Uncertain significance, no assertion criteria provided | clinical testing | Stanford Center for Inherited Cardiovascular Disease, Stanford University | Apr 21, 2014 | Note this variant was found in clinical genetic testing performed by one or more labs who may also submit to ClinVar. Thus any internal case data may overlap with the internal case data of other labs. The interpretation reviewed below is that of the Stanford Center for Inherited Cardiovascular Disease. p.Thr1069Met (T1069M; c.3206C>T) in exon 17 of the SCN5A gene (NM_198056.2) We do not believe there is enough evidence to call this variant “disease-causing” at this time. It may instead be a rare benign variant that is more common in individuals with Hispanic ancestry. It has only been published in one “case” of LQTS, and this individual was also Hispanic. Furthermore, there is no phenotype data available for that patient, and so we cannot confirm that the individual actually had LQTS. This variant has previously been reported in just one Hispanic individual (the ethnicity is important) who had genetic testing for LQTS through the Familion laboratory (Tester et al. 2005; Kapplinger et al. 2009, Kapa et al. 2009). There is no phenotype information available for this individual, and we cannot assume that they have a confirmed clinical diagnosis of LQTS. Of note, genetic testing for the 2500 Familion cases reported by Kapplinger et al (2009) have an unusually low yield of 36% (vs. 70% in cohorts with a firm diagnoses of long QT syndrome), which suggests that not all of these patients have a firm diagnosis. Also, these papers have a lack of clarity regarding which variants were seen with another pathogenic variant (9% of the cohort had multiple variants). This is a non-conservative amino acid change, resulting in the replacement of a polar Threonine with a nonpolar Methionine in interdomain linker II-III. The Threonine at this location is NOT conserved across vertebrate species, and in fact the default amino acid is a Methionine in alligators and in 2 species of bird. Variation at nearby residues (+/- 10 amino acids) has NOT been associated with LQTS except for at residue Ser1079, which may argue against the functional importance of this region of the protein: (HGMD professional version as of January 17, 2014; and GeneDx report). This site in the protein is also not conserved across paralogue proteins: http://cardiodb.org/Paralogue_Annotation/residue.php?gene=SCN5A&position=1069. In silico analysis with PolyPhen-2 (http://genetics.bwh.harvard.edu/pph2/) predicts the variant to be “Probably Damaging” with a score of 0.993. In total the variant has been seen in 15 published controls or individuals from publicly available population datasets. The p.Thr1069Met variant is overrepresented among “Latino” individuals in the ExAC dataset, which currently includes variant calls on ~60,000 individuals of multiple ethnic backgrounds (Latino, European (non-Finnish), Finnish, South Asian, African & East Asian). It is present in 11 out of 5,749 Latinos in that database, which is an allele frequency of 0.1%. This estimates that ~2 out of every 1000 Latinos would carry the variant, which is a higher incidence than the overall estimated incidence of LQTS (1 in 2500 people). This variant is otherwise present in only 1 South Asian individual (out of 6,634) and 2 Caucasian individuals (out of 35,669). These individuals took part in a range of disease-specific and population genetic studies, and the curators made an effort to exclude individuals with severe pediatric diseases. There is only one individual with this variant listed in 1000 Genomes (http://browser.1000genomes.org/index.htm) as of 3/26/2015, and this individual also has Mexican ancestry. The variant was not observed in published controls, including 1300 from Kapplinger et al. 2009 (143 of them Hispanic). There is also no variation at this residue listed in the NHLBI Exome Sequencing Project dataset (http://evs.gs.washington.edu/EVS/), which currently includes variant calls on ~4300 Caucasian and ~2200 African American individuals who are NOT ethnicity-matched to our patient (who ha - |
Likely benign, criteria provided, single submitter | clinical testing | Women's Health and Genetics/Laboratory Corporation of America, LabCorp | Jan 16, 2024 | Variant summary: SCN5A c.3206C>T (p.Thr1069Met) results in a non-conservative amino acid change located in the Sodium ion transport-associated domain of the encoded protein sequence. Three of five in-silico tools predict a benign effect of the variant on protein function. The variant allele was found at a frequency of 0.00015 in 246942 control chromosomes, predominantly at a frequency of 0.00093 within the Latino subpopulation in the gnomAD database. The observed variant frequency within Latino control individuals in the gnomAD database is approximately 9 fold of the estimated maximal expected allele frequency for a pathogenic variant in SCN5A causing Arrhythmia phenotype (0.0001), strongly suggesting that the variant is a benign polymorphism found primarily in populations of Latino origin. c.3206C>T has been reported in the literature in individuals affected with Arrhythmia. These report(s) do not provide unequivocal conclusions about association of the variant with Arrhythmia.To our knowledge, no experimental evidence demonstrating an impact on protein function has been reported. The following publication have been ascertained in the context of this evaluation (PMID: 31737537). ClinVar contains an entry for this variant (Variation ID: 67782). Based on the evidence outlined above, the variant was classified as likely benign. - |