A subtle alternative splicing event of the Na(V)1.8 voltage-gated sodium channel is conserved in human, rat, and mouse

The voltage-gated sodium channel subtype Na(V)1.8 (SCN10A) is exclusively expressed in dorsal root ganglia (DRG) and plays a critical role in pain perception. We isolated mRNA from human, rat, and mouse DRGs and screened for alternatively spliced isoforms of the SCN10A mRNA using 454 sequencing. In all three species, we found an event of subtle alternative splicing at a NAGNAG tandem acceptor that results in isoforms including or lacking glutamine 1030 (Na(V)1.8+Q and Na(V)1.8-Q, respectively) within the cytoplasmic loop between domains II and III. The relative amount of Na(V)1.8-Q mRNA in adult DRG was measured with 14.1 +/- 0.1% in humans and 11.2 +/- 0.2% in rats. This is in contrast to an abundance of 64.3 +/- 0.3% in mouse DRG. Thus, the NAGNAG tandem acceptor in SCN10A is conserved among rodents and humans but its alternative usage apparently occurs with species-specific abundance. Analysis of human Na(V)1.8+Q and -Q isoforms in whole-cell patch-clamp experiments after heterologous expression in the neuroblastoma cell line Neuro-2A revealed no obvious impact of the splicing event on channel function.