6-49435560-G-A

Variant names:

• chr6-49435560-G-A
• rs1164271240
• NM_000255.4:c.2020C>T

Variant summary

Our verdict is Pathogenic. The variant received 17 ACMG points: 17P and 0B. PM1 PM2 PM5 PP2 PP3_Moderate PP5_Very_Strong

The NM_000255.4(MMUT):​c.2020C>T​(p.Leu674Phe) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000000684 in 1,461,768 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 Likely pathogenic (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. L674V) has been classified as Likely pathogenic.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: MMUT NM_000255.4 missense
• Clinical Significance: Likely pathogenic criteria provided, multiple submitters, no conflicts P:3
• Conservation: PhyloP100: 2.26
• Publications: 1 publications found

Genes affected

MMUT (HGNC:7526): (methylmalonyl-CoA mutase) This gene encodes the mitochondrial enzyme methylmalonyl Coenzyme A mutase. In humans, the product of this gene is a vitamin B12-dependent enzyme which catalyzes the isomerization of methylmalonyl-CoA to succinyl-CoA, while in other species this enzyme may have different functions. Mutations in this gene may lead to various types of methylmalonic aciduria. [provided by RefSeq, Jul 2008]

MMUT Gene-Disease associations (from GenCC):

• methylmalonic aciduria due to methylmalonyl-CoA mutase deficiency

  Inheritance: AR Classification: DEFINITIVE, STRONG Submitted by: ClinGen, Labcorp Genetics (formerly Invitae), G2P
• vitamin B12-unresponsive methylmalonic acidemia type mut-

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet
• vitamin B12-unresponsive methylmalonic acidemia type mut0

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet

ACMG classification

Our verdict: Pathogenic. The variant received 17 ACMG points.

• PM1: In a hotspot region, there are 4 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 1 benign, 3 uncertain in NM_000255.4
• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr6-49435560-G-C is described in ClinVar as Likely_pathogenic. ClinVar VariationId is 466220.Status of the report is criteria_provided_single_submitter, 1 stars.
• PP2: Missense variant in the gene, where a lot of missense mutations are associated with disease in ClinVar. The gene has 150 curated pathogenic missense variants (we use a threshold of 10). The gene has 9 curated benign missense variants. Gene score misZ: 0.22855 (below the threshold of 3.09). Trascript score misZ: 1.0842 (below the threshold of 3.09). GenCC associations: The gene is linked to vitamin B12-unresponsive methylmalonic acidemia type mut-, methylmalonic aciduria due to methylmalonyl-CoA mutase deficiency, vitamin B12-unresponsive methylmalonic acidemia type mut0.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.931
• PP5: Variant 6-49435560-G-A is Pathogenic according to our data. Variant chr6-49435560-G-A is described in ClinVar as Likely_pathogenic. ClinVar VariationId is 583274.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
MMUT	NM_000255.4	c.2020C>T	p.Leu674Phe	missense_variant	Exon 12 of 13	ENST00000274813.4	NP_000246.2
MMUT	XM_005249143.4	c.2020C>T	p.Leu674Phe	missense_variant	Exon 12 of 13		XP_005249200.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
MMUT	ENST00000274813.4	c.2020C>T	p.Leu674Phe	missense_variant	Exon 12 of 13	1	NM_000255.4	ENSP00000274813.3

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD2 exomes AF: 0.00000398 AC: 1 AN: 251114 AF XY: 0.00000737

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 FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1461768 Hom.: 0 Cov.: 30 AF XY: 0.00000138 AC XY: 1 AN XY: 727178

African (AFR) AF: 0.00 AC: 0 AN: 33480

American (AMR) AF: 0.00 AC: 0 AN: 44682

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26130

East Asian (EAS) AF: 0.00 AC: 0 AN: 39686

South Asian (SAS) AF: 0.0000116 AC: 1 AN: 86244

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53416

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5762

European-Non Finnish (NFE) AF: 0.00 AC: 0 AN: 1111976

Other (OTH) AF: 0.00 AC: 0 AN: 60392

GnomAD4 genome Cov.: 32

ClinVar

Significance: Likely pathogenic

Submissions summary: Pathogenic:3

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not provided Pathogenic:1

Feb 07, 2021

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces leucine with phenylalanine at codon 674 of the MUT protein (p.Leu674Phe). The leucine residue is highly conserved and there is a small physicochemical difference between leucine and phenylalanine. This variant is not present in population databases (ExAC no frequency). This variant has been reported in the homozygous state in an individual affected with methylmalonic acidemia (PMID: 22727635). Algorithms developed to predict the effect of missense changes on protein structure and function do not agree on the potential impact of this missense change (SIFT: "Deleterious"; PolyPhen-2: "Probably Damaging"; Align-GVGD: "Class C15"). A different missense substitution at this codon (p.Leu674Val) has been determined to be likely pathogenic (Invitae). This suggests that the leucine residue is critical for MUT protein function and that other missense substitutions at this position may also be deleterious. 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. -

Methylmalonic aciduria due to methylmalonyl-CoA mutase deficiency Pathogenic:1

Sep 08, 2022

Department of Pathology and Laboratory Medicine, Sinai Health System

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: research

- -

Methylmalonic aciduria due to complete methylmalonyl-CoA mutase deficiency Pathogenic:1

Sep 11, 2020

Natera, Inc.

Significance: Likely pathogenic

Review Status: no assertion criteria provided

Collection Method: clinical testing

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.93
BayesDel_addAF	Pathogenic	0.42	D
BayesDel_noAF	Pathogenic	0.47
CADD	Benign	23
DANN	Uncertain	1.0
Eigen	Uncertain	0.67
Eigen_PC	Uncertain	0.51
FATHMM_MKL	Uncertain	0.92	D
LIST_S2	Pathogenic	1.0	D
M_CAP	Pathogenic	0.34	D
MetaRNN	Pathogenic	0.93	D
MetaSVM	Pathogenic	1.1	D
PhyloP100		2.3
PrimateAI	Uncertain	0.76	T
PROVEAN	Uncertain	-3.0	D
REVEL	Pathogenic	0.83
Sift	Uncertain	0.0030	D
Sift4G	Uncertain	0.0040	D
Vest4		0.92
MutPred		0.76		Gain of catalytic residue at L674 (P = 0.042);
MVP		0.98
MPC		0.49
ClinPred		0.99	D
GERP RS		4.9
gMVP		0.78
Mutation Taster		=27/73	disease causing (ClinVar)

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

Other links and lift over

dbSNP: rs1164271240; hg19: chr6-49403273;