Modified desmosomes in cultured epithelial cells.

Junctional complexes are described in various cultured cells of epithelial origin and morphology which show structural features different from those of both typical maculae adhaerentes and fasciae adhaerentes. Established rat kangaroo kidney-derived cell lines (PtK1 and PtK2) and secondary cultures of cells derived from lactating bovine mammary gland epithelium (BMGE) have been studied in particular detail. Several types of modified desmosomes are described which are characterized by altered dimensions and spacings of the individual desmosomal units, variations in intercellular gap width, less distinct submembranous coats and midline structures (dense strata) of the intercellular space, and lack of attachment of typical tonofibril-like bundles of tonofilaments. The observations suggest that progressive changes in junction morphology from desmosome-like to that of a more intermediate junction frequently occur during in vitro culturing of epithelial cells.