Claudin‐7 Expressed on Lateral Membrane of Rat Epididymal Epithelium does not Form Aberrant Tight Junction Strands

Abstract

Claudins are integral membrane proteins at tight junctions (TJs) and form TJ strands. In the present study, we found that claudin-7 was localized along the entire lateral membranes of epididymal epithelium, including the apical junctional region throughout the epididymis, but claudin-8 was restricted to the apical junctional region. This finding raises the possibility that aberrant TJ strands may be formed on lateral membranes. Thus, we focused on examining whether TJ strands exist on lateral membranes of epididymal epithelium. Freeze-fracture electron microscopy showed that aberrant TJ strands were observed in only a few principal cells in all segments of the epididymis except for the initial segment, indicating that the occurrence of aberrant strands is very rare. Aberrant TJ strands were smooth and not subdivided into individual particles in the protoplasmic face, and complementary grooves in the extracellular face were almost free of particles. Aberrant TJ strands in the distal caput and corpus epididymis were accompanied by many vesicle-like structures but those in the proximal caput and cauda epididymis were not. These results suggest that most of claudin-7 in lateral membranes may exist in a nonpolymerized form and may play some different roles other than the formation of TJ strands, for example, in the formation of a pool of claudin proteins or in the reinforcement of cell adhesion.

Single continuous lumen formation in the zebrafish gut is mediated by smoothened-dependent tissue remodeling

“…2E). Although Claudin proteins are components of tight junctions and typically localize to the subapical region (Furuse et al, 1998), studies have shown that several members of this protein family also localize to lateral membranes during morphogenesis (Gregory et al, 2001;Inai et al, 2007;Westmoreland et al, 2012), including the closely related zebrafish claudin Cldn15lb (Cheung et al, 2012). To determine whether Cldn15la-GFP lateral membrane localization represented the endogenous protein localization we generated an antibody against the C-terminus of Cldn15la.…”

Biology of claudins

“…A striking example is claudin-7, which is predominantly basolateral in the connecting tubule and collecting duct (68), as it is in airway, intestinal, and epididymal epithelia (23,42,51). At least in the epididymis it is not polymerized into strands (51).…”

Alterations in the Human Blood-Epididymis Barrier in Obstructive Azoospermia and the Development of Novel Epididymal Cell Lines from Infertile Men1

“…It has previously been reported that the rat and human epididymis contain a large number of CLDNs [24][25][26][27][28]. The combination of CLDNs determines the selective permeability of the barrier [29].…”