MicroRNA-mediated control of Drosophila midgut regeneration [miRNA]

The molecular mechanisms by which stem cell proliferation is precisely controlled during the course of regeneration are poorly understood. Namely, how a damaged tissue senses when to terminate the regeneration process, inactivates stem cell mitotic activity, and organizes ECM integrity remain fundamental unanswered questions. The Drosophila midgut intestinal stem cell (ISC) offers an excellent model system to study the molecular basis for stem cell inactivation. Here we show that a novel gene, CG6967 or dMOV10, is induced at the termination stage of midgut regeneration, and shows an inhibitory effect on ISC proliferation. dMOV10 encodes a putative component of the microRNA (miRNA) gene silencing complex (miRISC). Our data, along with previous studies on the mammalian MOV10, suggest that dMOV10 is not a core member of miRISC, but modulates miRISC activity as an additional component. Further analyses identified direct target mRNAs of dMOV10-containing miRISC, including Daughter against Dpp (Dad), a known inhibitor of BMP/TGF-β signaling. We show that RNAi knockdown of Dad significantly impaired ISC division during regeneration. We also identified miRNAs that are induced at the termination stage and their potential target transcripts. We propose that miRNA-mediated gene regulation contributes to the precise control of Drosophila midgut regeneration. Examination of the initiation and termination stages of regeneration in the Drosophila midgut

再生过程中干细胞增殖的精确调控分子机制，目前仍未得到充分阐明。具体而言，受损组织如何感知再生过程的终止时机、灭活干细胞的有丝分裂活性，以及维持细胞外基质(Extracellular Matrix, ECM)的完整性，这些仍是尚未解决的核心科学问题。果蝇中肠肠道干细胞(Intestinal Stem Cell, ISC)是研究干细胞失活分子机制的优秀模型系统。本研究发现，新型基因CG6967（又名dMOV10）在中肠再生的终止阶段被诱导表达，并对ISC增殖具有显著抑制作用。dMOV10编码微小RNA(miRNA)基因沉默复合体(miRISC)的潜在组分。结合本研究数据与此前针对哺乳动物MOV10的相关研究，我们认为dMOV10并非miRISC的核心成员，而是作为辅助组分调控miRISC的活性。进一步分析鉴定出了含dMOV10的miRISC的直接靶mRNA，包括抗Dpp蛋白(Daughter against Dpp, Dad)——一种已知的骨形态发生蛋白/转化生长因子-β(BMP/TGF-β)信号通路抑制剂。我们证实，在再生过程中通过RNA干扰(RNA interference, RNAi)敲低Dad的表达，会显著损害ISC的分裂活动。此外，我们还鉴定出了在终止阶段被诱导表达的miRNA及其潜在靶转录本。我们提出，miRNA介导的基因调控参与了果蝇中肠再生的精确调控过程。果蝇中肠再生起始与终止阶段的研究