Adhesion and signaling proteins spatiotemporally associated with spermiation in the rat.

Spermiation, the process by which late spermatids separate from the Sertoli cell, is disrupted by a number of toxicants. In this study, we used immunohistochemistry (IHC) to identify some of the proteins associated with the spermatid-Sertoli junction. We confirmed the presence of tubulin, actin, and vinculin at the luminal edge of the seminiferous tubule, and we determined that paxillin is also present here. In other cell types, these proteins have been reported to colocalize with beta integrins. Numerous attempts to identify beta integrins by IHC and by use of Western blots were unsuccessful. Clear evidence was found for the presence of N-cadherin and its associated intracellular proteins: beta-catenin, pp120, desmoglein, pp60(src), and Csk. In addition, N-cadherin and desmoglein were found around spermatids retained by the epithelium. From these data and previous literature reports, we propose a hypothetical model for spermatid adhesion and the control of that adhesion, thus providing a framework for hypotheses on the steps involved in the complex process of spermiation in rat testes.