GJA8 and early-onset non-syndromic cataract: Although Cx50N220D is the only variant in the fourth transmembrane domain of Cx50 identified to date, mutations in the corresponding region of other connexins have been associated with diseases, including autosomal dominant congenital cataract (Cx46F206I) and autosomal dominant and recessive hearing loss (Cx26C202F and Cx26N206S, respectively).