Cooperation between epitranscriptomics and the piRNA pathway in maternal mRNA regulation

mRNA调控在广泛的生物学和病理学过程中是必不可少的。 这种调节涉及RNA结合蛋白和非编码RNA，它们以复杂的协调方式起作用以决定细胞mRNA的命运和功能。Piwi相互作用RNA（piRNA）是一类参与生殖系中转座因子抑制的特定小的非编码RNA。除了这种充分研究的功能之外，我们先前已经描述了piRNA在果蝇模型中在早期胚胎发生期间控制母体mRNA衰变的新作用。最近，mRNA修饰，特别是N6-甲基腺苷（m6 A），已成为一种新的转录后基因调控的关键层，影响mRNA生物合成的每一步，包括鱼类和小鼠母体mRNA衰变的调节。然而，目前尚不清楚皮尔纳和m6 A通路是否以及如何协调以确保有效的母体mRNA降解。我们的初步数据表明，m6 A有助于在早期果蝇胚胎中充分研究的nanos母体mRNA的衰变，这表明这种m6 A功能在果蝇中是保守的。此外，我们发现m6 A位点的比例位于母体mRNA上的皮尔纳结合位点附近，这表明m6 A可能参与piRNA识别mRNA的特异性。 基于我们的初步工作，m6 ApiRNA项目的目标是破译动物发育早期阶段皮尔纳通路和RNA修饰之间的串扰。我们将研究m6 A（mRNA上最丰富的修饰）和皮尔纳通路在两个关键事件中的相互作用，这两个事件是早期果蝇胚胎发育过程中胚胎形成所需的：1）索马中的母体mRNA衰变和2）胚质mRNA在胚胎后极的定位及其翻译激活。具体的工作包包括：i）使用基因组、成像和CRISPR/Cas9介导的方法来检查m6 A在母体mRNA衰变中的贡献; ii）鉴定由m6 A和piRNA共同调节的mRNA，以及潜在的机制; iii）m6 A和piRNA在母体mRNA定位和翻译激活中的相互作用。 这项合作研究将结合联合收割机尖端果蝇遗传学，核糖体组学和成像方法，分子生物学和质谱，以解决m6 A和皮尔纳通路之间的关系，在早期胚胎发育过程中调节母体mRNA。破译这两种调控模式之间的合作将对mRNA调控中的皮尔纳生物学和表转录组学的新兴领域产生重大影响。

mRNA regulation is essential in a wide range of biological and pathological processes. This regulation involves RNA binding proteins and non-coding RNAs that act in a complex coordinated manner to determine the fate and function of cellular mRNAs. Piwi-interacting RNAs (piRNAs) are a specific class of small non-coding RNAs involved in the repression of transposable elements in the germline. Besides this well studied function, we have previously described a novel role for piRNAs in controlling maternal mRNA decay during early embryogenesis in the Drosophila model. Recently, mRNA modification, in particular N6-methyladenosine (m6A), has emerged as a novel critical layer of post-transcriptional gene regulation affecting every step of mRNA biogenesis, including the regulation of maternal mRNA decay in fish and mouse. Yet, it is unknown whether and how the piRNA and m6A pathways may coordinate to ensure efficient maternal mRNA degradation. Our preliminary data indicate that m6A contributes to the decay of the well-studied nanos maternal mRNA in early Drosophila embryo, suggesting that this m6A function is conserved in flies. In addition, we have found that a proportion of m6A sites lie near piRNA binding sites on maternal mRNAs, suggesting the possibility that m6A might participate in the specificity of mRNA recognition by piRNAs. Based on our preliminary work, the objective of the m6ApiRNA project is to decipher the crosstalk between the piRNA pathway and RNA modification during the early steps of animal development. We will investigate the interplay between m6A, the most abundant modification on mRNA, and the piRNA pathway in two critical events that are required during early Drosophila embryogenesis for embryonic patterning: 1) maternal mRNA decay in the soma and 2) the localization of germ plasm mRNAs at the posterior pole of the embryo and their translational activation. The specific work packages include: i) the use of genomic, imaging and CRISPR/Cas9-mediated approaches to examine the contribution of m6A in maternal mRNA decay; ii) the identification of mRNAs co-regulated by m6A and piRNAs, and the underlying mechanisms and iii) the interplay between m6A and piRNAs in maternal mRNA localization and translational activation. This collaborative study will combine cutting-edge Drosophila genetics, ribonomics and imaging approaches, molecular biology and mass spectrometry to address the relationships between m6A and the piRNA pathway in the regulation of maternal mRNAs during early embryogenesis. Deciphering the cooperation between these two modes of regulation will have a strong impact in the emerging fields of piRNA biology and epitranscriptomics in mRNA regulation.