1-241519722-T-G

Position:

• chr1-241519722-T-G

Variant summary

Our verdict is Likely pathogenic. Variant got 6 ACMG points: 10P and 4B. PVS1 PS1_Moderate BS2

The NM_000143.4(FH):​c.1A>C​(p.Met1?) variant causes a start lost change. The variant allele was found at a frequency of 0.0000158 in 1,391,288 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: not found (cov: 33)
  • Exomes 𝑓: 0.000016 (0 hom.)
• Consequence: FH NM_000143.4 start_lost
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:2 U:4
• Conservation: PhyloP100: 4.13

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]

ACMG classification

Verdict is Likely_pathogenic. Variant got 6 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
• BS2: High AC in GnomAdExome4 at 22 AD gene.

Transcripts

RefSeq

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

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
FH	ENST00000366560.4	c.1A>C	p.Met1?	start_lost	1/10	1	NM_000143.4	P1

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD3 exomes AF: 0.0000136 AC: 2 AN: 146594 Hom.: 0 AF XY: 0.0000128 AC XY: 1 AN XY: 78404

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.00

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad SAS exome AF: 0.0000451

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.0000182

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.0000158 AC: 22 AN: 1391288 Hom.: 0 Cov.: 31 AF XY: 0.0000204 AC XY: 14 AN XY: 685372

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.0000205

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 33

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:2 Uncertain:4

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Fumarase deficiency Pathogenic:1 Uncertain:1

Likely pathogenic, no assertion criteria provided	clinical testing	Natera, Inc.	Sep 01, 2020	- -
Uncertain significance, criteria provided, single submitter	clinical testing	Illumina Laboratory Services, Illumina	Jan 13, 2018	This variant was observed in the ICSL laboratory as part of a predisposition screen in an ostensibly healthy population. It had not been previously curated by ICSL or reported in the Human Gene Mutation Database (HGMD: prior to June 1st, 2018), and was therefore a candidate for classification through an automated scoring system. Utilizing variant allele frequency, disease prevalence and penetrance estimates, and inheritance mode, an automated score was calculated to assess if this variant is too frequent to cause the disease. Based on the score, this variant could not be ruled out of causing disease and therefore its association with disease required further investigation. A literature search was performed for the gene, cDNA change, and amino acid change (if applicable). No publications were found based on this search. This variant was therefore classified as a variant of unknown significance for this disease. -

Hereditary leiomyomatosis and renal cell cancer Uncertain:2

Uncertain significance, criteria provided, single submitter	clinical testing	Illumina Laboratory Services, Illumina	Jan 13, 2018	This variant was observed in the ICSL laboratory as part of a predisposition screen in an ostensibly healthy population. It had not been previously curated by ICSL or reported in the Human Gene Mutation Database (HGMD: prior to June 1st, 2018), and was therefore a candidate for classification through an automated scoring system. Utilizing variant allele frequency, disease prevalence and penetrance estimates, and inheritance mode, an automated score was calculated to assess if this variant is too frequent to cause the disease. Based on the score, this variant could not be ruled out of causing disease and therefore its association with disease required further investigation. A literature search was performed for the gene, cDNA change, and amino acid change (if applicable). No publications were found based on this search. This variant was therefore classified as a variant of unknown significance for this disease. -
Uncertain significance, criteria provided, single submitter	clinical testing	Illumina Laboratory Services, Illumina	Jun 14, 2016	- -

not provided Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Apr 06, 2023

This variant is present in population databases (no rsID available, gnomAD 0.004%). 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 hereditary leiomyomatosis and renal cell cancer. This variant has not been reported in the literature in individuals affected with FH-related conditions. 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 hereditary leiomyomatosis and renal cell cancer. 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. ClinVar contains an entry for this variant (Variation ID: 296878). -

Hereditary cancer-predisposing syndrome Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Ambry Genetics

Feb 16, 2023

The p.M1? variant (also known as c.1A>C), located in coding exon 1 of the FH gene, results from a A to C 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	0.41	D
BayesDel_noAF	Pathogenic	0.49
CADD	Uncertain	24
DANN	Benign	0.90
DEOGEN2	Benign	0.25	T
Eigen	Benign	0.11
Eigen_PC	Uncertain	0.23
FATHMM_MKL	Pathogenic	0.98	D
LIST_S2	Uncertain	0.90	D
M_CAP	Pathogenic	0.97	D
MetaRNN	Pathogenic	0.90	D
MetaSVM	Pathogenic	1.0	D
MutationTaster	Benign	1.0	D
PROVEAN	Benign	-0.20	N
REVEL	Pathogenic	0.68
Sift	Benign	0.20	T
Sift4G	Benign	0.21	T
Polyphen		0.17	B
Vest4		0.90
MutPred		0.64		Loss of methylation at R3 (P = 0.0929);
MVP		0.94
ClinPred		0.93	D
GERP RS		5.3
Varity_R		0.24
gMVP		0.58

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

Other links and lift over

dbSNP: rs776806414; hg19: chr1-241683022;