The impact of Connexin 43 deficiency on the cell shape and cytoskeleton of murine Sertoli cells: A house with ramshackle walls?

Genetically induced loss of the gap-junction protein Connexin 43 (Cx43) in murine Sertoli cells leads to an arrest of spermatogenesis at the level of spermatogonia, highly vacuolated tubules, and intratubular cell clusters. Transmission electron microscopy as well as 3D-reconstruction of Sertoli cells based on serial block-face scanning electron microscopy imaging revealed severe cell shape changes in Cx43 deficient Sertoli cells. Since the cytoskeleton is important for the transport of germ cells within the seminiferous epithelium and for keeping the cell shape, the study at hand aimed to reveal correlations of Cx43 loss and changes of cytoskeletal components and their spatial organization in the seminiferous epithelium. Immunohistochemistry, immunofluorescence, conventional transmission electron microcopy and immunogold labeling indicated alterations in microtubule and actin filament distribution patterns in Cx43 deficient Sertoli cells compared to wildtype mice. Firstly, microtubules seemed to be misoriented in mutant Sertoli cells. Secondly, the actin filament based basal ectoplasmic specializations were increased in spatial extension, but the apical ectoplasmic specialization was missing. Lastly, Sertoli cells of both genotypes immunostained positive for vimentin, the prevalent intermediate filament of Sertoli cells, but not for keratins, markers for Sertoli cell immaturity or dedifferentiation. In conclusion, Cx43 deficiency in Sertoli cells correlates not only with severe cell shape alterations but also with changes in microtubule and actin filament distribution patterns, while intermediate filament expression seems to be only negligibly influenced.