Damage to the zebrafish retina stimulates resident Müller glia to reprogram, reenter the cell cycle, divide asymmetrically, and produce neuronal progenitor cells that amplify and differentiate into the lost neurons. The transition from quiescent to proliferative Müller glia involves both positive and negative regulators. We previously demonstrated that the Notch signaling pathway represses retinal regeneration by maintaining Müller glia quiescence in zebrafish. Here we examine which Notch receptor is necessary to maintain quiescence. Quantitative RT‐PCR and RNA‐Seq analyses reveal that notch3 is expressed in the undamaged retina and is downregulated in response to light damage. Additionally, Notch3 protein is expressed in quiescent Müller glia of the undamaged retina, is downregulated as Müller glia proliferate, and is reestablished in the Müller glia. Knockdown of Notch3 is sufficient to induce Müller glia proliferation in undamaged retinas and enhances proliferation during light damage. Alternatively, knockdown of Notch1a, Notch1b, or Notch2 decreases the number of proliferating cells during light damage, suggesting that Notch signaling is also required for proliferation during retinal regeneration. We also knockdown the zebrafish Delta and Delta‐like proteins, ligands for the Notch receptors, and find that the deltaB morphant possesses an increased number of proliferating cells in the light‐damaged retina. As with Notch3, knockdown of DeltaB is sufficient to induce Müller glia proliferation in the absence of light damage. Taken together, the negative regulation of Müller glia proliferation in zebrafish retinal regeneration is mediated by Notch3 and DeltaB.

中文翻译：

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Notch3 和 DeltaB 维持 Müller 神经胶质细胞静止，并作为光损伤斑马鱼视网膜再生的负调节剂。

斑马鱼视网膜的损伤会刺激常驻的 Müller 神经胶质细胞重新编程、重新进入细胞周期、不对称分裂并产生神经元祖细胞，这些细胞会放大并分化成丢失的神经元。从静止到增殖的 Müller 神经胶质细胞的转变涉及正调节和负调节。我们之前证明了 Notch 信号通路通过维持斑马鱼的 Müller 胶质细胞静止来抑制视网膜再生。在这里，我们检查了维持静止所必需的 Notch 受体。定量 RT-PCR 和 RNA-Seq 分析表明，notch3在未受损的视网膜中表达，并响应光损伤而下调。此外，Notch3 蛋白在未受损视网膜的静止 Müller 胶质细胞中表达，随着 Müller 胶质细胞增殖而下调，并在 Müller 胶质细胞中重新建立。Notch3 的敲低足以在未受损的视网膜中诱导 Müller 胶质细胞增殖，并在光损伤期间增强增殖。或者，敲除 Notch1a、Notch1b 或 Notch2 会减少光损伤期间增殖细胞的数量，这表明在视网膜再生过程中增殖也需要 Notch 信号传导。我们还敲除斑马鱼 Delta 和 Delta 样蛋白、Notch 受体的配体，并发现deltaBmorphant 在光损伤的视网膜中拥有更多的增殖细胞。与 Notch3 一样，DeltaB 的敲低足以在没有光损伤的情况下诱导 Müller 胶质细胞增殖。总之，斑马鱼视网膜再生中 Müller 胶质细胞增殖的负调控是由 Notch3 和 DeltaB 介导的。