Campbell Leah J, Hobgood Joshua S, Jia Meng, Boyd Patrick, Hipp Rebecca I, Hyde David R
Department of Biological Sciences, Center for Zebrafish Research, and the Center for Stem Cells and Regenerative Medicine, Galvin Life Science Center, University of Notre Dame, Notre Dame, Indiana, USA.
Glia. 2021 Mar;69(3):546-566. doi: 10.1002/glia.23912. Epub 2020 Sep 23.
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.
斑马鱼视网膜损伤会刺激驻留的穆勒胶质细胞重新编程，重新进入细胞周期，进行不对称分裂，并产生神经元祖细胞，这些祖细胞会扩增并分化为丢失的神经元。从静止的穆勒胶质细胞向增殖性穆勒胶质细胞的转变涉及正性和负性调节因子。我们之前证明，Notch信号通路通过维持斑马鱼穆勒胶质细胞的静止状态来抑制视网膜再生。在此，我们研究维持静止状态需要哪种Notch受体。定量逆转录聚合酶链反应（qRT-PCR）和RNA测序（RNA-Seq）分析表明，notch3在未受损的视网膜中表达，并在受到光损伤时下调。此外，Notch3蛋白在未受损视网膜的静止穆勒胶质细胞中表达，随着穆勒胶质细胞增殖而下调，并在穆勒胶质细胞中重新建立。敲低Notch3足以诱导未受损视网膜中的穆勒胶质细胞增殖，并在光损伤期间增强增殖。或者，敲低Notch1a、Notch1b或Notch2会减少光损伤期间增殖细胞的数量，这表明Notch信号在视网膜再生过程中的增殖中也是必需的。我们还敲低了斑马鱼Delta和Delta样蛋白（Notch受体的配体），发现deltaB morphant在光损伤的视网膜中增殖细胞数量增加。与Notch3一样，敲低DeltaB足以在无光损伤的情况下诱导穆勒胶质细胞增殖。综上所述，斑马鱼视网膜再生中穆勒胶质细胞增殖的负性调节是由Notch3和DeltaB介导的。
