Abstract 3090: Missense Mutations in SNTA1-Encoded Syntrophin Alpha and Sudden Infant Death Syndrome
An estimated 10–15% of sudden infant death syndrome (SIDS) may be channelopathic with approximately half of the SIDS-associated channel mutations involving the sodium channel (NaV1.5) macromolecular complex. Recently, SNTA1, which encodes the sodium channel interacting protein (ChIP), syntrophin alpha, was discovered to be a novel long QT syndrome (LQTS) susceptibility gene (LQT12) with mutations causing increased late sodium current secondary to increased s-nitrosylation of the sodium channel’s alpha subunit. Therefore, SNTA1 is a plausible candidate gene for SIDS. In this IRB-approved study, mutational analysis of SNTA1’s eight translated exons was performed using PCR, DHPLC, and direct DNA sequencing of DNA derived from 286 SIDS cases (112 females, 197 white, average age 2.9 ± 1.9 months, range 3 days -12 months). The anonymized study design precluded a determination of mutation status as familial or sporadic. Overall, 8/286 cases of SIDS harbored missense mutations in SNTA1 that were absent in 800 reference alleles. Six distinct, rare SNTA1 missense mutations were detected in 7/112 (6.25%) female infants but only 1/174 (0.6%) male infants (p < 0.01). Comprehensive open reading frame analysis of all 800 reference alleles also revealed rare genetic variants in 1% of the control subjects. A common pair of non-synonymous single nucleotide polymorphisms (P74L/A257G), with a heterozygous frequency of 1%, was identified similarly in both cases and controls. This study provides the first molecular evidence implicating mutations in SNTA1 as a novel pathogenic substrate for channelopathic SIDS. However, given the ~1% background rate of rare variants in controls, mechanistic studies of each putative SIDS-associated SNTA1 mutation will be necessary to confirm that the mutant ChIP yields a functionally perturbed NaV1.5 macromolecular complex akin to the investigations that established SNTA1 as a novel LQTS-susceptibility gene.