We next asked if individual GABAB1 exon and intron expression levels were different in alcoholic brains. GABAB1 has 23 exons and 22 introns based on the RefSeq Genes model (Figure 4). Among the exon and intron RPGM values, intron RPGMs were much smaller than exon expression levels although exon RPGM values vary among individual exons (Figure 6). RPGMs for exons 1 to 6 were much lower than the other exons. This indicates that the GABAB1a splice variant containing all 23 exons cannot represent the overall GABAB1 gene expression even though it is regarded as a major GABAB1 transcript and used for most GABAB1 functional studies (7, 9). Various exon combinations can yield numerous short GABAB1 transcripts, and their combined expression levels are more representative of overall GABAB1 expression.
