Advertisement
Heart, Lung and Circulation

Human Connexin40 Mutations Slow Conduction and Increase Propensity for Atrial Fibrillation

Published:March 21, 2017DOI:https://doi.org/10.1016/j.hlc.2017.02.010

      Background

      Patch clamping studies using non-cardiomyocytes revealed that the human connexin40 mutations P88S, G38D, and A96S are associated with reduced gap junction conductances compared to wild type connexin40 (wtCx40). Their effects within myocytes however are unclear. We aimed to characterise P88S, G38D, and A96S after expression in rat hearts and primary cardiomyocyte cultures.

      Methods

      Adult Sprague-Dawley rat atria were transduced with a lentivector containing a transgene encoding wtCx40, P88S, G38D, A96S, or eGFP (n = 6 per transgene). Electrophysiology studies (EPS) were performed just prior to and 7 days after surgery. Left atria were assessed for connexin expression, mRNA levels, inflammation and fibrosis. Primary cardiomyocyte cultures were also transduced with the abovementioned vectors (n = 6 per transgene) and monolayer conduction velocities (CV) and protein expression were assessed at 96 hours.

      Results

      At day 7 EPS, P wave and induced atrial fibrillation (AF) durations were significantly longer in the mutant groups when compared to wtCx40 controls (p < 0.05). There were no significant differences in inflammation, fibrosis, or heart to body weight ratios. Monolayer CV’s were reduced in the A96S group compared to the wtCx40 group. While similar to wtCx40 controls, P88S velocities were reduced compared to eGFP controls. G38D monolayers possessed spontaneous fibrillatory activity and could not be paced. Immunofluorescence revealed that P88S and G38D reduced native connexin43 myocyte coupling while A96S appeared to co-localise with connexin43 in gap junctions. Connexin43 mRNA levels were similar between groups.

      Conclusions

      The A96S, G38D, and P88S Cx40 mutations slow conduction and increased the propensity for inducible AF.

      Keywords

      To read this article in full you will need to make a payment

      Purchase one-time access:

      Academic & Personal: 24 hour online accessCorporate R&D Professionals: 24 hour online access
      One-time access price info
      • For academic or personal research use, select 'Academic and Personal'
      • For corporate R&D use, select 'Corporate R&D Professionals'

      Subscribe:

      Subscribe to Heart, Lung and Circulation
      Already a print subscriber? Claim online access
      Already an online subscriber? Sign in
      Institutional Access: Sign in to ScienceDirect

