Polymorphism of Exon 1 of Dopamine Receptor D3 (DRD3) gene and Exon 2 of 5-hydroxytryptamine type 2a (HTR2A) in Schizophrenia Baghdad Patients Sample

Abstract

The aim of this study is to investigate the association between polymorphisms Exon1 of Dopamine Receptor D3 (DRD3) receptor and Exon 2 of  5-hydroxytryptamine type 2a (HTR2A) genes and schizophrenia patients from Baghdad Iraq. To achieve this goal, blood samples were collected from 50 patients with schizophrenia (25 samples of male and 25 samples of female) and 25 samples of healthy individual, DNA was isolated and the DRD3 receptor and HTR2A genes were amplified by using specific primers for exon1 and exon 2 of this genes, then sequencing of nucleic acid of genes was performed by machine is AB13730XL, (Applied Biosystem, Macro gen company, USA). The DNA sequencing results of flank sense of DRD3 receptor and HTR2A genes from healthy individual was found to be compatible 100% with wild type of Homo sapiens from the Gene Bank, the DNA sequencing results of flank sense of DRD3 receptor from 50 cases schizophrenia patients was found to be compatible 99%  and score 398 and expect 0.0 with the wild type sequences of gene bank, and the differences may be attributed to one transition mutations (G/A), at position 1804 of exon 1. It is a missense mutation that leads to changes in amino acid from Serine (S) to Glysine (G). Our results showed that the incidence of G/A mutation was highly significant (X2=100, P<0.01). In total, 8% of Shizophreina patients had two transition mutation +1804 G/A and +1830 G/A single nucleotide polymorphism, and compatibility 99%, score 397 and expect 0.0 with the wild type sequences of gene bank. The +1830 G/A SNP was silent mutation which result change of codon from GCG to GCA (Alanine to Alanine). However, the DNA sequencing results of flank sense HTR2A genes from 50 cases schizophrenia patients was found to be compatible 99%  and score 259 and expect 5e-132 with the wild type sequences of gene bank, there was no significant correlation between shizopherina and incidence of transition mutation G/A (Serine to Serine) at nucleotide 156 of exon 2 HTR2A gene (X2=0.055, P>0.05). In conclusion, our case study suggests that the 1804 A/G SNP of the DRD3 gene is strongly associated with genetic susceptibility to schizophrenia in the Baghdad / Iraqi population.