The INS-IGF2 transcript in schizophrenia or related psychosis: tendency towards association between an INS-IGF2 SNP and schizoaffective disorder, and one report of a patient with this SNP and diagnoses of both schizoaffective disorder and polycystic ovary syndrome.

OBJECTIVES: We found earlier increased antibody reactivity against the insulin receptor-A and insulin-like growth factor 1 receptor and their ligands (insulin and insulin-like growth factor 1) in patients with schizophrenia or related psychosis. Hypothetically, a newly-identified insulin-insulin-like growth factor 2 (INS-IGF2) protein may be a ligand to these receptors too, and recently, significantly higher antibody reactivity was found against a part of this protein in patients with schizophrenia or related psychosis in partial than full symptom remission. The aim of this study was to map the region of the INS-IGF2 transcript that codes this part of the protein in schizophrenia and related psychosis susceptibility. MATERIAL AND METHODS: The present INS-IGF2 region was DNA-sequenced by the Sanger method in a study population, consisting of 94 patients with schizophrenia, 11 patients with schizoaffective disorder and 58 controls. RESULTS: Two novel SNPs were identified solely in patients, but not in controls. Tendencies towards overall differences in genotype- and allele frequencies between patients with schizophrenia or schizoaffective disorder and controls were found for SNP no 1 (p = 0.067 and p = 0.067, respectively), with the G/A-genotype and G-allele appearing more frequently in patients with schizoaffective disorder. The patient with SNP no 1 was diagnosed with both schizoaffective disorder and polycystic ovary syndrome, and the patient with SNP no 2 was diagnosed with schizophrenia, paranoid type with affective features. CONCLUSION: The findings in this exploratory study suggest that SNPs in the INS-IGF2 transcript may be associated with psychosis, specifically with schizoaffective disorder, and warrant replication in larger samples.