Mutations in Arl13b are associated with Joubert syndrome (a ciliopathy), and Arl13b-null animals display a wide range of ciliary defects that compromise ciliogenesis, cilia length extension, ciliary motility and sonic hedgehog signaling (Caspary et al., 2007; Cevik et al., 2010; Duldulao et al., 2009; Larkins et al., 2011; Li et al., 2010; Lu et al., 2015; Sun et al., 2004). This evidence concerns the gene ARL13B and Joubert syndrome.