PDE6D and Joubert syndrome: Consistent with the previous observation in human fibroblasts derived from a Joubert syndrome patient with a 42-amino acid in-frame deletion (Thomas et al., 2014) and the relatively normal development of the photoreceptor outer segment in Pde6d−/− mice (Zhang et al., 2007), complete loss of Pde6d function did not cause any ciliogenesis defect (Fig. 3; n>100 in each cell line).