Fig. 4. Retinal phenotype of Crb1^-/- mice exposed to cycled light (12 hours dark/12 hours 100 lux). (A-C) Different stages of degeneration in 3-month-old Crb1^-/- retinas. (A) Start of degeneration in which some PRCs protrude through the OLM and ingress into the OPL. (B) More PRCs are involved in larger ingression areas and PRCs ingressed onto the INL. (C) Ingressed PRCs re-aggregate into half rosette structures, and form new inner segments and an OLM (arrow). (D,E) Morphology of 6-month-old Crb1^-/- retinas. (D) Formation of a giant half rosette of PRCs with outgrown inner segments. Note the presence of cells from the INL, possibly MGC nuclei, close to the edges of and inside this structure (arrowheads). (E) Complete degeneration of the ONL, presence of ghost structure (arrow) and ingression of RPE into the retina (arrowheads). Scale bars: 100 µm.