      References

        • Go A.S.
        • Hylek E.M.
        • Phillips K.A.
        • Chang Y.
        • Henault L.E.
        • Selby J.V.
        • et al.
        Prevalence of diagnosed atrial fibrillation in adults: national implications for rhythm management and stroke prevention: the AnTicoagulation and Risk Factors in Atrial Fibrillation (ATRIA) Study.
        JAMA. 2001; 285: 2370-2375
        • Feinberg W.M.
        • Blackshear J.L.
        • Laupacis A.
        • Kronmal R.
        • Hart R.G.
        Prevalence, age distribution, and gender of patients with atrial fibrillation. Analysis and implications.
        Arch Intern Med. 1995; 155: 469-473
        • Australian Bureau Of Statistics
        Population by age and sex, regions of Australia, 2011, cat. no. 3235.0.
        ABS, Canberra2011
        • Australian Bureau Of Statistics
        Australian Social Trends, March 2009, cat. no. 4102.0.
        ABS, Canberra2009
        • Kanagaratnam P.
        • Cherian A.
        • Stanbridge R.D.
        • Glenville B.
        • Severs N.J.
        • Peters N.S.
        • et al.
        Relationship between connexins and atrial activation during human atrial fibrillation.
        Journal of Cardiovascular Electrophysiology. 2004; 15: 206-216
        • Gollob M.H.
        • Jones D.L.
        • Krahn A.D.
        • Danis L.
        • Gong X.Q.
        • Shao Q.
        • et al.
        Somatic mutations in the connexin 40 gene (GJA5) in atrial fibrillation.
        N Engl J Med. 2006; 354: 2677-2688
        • Yang Y.Q.
        • Liu X.
        • Zhang X.L.
        • Wang X.H.
        • Tan H.W.
        • Shi H.F.
        • et al.
        Novel connexin40 missense mutations in patients with familial atrial fibrillation.
        Europace. 2010; 12: 1421-1427
        • Yang Y.Q.
        • Zhang X.L.
        • Wang X.H.
        • Tan H.W.
        • Shi H.F.
        • Jiang W.F.
        • et al.
        Connexin40 nonsense mutation in familial atrial fibrillation.
        Int J Mol Med. 2010; 26: 605-610
        • Sun Y.
        • Yang Y.Q.
        • Gong X.Q.
        • Wang X.H.
        • Li R.G.
        • Tan H.W.
        • et al.
        Novel germline GJA5/connexin40 mutations associated with lone atrial fibrillation impair gap junctional intercellular communication.
        Hum Mutat. 2013; 34: 603-609
        • Sun Y.
        • Tong X.
        • Chen H.
        • Huang T.
        • Shao Q.
        • Huang W.
        • et al.
        An atrial-fibrillation-linked connexin40 mutant is retained in the endoplasmic reticulum and impairs the function of atrial gap-junction channels.
        Dis Model Mech. 2014; 7: 561-569
        • Lubkemeier I.
        • Andrie R.
        • Lickfett L.
        • Bosen F.
        • Stockigt F.
        • Dobrowolski R.
        • et al.
        The Connexin40A96S mutation from a patient with atrial fibrillation causes decreased atrial conduction velocities and sustained episodes of induced atrial fibrillation in mice.
        J Mol Cell Cardiol. 2013; 65: 19-32
        • Patel D.
        • Gemel J.
        • Xu Q.
        • Simon A.R.
        • Lin X.
        • Matiukas A.
        • et al.
        Atrial fibrillation-associated connexin40 mutants make hemichannels and synergistically form gap junction channels with novel properties.
        FEBS Lett. 2014; 588: 1458-1464
        • Gemel J.
        • Simon A.R.
        • Patel D.
        • Xu Q.
        • Matiukas A.
        • Veenstra R.D.
        • et al.
        Degradation of a connexin40 mutant linked to atrial fibrillation is accelerated.
        J Mol Cell Cardiol. 2014; 74: 330-339
        • Igarashi T.
        • Finet J.E.
        • Takeuchi A.
        • Fujino Y.
        • Strom M.
        • Greener I.D.
        • et al.
        Connexin gene transfer preserves conduction velocity and prevents atrial fibrillation.
        Circulation. 2012; 125: 216-225
        • Valiunas V.
        • Weingart R.
        • Brink P.R.
        Formation of heterotypic gap junction channels by connexins 40 and 43.
        Circ Res. 2000; 86: E42-E49
        • Ackerman M.J.
        • Priori S.G.
        • Willems S.
        • Berul C.
        • Brugada R.
        • Calkins H.
        • et al.
        HRS/EHRA expert consensus statement on the state of genetic testing for the channelopathies and cardiomyopathies this document was developed as a partnership between the Heart Rhythm Society (HRS) and the European Heart Rhythm Association (EHRA).
        Heart Rhythm. 2011; 8: 1308-1339
        • Gu H.
        • Smith F.C.
        • Taffet S.M.
        • Delmar M.
        High incidence of cardiac malformations in connexin40-deficient mice.
        Circ Res. 2003; 93: 201-206
        • Kirchhoff S.
        • Kim J.S.
        • Hagendorff A.
        • Thonnissen E.
        • Kruger O.
        • Lamers W.H.
        • et al.
        Abnormal cardiac conduction and morphogenesis in connexin40 and connexin43 double-deficient mice.
        Circ Res. 2000; 87: 399-405
        • Napolitano C.
        • Bloise R.
        • Monteforte N.
        • Priori S.G.
        Sudden cardiac death and genetic ion channelopathies: long QT, Brugada, short QT, catecholaminergic polymorphic ventricular tachycardia, and idiopathic ventricular fibrillation.
        Circulation. 2012; 125: 2027-2034
        • Barth A.S.
        • Kizana E.
        • Smith R.R.
        • Terrovitis J.
        • Dong P.
        • Leppo M.K.
        • et al.
        Lentiviral vectors bearing the cardiac promoter of the Na+-Ca2+ exchanger report cardiogenic differentiation in stem cells.
        Mol Ther. 2008; 16: 957-964
        • Nag A.C.
        Study of non-muscle cells of the adult mammalian heart: a fine structural analysis and distribution.
        Cytobios. 1980; 28: 41-61
        • Ongstad E.L.
        • Gourdie R.G.
        Myocyte-fibroblast electrical coupling: the basis of a stable relationship?.
        Cardiovasc Res. 2012; 93: 215-217
        • Gaudesius G.
        • Miragoli M.
        • Thomas S.P.
        • Rohr S.
        Coupling of cardiac electrical activity over extended distances by fibroblasts of cardiac origin.
        Circ Res. 2003; 93: 421-428
        • Cohen S.A.
        Immunocytochemical localization of rH1 sodium channel in adult rat heart atria and ventricle. Presence in terminal intercalated disks.
        Circulation. 1996; 94: 3083-3086
        • Mays D.J.
        • Foose J.M.
        • Philipson L.H.
        • Tamkun M.M.
        Localization of the Kv1.5 K+ channel protein in explanted cardiac tissue.
        J Clin Invest. 1995; 96: 282-292
        • Johnson C.M.
        • Green K.G.
        • Kanter E.M.
        • Bou-Abboud E.
        • Saffitz J.E.
        • Yamada K.A.
        Voltage-gated Na+ channel activity and connexin expression in Cx43-deficient cardiac myocytes.
        J Cardiovasc Electrophysiol. 1999; 10: 1390-1401
        • Wang L.
        • Feng Z.P.
        • Kondo C.S.
        • Sheldon R.S.
        • Duff H.J.
        Developmental changes in the delayed rectifier K+ channels in mouse heart.
        Circ Res. 1996; 79: 79-85