GRIK4 and psychotic disorder: Within one family of 21 members, 9 of whom carried a 9p24 deletion and 12 of whom did not, they found elevated expression of glutamate receptor genes – GRIA1, GRIN2A, and GRM8 – and in particular, increased GRIK4 expression in 5 deletion subjects with psychosis compared to 4 deletion subjects without psychosis [53].