Polymorphism and Parkinson's Disease-Psychosis: Is there an Association?

Objective: Homer1, a postsynaptic protein coded by the gene, presumably has a role in homeostatic plasticity that dampens neuronal responsiveness when the input activity is too high. polymorphism has been studied in major psychiatric disorders such as schizophrenia. The objective of this study is to investigate if polymorphisms of the gene are associated with psychosis in Parkinson's disease (PD-P).

Methods: One hundred patients with Parkinson's disease (PD) and 100 healthy controls were enrolled consecutively in a PD-P biomarker study at the National Institute of Mental Health and Neurosciences, Bangalore, India. Of the 100 PD patients, 50 had psychosis (PD-P) and 50 did not have psychosis (PD-NP). Two single-nucleotide polymorphisms of (rs4704559 and rs4704560) were analyzed from the DNA isolated from peripheral blood. The allele and genotype frequencies in the PD-P and PD-NP groups were compared.

Results: Analysis of rs4704560 revealed a significant difference in both genotype and allele levels between PD-P and PD-NP groups. There was an overrepresentation of T-allele (42% vs. 16%; < 0.001) and TT genotype (24% vs. 6%; < 0.001) in the PD-P group compared to PD-NP group. There was no significant difference between PD-P and PD-NP groups when various genotypes and allele frequencies related to HOMER1 rs4704559 were compared.

Conclusion: PD-P is probably associated with overrepresentation of T-allele of rs4704560, and larger studies are warranted to confirm our results.