Ectoplasmic specialization, a testis-specific cell-cell actin-based adherens junction type: Is this a potential target for male contraceptive development?
Lee,Nikki P.Y.; Cheng,Chuen-yan
Human Reproduction Update 10(4): 349-369
Publication date: 2004
The seminiferous tubule of the mammalian testis is largely composedof Sertoli and germ cells, which coordinate with Leydig cellsin the interstitium and perform two major physiological functions,namely spermatogenesis and steroidogenesis respectively. Eachtubule is morphologically divided into (i) the seminiferousepithelium composing Sertoli and germ cells, and (ii) the basementmembrane (a modified form of extracellular matrix); underneaththis lies the collagen fibril network, the myoid cell layer,and the lymphatic vessel, which collectively constitute thetunica propia. In the seminiferous epithelium, of rodent testeseach type A1 spermatogonium (diploid, 2n) differentiates into256 elongated spermatids (haploid, 1n) during spermatogenesis.Additionally, developing germ cells must migrate progressivelyfrom the basal to the luminal edge of the adluminal compartmentso that fully developed spermatids can be released into thelumen at spermiation. Without this timely event of cell movement,spermatogenesis cannot reach completion and infertility willresult. Yet developing round elongating/elongated spermatidsmust remain attached to the epithelium via a specialized Sertoli-germcell actin-based adherens junction (AJ) type known as ectoplasmicspecialization (ES), which is crucial not only for cell attachmentbut also for spermatid movement and orientation in the epithelium.However, the biochemical composition and molecular architectureof the protein complexes that constitute the ES have only recentlybeen studied. Furthermore, the signalling pathways that regulateES dynamics are virtually unknown. This review highlights recentadvances in these two areas of research. It is expected that,if adequately expanded, these studies should yield new insightsinto the development of novel contraceptives targeted to perturbES function in the testis. The potential to specifically targetthe ES may also mean that contraceptive action could be achievedwithout perturbing the hypothalamic-pituitary-testicularaxis.