Dynamic of VE-cadherin-mediated spermatid-Sertoli cell contacts in the mouse seminiferous epithelium

Spermatids are haploid differentiating cells that, in the meantime they differentiate, translocate along the seminiferous epithelium towards the tubule lumen to be just released as spermatozoa. The success of such a migration depends on dynamic of spermatid-Sertoli cell contacts, the molecular nature of which has not been well defined yet. It was demonstrated that the vascular endothelial cadherin (VEC) is expressed transitorily in the mouse seminiferous epithelium. Here, we evaluated the pattern of VEC expression by immunohistochemistry first in seminiferous tubules at different stages of the epithelial cycle when only unique types of germ cell associations are present. Changes in the pattern of VEC localization according to the step of spermatid differentiation were analysed in detail using testis fragments and spontaneously released germ cells. Utilizing the first wave of spermatogenesis as an in vivo model to have at disposal spermatids at progressive steps of differentiation, we checked for level of looser VEC association with the membrane by performing protein solubilisation under mild detergent conditions and assays through VEC-immunoblotting. Being changes in VEC solubilisation paralleled in changes in phosphotyrosine (pY) content, we evaluated if spermatid VEC undergoes Y658 phosphorylation and if this correlates with VEC solubilisation and spermatid progression in differentiation. Altogether, our study shows a temporally restricted pattern of VEC expression that culminates with the presence of round spermatids to progressively decrease starting from spermatid elongation. Conversely, pY658-VEC signs elongating spermatids; its intracellular polarized compartmentalization suggests a possible involvement of pY658-VEC in the acquisition of spermatid cell polarity.