Yu Yang, Oko Richard, Miranda-Vizuete Antonio
Department of Anatomy and Cell Biology, Queen's University, Kingston, Ontario K7L 3N6, Canada.
Biol Reprod. 2002 Nov;67(5):1546-54. doi: 10.1095/biolreprod.102.004838.
The mammalian sperm tail presents a complex organization in which a number of additional structures, namely outer dense fibers and fibrous sheath, surround the central axoneme and are thought to regulate flagellar motility. We have previously described a novel member of the thioredoxin family of proteins with a spermatid specific expression pattern, spermatid-specific thioredoxin-1 (Sptrx-1). We report here the developmental analysis of Sptrx-1 expression during murine spermiogenesis. Immunocytochemical analysis of Sptrx-1 through the different steps of spermiogenesis in rat seminiferous tubule sections showed that its expression begins at step 9, gets progressively stronger until steps 14-16 (where a peak is reached), and then diminishes in steps 17 and 18 until practically no immunolabeling is detected in step 19 spermatid. During its transient expression in spermiogenesis, Sptrx-1 is most concentrated in the periaxonemal compartment of the tail of the elongating spermatid, except in the very last steps (steps 17-19), when periaxonemal labeling disappears and a residual buildup of Sptrx-1 occurs in the shrinking cytoplasmic lobe. Electron microscopic analysis by immunogold labeling pinpointed the localization of Sptrx-1 to the assembling longitudinal columns of the fibrous sheath, whereas the forming ribs of the fibrous sheath were unlabeled. Immunoblotting of isolated fibrous sheath and tails obtained from epididymal or ejaculated sperm of rat and human confirmed our immunocytochemical observation: Sptrx-1 is no longer a component of the mature fibrous sheath. To our knowledge, this is the first report of a protein that specifically associates to the fibrous sheath during development but does not become a permanent structural component. The expression pattern of Sptrx-1 during rat spermiogenesis suggests that it could be part of a nucleation center for the formation of the longitudinal columns and transverse ribs that bridge the latter.
哺乳动物的精子尾部呈现出一种复杂的结构，其中一些额外的结构，即外周致密纤维和纤维鞘，围绕着中央轴丝，被认为可以调节鞭毛运动。我们之前描述过一种具有精子细胞特异性表达模式的硫氧还蛋白家族的新成员，即精子细胞特异性硫氧还蛋白-1（Sptrx-1）。我们在此报告小鼠精子发生过程中Sptrx-1表达的发育分析。通过对大鼠生精小管切片精子发生不同阶段的Sptrx-1进行免疫细胞化学分析表明，其表达始于第9步，逐渐增强直至第14 - 16步（达到峰值），然后在第17步和第18步减弱，直至在第19步精子细胞中几乎检测不到免疫标记。在精子发生过程中其短暂表达期间，Sptrx-1最集中在伸长精子细胞尾部的轴丝周围区域，但在最后阶段（第17 - 19步）除外，此时轴丝周围标记消失，Sptrx-1在萎缩的细胞质叶中残留积累。通过免疫金标记的电子显微镜分析确定Sptrx-1定位于纤维鞘正在组装的纵向柱，而纤维鞘正在形成的肋未被标记。对从大鼠和人类附睾或射出精子中分离得到的纤维鞘和尾部进行免疫印迹证实了我们的免疫细胞化学观察结果：Sptrx-1不再是成熟纤维鞘的组成成分。据我们所知，这是关于一种在发育过程中特异性与纤维鞘结合但不会成为永久结构成分的蛋白质的首次报道。大鼠精子发生过程中Sptrx-1的表达模式表明，它可能是形成连接纵向柱的横向肋的成核中心的一部分。
