PRPF31 and retinal degeneration: Regarding the other cell types present in retinal organoids, immunolabeling with bipolar cell (VSX2, PKCα) and Müller glial cell (CRALBP) markers revealed no differences between PRPF31-mutated and Control organoids (Fig. 5e), thus confirming that the retinal degeneration due to PRPF31 mutations is restricted to photoreceptors.