Expression of Multiple Gap Junction Proteins in Human Fetal and Infant Hearts

ABSTRACT: Mammalian cardiac myocytes express multiple gap junction channel proteins or connexins. Expression patterns of the avian homologues of the mammalian cardiac connexins change during cardiac morphogenesis in association with changes in the electrophysiologic properties of intercellular junctions in chick cardiac myocytes. To determine whether expression of cardiac connexins is developmentally regulated in humans, we characterized connexin mRNA and protein content and distribution in hearts of 11 human fetuses (74 to 122 d gestational age), seven children (0.5 mo to 3 y of age), and two adults. Northern blot analysis identified transcripts of connexin40 (Cx40), connexin43 (Cx43), and connexin45 (Cx45) genes in all hearts analyzed. Cx40 mRNA was approximately 5-fold more abundant in samples from fetal hearts than in hearts of children or adults. However, fetal samples used for RNA extraction included atrial as well as ventricular myocardium, whereas samples from children and adults were exclusively ventricular. Northern analysis of adult human right atrial appendages revealed abundant Cx40 mRNA, thus suggesting that the greater amount of Cx40 signal seen on Northern blots from fetal hearts could have been attributable to atrial contributions. Neither Cx43 nor Cx45 mRNA varied significantly in amount in samples from the different developmental stages analyzed. Immunofluorescence identified abundant Cx43 in the known distribution of gap junctions in myocytes in sections of all hearts. Cx45 staining was inconspicuous in fetal hearts but was readily apparent in cardiac myocytes in hearts of older subjects. In contrast, Cx40 staining in the ventricle was confined to mural coronary arteries, apparently in endothelial cells, whereas in the atrium Cx40 staining at myocyte junctions was abundant. Junctions in hypertrophied myocardium of children with congenital or acquired heart disease appeared more prominent and complex than in normal tissues. Thus, the human heart contains multiple connexins, but their distribution and developmental patterns differ from each other and from those in other species. Cx45 expression is not restricted to the fetal human heart. Cx40 expression in ventricles occurs selectively in coronary arteries.

[1]  J. Saffitz,et al.  Distinct gap junction protein phenotypes in cardiac tissues with disparate conduction properties. , 1994, Journal of the American College of Cardiology.

[2]  J. Saffitz,et al.  Molecular cloning of two human cardiac gap junction proteins, connexin40 and connexin45. , 1994, Journal of molecular and cellular cardiology.

[3]  A. Moorman,et al.  Restricted distribution of connexin40, a gap junctional protein, in mammalian heart. , 1994, Circulation research.

[4]  D. Ganten,et al.  Gap junction protein connexin40 is preferentially expressed in vascular endothelium and conductive bundles of rat myocardium and is increased under hypertensive conditions. , 1993, Circulation research.

[5]  W H Lamers,et al.  Immunohistochemical delineation of the conduction system. I: The sinoatrial node. , 1993, Circulation research.

[6]  W H Lamers,et al.  Immunohistochemical delineation of the conduction system. II: The atrioventricular node and Purkinje fibers. , 1993, Circulation research.

[7]  J. Saffitz,et al.  Multiple connexins colocalize in canine ventricular myocyte gap junctions. , 1993, Circulation research.

[8]  R. P. Thompson,et al.  The spatial distribution and relative abundance of gap-junctional connexin40 and connexin43 correlate to functional properties of components of the cardiac atrioventricular conduction system. , 1993, Journal of cell science.

[9]  J. Saffitz,et al.  Distinct patterns of connexin expression in canine Purkinje fibers and ventricular muscle. , 1993, Circulation research.

[10]  C. Green,et al.  Evidence for a distinct gap-junctional phenotype in ventricular conduction tissues of the developing and mature avian heart. , 1993, Circulation research.

[11]  R. Veenstra,et al.  Multiple connexins confer distinct regulatory and conductance properties of gap junctions in developing heart. , 1992, Circulation research.

[12]  M Delmar,et al.  Gap junctional channels in adult mammalian sinus nodal cells. Immunolocalization and electrophysiology. , 1992, Circulation research.

[13]  C. Lo,et al.  Connexin 43 expression in the mouse embryo: Localization of transcripts within developmentally significant domains , 1992, Developmental dynamics : an official publication of the American Association of Anatomists.

[14]  J. Saffitz,et al.  Cardiac myocytes express multiple gap junction proteins. , 1992, Circulation research.

[15]  W H Lamers,et al.  Spatial distribution of connexin43, the major cardiac gap junction protein, in the developing and adult rat heart. , 1991, Circulation research.

[16]  L. Leinwand,et al.  Expression of connexin43 in the developing rat heart. , 1991, Circulation research.

[17]  A. el Aoumari,et al.  Changes in the expression of connexin 43, a cardiac gap junctional protein, during mouse heart development. , 1990, Journal of molecular and cellular cardiology.

[18]  E. Beyer.  Molecular cloning and developmental expression of two chick embryo gap junction proteins. , 1990, The Journal of biological chemistry.

[19]  L. Leinwand,et al.  Molecular characterization and functional expression of the human cardiac gap junction channel , 1990, The Journal of cell biology.

[20]  D. Paul,et al.  Antisera directed against connexin43 peptides react with a 43-kD protein localized to gap junctions in myocardium and other tissues , 1989, The Journal of cell biology.

[21]  D. Paul,et al.  Connexin43: a protein from rat heart homologous to a gap junction protein from liver , 1987, The Journal of cell biology.

[22]  P. Chomczyński,et al.  Single-step method of RNA isolation by acid guanidinium thiocyanate-phenol-chloroform extraction. , 1987, Analytical biochemistry.

[23]  J. Haefliger,et al.  Connexin40, a component of gap junctions in vascular endothelium, is restricted in its ability to interact with other connexins. , 1993, Molecular biology of the cell.