Functional studies for a dominant mutation in the <scp>EDAR</scp> gene responsible for hypohidrotic ectodermal dysplasia

Hypohidrotic ectodermal dysplasia (HED) is a rare genetic disorder characterized by hypotrichosis, hypohidrosis and hypodontia. The disease shows X-linked recessive, autosomal dominant or autosomal recessive inheritance traits. The X-linked form of HED is caused by mutations in the EDA gene, while autosomal forms result from mutations in either EDAR or EDARADD genes. Regarding recessive mutations in the EDAR gene, the pathomechanisms have been well characterized. However, it has remained largely unknown how dominant mutations in the EDAR cause HED. In this study, we performed in vitro analyses for a dominant EDAR gene mutation, p.F398*, as a representative. We showed that the p.F398* mutant EDAR completely lost its affinity to EDARADD, and suppressed the downstream nuclear factor-κB activation induced by wild-type EDAR in a dominant-negative manner. Furthermore, we demonstrated that the mutant EDAR was capable of binding with the wild-type EDAR, which led to reduced interaction between the wild-type EDAR and EDARADD. Our findings not only underscore an essential role of the interaction between EDAR and EDARADD in ectodermal development, but also disclose, in part, the molecular basis of autosomal dominant HED.