Cadherin-mediated cell-cell adhesion in the testis

During spermatogenesis, the differentiating germ cells migrate across the seminiferous epithelium while maintaining close contact with the surrounding Sertoli cells via specialized actin-based adherens junctions (ectoplasmic specializations) and intermediate filament-based anchoring junctions (desmosome-like junctions). Although this migration is essential for correct completion of spermatogenesis, the mechanisms that regulate these anchoring junctions are largely unknown, and most of our knowledge of cell-cell adhesion in testis is based on earlier studies in epithelial tissues. In most epithelia, members of the cadherin superfamily play key roles in intercellular adhesion. Cadherins are calcium-dependent cell-cell adhesion molecules mediating numerous homotypic cell-cell interactions. Until recently there has been controversy about the presence and localization of cadherins in the testis, but now there is increasing evidence that various types of cadherins are expressed in this organ, which underscores their importance in testicular functions. Here, we review the expression patterns, regulatory mechanisms and possible roles of the cadherin-mediated cell-cell adhesion in the testis, and particularly during spermatogenesis. Moreover, attention is paid to additional molecular adhesion complexes in the testis, to associated signaling pathways and to cell adhesion-related innovative ways for male contraception.