A study on novel regulation mechanism to repress precocious meiotic entry in Drosophila male

点击翻译按钮获取中文摘要

The G2 phase just prior to first meiotic division in male is called a growth phase that is an essential period to ensure gene expression required for meiotic divisions and later spermiogenesis in Drosophila. A timing to initiate the first meiotic division is therefore strictly regulated by activity of CDK1. A hypomorphic mutation at the mitotic gene, meteor (mtr) in Drosophila leads to a production of smaller cells in premeiotic cysts consisting of primary spermatocytes. We found that a chromosome condensation has precociously proceeded in the "wee" cells. Another distinctive features in M phase such as nuclear membrane-break-down and formation of spindle-like structure have also already occurred in these "wee" cells within premeiotic cysts. The precocious entry of meiotic divisions did not allow these cells to grow sufficiently. These cytological observations suggest that the mtr gene is involved in a negative regulation to repress initiation of first meiotic division until a completi … More on of the growth phase in Drosophila males. Surprisingly, these precocious meiotic entry in the mtr males occurred before a sufficient expression of both Cyclin A and Cyclin B. Immunostaining experiments to detect active form of CDK1 indicate that the active MPF has not yet accumulated in cytoplasm of the "wee" cells with precociously condensed chromatin in the mtr males. Consistently, this precocious meiotic entry in mtr was observed even in mutant background of twine gene encoding a Cdc25 orthologue exclusively active before meiotic division. In addition to the precocious meiotic entry, a failure of centrosome separation, spindle abnormality and non-disjunction was also observed during meiotic divisions in the mtr males. The mtr gene corresponds to dlarp that encode a Drosophila ortholog of the LA-related protein sharing a homologous domain with human Lupas Antigen. Our immunostaining experiments localized the Meteor protein to a peripheral region of nucleus at premeiotic stages and to the centrosomes at M phase. We speculate that the Meteor has essential roles in both meiotic entry and meiotic divisions in Drosophila males. Less