Molecular and Functional Characterization of Novel Glycerol-3-Phosphate Dehydrogenase 1–Like Gene ( GPD1-L ) Mutations in Sudden Infant Death Syndrome

Abstract

Background-Autopsy-negative sudden unexplained death, including sudden infant death syndrome, can be caused by cardiac channelopathies such as Brugada syndrome (BrS). Type 1 BrS, caused by mutations in the SCN5A-encoded sodium channel, accounts for Ϸ20% of BrS. Recently, a novel mutation in the glycerol-3-phosphate dehydrogenase 1-like gene (GPD1-L) disrupted trafficking of SCN5A in a multigenerational family with BrS. We hypothesized that mutations in GPD1-L may be responsible for some cases of sudden unexplained death/sudden infant death syndrome. Methods and Results-Using denaturing high-performance liquid chromatography and direct DNA sequencing, we performed comprehensive open-reading frame/splice site mutational analysis of GPD1-L on genomic DNA extracted from necropsy tissue of 83 unrelated cases of sudden unexplained death (26 females, 57 males; average age, 14.6Ϯ10.7 years; range, 1 month to 48 years). A putative, sudden unexplained death-associated GPD1-L missense mutation, E83K, was discovered in a 3-month-old white boy. Further mutational analysis was then performed on genomic DNA derived from a population-based cohort of 221 anonymous cases of sudden infant death syndrome (84 females, 137 males; average age, 3Ϯ2 months; range, 3 days to 12 months), revealing 2 additional mutations, I124V and R273C, in a 5-week-old white girl and a 1-month-old white boy, respectively. All mutations occurred in highly conserved residues and were absent in 600 reference alleles. Compared with wild-type GPD1-L, GPD1-L mutations coexpressed with SCN5A in heterologous HEK cells produced a significantly reduced sodium current (PϽ0.01). Adenovirus-mediated gene transfer of the E83K-GPD1-L mutation into neonatal mouse myocytes markedly attenuated the sodium current (PϽ0.01). These decreases in current density are consistent with sodium channel loss-of-function diseases like BrS. Conclusions-The present study is the first to report mutations in GPD1-L as a pathogenic cause for a small subset of sudden infant death syndrome via a secondary loss-of-function mechanism whereby perturbations in GPD1-L precipitate a marked decrease in the peak sodium current and a potentially lethal BrS-like proarrhythmic substrate. (Circulation.

Properties of WT and mutant hERG K+ channels expressed in neonatal mouse cardiomyocytes

“…Compared with adult mouse cardiomyocytes, neonatal mouse cardiomyocytes lack transverse tubules, which may have an advantage in voltage-clamp experiments (27). Neonatal mouse cardiomyocytes have been used as a model for ion channel expression, including for the Na ϩ channel Nav1.5 (39,44), Tand L-type Ca 2ϩ channels (17,21), the K ϩ channel Kv4.2 (18), and the pacemaker HCN channel (9). The study of WT and mutant ion channels in native cardiac myocyte models is important since ion channel mutations have been reported to function differently in native myocyte and HEK-293 cell expression systems (26).…”

The genetic basis of Brugada syndrome: A mutation update

“…In 304 unrelated SIDS cases, three missense mutations, E83K, I24V, and R273C, were identified (see Table 2). All mutations were coexpressed with SCN5A in HEK cells and neonatal cardiomyocytes, and found to reduce the I Na current [Van Norstrand et al, 2007]. This suggests that the mechanism of GPD1L-caused BrS2 is related to BrS1, as the electrophysiological phenotype is the result of decreased SCN5A expression.…”

Overrepresentation of the proarrhythmic, sudden death predisposing sodium channel polymorphism S1103Y in a population-based cohort of African-American sudden infant death syndrome

“…6 While the pathophysiological mechanisms underlying most of these tragic deaths remain elusive, heritable cardiac arrhythmia syndromes such as long QT syndrome (LQTS), Brugada syndrome (BrS), and catecholoaminergic polymorphic ventricular tachycardia (CPVT) appear to account for 10-15% of SIDS, with the majority of SIDS related mutations being identified in the SCN5A-encoded cardiac sodium channel alpha subunit (Nav1.5) or its interacting proteins. [7][8][9][10][11][12][13][14][15] In 2002, Splawski and colleagues reported on the common African American-specific polymorphism S1103Y-SCN5A (denoted previously as S1102Y) with a prevalence of 13% among African Americans and associated with an increased risk for arrhythmia susceptibility, particularly in the context of other acquired risk factors such as medications, hypokalemia or structural heart disease. 16 Subsequently, Burke and colleagues observed an overrepresentation of S1103Y among African American adolescents and adults whose deaths were classified as autopsy negative sudden unexplained death (SUD).…”