Kim K H, Griswold M D
Department of Biochemistry and Biophysics, Washington State University Pullman 99164.
Mol Endocrinol. 1990 Nov;4(11):1679-88. doi: 10.1210/mend-4-11-1679.
Retinoic acid receptor-alpha mRNAs were found in both Sertoli and germ cells of the testis. A 2.7-kilobase (kb) mRNA was expressed solely in Sertoli cells, whereas a 3.4-kb mRNA was distributed in both Sertoli and germ cells. In addition, we report two new, but minor, germ cell-specific mRNAs detected primarily in the pachytene spermatocytes. By contrast, only one transcript for retinoic acid receptor-beta was found in the testis, exclusively in Sertoli cells. These results suggest that each mRNA may have specific functions in mediating the effects of retinoids during spermatogenesis. The expression of retinoic acid receptor-alpha mRNAs was regulated during the spermatogenic cycle, showing a 7-fold increase in the level of 3.4-kb mRNA at stages VIII-IX. Since stage VIII is where the development of germ cells is arrested at the prophase of meiosis in the vitamin A-deficient testis, this result suggests that alpha mRNA transcription may be necessary before more advanced germ cells than preleptotene spermatocytes would be observed in the testis. The most striking finding was that the treatment of vitamin A-deficient rats with retinol led to a rapid increase in the retinoic acid receptor-alpha mRNA levels. The level of mRNAs was increased 3-fold at its peak, but diminished by 12 h. This precise regulation of receptor by retinol suggests that its synthesis is required before it can be used to modulate the transcription of retinoid-inducible genes. In contrast, the regulation of retinoic acid receptor-beta mRNA was different from the alpha mRNAs, in that its level remained unchanged for 48 h after the injection of retinol.
在睾丸的支持细胞和生殖细胞中均发现了视黄酸受体α的信使核糖核酸（mRNA）。一种2.7千碱基（kb）的mRNA仅在支持细胞中表达，而一种3.4 kb的mRNA则分布于支持细胞和生殖细胞中。此外，我们报告了两种新的、但含量较少的生殖细胞特异性mRNA，主要在粗线期精母细胞中检测到。相比之下，在睾丸中仅发现一种视黄酸受体β的转录本，且仅存在于支持细胞中。这些结果表明，每种mRNA在介导视黄酸类物质在精子发生过程中的作用时可能具有特定功能。视黄酸受体α的mRNA表达在生精周期中受到调控，在VIII - IX期3.4 kb mRNA的水平增加了7倍。由于在维生素A缺乏的睾丸中，VIII期是生殖细胞在减数分裂前期停滞发育的阶段，这一结果表明，在睾丸中观察到比前细线期精母细胞更成熟的生殖细胞之前，α mRNA转录可能是必要的。最显著的发现是，用视黄醇治疗维生素A缺乏的大鼠会导致视黄酸受体α的mRNA水平迅速升高。mRNA水平在峰值时增加了3倍，但在12小时后下降。视黄醇对受体的这种精确调控表明，在其用于调节视黄酸诱导基因的转录之前，需要先进行合成。相比之下，视黄酸受体β的mRNA调控与α mRNA不同，注射视黄醇后48小时内其水平保持不变。
