1-241519722-T-C

Position:

chr1-241519722-T-C

Variant summary

Our verdict is Pathogenic. Variant got 12 ACMG points: 12P and 0B. PVS1PS1_ModeratePM2

The NM_000143.4(FH):c.1A>G(p.Met1?) variant causes a start lost change. The variant allele was found at a frequency of 0.00000324 in 1,543,456 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars).

Frequency

Genomes: 𝑓 0.000013 ( 0 hom., cov: 33)

Exomes 𝑓: 0.0000022 ( 0 hom. )

Consequence

FH
NM_000143.4 start_lost

Scores

Clinical Significance

Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:1U:3

Conservation

PhyloP100: 4.13

Variant links:

Genes affected

FH (HGNC:3700): (fumarate hydratase) The protein encoded by this gene is an enzymatic component of the tricarboxylic acid (TCA) cycle, or Krebs cycle, and catalyzes the formation of L-malate from fumarate. It exists in both a cytosolic form and an N-terminal extended form, differing only in the translation start site used. The N-terminal extended form is targeted to the mitochondrion, where the removal of the extension generates the same form as in the cytoplasm. It is similar to some thermostable class II fumarases and functions as a homotetramer. Mutations in this gene can cause fumarase deficiency and lead to progressive encephalopathy. [provided by RefSeq, Jul 2008]

FH links:

Genome browser will be placed here

ACMG classification

Classification made for transcript

Verdict is Pathogenic. Variant got 12 ACMG points.

PVS1

Start lost variant, no new inframe start found.

PS1

Another start lost variant in NM_000143.4 (FH) was described as [Conflicting_classifications_of_pathogenicity] in ClinVar as 1502868

PM2

Very rare variant in population databases, with high coverage;

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
FH	NM_000143.4 linkuse as main transcript	c.1A>G	p.Met1?	start_lost	1/10	ENST00000366560.4

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
FH	ENST00000366560.4 linkuse as main transcript	c.1A>G	p.Met1?	start_lost	1/10	1	NM_000143.4	P1	P07954-1

Frequencies

GnomAD3 genomes

AF:

0.0000131

AC:

AN:

152168

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.0000482

Gnomad AMI

AF:

0.00

Gnomad AMR

AF:

0.00

Gnomad ASJ

AF:

0.00

Gnomad EAS

AF:

0.00

Gnomad SAS

AF:

0.00

Gnomad FIN

AF:

0.00

Gnomad MID

AF:

0.00

Gnomad NFE

AF:

0.00

Gnomad OTH

AF:

0.00

GnomAD3 exomes

AF:

0.00000682

AC:

AN:

146594

Hom.:

AF XY:

0.00

AC XY:

AN XY:

78404

show subpopulations

Gnomad AFR exome

AF:

0.00

Gnomad AMR exome

AF:

0.00

Gnomad ASJ exome

AF:

0.00

Gnomad EAS exome

AF:

0.0000936

Gnomad SAS exome

AF:

0.00

Gnomad FIN exome

AF:

0.00

Gnomad NFE exome

AF:

0.00

Gnomad OTH exome

AF:

0.00

GnomAD4 exome

AF:

0.00000216

AC:

AN:

1391288

Hom.:

Cov.:

AF XY:

0.00

AC XY:

AN XY:

685372

show subpopulations

Gnomad4 AFR exome

AF:

0.00

Gnomad4 AMR exome

AF:

0.00

Gnomad4 ASJ exome

AF:

0.00

Gnomad4 EAS exome

AF:

0.0000564

Gnomad4 SAS exome

AF:

0.00

Gnomad4 FIN exome

AF:

0.00

Gnomad4 NFE exome

AF:

9.30e-7

Gnomad4 OTH exome

AF:

0.00

GnomAD4 genome

AF:

0.0000131

AC:

AN:

152168

Hom.:

Cov.:

AF XY:

0.0000269

AC XY:

AN XY:

74334

show subpopulations

Gnomad4 AFR

AF:

0.0000482

Gnomad4 AMR

AF:

0.00

Gnomad4 ASJ

AF:

0.00

Gnomad4 EAS

AF:

0.00

Gnomad4 SAS

AF:

0.00

Gnomad4 FIN

AF:

0.00

Gnomad4 NFE

AF:

0.00

Gnomad4 OTH

AF:

