chr9-69035900-C-T
Variant summary
Our verdict is Uncertain significance. Variant got 2 ACMG points: 3P and 1B. PM2PP3BS1_Supporting
The NM_000144.5(FXN):c.118C>T(p.Arg40Cys) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000662 in 1,487,292 control chromosomes in the GnomAD database, including 1 homozygotes. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars).
Frequency
Consequence
NM_000144.5 missense
Scores
Clinical Significance
Conservation
Genome browser will be placed here
ACMG classification
Verdict is Uncertain_significance. Variant got 2 ACMG points.
Transcripts
RefSeq
Gene | Transcript | HGVSc | HGVSp | Effect | Exon rank | MANE | Protein | UniProt |
---|---|---|---|---|---|---|---|---|
FXN | NM_000144.5 | c.118C>T | p.Arg40Cys | missense_variant | Exon 1 of 5 | ENST00000484259.3 | NP_000135.2 | |
FXN | NM_181425.3 | c.118C>T | p.Arg40Cys | missense_variant | Exon 1 of 5 | NP_852090.1 |
Ensembl
Gene | Transcript | HGVSc | HGVSp | Effect | Exon rank | TSL | MANE | Protein | Appris | UniProt |
---|---|---|---|---|---|---|---|---|---|---|
FXN | ENST00000484259.3 | c.118C>T | p.Arg40Cys | missense_variant | Exon 1 of 5 | 3 | NM_000144.5 | ENSP00000419243.2 | ||
ENSG00000285130 | ENST00000642889.1 | c.118C>T | p.Arg40Cys | missense_variant | Exon 1 of 25 | ENSP00000493780.1 |
Frequencies
GnomAD3 genomes AF: 0.000401 AC: 61AN: 151944Hom.: 0 Cov.: 33
GnomAD3 exomes AF: 0.000299 AC: 27AN: 90414Hom.: 0 AF XY: 0.000255 AC XY: 13AN XY: 50990
GnomAD4 exome AF: 0.000692 AC: 924AN: 1335348Hom.: 1 Cov.: 36 AF XY: 0.000668 AC XY: 440AN XY: 658314
GnomAD4 genome AF: 0.000401 AC: 61AN: 151944Hom.: 0 Cov.: 33 AF XY: 0.000431 AC XY: 32AN XY: 74206
ClinVar
Submissions by phenotype
not provided Uncertain:2
Uncertain significance, criteria provided, single submitter | clinical testing | GeneDx | Dec 26, 2023 | Reported in the heterozygous state in an individual with hypertrophic cardiomyopathy, however the individual also harbored a variant in MYBPC3 (PMID: 15936968); In silico analysis supports that this missense variant does not alter protein structure/function; This variant is associated with the following publications: (PMID: 15936968) - |
Uncertain significance, criteria provided, single submitter | clinical testing | ARUP Laboratories, Molecular Genetics and Genomics, ARUP Laboratories | Aug 22, 2024 | The FXN c.118C>T; p.Arg40Cys variant (rs145854903, ClinVar Variation ID 264451) is reported along with a likely pathogenic MYBPC3 variant in an individual with hypertrophic cardiomyopathy (Van Driest 2005). This variant is found predominantly in the non-Finnish European population with an allele frequency of 0.07% (36/48340 alleles) in the Genome Aggregation Database (v2.1.1). In vitro functional analysis of the variant protein showed defective cleavage leading to poor protein maturation; however, both FXN mRNA and protein levels were unaffected in patient’s cultured fibroblasts (Van Driest 2005). Additionally, expression of FXN mutant protein in yeast devoid of endogenous FXN were phenotypically indistinguishable. Computational analyses are uncertain whether this variant is neutral or deleterious (REVEL: 0.597). Due to conflicting information, the clinical significance of this variant is uncertain at this time. References: Van Driest SL et al. Molecular and functional characterization of a human frataxin mutation found in hypertrophic cardiomyopathy. Mol Genet Metab. 2005 Aug. PMID: 15936968. - |
not specified Uncertain:1Benign:1
Likely benign, criteria provided, single submitter | clinical testing | Athena Diagnostics | Jul 24, 2024 | - - |
Uncertain significance, criteria provided, single submitter | clinical testing | Women's Health and Genetics/Laboratory Corporation of America, LabCorp | Sep 16, 2024 | Variant summary: FXN c.118C>T (p.Arg40Cys) results in a non-conservative amino acid change in the encoded protein sequence. Four of five in-silico tools predict a damaging effect of the variant on protein function. The variant allele was found at a frequency of 0.0003 in 90414 control chromosomes (gnomAD). This frequency is not significantly higher than estimated for a pathogenic variant in FXN causing Friedreich Ataxia (0.0003 vs 0.0011), allowing no conclusion about variant significance. c.118C>T has been reported in the heterozygous state in an individual affected with hypertrophic cardiomyopathy (Van Driest_2005). However, this individual was also found carrying MYBPC3 c.2429G>A (p.Arg810His), which may have contributed to the patient's phenotype. This report does not provide unequivocal conclusions about association of the variant with Friedreich Ataxia. Van Driest_2005 also provided experimental evidence demonstrating that the variant prevented the cleavage of the inactive-precursor form of frataxin to the active-mature form. However, when the investigators examined protein levels in patient fibroblasts, the levels of mature frataxin were similar to those seen in controls, not allowing for convincing conclusions about the variant effect. The following publication has been ascertained in the context of this evaluation (PMID: 15936968). ClinVar contains an entry for this variant (Variation ID: 264451). Based on the evidence outlined above, the variant was classified as uncertain significance. - |
Inborn genetic diseases Uncertain:1
Uncertain significance, criteria provided, single submitter | clinical testing | Ambry Genetics | Jan 23, 2017 | The p.R40C variant (also known as c.118C>T), located in coding exon 1 of the FXN gene, results from a C to T substitution at nucleotide position 118. The arginine at codon 40 is replaced by cysteine, an amino acid with highly dissimilar properties. This variant co-occurred with a missense alteration in MYBPC3 in a male patient diagnosed with hypertrophic cardiomyopathy at 12 years of age. The same group performed in vitro studies of the p.R40C variant and showed it was more sensitive to oxidative stress under metabolically demanding conditions; however, a skin biopsy from the patient mentioned above showed normal levels of frataxin mRNA and protein (Van Driest SL, Mol. Genet. Metab. 2005 Aug; 85(4):280-5). This amino acid position is well conserved on limited sequence alignment. In addition, this alteration is predicted to be deleterious by in silico analysis. Since supporting evidence is limited at this time, the clinical significance of this alteration remains unclear. - |
Hypertrophic cardiomyopathy Uncertain:1
Uncertain significance, criteria provided, single submitter | clinical testing | Center for Advanced Laboratory Medicine, UC San Diego Health, University of California San Diego | Apr 18, 2018 | - - |
Computational scores
Source:
Splicing
Find out detailed SpliceAI scores and Pangolin per-transcript scores at