Lee Jiwoon, Lee Bum-Kyu, Gross Jeffrey M
Departments of Ophthalmology and Developmental Biology, Louis J. Fox Center for Vision Restoration, The University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA.
Department of Biomedical Sciences, Cancer Research Center, University at Albany, State University of New York, Rensselaer, New York, USA.
Glia. 2023 Dec;71(12):2866-2883. doi: 10.1002/glia.24457. Epub 2023 Aug 16.
The zebrafish retina possesses tremendous regenerative potential. Müller glia underlie retinal regeneration through their ability to reprogram and generate multipotent neuronal progenitors that re-differentiate into lost neurons. Many factors required for Müller glia reprogramming and proliferation have been identified; however, we know little about the epigenetic and transcriptional regulation of these genes during regeneration. Here, we determined whether transcriptional regulation by members of the Bromodomain (Brd) family is required for Müller glia-dependent retinal regeneration. Our data demonstrate that three brd genes were expressed in Müller glia upon injury. brd2a and brd2b were expressed in all Müller glia and brd4 was expressed only in reprogramming Müller glia. Utilizing (+)-JQ1, a pharmacological inhibitor of Brd function, we demonstrate that transcriptional regulation by Brds plays a critical role in Müller glia reprogramming and regeneration. (+)-JQ1 treatment prevented cell cycle re-entry of Müller glia and the generation of neurogenic progenitors. Modulating the (+)-JQ1 exposure window, we identified the first 48 h post-injury as the time-period during which Müller glia reprogramming occurs. (+)-JQ1 treatments after 48 h post-injury had no effect on the re-differentiation of UV cones, indicating that Brd function is required only for Müller glia reprogramming and not subsequent specification/differentiation events. Brd inhibition also prevented the expression of reprogramming genes like ascl1a and lepb in Müller glia, but not effector genes like mmp9, nor did it affect microglial recruitment after injury. These results demonstrate that transcriptional regulation by Brds plays a critical role during Müller glia-dependent retinal regeneration in zebrafish.
斑马鱼视网膜具有巨大的再生潜力。穆勒胶质细胞是视网膜再生的基础，它们能够重新编程并产生多能神经元祖细胞，这些祖细胞会重新分化为丢失的神经元。已经确定了穆勒胶质细胞重新编程和增殖所需的许多因素；然而，我们对再生过程中这些基因的表观遗传和转录调控知之甚少。在这里，我们确定了溴结构域（Brd）家族成员的转录调控是否是穆勒胶质细胞依赖性视网膜再生所必需的。我们的数据表明，损伤后三个brd基因在穆勒胶质细胞中表达。brd2a和brd2b在所有穆勒胶质细胞中表达，而brd4仅在重新编程的穆勒胶质细胞中表达。利用Brd功能的药理抑制剂（+）-JQ1，我们证明Brd的转录调控在穆勒胶质细胞重新编程和再生中起关键作用。（+）-JQ1处理可防止穆勒胶质细胞重新进入细胞周期并阻止神经源性祖细胞的产生。通过调节（+）-JQ1的暴露窗口，我们确定损伤后的前48小时是穆勒胶质细胞重新编程发生的时间段。损伤后48小时进行（+）-JQ1处理对紫外线锥细胞的重新分化没有影响，这表明Brd功能仅对穆勒胶质细胞重新编程是必需的，而对随后的细胞特化/分化事件则不是必需的。Brd抑制还可阻止穆勒胶质细胞中ascl1a和lep等重编程基因的表达，但不会阻止效应基因如mmp9的表达，也不会影响损伤后小胶质细胞的募集。这些结果表明，Brd的转录调控在斑马鱼穆勒胶质细胞依赖性视网膜再生过程中起关键作用。
