The long-term objective of this proposal is to understand the biology and regulation of blood-testis barrier (BTB) dynamics during spermatogenesis using the adult rat testis as a study model. Specifically, it seeks to unravel the mechanism(s) that maintains BTB integrity as preleptotene and leptotene spermatocytes traverse the BTB that occurs at stage VIII of the seminiferous epithelial cycle of spermatogenesis. This study is important since it answers an open question in the field regarding the biochemical and/or molecular mechanism(s) utilized by the testis that regulates the timely 'restructuring'of the BTB to permit spermatocyte transit while maintaining the immunological barrier function at the BTB. This information is also helpful to develop innovative approaches to design new drugs (e.g., male contraceptives that exert their effects by disrupting germ cell function in the seminiferous epithelium) that can be targeted to the seminiferous epithelium behind the BTB. Recent studies have shown that cytokines (e.g., tumor necrosis factor ?, TNF?, and transforming growth factor-?2/-3, TGF-?2 or -?3) have a disruptive effect on BTB integrity, whereas testosterone promotes BTB function, illustrating that the opposing effects of these molecules are crucial to maintain the timely "opening" and "closing" of the BTB during spermatogenesis while facilitating germ cell movement across the barrier. Since both TNF? and TGF-?3 are products of Sertoli and germ cells, and testosterone is a product of Leydig cells (but the androgen receptor resides mostly on the Sertoli cell), in the testis, it is likely that these molecules are released into the BTB microenvironment during spermatogenesis to regulate BTB dynamics. In this application, the P.I. will examine the hypothesis that TNF? regulates BTB dynamics via its effects on basement membrane proteins, such as collagens, proteases and protease inhibitors, which, in turn, regulates the steady-state levels of integral membrane proteins at the BTB. This will determine the status of the BTB to facilitate or prohibit the transit of preleptotene/leptotene spermatocytes across the barrier (Specific Aim 1). Furthermore, the P.I. will test the hypothesis that cytokines and testosterone mediate their opposing effects on the BTB via their differential actions on endocytosis, recycling, endosome-mediated intracellular degradation and transcytosis/relocation of integral membrane proteins at the BTB (Specific Aim 2). The proposed studies will be performed using cutting-edge techniques of biochemistry, molecular biology, and cell biology. The P.I. will also develop and characterize a novel in vitro model using Sertoli-germ cell cocultures to investigate the regulation of germ cell movement across the BTB, which can become a valuable research tool for investigators in the field. In short, this proposal addresses a long-standing mystery in spermatogenesis regarding the biology and regulation of the BTB during the epithelial cycle.
This project seeks to understand the mechanism(s) that regulates blood-testis barrier (BTB) dynamics during the seminiferous epithelial cycle of spermatogenesis using the adult rat testis as a study model. The BTB must `open'or `restructure'transiently during spermatogenesis to facilitate the transit of spermatocytes across the barrier. This, in turn, poses a unique opportunity to transport a drug, such as a male contraceptive that disrupts cell adhesion, behind the BTB to exert its effects, if the mechanism(s) that regulates the timely opening of the BTB is known. In short, this proposal seeks to understand the biology of BTB dynamics during spermatogenesis. It also offers new insight into: (i) developing novel approaches for male contraception, and (ii) the causes of unexplained male infertility.
|Xiao, Xiang; Mruk, Dolores D; Tang, Elizabeth I et al. (2014) N-wasp is required for structural integrity of the blood-testis barrier. PLoS Genet 10:e1004447|
|Qian, Xiaojing; Mruk, Dolores D; Cheng, Yan-Ho et al. (2014) Actin binding proteins, spermatid transport and spermiation. Semin Cell Dev Biol 30:75-85|
|Wan, H T; Mruk, Dolores D; Tang, Elizabeth I et al. (2014) Role of non-receptor protein tyrosine kinases in spermatid transport during spermatogenesis. Semin Cell Dev Biol 30:65-74|
|Gungor-Ordueri, N Ece; Tang, Elizabeth I; Celik-Ozenci, Ciler et al. (2014) Ezrin is an actin binding protein that regulates sertoli cell and spermatid adhesion during spermatogenesis. Endocrinology 155:3981-95|
|Xiao, Xiang; Mruk, Dolores D; Wong, Elissa W P et al. (2014) Differential effects of c-Src and c-Yes on the endocytic vesicle-mediated trafficking events at the Sertoli cell blood-testis barrier: an in vitro study. Am J Physiol Endocrinol Metab 307:E553-62|
|Gungor-Ordueri, N Ece; Celik-Ozenci, Ciler; Cheng, C Yan (2014) Fascin 1 is an actin filament-bundling protein that regulates ectoplasmic specialization dynamics in the rat testis. Am J Physiol Endocrinol Metab 307:E738-53|
|Xiao, Xiang; Wong, Elissa W P; Lie, Pearl P Y et al. (2014) Cytokines, polarity proteins, and endosomal protein trafficking and signaling-the sertoli cell blood-testis barrier system in vitro as a study model. Methods Enzymol 534:181-94|
|Wan, Hin-Ting; Mruk, Dolores D; Wong, Chris K C et al. (2014) Perfluorooctanesulfonate (PFOS) perturbs male rat Sertoli cell blood-testis barrier function by affecting F-actin organization via p-FAK-Tyr(407): an in vitro study. Endocrinology 155:249-62|
|Gungor-Ordueri, N Ece; Mruk, Dolores D; Wan, Hin-ting et al. (2014) New insights into FAK function and regulation during spermatogenesis. Histol Histopathol 29:977-89|
|Xiao, Xiang; Mruk, Dolores D; Tang, Elizabeth I et al. (2014) Environmental toxicants perturb human Sertoli cell adhesive function via changes in F-actin organization mediated by actin regulatory proteins. Hum Reprod 29:1279-91|
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