Analysis of the Hemichannel properties of Cx26 mutants causing Keratitis-Ichthyosis-Deafness Syndrome

Abstract

Keratitis-Ichthyosis-Deafness (KID) Syndrome has been linked with various mutations of the Cx26 encoding GJB2 (Gap Junction beta2) gene. Each mutation was associated with symptoms and severity of varying degree in both adult and neonatal patients. Here, the hemichannel activity of two recently discovered mutations of GJB2 - the A88V and D50A mutants found in patients of KID syndrome were examined using Xenopus oocytes. The data recordings show that while the oocytes were able to express both the wild type and mutant Cx26 genes, the hemichannel activity of the mutants was much greater. This increase in hemichannel activity led to the lysis of the oocytes within 24 hours of protein expression. The presence of increased levels of extracellular calcium led to better survival of the A88V and D50A injected oocytes delaying cell death. Although the exact molecular mechanism of disease progression is not known, the analysis suggests that mutant hemichannels may play a role in the patho-physiology of skin abnormalities characteristic of KID syndrome.