CADHERINS AND CADHERIN-ASSOCIATED MOLECULES IN THE DEVELOPING AND MATURING RAT TESTIS

The calcium-dependent class of cell adhesion molecules known as cadher ins mediate homotypic cell interactions in most epithelia. We have now investigated the expression and distribution of cadherins and cadheri n-associated molecules in the developing and maturing rat testis. E-Ca dherin was not detected in the seminiferous tubule at any time in deve lopment or in the adult. In contrast, Leydig cells expressed E-cadheri n between day 15 of gestation and postnatal day 3. alpha- and beta-cat enins were expressed throughout the developing testis, but were partic ularly prominent in Leydig cells. In the maturing testis, alpha-cateni n and plakoglobin became progressively more restricted to the basal pa rt of the seminiferous epithelium and by 23 days exhibited a pattern c haracteristic of the Sertoli cell junctional complex. beta-Catenin rec ruit ment to the Sertoli cell junctional complex was not complete unti l 60 days. alpha-Catenin and plakoglobin were not present at sites of Sertolicell-germ cell contacts. Northern blot analysis of testicular R NA showed three mRNA species hybridizing with N-cadherin cDNA. A pan-c adherin antibody specific for a region of the highly conserved C-termi nal of all cadherins stained sites of Sertoli-spermatocyte and Sertoli -round spermatid contact in the adult rat seminiferous epithelium, but did not stain the Sertoli cell tight junctional complex. Western blot s of testicular extracts indicated that the molecule(s) recognized by these antibodies had an approximate molecular mass of 120 kilodalton, typical of members of the cadherin family. Therefore, although Sertoli cells do not express E-cadherin, another member(s) of the cadherin fa mily is present in the testis, but may not be directly involved in tig ht junction dynamics as in other cells. Instead, cadherin-mediated adh esion is likely to be involved in Sertoli cell-germ cell interactions. As catenins are not present at these sites, our results suggest a cat enin-independent role of cadherins in germ cell adhesion to Sertoli ce lls.