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研究発表を行った学会；
・第３５回日本分子生物学会年会
　２０１２年１２月１１日〜１４日（福岡）

タイトル；Pgc protects germ plasm RNAs from microRNA-mediated degradation in Drosophila primordial germ cells.
発表者；羽生-中村　賀津子　氏
　　　（熊本大学　発生医学研究所　生殖発生分野）
Abstract；
In many animal species, germ cell formation depends on maternal factors localized in the germ plasm. One of key functions of the germ plasm is the global inhibition of mRNA transcription in newly formed germ cells. This transcriptional repression is thought to be a mechanism that ensure germ cell fate by preventing somatic transcriptional program. In Drosophila, germ plasm factor, polar granule component (pgc) RNA, encodes a 71-aa protein that is essential for the repression of zygotic mRNA transcription in newly formed pole cells (the germline progenitors). Although Pgc-mediated transcriptional repression is crucial for pole cell survival during subsequent embryogenesis, underlying mechanism remains elusive. We found that germ plasm RNAs, including nanos (nos) mRNA, which encodes an evolutionally conserved protein essential for germ cell development, failed to be maintained in pgc-null pole cells. Consequently, Nos protein was precociously disappeared from these cells, leading pole cell apoptosis. It has been known that maternal mRNAs, including nos, are eliminated in the somatic region during the maternal-to-zygotic transition (MZT). The MZT is operated, in part, by microRNA-309 (miR-309) cluster miRNAs. The miR-309 and several other miRNAs start to express in the somatic region before the onset of widespread zygotic transcription. We found that these early zygotic miRNAs were misexpressed in pgc-null pole cells. Luciferase reporter assays using Drosophila cell lines revealed that they could target the nos 3′ UTR. We therefore propose that germ plasm RNAs in pole cells are protected from miRNA-mediated degradation at the level of miRNA expression.