title: Connexin43 ablation in foetal atrial myocytes decreases electrical coupling, partner connexins, and sodium current.
abstract: OBJECTIVE
  Remodelling and regional gradients in expression of connexins (Cx) are thought to contribute to atrial electrical dysfunction and atrial fibrillation. We assessed the effect of interaction between Cx43, Cx40, and Cx45 on atrial cell-to-cell coupling and inward Na current (I(Na)) in engineered pairs of atrial myocytes derived from wild-type mice (Cx43(+/+)) and mice with genetic ablation of Cx43 (Cx43(-/-)).
  
  
  RESULTS
  Cell pairs were engineered by microcontact printing from atrial Cx43(+/+) and Cx43(-/-) murine myocytes (1 day before birth, 3-5 days in culture). Dual and single voltage clamp were used to measure intercellular electrical conductance, g(j), and its dependence on transjunctional voltage, V(j), single gap junction channel conductances, and I(Na). 3D reconstructions of Cx43, Cx40, and Cx45 immunosignals in gap junctions were made from confocal slices. Full genetic Cx43 ablation produced a decrease in immunosignals of Cx40 to 62 ± 10% (mean ± SE; n= 17) and Cx45 to 66 ± 8% (n= 16). G(j) decreased from 80 ± 9 nS (Cx43(+/+), n= 17) to 24 ± 2 nS (Cx43(-/-), n= 35). Single channel analysis showed a shift in the main peak of the channel histogram from 49 ± 1.7 nS (Cx43(+/+)) to 67 ± 1.8 nS (Cx43(-/-)) with a second minor peak appearing at 27 ± 1.5 pS. The dependence of g(j) on V(j) decreased with Cx43 ablation. Importantly, peak I(Na) decreased from -350 ± 44 pA/pF (Cx43(+/+)) to -154 ± 28 pA/pF (Cx43(-/-)).
  
  
  CONCLUSIONS
  The dependence of Cx40, Cx45, and I(Na) on Cx43 expression indicates a complex interaction between connexins and I(Na) in the atrial intercalated discs that is likely to be of relevance for arrhythmogenesis.
authors.affiliation: Department of Physiology,  University of Bern, Bern,  Switzerland.
authors.forename: Thomas
authors.initials: T
authors.lastname: Desplantez
authors.forename: Megan L
authors.initials: ML
authors.lastname: McCain
authors.forename: Philippe
authors.initials: P
authors.lastname: Beauchamp
authors.forename: Ghislaine
authors.initials: G
authors.lastname: Rigoli
authors.forename: Barbara
authors.initials: B
authors.lastname: Rothen-Rutishauser
authors.forename: Kevin Kit
authors.initials: KK
authors.lastname: Parker
authors.forename: Andre G
authors.initials: AG
authors.lastname: Kleber
mesh_terms: D000818:Animals; D001145:Arrhythmias, Cardiac / Q000378:metabolism; D002450:Cell Communication; D002478:Cells, Cultured; D018031:Connexin 43 / Q000172:deficiency* / Q000235:genetics; D017630:Connexins / Q000378:metabolism; D004553:Electric Conductivity; D005318:Fetal Heart / Q000166:cytology / Q000378:metabolism*; D017629:Gap Junctions / Q000378:metabolism; D006325:Heart Atria / Q000196:embryology / Q000378:metabolism; D007150:Immunohistochemistry; D015640:Ion Channel Gating; D008564:Membrane Potentials; D051379:Mice; D018345:Mice, Knockout; D018613:Microscopy, Confocal; D032383:Myocytes, Cardiac / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D012964:Sodium / Q000378:metabolism*; D015222:Sodium Channels / Q000378:metabolism*; D000097003:Gap Junction alpha-5 Protein
chemical_list: D018031:Connexin 43; D017630:Connexins; D012964:Sodium; D015222:Sodium Channels; D000097003:Gap Junction alpha-5 Protein; C543076:GJA1 protein, mouse; C082920:connexin 45