Regulated RNA degradation is required for Drosophila oogenesis

摘要 生殖细胞系产生配子，通过将遗传信息从父母传递到 后代在卵子发生过程中，卵子从母亲那里接收关键的mRNA，帮助启动下一个卵子。 这一过程中的任何错误都可能对后代有害。然而，目前尚不清楚， 监测母体提供的mRNA的质量或异常表达的mRNA如何影响卵子发生。 Twister（Tst）是一种从酵母到人类都保守的RNA解旋酶，可促进缺陷mRNA的降解。损失 tst人类同源物SKIV 2L导致肝肠综合征，其未知 治疗Tst是Ski复合物的一部分，该复合物解旋RNA双链体，然后RNA双链体被 外泌体复合体质量控制机制的mRNA靶点，如无义介导的衰变 (NMD)、不进行衰变（NGD）和不停止衰变（NSD）是Ski复合物和外泌体的底物。 我们发现，tst纯合子果蝇是可行的，但女性不育，表现出卵子发生缺陷。我们发现tst 是生殖细胞系所必需的，而不是性腺的索马体所必需的。使用RNA-Seq和 通过生物信息学分析，我们发现，在tst突变体中，大部分转录组不受影响，但有明显的 转录子亚组上调，只有少数转录子下调。这与Tst扮演一个 在RNA降解中的重要作用。在tst突变体中上调的转录本在野生型中表达很差 这些mRNA通常在其5 'UTR、ORF和3' UTR区域较短。令人惊讶的是，我们发现 Tst靶不具有典型的mRNA衰变途径的特征，如NMD、NGD和 NSD。我们假设Tst在监控向发育中细胞供应的mRNA中起着核心作用。 在卵母细胞中表达，并通过其3 'UTR促进发育表达的mRNA的周转。的 本研究的主要目的是：1）确定Tst介导的mRNA降解如何促进适当的 卵子发生，2）鉴定Tst的mRNA靶点，3）阐明Tst被招募到这些细胞中的机制。 mRNA靶向启动其降解。这些研究的目的是确定Tst对卵的贡献 发育和女性生育力通过周转发育调节的mRNA。如果Tst介导 周转的发育调节转录，这可以提供洞察疾病，如THE。我们的工作 将使我们能够阐明设计治疗的目标， mRNA代谢和周转不足导致的症状。 !

Abstract The germ line generates gametes that link generations by passing genetic information from parent to offspring. During oogenesis, the egg receives critical mRNAs from the mother that help launch the next generation; any mistakes in this process could be detrimental to the offspring. However, it is not known if the maternally provided mRNAs are surveilled for quality or how aberrantly expressed mRNAs impact oogenesis. Twister (Tst), an RNA helicase conserved from yeast to humans, promotes decay of defective mRNAs. Loss of the tst human homolog, SKIV2L, results in trichohepatoenteric (THE) syndrome, which has no known treatment. Tst is part of the Ski complex that unwinds RNA duplexes, which are then subject to degradation by the exosome complex. mRNA targets of quality control mechanisms such as nonsense-mediated decay (NMD), no-go decay (NGD) and nonstop decay (NSD) are substrates for the Ski complex and the exosome. We find that the tst homozygous flies are viable but female sterile, exhibiting an oogenesis defect. We find tst is required in the germ line but not the soma of the gonad for proper oogenesis. Using RNA-Seq and bioinformatic analyses, we found that in tst mutants most of the transcriptome is not affected, but a distinct subset is upregulated and only a few transcripts are down regulated. This is consistent with Tst playing a central role in RNA degradation. The transcripts upregulated in tst mutants are poorly expressed in wild type conditions and these mRNAs are typically shorter in their 5’UTR, ORF and 3’UTR regions. Surprisingly, we find that the Tst targets do not have features of the canonical mRNA decay pathways such as NMD, NGD and NSD. We hypothesize that Tst plays a central role in surveilling the mRNAs supplied to the developing oocyte and facilitates the turnover of developmentally expressed mRNAs through their 3’UTRs. The main goals of this research are to: 1) determine how mRNA degradation mediated by Tst promotes proper oogenesis, 2) identify mRNAs targets of Tst, and 3) elucidate the mechanism by which Tst is recruited to these mRNA targets to initiate their degradation. These studies aim to establish the contributions of Tst to egg development and female fertility through turnover of developmentally regulated mRNAs. If Tst mediates turnover of developmentally regulated transcripts, this can provide insight to diseases such as THE. Our work in a genetically tractable organism will allow us to elucidate a target to design treatments against to alleviate symptoms resulting from insufficient mRNA metabolism and turnover. !