Clathrin is present in regions containing tubulobulbar complexes in the testis

Abstract

Tubuobulbar complexes (TCs) are elongate 2–3μm membrane‐based and actin‐related structures that form at intercellular junctions in the seminiferous epithelium. They are proposed to be responsible for the internalization of “intact” junctions during spermatogenesis. Large swollen regions develop and bud from the end of each TC that is internalized by the related Sertoli cell. A “coated pit” caps the end of each TC and is suspected to induce TC formation. To determine if clathrin is associated with the coated pits, we immunolocalized fixed seminiferous epithelial fragments, of rat testis with an antibody raised against clathrin. Small foci of staining were evident in Sertoli cell regions associated with late spermatids, known to contain tubulobulbar complexes. The antibody reacted specifically with a band at the appropriate molecular weight for clathrin heavy chain on Western blots of rat testis and seminiferous epithelium that was not present on control replicate blots. We confirmed the staining by immunoelectron microscopy where gold particles in antibody treated sections were concentrated in small patches in regions containing tubulobulbar complexes. We conclude that clathrin is associated with TCs.