Structural associations of synemin and vimentin filaments in avian erythrocytes revealed by immunoelectron microscopy.

Intermediate filament structure and distribution were studied by antibody decoration and low-angle shadowing of sonicated chicken erythrocytes and embryonic erythroid cells. Intermediate filaments containing vimentin and synemin form a three-dimensional network in these cells, interlinking the nucleus and plasma membrane. This filament network is spatially segregated from the marginal band of microtubules, indicating that these two systems do not interact directly in the development or maintenance of cell shape. Incubation of sonicated cells with an antiserum specific for vimentin results in uniform decoration of the intermediate filaments; incubation with antisynemin results in decoration of periodically spaced foci. Measurement of the synemin periodicity under a specified set of sample preparation conditions gives average values of 180 nm for adult erythrocytes and 230 nm for 10 day old embryonic erythroid cells, suggesting some fundamental change in the structure of the filaments during erythropoiesis. Registration of these foci in laterally associated filaments, and decoration of bridges between slightly separated filaments, suggest that synemin mediates crosslinking of intermediate filaments through self-interaction.