Aberrant Cytoplasmic Accumulation of Connexin 43 in Human Testicular Seminoma

In the present study Cx43 mRNA and protein were analyzed in germ cells of men with normal spermatogenesis and in human testicular seminoma. In normal testis Cx43 mRNAs were basally located within seminiferous tubules and expressed in the most basally located germ cells (spermatogonia, early spermatocytes, and pachytene spermatocytes) and in Sertoli cells. Immunofluorescence analysis showed that Cx43 signal was mainly located in the basal compartment of seminiferous tubules and was stage-dependent. Cx43 mRNAs were also detected in human testicular seminoma. Transcripts were present within seminoma cells identified by PLAP staining. However, Cx43 protein exhibited an intracytoplasmic accumulation, within an intracellular compartment distinct from the Golgi apparatus and was undetectable at the plasma membrane level, suggesting post-translational rather than transcriptional abnormalities. This aberrant intracytoplasmic accumulation of Cx43 is due neither to a dysfunction of the protein trafficking machinery nor to a specific alteration of its major protein partner, ZO-1, since the tight junction associated protein was detected at the plasma membrane level and did not colocalize with Cx43.