The importance of the 5′-phosphatase activity for ciliary function is underscored by the finding that INPP5E is mutated in Joubert syndrome, a ciliopathy characterized by motor and intellectual disabilities18, 19, 20, and that the gene mutated in the OCRL (Oculocerebrorenal) or Lowe syndrome also encodes an inositol polyphosphate 5′-phosphatase21, 22. This evidence concerns the gene INPP5E and Joubert syndrome.