Furthermore, the associated gene region with both impulsiveness and LAPS comprises intron 3 to intron 4. No coding variation has been reported for exon 4. However, isoforms of human GABRA2 mRNA where exon 4 (68 bp) has been spliced out were discovered in many brain regions. The product of this isoform would be a truncated protein (non-functional) of only 66 amino acids due to the creation of a stop codon (Tian et al., 2005). Notably, one of the associated SNPs rs279827 is located next to the acceptor splice site (Tian et al., 2005). It is not known if SNP rs279827 would have an effect on splicing. But it is intriguing to note that of eleven SNPs in the GABRA2 gene tested, the SNP near this splice site is the most strongly associated. The haplotype analysis comprising the SNPs in the proximal block (Figure 1) shows similar results as the individual SNPs supporting the notion that in this study the haplotype does not unveil a better not genotyped SNP in the region or independent contribution of the genotyped SNPs.
