Fig. 1

RGC development, subtype specification, differentiation, and regeneration. Retinal progenitor cells (RPC), RGC precursors, and mature RGCs can be defined and isolated from various species. Neuronal replacement therapies will be advanced by defining the RGC subtypes affected by various optic neuropathies and developing methods to target donor RGC maturation into specific subtypes. In vitro systems serve as a source of RGCs for cell replacement therapies and are useful for screening factors that promote RGC differentiation, maturation, and survival. RGCs can be cultured in monolayers, 3D retinal organoids, retinospheres, and assembloids. Through direct reprogramming in vivo and in vitro, Müller glia can also be a source for newborn mammalian RGCs, and factors that promote neuron reprogramming can be identified. While RGCs can be isolated from various species, RGC repopulation through reprogramming is currently only studied in mice, but in vitro studies can be performed using human samples