Nrf2 dictates the neuronal survival and differentiation of embryonic zebrafish harboring compromised tRNA synthetase. Nrf2 dictates the neuronal survival and differentiation of embryonic zebrafish harboring compromised tRNA synthetase

tRNA synthetase deficiency leads to unfolded protein responses in neuronal disorders; however, its function in embryonic neurogenesis remains unclear. This study identified an aars1cq71/cq71 mutant zebrafish allele that showed increased neuronal apoptosis and compromised neurogenesis. aars1 transcripts were highly expressed in primary neural progenitor cells, and their aberration resulted in protein overloading and activated Perk. nfe2l2b, a paralog of mammalian Nfe2l2, which encodes Nrf2, is a pivotal executor of Perk signaling that regulates neuronal phenotypes in aars1cq71/cq71 mutants. Interference of nfe2l2b in nfe2l2bΔ1/Δ1 mutants did not affect global larval development. However, aars1cq71/cq71;nfe2l2bΔ1/Δ1 mutant embryos exhibited increased neuronal cell survival and neurogenesis compared with their aars1cq71/cq71 siblings. nfe2l2b was harnessed by Perk at two levels. Its transcript was regulated by Chop, an implementer of Perk. It was also phosphorylated by Perk. Both pathways synergistically assured the nuclear functions of nfe2l2b to control cell survival by targeting p53. Our study extends the understanding of tRNA synthetase in neurogenesis and implies that Nrf2 is a cue to mitigate neurodegenerative pathogenesis. Overall design: Single cell analyses of zebrafish midbrain by 10X Genomics

氨酰tRNA合成酶（tRNA synthetase）缺陷可引发神经疾病中的未折叠蛋白反应，但其在胚胎神经发生中的功能仍有待阐明。本研究鉴定出一种aars1^cq71/cq71突变斑马鱼等位基因，该模型表现出神经元凋亡增加、神经发生受损的表型。aars1的转录本在初级神经前体细胞中高表达，其异常会引发蛋白质过载并激活蛋白激酶R样内质网激酶（Perk）。nfe2l2b是哺乳动物Nfe2l2（编码核因子红细胞2相关因子2，即Nrf2）的旁系同源基因，是Perk信号通路的关键效应分子，可调控aars1^cq71/cq71突变体的神经元表型。在nfe2l2b^Δ1/Δ1突变体中对nfe2l2b进行基因干扰，并不会影响斑马鱼幼体的整体发育。然而，与仅携带aars1^cq71/cq71突变的同窝胚胎相比，aars1^cq71/cq71;nfe2l2b^Δ1/Δ1双突变胚胎的神经元存活与神经发生水平均显著提升。nfe2l2b在两个层面受到Perk的调控：其一，其转录本受Perk通路效应分子CCAAT增强子结合蛋白同源蛋白（CHOP）的调控；其二，nfe2l2b本身可被Perk磷酸化。这两条通路协同作用，保障nfe2l2b的核定位功能，通过靶向调控p53以控制细胞存活。本研究拓展了我们对氨酰tRNA合成酶在神经发生中作用的认知，并提示Nrf2可作为缓解神经退行性疾病发病进程的潜在干预靶点。
实验整体设计：采用10X Genomics技术对斑马鱼中脑进行单细胞测序分析。