CEP290 and Joubert syndrome: The Cep290 and Cc2d2a proteins colocalize to the transition zone and are two components of a larger MKS complex.38, –40 Mutations in those genes also lead to JBTS in humans.41,42 Using a rabbit polyclonal antibody against the N-terminus of Cep290, we detected punctate immunoreactivity in the region consistent with the connecting cilium of wild-type and ahi1lri46 mutants (Figs. 9E, 9F).