9692ab76-af89-4743-90fc-31da7a6a4faa
title
A novel  A/G SNP in the -615th position  of the  dopamine D4 receptor  promoter region as a source of misgenotyping of the  -616 C/G  SNP.
a2f3fb68-0941-4776-ac11-8bd49b2daf51
abstract
The polymorphic 5' upstream region of the  dopamine D4 receptor  ( DRD4 ) gene containing several single nucleotide polymorphisms (SNPs) has recently become a focus of association studies in psychiatric genetics. Most SNP genotyping methods are based on the two-step procedure of restriction fragment length polymorphism (RFLP). An alternative technique is a single-step method of allele-specific amplification (ASA), previously introduced for genotyping the  -521 C/T  SNP of the  DRD4  promoter region and applied here for the  -616 C/G  SNP. Parallel genotyping of individuals with the novel ASA method and the conventionally used Ava II RFLP showed a potential underestimation of the  -616 GG  genotype frequency by the conventional method. Sequencing the dubious samples clearly demonstrated a novel  A/G SNP at the -615th  position influencing the Ava II digestion and thus resulting in misgenotyping. To avoid this problem, we introduced the Sau96 I RFLP for the  -616 C/G  genotyping as this restriction enzyme is not sensitive for the  -615 A/G  sequence variation. Allele ( -616 G  = 0.48;  -616 C  = 0.52) and genotype ( -616 GG  = 0.25;  -616 GC  = 0.46;  -616 CC  = 0.29) frequencies were determined by both the novel ASA and the Sau96 I methods. The obtained genotype frequencies corresponded to the Hardy-Weinberg equilibrium in our healthy Caucasian sample (N = 534, P = 0.168). Using these methods, no association was found between the  -616 C/G  SNP and personality factors of Cloninger's temperament and character inventory (N = 153) in our population.