Desmosome development in normal and reassociating cells in the early chick blastoderm

Desmosomes have been studied in the 1–2-day chick blastoderm in a strip just lateral to the embryonic axis in normal development and in reaggregating cells. A correlation was found between the time at which desmosomes appear and the degree of cohesion of developing epithelial sheets. Desmosomes in ectoderm, mesoderm, and endoderm are similar in structure. Development of fine structure appeared to be as follows: first, an electron-dense region in and between cell surfaces; second, condensation of desmosomal plaques; and third, development of an extensive fibrillar system. In reassociating cells, stages appearing to be parallel to those in normal development could be found. In addition, in newly dispersed cells intracellular desmosomal components appeared very frequently in channels or vacuoles within the cell, and after reassociation misaligned desmosomes occasionally occurred at adjacent cell surfaces where aligned desmosomes were also present.