Impulsivity is a personality trait of high impact and is connected with several 
types of maladaptive behavior and psychiatric diseases, such as attention 
deficit hyperactivity disorder, alcohol and drug abuse, as well as pathological 
gambling and mood disorders. Polymorphic variants of the SNAP-25 gene emerged as 
putative genetic components of impulsivity, as SNAP-25 protein plays an 
important role in the central nervous system, and its SNPs are associated with 
several psychiatric disorders. In this study we aimed to investigate if 
polymorphisms in the regulatory regions of the SNAP-25 gene are in association 
with normal variability of impulsivity. Genotypes and haplotypes of two 
polymorphisms in the promoter (rs6077690 and rs6039769) and two SNPs in the 3' 
UTR (rs3746544 and rs1051312) of the SNAP-25 gene were determined in a healthy 
Hungarian population (N = 901) using PCR-RFLP or real-time PCR in combination 
with sequence specific probes. Significant association was found between the T-T 
3' UTR haplotype and impulsivity, whereas no association could be detected with 
genotypes or haplotypes of the promoter loci. According to sequence alignment, 
the polymorphisms in the 3' UTR of the gene alter the binding site of 
microRNA-641, which was analyzed by luciferase reporter system. It was observed 
that haplotypes altering one or two nucleotides in the binding site of the seed 
region of microRNA-641 significantly increased the amount of generated protein 
in vitro. These findings support the role of polymorphic SNAP-25 variants both 
at psychogenetic and molecular biological levels.