| Abstract: | Occludin is theonly integral membrane protein identified to date as a component oftight junctions (TJs). Here, we examined the distribution andexpression of occludin in murine testis bearing well-developed TJ. Inthe adult mouse testis, occludin was concentrated at TJ strands, whichare located at the most basal regions of lateral membranes of Sertolicells. In immunoblotting, occludin showed a characteristic multiplebanding pattern, suggesting that occludin is highly phosphorylated inthe testis. In 1-wk-old mouse testis, occludin was distributeddiffusely at the lateral membranes of Sertoli cells, and even at thisstage, highly phosphorylated occludin was detected. With development,occludin gradually became concentrated at the most basal regions ofSertoli cells. The same results were obtained in rat, but unexpectedlyoccludin was not detected in human or guinea pig Sertoli cells byimmunofluorescence microscopy as well as by immunoblotting. Inasmuch asTJs are also well developed in Sertoli cells of these species, weconcluded that, at least in the testes of these species, there are some Sertoli cell-specific isoforms of occludin or other TJ-associated integral membrane proteins that differ from occludin. |
