Ravnik S E, Wolgemuth D J
Department of Genetics and Development, College of Physicians, New York, New York 10032, USA.
Dev Biol. 1996 Jan 10;173(1):69-78. doi: 10.1006/dbio.1996.0007.
We have isolated cDNAs encoding a murine cyclin A, designated cyclinA2, and have examined its in vivo expression at the level of both mRNA and protein, with particular focus on the male germ line. Cyclin A2 is expressed in embryos and in a variety of adult tissues, including the testis. In the testis, however, a striking cellular specificity of expression was observed. At both the DNA and protein levels, the predominant sites of cyclin A2 expression were in the germ line stem cells, the spermatogonia, and in highest levels in preleptotene spermatocytes, cells in which premeiotic DNA synthesis occurs. The concurrent localization of cyclin A2 mRNA and protein further suggested that cyclin A2 is regulated at the level of transcription in these cells. The observed cellular specificity of cyclin A2 expression is consistent with its function during mitosis in the stem cell stage of this lineage, while the restricted meiotic stage localization suggests function in G1/S or S but not in the meiotic divisions per se.
我们分离出了编码小鼠细胞周期蛋白A的cDNA，命名为细胞周期蛋白A2，并在mRNA和蛋白质水平上研究了其在体内的表达情况，特别关注雄性生殖系。细胞周期蛋白A2在胚胎以及包括睾丸在内的多种成年组织中表达。然而，在睾丸中，观察到了明显的细胞特异性表达。在DNA和蛋白质水平上，细胞周期蛋白A2表达的主要部位是生殖系干细胞、精原细胞，而在细线前期精母细胞（发生减数分裂前DNA合成的细胞）中表达水平最高。细胞周期蛋白A2 mRNA和蛋白质的同时定位进一步表明，细胞周期蛋白A2在这些细胞中是在转录水平上受到调控的。观察到的细胞周期蛋白A2表达的细胞特异性与其在该谱系干细胞阶段有丝分裂过程中的功能一致，而其在减数分裂阶段的定位受限表明其在G1/S期或S期发挥作用，而非在减数分裂本身发挥作用。
