Role of dopamin receptor gene polymorphisms (DRD2, Taq1A and Taq1B) in the pathogenesis of glaucoma

Glaucoma is the leading cause of irreversible blindness worldwide. Primary open angle glaucoma (POAG) is the most common type of glaucoma and is characterized by the presence of glaucomatous optic neuropathy in the absence of an identifiable secondary cause. Abnormally elevated intraocular pressure (IOP) is a major risk factor for this disease. It is known that genetic as well as environmental factors are likely to contribute to the phenotype.Dopamine (DA) has been shown to be involved in the regulation of reward, motor activity, mood, memory, prolactin secretion, and vision. Studies indicate that DA is also involved in the regulation of IOP and DA receptors are found in various tissues in the eye, including those which control IOP. Based on these observations it was proposed that D1 receptors mediate an increase and D2 receptors a decrease of IOP.Here we speculated that changes in D2 receptor function due to a polymorphism might be a factor related to elevated IOP in POAG. We examined the role of Taq1A and Taq1B polymorphisms of DRD2 gene in Turkish POAG patients. Ninety nine patients with POAG and 135 control subjects were analysed by polymerase chain reaction restriction fragment length polymorphism. (PCR-RFLP). A significant association was found between DRD2 gene Taq1A polymorphism and POAG. Thus, our data suggest for the first time that Taq1A polymorphism of DRD2 gene might be a risk factor in development of POAG.