Abelson helper integration site 1 (Ahi-1) is highly expressed in the most primitive normal hematopoietic cells, in brain neurons and in kidney. Ahi-1 is a unique protein with a SH3 domain, multiple SH3 binding sites and a WD40-repeat domain, which are all known to be important mediators of protein–protein interactions. Defects in Ahi-1 are the cause of Joubert syndrome type 3 (JBTS3).