Referenced in: none

Automatically associated channels: Nav1.5 , Nav1.8 , Nav1.9

Title: Structure of the sodium channel gene SCN11A: evidence for intron-to-exon conversion model and implications for gene evolution.

Authors: Sulayman D Dib-Hajj, Lynda Tyrrell, Stephen G Waxman

Journal, date & volume: Mol. Neurobiol., 2002 Oct-Dec , 26, 235-50

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/12428758

Abstract
Exon/intron boundaries in the regions encoding the trans-membrane segments of voltage-gated Na channel genes are conserved, supporting their proposed evolution from a single domain channel, while the exons encoding the cytoplasmic loops are less conserved with their evolutionary heritage being less defined. SCN11A encodes the tetrodotoxin-resistant (TTX-R) sodium channel Nav1.9a/NaN, which is preferentially expressed in nociceptive primary sensory neurons of dorsal root ganglia (DRG) and trigeminal ganglia. SCN11A is localized to human chromosome 3 (3p21-24) close to the other TTX-R sodium channel genes SCN5A and SCN10A. An alternative transcript, Nav1.9b, has been detected in rat DRG and trigeminal ganglion. Nav1.9b is predicted to produce a truncated protein due to a frame-shift, which is introduced by the new sequence of exon 23c (E23c). In human and mouse SCN11A, divergent splicing signals prevent utilization of E23c. Unlike exons 5A/N in genes encoding TTX-sensitive sodium channels, which appear to have resulted from exon duplication, E23c might have evolved from the conversion of an intronic sequence. Although a functional role for Nav1.9b has yet to be established, intron-to-exon conversion may represent a mechanism for ion channels to acquire novel features.