The area composita of adhering junctions connecting heart muscle cells of vertebrates. I. Molecular definition in intercalated disks of cardiomyocytes by immunoelectron microscopy of desmosomal proteins

Eur J Cell Biol. 2006 Feb;85(2):69-82. doi: 10.1016/j.ejcb.2005.11.003. Epub 2006 Jan 9.


Among sarcomeric muscles the cardiac muscle cells are unique by, inter alia, a systemic and extended cell-cell contact structure, the intercalated disk (ID), comprising frequent and closely spaced arrays of plaque-coated cell-cell adhering junctions (AJs). As some of these junctions may look somewhat like desmosomes and others like fasciae adhaerentes, the dogma has emerged in the literature that IDs contain - like epithelial cells - both kinds of AJs formed by - for the most - mutually exclusive molecular ensembles. This, however, is not the case. In comprehensive immunoelectron microscopic studies of mammalian (human, bovine, rat, mouse) and non-mammalian (chicken, amphibia, fishes) heart muscle tissues, we have localized major constituents of the desmosomal plaques of polar epithelia, desmoplakin, plakophilin-2 and plakoglobin, as well as the desmosomal cadherins, desmoglein Dsg2 and desmocollin Dsc2, in both kinds of ID AJs, independent of the specific morphological appearance. The desmosomal molecules are not restricted to the desmosome-like-looking junctions but can also be detected in junctions appearing similar to the zonula or fascia adhaerens structures. These AJs of cardiac ID are therefore subsumed under the collective term area composita. We discuss our results with respect to the importance of ID junction molecules for the formation, maintenance and function of the heart, particularly in relation to recent findings that deletions of - or mutations in - genes encoding such proteins can cause severe, sometimes lethal damages.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adherens Junctions / chemistry*
  • Adherens Junctions / physiology
  • Adherens Junctions / ultrastructure*
  • Amphibians
  • Animals
  • Cadherins / analysis
  • Cadherins / physiology
  • Cattle
  • Cell Adhesion Molecules / analysis*
  • Cell Adhesion Molecules / physiology
  • Cell Adhesion*
  • Chickens
  • Desmocollins
  • Desmoglein 2 / analysis
  • Desmoglein 2 / physiology
  • Desmoplakins / analysis
  • Desmoplakins / physiology
  • Desmosomes / chemistry*
  • Desmosomes / physiology
  • Fishes
  • Humans
  • Intercellular Junctions / chemistry*
  • Intercellular Junctions / physiology*
  • Membrane Glycoproteins / analysis
  • Membrane Glycoproteins / physiology
  • Mice
  • Microscopy, Immunoelectron
  • Myocytes, Cardiac / cytology
  • Myocytes, Cardiac / physiology
  • Myocytes, Cardiac / ultrastructure*
  • Plakophilins / analysis
  • Plakophilins / physiology
  • Rats
  • gamma Catenin / analysis
  • gamma Catenin / physiology


  • Cadherins
  • Cell Adhesion Molecules
  • DSC2 protein, human
  • Desmocollins
  • Desmoglein 2
  • Desmoplakins
  • Membrane Glycoproteins
  • Plakophilins
  • gamma Catenin