ITPR1 and cerebellar ataxia: ITPR1 encodes a receptor for inositol 1,4,5-triphosphate (IP3), which mediates Ca2+ release from the endoplasmic reticulum upon stimulation, and mutations in ITPR1 are the cause of spinocerebellar ataxias [72]; thus, the role of ITPR1 in the nervous system is well-established.