Functional analysis of microRNA genes in Drosophila

描述（由申请人提供）： C. lin-4和let-7基因的小调控RNA产物。线虫是控制蠕虫幼虫发育时间的微小RNA（miRNAs）。 lin-4和let-7通过RNA：RNA反义碱基配对抑制特异性靶信使RNA的翻译而发挥功能。lin-4、let-7和某些其它miRNA在蠕虫、昆虫和脊椎动物中进化上保守，并且在某些情况下，同源物在不同动物中以相似的谱表达。这些保守的microRNA在脊椎动物和无脊椎动物发育过程中可能在基因表达的转录后调控中发挥类似的作用。该项目旨在确定果蝇中四种发育调节的、进化上保守的microRNA的体内功能，let-7，mir-34，mir-100和mir-125（lin-4的果蝇直系同源物）。let-7、mir-125和mir-100基因在果蝇基因组中聚集，并且通过蜕皮激素信号转导与果蝇中的主要发育转变（幼虫至成虫变态）相结合而上调。相比之下，mir-34的表达在变态开始时被蜕皮激素下调。本项目的目标是：1）分离let-7、mir-125、mir-100和mir-34中功能缺失的突变，并分析果蝇发育过程中的缺陷; 2）确定let-7、mir-125、mir-100和mir-34在果蝇发育过程中的时空表达模式; 4）鉴定作为let-7、mir-125、mir-100和mir-34的反义靶标的信使RNA; 5）鉴定在果蝇发育期间被蜕皮激素信号激活或抑制的另外的进化上保守的miRNA基因。该项目将利用果蝇遗传学来定义进化上保守的miRNAs控制的生物过程，并将阐明动物发育的基本分子机制，包括哺乳动物和对人类健康具有重要意义的昆虫。

DESCRIPTION (provided by applicant): The small regulatory RNA products of the lin-4 and let-7 genes of C. elegans are microRNAs (miRNAs) that control developmental timing in worm larvae. lin-4 and let-7 function by repressing the translation of specific target messenger RNAs via RNA: RNA antisense base-pairing. lin-4, let-7 and certain other miRNAs are evolutionarily conserved among worms, insects and vertebrates, and in some cases, homologs are expressed in similar profiles in diverse animals. These conserved microRNAs may play similar roles in the post-transcriptional control of gene expression during development of vertebrates and invertebrates. This project is designed to determine the in vivo function of four developmentally regulated, evolutionarily conserved, microRNAs in Drosophila melanogaster, let-7, mir-34, mir-100, and mir-125 (the fly ortholog of lin-4). The let-7, mir-125 and mir-100 genes are clustered in the Drosophila genome, and are up-regulated by ecdysone signaling in conjunction with a major developmental transition in flies, larva-to-adult metamorphosis. By contrast, mir-34 expression is down-regulated by ecdysone at the onset of metamorphosis. The goals of this project are to 1) isolate loss-of-function mutations in let-7, mir-125, mir-100, and mir-34, and analyze any resulting defects in fly development; 2) determine the temporal and spatial patterns of expression of let-7, mir-125, mir-100, and mir-34 during Drosophila development; 3) analyze developmental defects resulting from the over-expression and ectopic expression of these miRNAs; 4) identify messenger RNAs that are antisense targets of let-7, mir-125, mir-100, and mir-34; 5) identify additional evolutionarily conserved miRNA genes that are activated or repressed by ecdysone signaling during Drosophila development. This project will exploit Drosophila genetics to define the biological processes that evolutionarily conserved miRNAs control and will illuminate molecular mechanisms fundamental to animal development, including mammals, and insects significant to human health.