DLG4 and schizophrenia: Thus, we speculated that three out of these four ultrarare LoF mutations (GRIK1p.Phe24fs, GRIK1p.Thr882fs, and GRIK2p.Arg300Ter) may affect the interaction of PSD95 protein with kainate receptors in the brain and consequently affect synaptic function in patients with schizophrenia.