Exploratory study of selected nucleotide variants in GRIN1, GRIN2A and GRIN2B encoding subunits of the NMDA receptor in a targeted group of schizophrenia patients with chronic cognitive impairment

Background Schizophrenia is a mental disease that affects approximately 1% of the population. Despite over 100 years of research, its pathomechanism has still not been clarified. Cognitive deficits, which are one of the symptomatic dimensions of schizophrenia, usually appear a few years before the first psychotic episode. Therefore, this is why they are probably the clinical manifestation of the primary pathomechanism of schizophrenia. It is also supposed that N-methyl-d-aspartate receptor (NMDA-R) insufficiency in the prefrontal cortex is responsible for cognitive deficits in schizophrenia. The study aimed to examine whether four selected single nucleotide variants in GRIN1, GRIN2A and GRIN2B encoding NMDA-R subunits, of which two have not been tested before, are linked with the selected clinical phenotype of cognitive dysfunction in schizophrenia. Methods The study included the targeted group of 117 patients diagnosed with schizophrenia, all with cognitive deficits and in symptomatic remission. DNA fragments including the studied polymorphisms of the NMDA receptors subunit genes were amplified by polymerase chain reaction and subjected to sequencing. Results The study did not confirm the presence of any of the four selected single nucleotide variants in GRIN1, GRIN2A and GRIN2B subunits of NMDA-R. Conclusions The finding indicates that selected single nucleotide variants in GRIN2A and GRIN2B encoding subunits of the NMDA receptor are not associated with the presence of cognitive deficits in schizophrenia.