6, P63, and Keratin 10 were determined by immunofluorescence. Keratinocytes were isolated and their proliferation potential was assessed by colony-forming efficiency assay. Hip skin from children with VWS showed a thicker epidermis when compared with that from children with NSCLP. Proliferating Cell Nuclear Antigen staining revealed an increase in proliferation in syndromic tissues when compared with controls. However, P63 and Keratin 10 expression were similar between groups. Finally, keratinocytes from VWS showed increased long-term proliferation when compared with NSCLP. These results support, in vivo and in vitro, a previously described role for IRF6 in epidermal proliferation in humans. They further demonstrate a critical function for IRF6 in cutaneous homeostasis.