Immunocytochemical study of gap junction formation

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Gap junction formation involves coordinated interaction between two cells and has implications in cell-cell recognition and specific cell adnesion. Thus, there might be some interactions of cell adhesion molecules for the formation of the gap junctions. In this project we have examined the dynamics of connexins and most widespread and abundant cell adhesion molecules, cadnerins, in the developing mouse hepatocytes. In adult liver, almost all cells showed a positive immunoreaction of connexin32, and the immunostaining consisted of numerous thread-like regions along the lateral aspect of the cell borders. At birth, however, the staining was present in only a few hepatocytes. Neonatal (2-or 3-day-old) liver showed the intense immnunoreaction positive spots over the cytoplasmic compartments of the hepatocytes. At 10 days after birth the immunoreaction was approximately equal to that of the adults. Immunoelectron microscopy of connexin32 revealed that the immunogold particles bound directly to the adherens junction and the vesicles beneath the plasma membrane as well as the gap junction in neonatal hepatocytes. Double immnogold staining using anti-connexin32 and anti-E-cadherin antibodies revealed that E-cadherin is present in the same adherens junctions as connexin32 in the neonatal hepatocytes. These findings imply that cadherins may mediate an early adhesion event between cells that is a prerequisite for the assembly of connexins into gap junction plaques.