MUTATIONS OF THE CONNEXIN43 GAP-JUNCTION GENE IN PATIENTS WITH HEART MALFORMATIONS AND DEFECTS OF LATERALITY

Background. Gap junctions are thought to have a crucial role in the sy nchronized contraction of the heart and in embryonic development. Conn exin43, the major protein of gap junctions in the heart, is targeted b y several protein kinases that regulate myocardial cell-cell coupling. We hypothesized that mutations altering sites critical to this regula tion would lead to functional or developmental abnormalities of the he art. Methods. Connexin43 DNA from 25 normal subjects and 30 children w ith a Variety of congenital heart diseases was amplified by the polyme rase chain reaction and sequenced. Mutant DNA was expressed in cell cu lture and examined for its effect on the regulation of cell-cell commu nication. Results. The 25 normal subjects and 23 of the 30 children wi th heart disease had no amino acid substitutions in connexin43. All si x children with syndromes that included complex heart malformations ha d substitutions of one or more phosphorylatable serine or threonine re sidues. Four of these children had two independent mutations, suggesti ng an autosomal recessive disorder. Five of these children had substit utions of proline for serine at position 364. A seventh child, with a different heart condition, also had a point mutation in connexin43. Tr ansfected cells expressing the Ser364Pro mutant connexin43 sequence sh owed abnormalities in the regulation of cell-cell communication, as co mpared with cells expressing normal connexin43. Conclusions. Mutations in the connexin43 gap-junction gene, which lead to abnormally regulat ed cell-cell communication, are associated with visceroatrial heterota xia.