rs28941784

Positions:

chr12-109561068-G-A

Variant summary

Our verdict is Pathogenic. Variant got 18 ACMG points: 18P and 0B. PM1PM2PM5PP3_StrongPP5_Very_Strong

The NM_052845.4(MMAB):c.556C>T(p.Arg186Trp) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000265 in 1,525,838 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. R186Q) has been classified as Likely pathogenic.

Frequency

Genomes: 𝑓 0.00015 ( 0 hom., cov: 30)

Exomes 𝑓: 0.00028 ( 0 hom. )

Consequence

MMAB
NM_052845.4 missense

Scores

Clinical Significance

Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:18O:1

Conservation

PhyloP100: 1.64

Variant links:

Genes affected

MMAB (HGNC:19331): (metabolism of cobalamin associated B) This gene encodes a protein that catalyzes the final step in the conversion of vitamin B(12) into adenosylcobalamin (AdoCbl), a vitamin B12-containing coenzyme for methylmalonyl-CoA mutase. Mutations in the gene are the cause of vitamin B12-dependent methylmalonic aciduria linked to the cblB complementation group. Alternatively spliced transcript variants have been found. [provided by RefSeq, Apr 2011]

MMAB links:

Genome browser will be placed here

ACMG classification

Classification made for transcript

Verdict is Pathogenic. Variant got 18 ACMG points.

PM1

In a hotspot region, there are 7 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 6 uncertain in NM_052845.4

PM2

Very rare variant in population databases, with high coverage;

PM5

Other missense variant is known to change same aminoacid residue: Variant chr12-109561067-C-G is described in ClinVar as [Likely_pathogenic]. Clinvar id is 2954625.Status of the report is criteria_provided_single_submitter, 1 stars.

PP3

MetaRNN computational evidence supports a deleterious effect, 0.991

PP5

Variant 12-109561068-G-A is Pathogenic according to our data. Variant chr12-109561068-G-A is described in ClinVar as [Likely_pathogenic]. Clinvar id is 3095.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr12-109561068-G-A is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
MMAB	NM_052845.4 linkuse as main transcript	c.556C>T	p.Arg186Trp	missense_variant	7/9	ENST00000545712.7

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
MMAB	ENST00000545712.7 linkuse as main transcript	c.556C>T	p.Arg186Trp	missense_variant	7/9	1	NM_052845.4	P1

Frequencies

GnomAD3 genomes

AF:

0.000150

AC:

AN:

146782

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.0000248

Gnomad AMI

AF:

0.00

Gnomad AMR

AF:

0.00

Gnomad ASJ

AF:

0.00

Gnomad EAS

AF:

0.00

Gnomad SAS

AF:

0.000476

Gnomad FIN

AF:

0.00

Gnomad MID

AF:

0.00

Gnomad NFE

AF:

0.000285

Gnomad OTH

AF:

0.00

GnomAD3 exomes

AF:

0.000140

AC:

AN:

249262

Hom.:

AF XY:

0.000111

AC XY:

AN XY:

135152

show subpopulations

Gnomad AFR exome

AF:

0.0000618

Gnomad AMR exome

AF:

0.0000868

Gnomad ASJ exome

AF:

0.00

Gnomad EAS exome

AF:

0.00

Gnomad SAS exome

AF:

0.0000980

Gnomad FIN exome

AF:

0.0000496

Gnomad NFE exome

AF:

0.000230

Gnomad OTH exome

AF:

0.000164

GnomAD4 exome

AF:

0.000278

AC:

383

AN:

1378920

Hom.:

Cov.:

AF XY:

0.000265

AC XY:

182

AN XY:

685538

show subpopulations

Gnomad4 AFR exome

AF:

0.0000967

Gnomad4 AMR exome

AF:

0.0000474

Gnomad4 ASJ exome

AF:

0.0000435

Gnomad4 EAS exome

AF:

0.00

Gnomad4 SAS exome

AF:

0.0000702

Gnomad4 FIN exome

AF:

0.000135

Gnomad4 NFE exome

AF:

0.000336

Gnomad4 OTH exome

AF:

0.000165

GnomAD4 genome

AF:

0.000150

AC:

AN:

146918

Hom.:

Cov.:

AF XY:

0.000140

AC XY:

AN XY:

71552

show subpopulations

Gnomad4 AFR

AF:

0.0000248

Gnomad4 AMR

AF:

0.00

Gnomad4 ASJ

AF:

0.00

Gnomad4 EAS

AF:

0.00

Gnomad4 SAS

AF:

0.000475

Gnomad4 FIN

AF:

0.00

Gnomad4 NFE

AF:

