Wang Z Q, Kim K H
Department of Genetics and Cell Biology, Washington State University, Pullman 99164.
Biol Reprod. 1993 Nov;49(5):951-64. doi: 10.1095/biolreprod49.5.951.
Retinol down-regulates male germ cell-associated kinase (mak) transcripts during the spermatogonial proliferation phase of spermatogenesis. Mak transcripts of 2.6- and 3.4 kb were detected in vitamin A-deficient germ cells, but decreased to undetectable levels shortly after retinol replacement to vitamin A-deficient rats. In contrast, mak seems to play a role in spermatocytes and round spermatids during meiotic and post-meiotic events. The 3.4-kb transcript initially appeared in pachytene spermatocytes and continued to increase in round spermatids; the level of the 2.6-kb transcript increased markedly only in round spermatids. These transcripts also exhibited stage-specificity in synchronized retinol-regenerated rat seminiferous tubules. Silver grains were intensely localized mainly in round spermatids in stages IV-VI of the spermatogenic cycle in normal tests after in situ hybridization. These results suggest that the mak gene in early germ cells responds to retinol in an opposite manner from the mak gene in spermatocytes or in round spermatids. The findings support the existence of two distinct pathways of retinol signaling in the testis that depend on the spatial localization and development ages of the individual germ cells.
在精子发生的精原细胞增殖阶段，视黄醇可下调雄性生殖细胞相关激酶（MAK）的转录本。在维生素A缺乏的生殖细胞中检测到2.6 kb和3.4 kb的MAK转录本，但在给维生素A缺乏的大鼠补充视黄醇后不久，其水平降至无法检测到的程度。相反，MAK似乎在减数分裂和减数分裂后事件中的精母细胞和圆形精子细胞中发挥作用。3.4 kb的转录本最初出现在粗线期精母细胞中，并在圆形精子细胞中持续增加；2.6 kb的转录本水平仅在圆形精子细胞中显著增加。这些转录本在同步视黄醇再生的大鼠曲细精管中也表现出阶段特异性。原位杂交后，在正常睾丸生精周期的IV-VI期，银颗粒主要强烈定位于圆形精子细胞中。这些结果表明，早期生殖细胞中的MAK基因对视黄醇的反应方式与精母细胞或圆形精子细胞中的MAK基因相反。这些发现支持睾丸中存在两条不同的视黄醇信号通路，这两条通路取决于单个生殖细胞的空间定位和发育年龄。
