6-49451670-TGC-T

Variant names:

• chr6-49451670-TGC-T
• rs1554159950
• NM_000255.4:c.1126_1127delGC

Variant summary

Our verdict is Pathogenic. The variant received 18 ACMG points: 18P and 0B. PVS1 PM2 PP5_Very_Strong

The NM_000255.4(MMUT):​c.1126_1127delGC​(p.Ala376SerfsTer15) variant causes a frameshift change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000274 in 1,461,700 control chromosomes in the GnomAD database, with no homozygous occurrence. Variant has been reported in ClinVar as Pathogenic (★★). Variant results in nonsense mediated mRNA decay.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000027 (0 hom.)
• Consequence: MMUT NM_000255.4 frameshift
• Clinical Significance: Pathogenic criteria provided, multiple submitters, no conflicts P:4
• Conservation: PhyloP100: 10.0
• Publications: 0 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 18 ACMG points.

• PVS1: Loss of function variant, product undergoes nonsense mediated mRNA decay. LoF is a known mechanism of disease.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 6-49451670-TGC-T is Pathogenic according to our data. Variant chr6-49451670-TGC-T is described in ClinVar as Pathogenic. ClinVar VariationId is 488555.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.1126_1127delGC	p.Ala376SerfsTer15	frameshift_variant	Exon 6 of 13	ENST00000274813.4	NP_000246.2
MMUT	XM_005249143.4	c.1126_1127delGC	p.Ala376SerfsTer15	frameshift_variant	Exon 6 of 13		XP_005249200.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
MMUT	ENST00000274813.4	c.1126_1127delGC	p.Ala376SerfsTer15	frameshift_variant	Exon 6 of 13	1	NM_000255.4	ENSP00000274813.3

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 0.00000274 AC: 4 AN: 1461700 Hom.: 0 AF XY: 0.00000275 AC XY: 2 AN XY: 727162

African (AFR) AF: 0.00 AC: 0 AN: 33466

American (AMR) AF: 0.00 AC: 0 AN: 44714

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

East Asian (EAS) AF: 0.00 AC: 0 AN: 39688

South Asian (SAS) AF: 0.0000464 AC: 4 AN: 86254

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53408

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

European-Non Finnish (NFE) AF: 0.00 AC: 0 AN: 1111890

Other (OTH) AF: 0.00 AC: 0 AN: 60388

GnomAD4 genome Cov.: 32

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:4

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Methylmalonic aciduria due to methylmalonyl-CoA mutase deficiency Pathogenic:2

May 31, 2018

Counsyl

Significance: Likely pathogenic

Review Status: no assertion criteria provided

Collection Method: clinical testing

This submission and the accompanying classification are no longer maintained by the submitter. For more information on current observations and classification, please contact variantquestions@myriad.com. -

Nov 08, 2017

Institute of Human Genetics Munich, TUM University Hospital

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

MMUT-related disorder Pathogenic:1

Jul 23, 2024

PreventionGenetics, part of Exact Sciences

Significance: Pathogenic

Review Status: no assertion criteria provided

Collection Method: clinical testing

The MMUT c.1126_1127delGC variant is predicted to result in a frameshift and premature protein termination (p.Ala376Serfs*15). This variant has been reported in the homozygous state in an individual with methylmalonic acidemia (Devi et al. 2017. PubMed ID: 27591164). This variant has not been reported in a large population database, indicating this variant is rare. Frameshift variants in MMUT are expected to be pathogenic. This variant is interpreted as pathogenic. -

not provided Pathogenic:1

Feb 10, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change creates a premature translational stop signal (p.Ala376Serfs*15) in the MUT gene. It is expected to result in an absent or disrupted protein product. Loss-of-function variants in MUT are known to be pathogenic (PMID: 15781192). This variant is not present in population databases (gnomAD no frequency). This premature translational stop signal has been observed in individual(s) with methylmalonic aciduria (PMID: 27591164). ClinVar contains an entry for this variant (Variation ID: 488555). For these reasons, this variant has been classified as Pathogenic. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
PhyloP100		10
Mutation Taster		=1/199	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: rs1554159950; hg19: chr6-49419383;