Graduate Student University of British Columbia | Vancouver Campus Vancouver, British Columbia, Canada
Abstract Body : Myosin VI has been shown by others to localize in association with various regions of apical tubulobulbar complexes at sites of attachment between Sertoli cells and late spermatids in the mouse. Localization to tubulobulbar complexes at basal sites of attachment between adjacent Sertoli cells has not been studied. Tubulobulbar complexes (TBCs) are subcellular machines responsible for the internalization of ‘intact’ intercellular junctions during the removal of Sertoli cell attachments to spermatids during sperm release at the apex of the seminiferous epithelium and during the turnover of the blood-testis barrier formed between Sertoli cells at the base of the epithelium during the translocation of spermatocytes. Here, we use super-resolution (STED – Stimulated Emission Depletion) of immunolabeled sections of rat testis to clearly define the localization of Myosin VI both at apical and basal sites in the epithelium. In addition to immunolabeling Myosin VI, probes for actin were used to define tubular regions of TBCs and adjacent filaments in ectoplasmic specializations, and probes for oxysterol binding protein-related Protein 9 (ORP9) were used to label TBC ‘bulbs.’ Staining at TBCs was predominantly associated with bulb regions. At apical sites, when data stacks were analyzed with Imaris software, staining appeared around and extended between adjacent bulbs. At basal sites, in addition to labeling TBC bulbs, labeling appeared in regions close to but not directly associated with intercellular junctions. Our data indicates that the motor protein may be associated with specific subdomains of the endoplasmic reticulum at TBC bulbs and in selected other regions of the Sertoli cell.