0.00

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:1Uncertain:3

Revision: criteria provided, conflicting classifications

LINK: link

Submissions by phenotype

not provided

Pathogenic:1Uncertain:2

Uncertain significance, criteria provided, single submitter	clinical testing	GeneDx	Oct 03, 2023	Not observed at significant frequency in large population cohorts (gnomAD); Initiation codon variant in a gene for which loss of function is a known mechanism of disease but an alternate initiation codon at Met44 could serve as an in-frame site (Dik et al., 2016); Published functional studies demonstrate that when this alternate start codon is used there is aberrant localization of the FH protein exclusively to the cytosol, without any mitochondrial targeting (Dik et al., 2016); This variant is associated with the following publications: (PMID: 27037871) -
Likely pathogenic, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	Sep 06, 2023	This sequence change affects the initiator methionine of the FH mRNA. The next in-frame methionine is located at codon 44. FH has two initiator codons, p.Met1 and p.Met44, which result in two different functional isoforms that localize to the mitochondria and cytosol, respectively (PMID: 21929734, 27037871). Loss-of-function variants in FH are known to be pathogenic (PMID: 11865300, 21398687). Variants affecting the mitochondrial isoform confer risk for fumarate hydratase deficiency, while variants that affect the cytosolic isoform confer risk for FH tumor predisposition syndrome. This variant is present in population databases (no rsID available, gnomAD 0.009%). A different variant (c.1A>C) giving rise to the same protein effect has been determined to be pathogenic (PMID: 27037871). This suggests that this variant is also likely to be causative of disease. ClinVar contains an entry for this variant (Variation ID: 237113). This variant disrupts the mitochondria-targeting sequence (MTS) of the FH protein, which is important for protein import into the mitochondria (PMID: 27037871). This suggests that disruption of this region is causative of fumarate hydratase deficiency. In summary, the currently available evidence indicates that the variant is pathogenic, but additional data are needed to prove that conclusively. Therefore, this variant has been classified as Likely Pathogenic for autosomal recessive fumarate hydratase deficiency. However, this variant is not likely to confer risk for autosomal dominant FH tumor predisposition syndrome. -
Uncertain significance, criteria provided, single submitter	clinical testing	Quest Diagnostics Nichols Institute San Juan Capistrano	Aug 25, 2021	- -

Hereditary cancer-predisposing syndrome

Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Ambry Genetics

Oct 12, 2023

The p.M1? variant (also known as c.1A>G), located in coding exon 1 of the FH gene, results from a A to G substitution at nucleotide position 1. This alters the methionine residue at the initiation codon. Variations that modify the initiation codon (ATG) are expected to result in either loss of translation initiation, N-terminal truncation, or cause a shift in the mRNA reading frame; however, there is an alternate in-frame methionine 44 amino acids from the initiation site. Proteins initiated from the first methionine are targeted to the mitochondrion while proteins initiated from the second methionine are targeted to the cytoplasm due to the lack of the mitochondrial targeting sequence encoded between them (Dik E et al. Traffic, 2016 Jul;17:720-32, Magrane M et al., Database (Oxford) 2011; bar009). Data suggest that it is the cytoplasmic protein that conveys the tumor suppressor function of FH (Yogev O et al. PLoS Biol., 2010 Mar;8:e1000328). This nucleotide position is highly conserved in available vertebrate species. Since supporting evidence is limited at this time, the clinical significance of this alteration remains unclear. -

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

BayesDel_addAF

Pathogenic

0.38

BayesDel_noAF

Pathogenic

0.51

CADD

Uncertain

DANN

Uncertain

0.99

DEOGEN2

Benign

0.25

Eigen

Benign

0.18

Eigen_PC

Uncertain

0.28

FATHMM_MKL

Pathogenic

0.97

LIST_S2

Uncertain

0.90

M_CAP

Pathogenic

0.97

MetaRNN

Pathogenic

0.89

MetaSVM

Pathogenic

1.1

MutationTaster

Benign

1.0

PROVEAN

Benign

-0.27

REVEL

Pathogenic

0.68

Sift

Uncertain

0.0090

Sift4G

Uncertain

0.014

Polyphen

0.32

Vest4

0.88

MutPred

0.62

Loss of loop (P = 0.1258);

MVP

0.94

ClinPred

0.83

GERP RS

5.3

Varity_R

0.43

gMVP

0.69

Splicing

Name

Calibrated prediction

Score

Prediction

SpliceAI score (max)

0.0

Details are displayed if max score is > 0.2

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Publications

LitVar

Below is the list of publications found by LitVar. It may be empty.

Variant summary

Frequency

Consequence

Scores

Clinical Significance

Conservation

ACMG classification

Transcripts

RefSeq

Ensembl

Frequencies

ClinVar

Submissions by phenotype

Computational scores

Splicing

Publications

LitVar

Other links and lift over