PERIOD3 (PER3) VNTR Variant Associated with Seasonal Pattern and Family History in Bipolar Disorder

Dysregulation of circadian rhythms has been thought to be associated with psychiatric disorders such as bipolar disorder (BD) and depression. We aimed to evaluate the relationship between clinical specifiers of BD, mainly seasonal pattern (SP), and the variable number tandem repeat (VNTR) variant of the PERIOD3 (PER3) gene (rs57875989) in BD patients by comparing genotype distributions with healthy controls considering clinical parameters.

A sample of 98 BD patients and 97 healthy volunteers were included in the study. The Clinical Interview for DSM-IV Axis-I Disorders (SCID-I) was administered to all participants. The patients were evaluated with some scales (Sociodemographic and Clinical Data Form, The Young Mania Rating Scale (YMRS), the Hamilton Depression Rating Scale (HAM-D), and The Clinical Global Impression Scale (CGI)) in terms of clinical features and symptom severity. Blood samples were obtained from participants to isolate their DNA. PCR-RFLP was used to determine the PER3 gene variant.

The PER3 genotype (4/4, 4/5, 5/5) distribution of BD was found to be significantly different from the control group. There was a statistically significant difference in the PER3 genotype distribution between BD patients with SP and BD patients without SP. Again, the PER3 allele (4, 5) distributions of BD patients with the SP were statistically different from the control group. The BD patients' PER3 genotype distributions with a family history of BD were significantly different from the BD patients without family history or control group.

It was found that the VNTR variant of the PER3 gene (rs57875989) may be associated with the SP and family history of BD as well as the BD itself. Further studies with the VNTR variant of the PER3 gene (rs57875989) in different ethnic populations are also required to determine these polymorphisms' exact role in BD.