The regeneration-responsive element careg monitors activation of Müller glia after MNU-induced damage of photoreceptors in the zebrafish retina

Abstract

In contrast to mammals, zebrafish can regenerate their damaged photoreceptors. This capacity depends on the intrinsic plasticity of Müller glia (MG). Here, we identified that the transgenic reporter careg, a marker of regenerating fin and heart, also participates in retina restoration in zebrafish. After methylnitrosourea (MNU) treatment, the retina became deteriorated and contained damaged cell types including rods, UV-sensitive cones and the outer plexiform layer. This phenotype was associated with the induction of careg expression in a subset of MG until the reconstruction of the photoreceptor synaptic layer. Single-cell RNA sequencing (scRNAseq) analysis of regenerating retinas revealed a population of immature rods, defined by high expression of rhodopsin and the ciliogenesis gene meig1, but low expression of phototransduction genes. Furthermore, cones displayed deregulation of metabolic and visual perception genes in response to retina injury. Comparison between careg:EGFP expressing and non-expressing MG demonstrated that these two subpopulations are characterized by distinct molecular signatures, suggesting their heterogenous responsiveness to the regenerative program. Dynamics of ribosomal protein S6 phosphorylation showed that TOR signaling became progressively switched from MG to progenitors. Inhibition of TOR with rapamycin reduced the cell cycle activity, but neither affected careg:EGFP expression in MG, nor prevented restoration of the retina structure. This indicates that MG reprogramming, and progenitor cell proliferation might be regulated by distinct mechanisms. In conclusion, the careg reporter detects activated MG, and provides a common marker of regeneration-competent cells in diverse zebrafish organs, including the retina.

Fishing Innate Immune System Properties through the Transcriptomic Single-Cell Data of Teleostei

“…This experiment is suitable for the reconstruction of the properties of glial cells (3/6), macrophages (3/6), B lymphocytes (2/6), and T lymphocytes (2/6) and presents clusters of dendritic cells, NK-like cells, and HSPCss. Also, we found other scRNAseq experiments including glial cells from the telencephalon (4): GSE161834 [88], GSE179134 [89], GSE212314 [90], GSE225863 [91]; microglia (2): GSE120467 [92], GSE164772 [93]; neuronal retina (2): GSE202212 [94], GSE226373 [95]; radial glia (1): GSE134705 [84]; and retinal glia: GSE135406 [96]. Additionally, we found scRNAseq data from the peripheral nervous system.…”

Skeletal muscle regeneration after extensive cryoinjury of caudal myomeres in adult zebrafish

“…In mice, TOR signaling is essential for the regulation of myogenic gene expression in muscle stem cells 86 – 90 , suggesting a conserved role of this pathway among vertebrates. In adult zebrafish, TOR is required for heart and retina regeneration 91 , 92 . Further studies will elucidate the molecular mechanisms underlying the rapamycin-mediated impairment of muscle regeneration.…”

“…In case of PCNA immunostaining, antigen retrieval was performed as previously described 91 . Briefly, the sections were permeabilized for 10 min in 0.3% PBST and then subjected to a heat-mediated epitope retrieval step.…”