Reactive gliosis in the adult zebrafish retina

In contrast to mammals, zebrafish posses the remarkable ability to regenerate retinal neurons. Damage to the zebrafish retina induces Muller glia to act as stem cells, generating retinal progenitors for regeneration. In contrast, injury in the mammalian retina results in Muller glial reactive gliosis, a characteristic gliotic response that is normally detrimental to vision. Understanding the signaling pathways that determine how Muller glia respond to injury is a critical step toward promoting regeneration in the mammalian retina. Here we report that zebrafish Mier glia exhibit signs of reactive gliosis even under normal regenerative conditions and that cell cycle inhibition increases this response. Persistently reactive Muller glia increase their neuroprotective functions, temporarily saving photoreceptors from a cytotoxic light lesion. However, the absence of a sustained proliferation response results in a significant inhibition of retinal regeneration. Interestingly, when cell cycle inhibition is released, a partial recovery of regeneration is observed. Together, these data demonstrate that zebrafish Muller glia possess both gliotic and regenerative potential. (C) 2015 Elsevier Ltd. All rights reserved.