The deletion of the nearby residue K2603 (K2563 in human IP3R1) at the cytosolic extension of TM6 has been linked to Gillespie Syndrome and causes dysfunctional IP3R1 channels that are unable to release Ca2+ (Fig. 5)20,21. The gene discussed is ITPR1; the disease is Aniridia - cerebellar ataxia - intellectual disability.