Müller glia-microglia cross talk reprograms the Müller glia transcriptome for cell division-related processes during retina regeneration

In the injured zebrafish retina, Müller glia (MG) reprogram their transcriptome and undergo an asymmetric division that produces a multipotent progenitor for retinal repair. Although MG cell division is regulated by microglia, its underlying mechanism remains unknown. Here we report that microglia contribute to MG reprogramming by preferentially stimulating the expression of genes associated with cell division-related processes like chromosome segregation, DNA replication, and mitotic cell cycle. Furthermore, we report that depleting microglia systemically from early development leads to a compensatory immune cell response in the retina. Our studies illustrate the profound effects microglia can have on neighboring cells and support a two-step model of MG reprogramming, where dying neurons initiate and microglia complete this reprogramming process. Overall design: There are two sets/batches of experiments (RS14 and RS19). In the first, all fish are wild-type, and there are four groups with 3 samples each : (1) uninjured-untreated control, (2) needle poke-induced retinal injury treated with PLX3397 (pexidartinib), (3) needle poke-induced retinal injury treated with Z-VAD-FMK (carbobenzoxy-valyl-alanyl-aspartyl-[O-methyl]-fluoromethylketone), and (4) needle poke-induced retinal injury treated with DMSO (Dimethyl sulfoxide). In the second, wild-type and mutant fish are used, with 3 samples per group: (1) uninjured WT control, (2) NMDA-induced retinal injury in WT, (3) NMDA-induced retinal injury in csf1ra-mutants, (4) NMDA-induced retinal injury in csf1rb-mutants, (5) uninjured csf1ra-mutants, (6) uninjured csf1rb-mutants.