Transcriptomic comparison of two selective retinal cell ablation paradigms in zebrafish reveals shared and cell-specific regenerative responses

Retinal Müller glia (MG) can act as stem-like cells to generate new neurons in both zebrafish in mice. In zebrafish, retinal regeneration is innate and robust, resulting in the replacement of lost neurons and restoration of visual function. In mice, exogenous stimulation of MG is required to reveal a dormant and, to date, limited regenerative capacity. Zebrafish studies have been key in revealing factors that promote regenerative responses in the mammalian eye. Increased understanding of how the regenerative potential of MG is regulated in zebrafish may therefore aid efforts to promote retinal repair therapeutically. Developmental signaling pathways are known to coordinate regeneration following widespread retinal cell loss. In contrast, less is known about how regeneration is regulated in the context of retinal degenerative disease, i.e., following the loss of specific retinal cell types. To address this knowledge gap, we compared transcriptomic changes between two selective cell ablation paradigms, targeted loss of rod photoreceptors or bipolar cells. Our study spanned twelve time points encompassing the entire degenerative and regenerative process of each targeted cell type. 2,531 differentially expressed genes (DEGs) were identified. Interestingly, the majority of DEGs were paradigm specific, including during MG activation phases, suggesting the nature of the injury/cell loss informs the regenerative process from initiation onward. For example, early modulation of Notch signaling was implicated in the rod but not bipolar cell ablation paradigm. Components of JAK/STAT signaling were activated in both paradigms but were more strongly induced during rod cell regeneration. We functionally validated the role of JAK/STAT signaling during rod cell regeneration using CRISPR/Cas9-based knockdown of stat3 which inhibited both MG proliferation and rod cell regeneration kinetics. Additionally, although more than a third of all DEGs are implicated as immune-system regulators, individual immune-related factors were largely paradigm specific. These data support emerging evidence that discrete “fate-biased” regenerative processes follow from selective retinal cell loss. Microarrays were used to follow gene expression changes in the eyes of fish following either rod or bipolar specific induced death. Larval fish were screened for transgenic expression and collected following ablation at times from 0-240h post ablation for RNA extraction and hybridization on Affymetrix microarrays.