Associations between depression severity and purinergic receptor P2RX7 gene polymorphisms

Background: Major depressive disorder (MDD) and bipolar disorder (BPD) have significant genetic predisposition. The P2RX7 gene (coding for P2X7 purinergic receptor) has been suggested as a susceptibility gene for both MDD and BPD. In the current study the genetic effects of rs2230912 (Gln460Arg) and rs1653625 (located in the 3' untranslated region of the P2RX7 gene) were explored in mood disorders. Methods: Genotype frequencies were established in 315 patients (195 with MDD and 120 with BPD diagnosis) and in 373 controls. Depression severity was assessed by the clinician-rated Montgomery-Asberg Depression Rating Scale (MADRS) and by the self-report Hospital Anxiety and Depression Scale (HADS). Results: In the case-control analysis we did not find any significant differences between genotype frequencies of either BPD or MDD cases and controls. However, BPD patients carrying at least one rs2230912 G-allele scored higher on both MADRS and HADS-depression scale (nominal p-value was 0.028 and 0.003, respectively). The rs1653625 AA genotype was also associated with higher depression scores in the BPD group (nominal p-value of MADRS: 0.019, HADS-depression: 0.017). After correction for multiple testing, the association between rs2230912 and HADS-depression score remained significant in the BPD group (p < 0.006); this genetic effect explained 9% of the variance (partial eta(2)=0.09). In the MDD group we did not find any significant genetic effect. Limitations: The relatively small number of BPD patients warrants for a replication study. Conclusions: Our genetic association study supports the association between P2RX7 gene and severity of depressive symptoms in BPD patients. (C) 2013 Elsevier B.V. All rights reserved.