Type I inositol 1,4,5-trisphosphate 5-phosphatase (INPP5A) catalyzes the removal of the 4-position phosphate from inositol 3,4-bisphosphate (Ins(3,4)P2), inositol 1,3,4-triphosphate (Ins(1,3,4)P3), and phosphatydlinositol 3,4-bisphosphate (PtdIns(3,4)P2) []. In mice, a frame shift mutation in the INPP5A gene causes the weeble mutant phenotype, which is characterised by an early onset cerebellar ataxia and neurodegeneration, especially apparent in the Purkinje cells [].
