Department of Neuroscience, College of Medicine, The Ohio State University, Columbus, Ohio, USA.
Center for Gene Therapy, Nationwide Children's Hospital, Columbus, Ohio, USA.
J Comp Neurol. 2022 Jun;530(8):1213-1230. doi: 10.1002/cne.25270. Epub 2021 Dec 15.
The regenerative potential of Müller glia (MG) is extraordinary in fish, poor in chick and terrible in mammals. In the chick model, MG readily reprogram into proliferating Müller glia-derived progenitor cells (MGPCs), but neuronal differentiation is very limited. The factors that suppress the neurogenic potential of MGPCs in the chick are slowly being revealed. Isoforms of Nuclear Factor I (NFI) are cell-intrinsic factors that limit neurogenic potential; these factors are required for the formation of MG in the developing mouse retina and deletion of these factors reprograms MG into neuron-like cells in mature mouse retina. Accordingly, we sought to characterize the patterns of expression of NFIs in the developing, mature and damaged chick retina. In addition, we characterized patterns of expression of NFIs in the retinas of large mammals, pigs and monkeys. Using a combination of single-cell RNA-sequencing (scRNA-seq) and immunolabeling, we probed for patterns of expression. In embryonic chick, levels of NFIs are very low in early E5 (embryonic day 5) retinal progenitor cells (RPCs), upregulated in E8 RPCs, further upregulated in differentiating MG at E12 and E15. NFIs are maintained in mature resting MG, microglia and neurons. Levels of NFIs are reduced in activated MG in retinas treated with NMDA and/or insulin+FGF2, and further downregulated in proliferating MGPCs. However, levels of NFIs in MGPCs were significantly higher than those seen in RPCs. Immunolabeling for NFIA and NFIB closely matched patterns of expression revealed in different types of retinal neurons and glia, consistent with findings from scRNA-seq. In addition, we find expression of NFIA and NFIB through progenitors in the circumferential marginal zone at the far periphery of the retina. We find similar patterns of expression for NFIs in scRNA-seq databases for pig and monkey retinas. Patterns of expression of NFIA and NFIB were validated with immunofluorescence in pig and monkey retinas wherein these factors were predominantly detected in MG and a few types of inner retinal neurons. In summary, NFIA and NFIB are prominently expressed in developing chick retina and by mature neurons and glia in the retinas of chicks, pigs and monkeys. Although levels of NFIs are decreased in chick, in MGPCs these levels remain higher than those seen in neurogenic RPCs. We propose that the neurogenic potential of MGPCs in the chick retina is suppressed by NFIs.
Müller 胶质细胞（MG）的再生潜能在鱼类中非常出色，在鸡中较差，在哺乳动物中极差。在鸡模型中，MG 很容易重新编程为增殖的 Müller 胶质细胞衍生祖细胞（MGPC），但神经元分化非常有限。抑制鸡 MGPC 神经发生潜能的因素正在慢慢被揭示。核因子 I（NFI）的同种型是限制神经发生潜能的细胞内因素；这些因素是发育中小鼠视网膜中 MG 形成所必需的，并且这些因素的缺失可将 MG 重新编程为成熟小鼠视网膜中的神经元样细胞。因此，我们试图描述 NFIs 在发育、成熟和受损鸡视网膜中的表达模式。此外，我们还描述了 NFIs 在大型哺乳动物、猪和猴子视网膜中的表达模式。我们使用单细胞 RNA 测序（scRNA-seq）和免疫标记相结合的方法进行探测。在胚胎鸡中，NFIs 的水平在早期 E5（胚胎第 5 天）视网膜祖细胞（RPC）中非常低，在 E8 RPC 中上调，在 E12 和 E15 分化的 MG 中进一步上调。NFIs 维持在成熟静止的 MG、小胶质细胞和神经元中。用 NMDA 和/或胰岛素+FGF2 处理的视网膜中激活的 MG 中 NFIs 的水平降低，在增殖的 MGPC 中进一步下调。然而，MGPC 中的 NFIs 水平明显高于 RPC 中的水平。NFIA 和 NFIB 的免疫标记与不同类型的视网膜神经元和胶质细胞中揭示的表达模式非常匹配，与 scRNA-seq 的结果一致。此外，我们在视网膜远周边缘的周向边缘区的祖细胞中发现了 NFIA 和 NFIB 的表达。我们在猪和猴子视网膜的 scRNA-seq 数据库中发现了 NFIs 的相似表达模式。NFIA 和 NFIB 的表达通过免疫荧光在猪和猴子视网膜中得到验证，其中这些因子主要在 MG 和少数类型的内视网膜神经元中检测到。总之，NFIA 和 NFIB 在发育中的鸡视网膜中以及在鸡、猪和猴子视网膜中的成熟神经元和胶质细胞中大量表达。尽管 NFIs 的水平在鸡中降低，但在 MGPC 中，其水平仍高于神经发生性 RPC。我们提出，鸡视网膜 MGPC 的神经发生潜能受 NFIs 抑制。
