title: A novel subcellular machine contributes to basal junction remodeling in the seminiferous epithelium.
abstract: Tubulobulbar complexes are cytoskeleton-related membrane structures that develop at sites of intercellular attachment in mammalian seminiferous epithelium. At apical junctions between Sertoli cells and spermatids, the structures internalize adhesion junctions and are a component of the sperm release mechanism. Here we explore the possibility that tubulobulbar complexes that form at the blood-testis barrier are subcellular machines that internalize basal junction complexes. Using electron microscopy, we confirmed that morphologically identifiable tight and gap junctions are present in basal tubulobulbar complexes in rats. In addition, immunological probes for claudin-11 (CLDN11), connexin-43 (GJA1), and nectin-2 (PVRL2) react with linear structures at the light level that we interpret as tubulobulbar complexes, and probes for early endosome antigen 1 (EEA1) and Rab5 (RAB5A) react in similar locations. Significantly, fluorescence patterns for actin and claudin-11 indicate that the amount of junction present is dramatically reduced over the time period that tubulobulbar complexes are known to be most prevalent during spermatogenesis. We also demonstrated, using electron microscopy and fluorescence microscopy, that tubulobulbar complexes develop at basal junctions in primary cultures of Sertoli cells and that like their in vivo counterparts, the structures contain junction proteins. We use this culture system together with transfection techniques to show that junction proteins from one transfected cell occur in structures that project into adjacent nontransfected cells as predicted by the junction internalization hypothesis. On the basis of our findings, we present a new model for basal junction remodeling as it relates to spermatocyte translocation in the seminiferous epithelium.
authors.affiliation: Department of Cellular and Physiological Sciences, Faculty of Medicine, Life Sciences Centre, The University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Min
authors.initials: M
authors.lastname: Du
authors.forename: J'Nelle
authors.initials: J
authors.lastname: Young
authors.forename: Marc
authors.initials: M
authors.lastname: De Asis
authors.forename: Jane
authors.initials: J
authors.lastname: Cipollone
authors.forename: Calvin
authors.initials: C
authors.lastname: Roskelley
authors.forename: Yoshimi
authors.initials: Y
authors.lastname: Takai
authors.forename: Peter K
authors.initials: PK
authors.lastname: Nicholls
authors.forename: Peter G
authors.initials: PG
authors.lastname: Stanton
authors.forename: Wanyin
authors.initials: W
authors.lastname: Deng
authors.forename: B Brett
authors.initials: BB
authors.lastname: Finlay
authors.forename: A Wayne
authors.initials: AW
authors.lastname: Vogl
mesh_terms: D000818:Animals; D015815:Cell Adhesion Molecules / Q000378:metabolism; D002478:Cells, Cultured; D057167:Claudins / Q000378:metabolism; D018031:Connexin 43 / Q000378:metabolism; D004705:Endocytosis; D007365:Intercellular Junctions / Q000502:physiology* / Q000648:ultrastructure; D008297:Male; D000075983:Nectins; D051381:Rats; D017207:Rats, Sprague-Dawley; D012670:Seminiferous Epithelium / Q000502:physiology*; D012708:Sertoli Cells / Q000502:physiology; D033921:Vesicular Transport Proteins / Q000378:metabolism; D020696:rab5 GTP-Binding Proteins / Q000378:metabolism
chemical_list: D015815:Cell Adhesion Molecules; D057167:Claudins; C492353:Cldn11 protein, rat; D018031:Connexin 43; C580592:Gja1 protein, rat; D000075983:Nectins; D033921:Vesicular Transport Proteins; C093846:early endosome antigen 1; D020696:rab5 GTP-Binding Proteins