Figure 5

Midkine expression in zebrafish retinal regeneration. A: Cone photoreceptors are immunolabelled (red signal) in an unlesioned retina. B: Photoreceptors are nearly completely killed following exposure to a photolytic lesion. C: In situ hybridization showing that mdka is expressed in proliferating photoreceptor progenitors (pink label) following photoreceptor death. The mdka message co-localizes with antibody staining for bromodeoxyuridine (BrdU, green signal). D: Fourteen days following the onset of a photolytic lesion, rod (not shown) and cone photoreceptors (red signal) are regenerated. E: Timeline of the different processes that occur in the adult zebrafish retina after light-induced damage and the proliferative response of Müller glia. The pink colour represents the onset and duration of mdka expression in Müller glia and photoreceptor progenitors. Scale bar = 25 μm (C) and 50μm (A, B and D). GCL, ganglion cell layer; INL, inner nuclear layer; ONL, outer nuclear layer; dpl: days post-lesion.