DIS3L2 clears terminal-uridylated RNA to ensure oocyte maturation and female fertility

During mammalian oocyte development, transcriptome undergoes accumulation in the oocyte growth phase and elimination in the oocyte maturation phase. At the transition point between growth and maturation, which is the germinal vesicle intact oocyte (GV), terminal uridylation labels RNA for degradation. In our study, we show that a small cohort of RNA are polyadenylated after tail uridylation (defined as uridylated-poly(A) RNA). Upon genetic depletion of DIS3L2 (Dis3l2cKO) in mouse oocytes, uridylated-poly(A) RNA is extensively stabilized and dominates the oocyte transcriptome, which results in increased transcriptome in Dis3l2cKO oocytes. Consequently, Dis3l2cKO female mice are infertile and almost all oocytes are arrested at the GV stage. Uridylated-poly(A) RNA generally has shorter poly(A) tails and lower translation activity. The uridylated-poly(A) RNA in Dis3l2cKO oocytes not only generates from the insufficient RNA degradation, but also comes from the tail dynamics of RNA. Our study demonstrates more possibilities of RNA fates after being terminally uridylated, and highlights the role of DIS3L2 in safeguarding the transcriptome by degrading uridylated-poly(A) RNA. We performed transcriptome profiling using single oocyte RNA-seq (polyA RNA and total RNA) and single oocyte PAIso-seq. The single oocyte RNA-seq is done at GV and MII stages and the PAIso-seq is done at the GV stage.在哺乳动物卵母细胞发育过程中，转录组（transcriptome）会在卵母细胞生长阶段发生积累，而在卵母细胞成熟阶段发生清除。在生长与成熟的过渡节点——生发泡完整卵母细胞（germinal vesicle intact oocyte，GV）处，末端尿苷化修饰会标记RNA并启动其降解过程。本研究发现，有一小部分RNA会在尾部发生尿苷化修饰后进行多聚腺苷酸化，这类RNA被定义为尿苷化-多聚腺苷酸化RNA（uridylated-poly(A) RNA）。在小鼠卵母细胞中对DIS3L2进行遗传敲除（Dis3l2cKO）后，尿苷化-多聚腺苷酸化RNA会被广泛稳定，并主导卵母细胞的转录组，进而导致Dis3l2cKO卵母细胞的转录组总量显著上升。因此，Dis3l2cKO雌性小鼠完全不育，且几乎所有卵母细胞均停滞在GV期。尿苷化-多聚腺苷酸化RNA通常具有更短的多聚腺苷酸尾，且翻译活性更低。Dis3l2cKO卵母细胞中的尿苷化-多聚腺苷酸化RNA，既源于RNA降解不足，也来源于RNA的尾部动态变化过程。本研究揭示了RNA在发生末端尿苷化修饰后更多的命运走向，并阐明了DIS3L2通过降解尿苷化-多聚腺苷酸化RNA以维持转录组稳态的关键作用。我们采用单卵母细胞RNA测序（polyA RNA与总RNA）及单卵母细胞PAIso-seq技术开展了转录组谱分析，其中单卵母细胞RNA测序覆盖GV期与MII期卵母细胞，而单卵母细胞PAIso-seq仅针对GV期卵母细胞。