GCK and diabetes mellitus: Non-syndromic diabetes can be caused by dominant or recessive mutations in the potassium channel genes KCNJ11 and ABCC8, or the insulin gene (INS), or by recessive mutations in glucokinase gene (GCK); additional neuro-motor and neuro-psychological abnormalities are frequently observed in patients with KCNJ11 and ABCC8 mutations.