Investigation of the functional vesicular monoamine transporter 1 (VMAT1/SLC18A1) Thr136Ile gene variant in bipolar disorder

Background and objectives Bipolar disorder (BD) is an episodic and recurrent mood disturbance ranging from mania to severe depression. Because of the heterogeneity of psychiatric disorders, enlightening the possible molecular risk drivers is crucial. Vesicular monoamine transporter 1 (VMAT1) is an important candidate gene to study the underlying molecular mechanisms in BD pathogenesis since it has a significant role in the packaging of monoaminergic neurotransmitters into presynaptic storage vesicles. The aim of this study was to ascertain whether functional and evolutionarily important variant of VMAT1 gene (Thr136Ile (rs1390938)) would affect the susceptibility of the individuals to BD in a Turkish population. Method One hundred twenty BD patients and one hundred one healthy control individuals were recruited for the study. Samples were genotyped using PCR-RFLP method to detect VMAT1 gene variant (Thr136Ile (rs1390938)). Results Contrary to our expectations, VMAT1 Thr136Ile (rs1390938) gene variant was not associated with BD in our population. There was also no relationship between VMAT1 genotypes and some clinically significant parameters in BD patients. Conclusion Our data showed no association between VMAT1 Thr136Ile (rs1390938) and BD in Turkish population. We strongly recommend the analysis of this variant in other populations to draw a precise conclusion about the role of this variant in bipolar disorder. Further large-scale research for the other variants of VMAT1 is also required to clarify the strong hypothesis focused on VMAT1 variants in the development of neuropsychiatric disorders.