SCN5A Variant L128M Detail

We estimate the penetrance of LQTS for SCN5A L128M around 3% and the Brugada syndrome penetrance around 55%. SCN5A L128M was found in a total of 0 carriers in 0 papers and/or in gnomAD: 0 had Brugada syndrome, 0 had LQTS. L128M is not present in gnomAD. L128M has been functionally characterized in 0 papers. This residue is located in a Hotspot region for Brugada syndrome and a Non_Hotspot region for LQTS. In silico predictions, functional data (if available), and location in structure are equivalent to phenotyping 10 individuals for Brugada syndrome (5 diagnosed with Brugada syndrome) and 5 individuals for LQTS (0 with LQTS). These data combined with observations of carriers lead us to estimate the LQTS penetrance for SCN5A L128M around 3% (0/10) and the Brugada syndrome penetrance around 55% (5/10).

In Silico Data

PROVEAN PolyPhen-2 BLAST-PSSM REVEL Penetrance Density BrS (%) Penetrance Density LQT3 (%)
NA NA NA 0.696 86 0
PROVEAN scores less than -2 are considered deleterious. REVEL scores higher than 0.5 or 0.75 are considered likely pathogenic (higher sensitivity with the former cutoff, higher specificity with the latter cutoff). A PolyPhen-2 score of 0.85 or greater is considered likely pathogenic. BLAST-PSSM reflects the evolutionary conservation of residue substitutions, more negative numbers indicate fewer observations of the specific substitution than is expected. Penetrance Density is our previously published method to calculate the average BrS/LQTS probability density in a shell of residues surrounding a residue of interest (Kroncke et al. 2019).

Reported Carrier Data

PubMed ID Year Carriers Unaffected LQT3 BrS1 Other Other Disease
LITERATURE, COHORT, AND GNOMAD: - 0 0 0 0 -
VARIANT FEATURES ALONE: - 15 10 0 5 - -
Summary totals might not agree with the literature table because of duplicate patients, which were excluded from the total counts. We do not distinguish here between multiple missense codons. Missense variants are combined across degenerate codon substitutions since codon-level data were not consistently available for curation.

L128M has 41 previously observed neighbors within 15 angstroms

A residue within a folded protein on average has nearest neighbors that fall roughly into two shells: a "nearest" neighbor around 5-6 angstroms and a second shell around 11 angstroms. All variants shown in the rightmost column have been observed in at least one individual in the literature or gnomAD.

Neighbor Distance (Angstroms) Variants Observed in Individuals
121 10 R121Q, R121W,
231 15 c.692_693delCA,
198 13
124 6 A124D,
131 9
130 8
114 14
170 10 F170I,
184 14 H184R,
228 14 K228R,
138 13 M138I,
122 13
171 8
137 10 I137V,
197 12
129 4
169 14
177 10 L177P,
123 9 A123G, A123V,
127 5
125 6 V125L,
174 6 V174I,
133 6
132 10 c.393-5C>A,
134 7 N134S,
179 8 R179X, R179Q,
172 10
180 12 G180V,
120 13
126 8 K126E,
136 11 L136P,
168 14
175 6 K175N,
194 12
188 12
135 12 M135V,
167 13
178 7 A178G,
128 0 c.381dupT,
176 10
173 10