AHI1 and Joubert syndrome: Ahi1, Abelson helper integration site 1, encodes a cytoplasmic adaptor protein [34]. It is primarily expressed in the CNS including the spinal cord [35]. Mutation of this gene causes Joubert syndrome, a congenital malformation of the cerebellum and brainstem with axonal decussating abnormalities of the corticospinal tract [35].