Similar to our cct5 mutant, cct1, cct2, cct3, cct4 and cct8 mutant zebrafish show retinal degeneration (Berger et al., 2018; Matsuda and Mishina, 2004; Minegishi et al., 2018), suggesting that the cct5/tcf7l1a double mutant phenotype is due to abrogation of TRiC chaperonin function, a conclusion supported by cct3 knockdown in tcf7l1a mutants. This evidence concerns the gene MARVELD2 and retinal degeneration.