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(737) PROTOCADHERIN-SPECIFIC MEMBRANE ADHESION IN THE RAT SEMINIFEROUS EPITHELIUM. Johnson, Kamin 1, Abernethy, Diane 1, Beall, Stephanie 2, Wallace, Duncan 1, 1 CIIT Centers for Health Research, Research Triangle Park, NC2 Brown University Medical Center, Providence, RI ABSTRACT- Intra- and intercellular membrane adhesion is obligatory for spermatogenesis, examples being between Sertoli/germ cell plasma membranes and acrosome/nuclear membranes. The transmembrane proteins organizing these adhesive events largely are unknown, especially for intracellular membrane adhesion. Using protocadherin-specific antibodies and recombinant proteins, we show that celsr2 protocadherin functions in Sertoli/germ cell adhesion while gamma protocadherins localize to the acrosome marginal ring. In testis cryosections, celsr2-specific antibodies presented a spoke-like immunostaining pattern, indicating Sertoli cell localization. A recombinant protein consisting of celsr2 cadherin repeats 4 through 8 induced germ cell release from Sertoli cells in primary cocultures; however, a homologous recombinant protein from a related cadherin (celsr3) had no effect. Gamma protocadherin antibodies against a fragment conserved across different gamma protocadherins, immunostained the acrosome leading edge (marginal ring) in step 5 through 17 spermatids. In step 5 through approximately step 11 spermatids, a continuous gamma protocadherin-positive ring was observed at the acrosome leading edge. Thereafter, the anterior portion of the gamma-protocadherin-positive marginal ring appeared to meet at the ventral aspect of the spermatid head while the posterior marginal ring remained in a loop encircling the spermatid head. This pattern resembled a lasso. From this timepoint through step 17, gamma protocadherin was concentrated at the anterior ventral fin and posterior tip of the spermatid head in two discontinuous structures. In step 18 spermatids, gamma protocadherin immunostaining was negative. These data indicate that protocadherins show diverse, protocadherin-specific functions during spermatogenesis, with celsr2 involved in Sertoli-germ cell adhesion and gamma protocadherin implicated in acrosome-nuclear envelope adhesion during acrosome biogenesis. KEY WORDS: cadherin, germ, testis, Sertoli |
