Population Council, Center for Biomedical Research, 1230 York Avenue, New York, NY 10065, USA.
Philos Trans R Soc Lond B Biol Sci. 2010 May 27;365(1546):1593-605. doi: 10.1098/rstb.2009.0251.
Spermatogenesis is a process that involves an array of cellular and biochemical events, collectively culminating in the formation of haploid spermatids from diploid precursor cells known as spermatogonia. As germ cells differentiate from spermatogonia into elongated spermatids, they also progressively migrate across the entire length of the seminiferous epithelium until they reach the luminal edge in anticipation of spermiation at late stage VIII of spermatogenesis. At the same time, these germ cells must maintain stable attachment with Sertoli cells via testis-unique intermediate filament- (i.e. desmosome-like junctions) and actin- (i.e. ectoplasmic specializations, ESs) based cell junctions to prevent sloughing of immature germ cells from the seminiferous epithelium, which may result in infertility. In essence, both desmosome-like junctions and basal ESs are known to coexist between Sertoli cells at the level of the blood-testis barrier where they cofunction with the well-studied tight junction in maintaining the immunological barrier. However, the type of anchoring device that is present between Sertoli and germ cells depends on the developmental stage of the germ cell, i.e. desmosome-like junctions are present between Sertoli and germ cells up to, but not including, step 8 spermatids after which this junction type is replaced by the apical ES. While little is known about the biology of the desmosome-like junction in the testis, we have a relatively good understanding of the molecular architecture and the regulation of the ES. Here, we discuss recent findings relating to these two junction types in the testis, highlighting prospective areas that should be investigated in future studies.
精子发生是一个涉及一系列细胞和生化事件的过程，最终将二倍体前体细胞（称为精原细胞）形成单倍体精母细胞。随着生殖细胞从精原细胞分化为长形精母细胞，它们也逐渐迁移穿过生精上皮的整个长度，直到到达生精上皮的管腔边缘，为晚期 VIII 期精子发生的精子释放做准备。同时，这些生殖细胞必须通过睾丸特有的中间丝（即桥粒样连接）和肌动蛋白（即外质特化，ES）为基础的细胞连接与支持细胞保持稳定的附着，以防止未成熟的生殖细胞从生精上皮脱落，这可能导致不育。本质上，桥粒样连接和基底 ES 都存在于血睾屏障处的支持细胞之间，与研究充分的紧密连接共同发挥作用，维持免疫屏障。然而，存在于支持细胞和生殖细胞之间的锚定装置的类型取决于生殖细胞的发育阶段，即桥粒样连接存在于支持细胞和生殖细胞之间，直到但不包括第 8 步精母细胞，此后这种连接类型被顶 ES 取代。虽然关于睾丸中桥粒样连接的生物学了解甚少，但我们对 ES 的分子结构和调节有了相对较好的理解。在这里，我们讨论了与睾丸中这两种连接类型相关的最新发现，强调了未来研究中应调查的有前景的领域。
