Connexin43 in Germ Cells Seems to Be Dispensable for Murine Spermatogenesis.

Kristina Rode,Ralph Brehm,Marion Langeheine,Bettina Seeger

doi:10.3390/ijms22157924

Kristina Rode, Ralph Brehm + Show 2 more

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https://doi.org/10.3390/ijms22157924

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Abstract

Testicular Connexin43 (Cx43) connects adjacent Sertoli cells (SC) and SC to germ cells (GC) in the seminiferous epithelium and plays a crucial role in spermatogenesis. However, the distinction whether this results from impaired inter-SC communication or between GC and SC is not possible, so far. Thus, the question arises, whether a GC-specific Cx43 KO has similar effects on spermatogenesis as it is general or SC-specific KO. Using the Cre/loxP recombinase system, two conditional KO mouse lines lacking Cx43 in premeiotic (pGCCx43KO) or meiotic GC (mGCCx43KO) were generated. It was demonstrated by qRT-PCR that Cx43 mRNA was significantly decreased in adult pGCCx43KO mice, while it was also reduced in mGCCx43KO mice, yet not statistically significant. Body and testis weights, testicular histology, tubular diameter, numbers of intratubular cells and Cx43 protein synthesis and localization did not show any significant differences in semi-quantitative Western blot analysis and immunohistochemistry comparing adult male KO and WT mice of both mouse lines. Male KO mice were fertile. These results indicate that Cx43 in spermatogonia/spermatids does not seem to be essential for successful termination of spermatogenesis and fertility as it is known for Cx43 in somatic SC, but SC-GC communication might rather occur via heterotypic GJ channels.

Highlights

Spermatogenesis, as a highly regulated process of mitosis and meiosis, requires intensive regulation to synchronize processes of germ cell (GC) proliferation, migration and differentiation
We addressed this issue by creating GC specific KO of the predominant testicular gap junctions (GJ) protein
In pGCCx43KO mice, Cx43 was knocked out in premeiotic spermatogonia and early spermatocytes using stimulated by retinoic acid gene 8 (Stra8)-Cre mice, whereas in mGCCx43KO mice, Gja1 was deleted in meiotic spermatids to study the role of Cx43 based GJ intercellular communication (GJIC) in those cell types

Summary

Introduction

Spermatogenesis, as a highly regulated process of mitosis and meiosis, requires intensive regulation to synchronize processes of germ cell (GC) proliferation, migration and differentiation. Paracrine and autocrine regulation, intercellular communication via gap junctions (GJ) is essential for the completion of normal spermatogenesis [1,2]. GJs are intercellular plasma membrane channels allowing for direct electric and metabolic coupling of the connected cells. The constituting proteins of GJ channels are connexins (Cxs). Cxs are composed of four transmembrane domains, two extracellular loops, one cytoplasmic loop and the cytoplasmic N- and C-terminus. Forming a GJ channel between two cells, each participating cell contributes one hemichannel (=connexon) at opposing plasma membranes, which in turn consists of six Cx [3,4,5]. Besides classical GJ intercellular communication (GJIC), GJs are able to provide GJ mediated cell adhesion independent from their channel function, which is critical for cell migration [6,7,8]

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