Physiology and Neurobiology Department, University of Connecticut, Storrs, CT 06269, USA.
Department of Genetics, Yale School of Medicine, New Haven, CT 06510, USA.
Development. 2021 Oct 15;148(20). doi: 10.1242/dev.199591. Epub 2021 Oct 19.
Minor spliceosome inhibition due to mutations in RNU4ATAC are linked to primary microcephaly. Ablation of Rnu11, which encodes a minor spliceosome snRNA, inhibits the minor spliceosome in the developing mouse pallium, causing microcephaly. There, cell cycle defects and p53-mediated apoptosis in response to DNA damage resulted in loss of radial glial cells (RGCs), underpinning microcephaly. Here, we ablated Trp53 to block cell death in Rnu11 cKO mice. We report that Trp53 ablation failed to prevent microcephaly in these double knockout (dKO) mice. We show that the transcriptome of the dKO pallium was more similar to the control compared with the Rnu11 cKO. We find aberrant minor intron splicing in minor intron-containing genes involved in cell cycle regulation, resulting in more severely impaired mitotic progression and cell cycle lengthening of RGCs in the dKO that was detected earlier than in the Rnu11 cKO. Furthermore, we discover a potential role of p53 in causing DNA damage in the developing pallium, as detection of γH2aX+ was delayed in the dKO. Thus, we postulate that microcephaly in minor spliceosome-related diseases is primarily caused by cell cycle defects.
由于 RNU4ATAC 突变导致的小核核糖体失活，与原发性小头畸形有关。编码小核核糖体 snRNA 的 Rnu11 的缺失，抑制了发育中的小鼠大脑皮层的小核核糖体，导致小头畸形。在那里，细胞周期缺陷和 p53 介导的对 DNA 损伤的凋亡导致放射状胶质细胞（RGC）丢失，从而导致小头畸形。在这里，我们敲除了 Trp53 以阻止 Rnu11 cKO 小鼠中的细胞死亡。我们报告说，Trp53 敲除未能预防这些双敲除（dKO）小鼠的小头畸形。我们表明，与 Rnu11 cKO 相比，dKO 大脑皮层的转录组与对照更相似。我们发现，参与细胞周期调控的含有小内含子的基因中的小内含子剪接异常，导致 dKO 中的有丝分裂进程和 RGC 细胞周期延长受到更严重的损害，并且比 Rnu11 cKO 更早检测到。此外，我们发现 p53 在引起发育中的大脑皮层中的 DNA 损伤方面可能具有潜在作用，因为在 dKO 中γH2aX+的检测延迟。因此，我们假设小核核糖体相关疾病中的小头畸形主要是由细胞周期缺陷引起的。
