Fate of connexin43 in Cardiac Tissue Harbouring a Disease-Linked connexin43 Mutant

Cardiovasc Res. 2008 Dec 1;80(3):385-95. doi: 10.1093/cvr/cvn203. Epub 2008 Aug 4.

Abstract

Aims: More than 40 mutations in the GJA1 gene encoding connexin43 (Cx43) have been linked to oculodentodigital dysplasia (ODDD), a pleiotropic, autosomal dominant disorder. We hypothesized that even with a significant reduction in the levels of Cx43 in a mutant mouse model of ODDD (Gja1(Jrt/+)) harbouring a G60S mutation (Cx43(G60S)), cardiomyocyte function may only be moderately compromised given that a majority of mutant mice typically survive.

Methods and results: Western blotting and quantitative reverse transcriptase-polymerase chain reaction in conjunction with immunofluorescence were used to assess the expression and localization of Cx43 in hearts and cultured cardiomyocytes from wild-type and Gja1(Jrt/+) mice. Dye-coupling and dual whole cell patch-clamp recordings were also used to assess the gap junction channel status in cultured cardiomyocytes from wild-type and mutant mice. Cardiac tissue from adult Gja1(Jrt/+) mice revealed a 60-80% reduction in Cx43 protein with a preferential loss of the highly phosphorylated forms of Cx43. Compensation via the up-regulation of Cx40 or Cx45 was not observed. Immunofluorescent analysis of cultured cardiomyocytes revealed a trafficking defect, with a decrease in Cx43 plaques and a large population of Cx43 being retained in the Golgi apparatus. However, cultured cardiomyocytes from mutant mice remained beating with a 50% decrease in coupling conductance.

Conclusion: These results suggest that the Cx43(G60S) mutant impairs normal trafficking and function of co-expressed Cx43 with no dramatic effect on cardiomyocyte function, suggesting that Cx43 is biosynthesized in excess of an essential need.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Communication / genetics
  • Cell Communication / physiology
  • Cells, Cultured
  • Congenital Abnormalities / genetics*
  • Congenital Abnormalities / metabolism*
  • Congenital Abnormalities / pathology
  • Connexin 43 / genetics*
  • Connexin 43 / metabolism*
  • Connexins / metabolism
  • Disease Models, Animal
  • Female
  • Gap Junctions / metabolism
  • Golgi Apparatus / metabolism
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mice, Mutant Strains
  • Mutation / genetics*
  • Myocardial Contraction / genetics
  • Myocardial Contraction / physiology
  • Myocardium / metabolism
  • Myocardium / pathology
  • Myocytes, Cardiac / metabolism*
  • Myocytes, Cardiac / pathology
  • Patch-Clamp Techniques

Substances

  • Connexin 43
  • Connexins
  • connexin 40
  • connexin 45