Loss of connexin43 (Cx43) in Sertoli cells leads to spatio-temporal alterations in occludin expression

Within the testis, Sertoli cell (SC) junctional complexes between somatic SC create a basal and apical polarity within the seminiferous epithelium, restrict movement of molecules between cells, and separate the seminiferous epithelium into a basal and adluminal compartment. This barrier consists of membrane integrated proteins known as tight, adherens, and gap junctions, which promote cell-cell contact along the blood-testis-barrier (BTB). Nevertheless, these junctions, which form the basis of the BTB are structures whose function and dynamic regulation is still poorly understood. Thus, in this study, through the use of immunohistochemistry (IHC), semi quantitative western blot (WB) analysis, and real-time-quantitative-PCR (qRT-PCR) we focused on the expression pattern of the main testicular tight junction protein, occludin, in SC. For this, the established transgenic SC specific connexin 43 (Cx43) knockout (SCCx43KO) mouse line was used; both knockout (KO) and wildtype (WT) males of different ages from juvenile to adult were compared. The object was to elucidate a possible role of Cx43 on the expression pattern and regulation of occludin. This conditional KO mouse line lacks the gap junction gene Gja1 (coding for Cx43) only in SC and reveals impaired spermatogenesis. The qRT-PCR indicates an increase in occludin mRNA in adult KO mice. These results correspond to the occludin protein synthesis of adult mice. Additionally, during puberty, occludin localization at the BTB barrier in KO mice is delayed. Our study demonstrates spatiotemporal alterations in occludin mRNA-and protein-expression, indicating that Cx43 might act as a regulator for BTB formation (and function).