Association Study of the SLC1A2 (rs4354668), SLC6A9 (rs2486001), and SLC6A5 (rs2000959) Polymorphisms in Major Depressive Disorder

The membrane excitatory amino acid transporter 2 (EAAT2), encoded by SLC1A2, is responsible for the uptake and redistribution of synaptic glutamate. Glycine modulates excitatory neurotransmission. The clearance of synaptic glycine is performed by glycine transporters encoded by SLC6A9 and SLC6A5. Higher synaptic glycine and glutamate levels could enhance the activation of NMDA receptors and counteract the hypofunction of glutamate neurotransmission described in major depressive disorder (MDD). The aim of the study was to assess whether polymorphisms of SCL1A2 (rs4354668), SCL6A5 (rs2000959), and SCL6A9 (rs2486001) play a role in the development of MDD and its clinical picture in the Polish population. The study group consisted of 161 unrelated Caucasian patients with MDD and 462 healthy unrelated individuals for control. Polymorphisms were genotyped with PCR-RLFP assay. We observed that the frequency of genotype CC and allele C of the SLC1A2 polymorphism rs4354668 was twice as high in the MDD group as in control. Such differences were not detected in SLC6A5 and SLC6A9 polymorphisms. No statistically significant association of the studied SNPs (Single Nucleotide Polymorphisms) on clinical variables of the MDD was observed. The current study indicates an association of polymorphism rs4354668 in SCL1A2 with depression occurrence in the Polish population; however, further studies with larger samples should be performed to clarify these findings.