Cadherin-Mediated Cell Adhesion within the Seminiferous Tubules

Abstract

Cadherins (Cadh) are key-molecules in Adherens junctions (AJs). They are multiprotein complexes mediating cell-cell adhesion, and particularly important to shape cell polarity, provide plasticity and maintain architectural integrity. Cadh, a large superfamily of cell surface glycoproteins, present a unique extracellular region domain folding like the immunoglobulin domains. They are found in a wide array of species and a multitude of tissues, including the testis. In the mammalian testis, the seminiferous tubules represent a unique type of epithelium-like tissue, composed of two different cellular populations: the Sertoli somatic cells and the spermatogenic cells. Different sorts of cell-to-cell attachments connect adjacent Sertoli cells and Sertoli to germ cells. The overall arrangement of junctions forms the blood-testis barrier. These connections offer an immune-privileged environment to the developing germ cells, and the nutritional and metabolic support to germ cells while offering particular plasticity to the tubular structure. They allow the migration of differentiated germ cells from the basal towards the adluminal compartment while providing a tight-fitting barrier for paracellular translocation of molecules and particles. Between adjacent Sertoli cells, various types of homotypic adherens junctions exists, while heterotypic junctions are present between Sertoli and spermatogonia (basolateral junctions) or spermatid heads (apical junctions). Intercellular N-cadherin connections, anchored in cytoplasmic plaques involving (but not limited to) actin filaments, form different morphological types of AJs. All sorts of AJs work together with tight and gap junctions to form the blood-testis barrier. The integrity of the different adherens junctions are critical for the spermatogenic process and the production of viable spermatozoa. In this chapter, we propose to review and discuss the structure of the cadherin-mediated junctions in the seminiferous tubules and their function in male fertility.