The first evidence linking dysregulation of axoneme glutamylation to human ciliopathies was the discovery that causative mutations in the centrosomal protein CEP41, which is mutated in Joubert syndrome, does not affect cilia biogenesis but disrupts the proper ciliary entry of the glutamylase TTLL6, which leads to dramatically reduced polyglutamylation along the axoneme in primary cultured fibroblasts isolated from Joubert syndrome patients (Lee et al., 2012). Here, TTLL6 is linked to Joubert syndrome.