Spermatogenesis is a fundamental and complex biological process that ensures male fertility. Spermatogonia are the precursors of all germ cell stages. Their differentiation assures the lifelong production of mature sperm. However, virtually nothing is known about testicular cell communication during spermatogenesis. As we have previously shown that Sertoli cells communicate via ATP (Veitinger et al., 2011), we hypothesize a general role for testicular purinergic signaling.

Using wildtype C57BL/6 pups, we developed a coculture of Sertoli cells and spermatogonia and investigated ATP-dependent signaling in spermatogonia using the whole-cell patch-clamp technique.

Here, we report that cultured spermatogonia respond to extracellular ATP (10 - 100 mM). ATP-induced currents show fast activation and moderate desensitization in presence of ATP. The current-voltage relationship reveals strong inward rectification. These characteristics are typical for ionotropic receptors of the P2X receptor (P2XR) family. Interestingly, a high ATP concentration (1000 mM) activates an additional current with different kinetics, likely mediated by the low sensitivity P2X7R. Combined with molecular evidence, our results indicate that at least two different subunits of P2XRs (P2X7, P2X2 and/or P2X4) are functionally expressed in spermatogonia. Downstream P2XR activation, we recorded an additional slowly activating calcium-dependent potassium current that might represent a functional antagonist of the depolarizing P2XRs.

Together, these data represent a first important step towards a deeper understanding of cellular communication during spermatogenesis. On-going electrophysiological as well as immunohistochemical analysis will confirm the identity and function of different ion channels in mouse spermatogonia. Thus, our results will open new avenues toward the understanding of spermatogenesis.