In Silico AnalysisGABRB3, located o

In Silico AnalysisGABRB3, located on chromosome 15q11.2-q12, spans almost 230 kb (UCSC Genome Browser, March 2006).The mRNA of GABRB3 consists of nine exons. Two alternative first exons, exon 1a and exon 1, encode the signal peptides of GABRB3.31 Exon 1a to exon 3 spans a 1.4 kb genomic region (GenBank accession number L04311) and contains a GC-rich (55%–80%) region with high contentof CpG islands. The P11S, S15F, and G32R missense mutations reside in evolutionarily conserved amino acid sequences of exon 1a and exon 2 (Figure 4A). All missense mutations are predicted to have the same cleavage site as the wild-type, cleaved between Gly22 and Ser23 amino acids as predicted by software programs Signal P 3.1 and Signal CF (Figure 4B). The G32R missense mutation is also predicted to have the same cleavage site as the wildtype pre-peptide, GABRB3 protein isoform 1 precursor that is translated from the exon 1 mRNA, namely GABRB3 transcript variant 1 (NM_000814). On the basis of the predicted cleavage site, we calculate the location of the G32R mutation in exon 2 to occur at position 10 fromthe N terminus of the mature polypeptide. This polypeptide is produced from the isoform 2 precursor translated by exon 1a mRNA, namely GABRB3 transcript variant 2 (NM_021912). The secondary structure of all mutations can be predicted to show significant changes in secondarystructure, according to the software GOR4 IV (Figure 4C).