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.