0.000285

Gnomad4 OTH

AF:

0.00

Alfa

AF:

0.000206

Hom.:

Bravo

AF:

0.000147

ESP6500AA

AF:

0.00

AC:

ESP6500EA

AF:

0.000233

AC:

ExAC

AF:

0.000107

AC:

EpiCase

AF:

0.000273

EpiControl

AF:

0.000178

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:18Other:1

Revision: criteria provided, multiple submitters, no conflicts

LINK: link

Submissions by phenotype

Methylmalonic aciduria, cblB type

Pathogenic:12Other:1

Pathogenic, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	Jan 28, 2024	This sequence change replaces arginine, which is basic and polar, with tryptophan, which is neutral and slightly polar, at codon 186 of the MMAB protein (p.Arg186Trp). This variant is present in population databases (rs28941784, gnomAD 0.02%). This missense change has been observed in individuals with MMAB-related conditions (PMID: 12471062, 16410054). ClinVar contains an entry for this variant (Variation ID: 3095). Advanced modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) performed at Invitae indicates that this missense variant is expected to disrupt MMAB protein function with a positive predictive value of 80%. Experimental studies have shown that this missense change affects MMAB function (PMID: 16439175, 19625202). For these reasons, this variant has been classified as Pathogenic. -
Pathogenic, criteria provided, single submitter	clinical testing	Fulgent Genetics, Fulgent Genetics	May 06, 2022	- -
Pathogenic, no assertion criteria provided	literature only	OMIM	Dec 15, 2002	- -
Pathogenic, no assertion criteria provided	research	Institute of Medical Genetics and Genomics, Sir Ganga Ram Hospital	Jun 15, 2014	- -
Pathogenic, criteria provided, single submitter	clinical testing	Myriad Genetics, Inc.	Dec 20, 2019	NM_052845.3(MMAB):c.556C>T(R186W) is classified as pathogenic in the context of methylmalonic acidemia, cblB type. Sources cited for classification include the following: PMID 19625202, 16439175, 12471062, 16410054, 17957493, 20696242, 22614770 and 24059531. Classification of NM_052845.3(MMAB):c.556C>T(R186W) is based on the following criteria: This is a well-established pathogenic variant in the literature that has been observed more frequently in patients with clinical diagnoses than in healthy populations. Please note: this variant was assessed in the context of healthy population screening. -
Pathogenic, criteria provided, single submitter	clinical testing	Illumina Laboratory Services, Illumina	Apr 28, 2017	The MMAB c.556C>T (p. Arg186Trp) missense variant has been reported in six studies in which it is found in a total of 29 methylmalonic acidemia (MMA) patients, including 15 homozygotes, 13 compound heterozygotes, and one heterozygote in whom a second variant was not identified (Dobson et al. 2002; Lerner-Ellis et al. 2006; Hauser et al. 2011; O'Shea et al. 2012; Illson et al. 2013; Nizon et al. 2013). The variant was present in a heterozygous state in four of 120 non-cblB cell lines, absent from 100 control alleles, and is reported at a frequency of 0.00017 in the European (non-Finnish) population of the Exome Aggregation Consortium. Functional studies suggest that the p.Arg186Trp variant results in an unstable protein and disrupts affinity binding between MMAB and adenosylcobalamin (Zhang et al. 2006; Zhang et al. 2009). Based on the collective evidence, the p.Arg186Trp variant is classified as pathogenic for methylmalonic acidemia. This variant was observed by ICSL as part of a predisposition screen in an ostensibly healthy population. -
Pathogenic, no assertion criteria provided	clinical testing	Baumgartner lab, University Children's Hospital Zurich	Jun 01, 2021	- -
Pathogenic, no assertion criteria provided	clinical testing	Natera, Inc.	Sep 16, 2020	- -
Pathogenic, criteria provided, single submitter	clinical testing	Victorian Clinical Genetics Services, Murdoch Childrens Research Institute	Jul 17, 2023	Based on the classification scheme VCGS_Germline_v1.3.4, this variant is classified as Pathogenic. Following criteria are met: 0102 - Loss of function is a known mechanism of disease in this gene and is associated with vitamin B12-responsive methylmalonic aciduria cblB type (MIM#251110). (I) 0106 - This gene is associated with autosomal recessive disease. (I) 0115 - Variants in this gene are known to have variable expressivity (GeneReviews). (I) 0200 - Variant is predicted to result in a missense amino acid change from arginine to tryptophan. (I) 0251 - This variant is heterozygous. (I) 0304 - Variant is present in gnomAD <0.01 for a recessive condition (v2 & v3: 59 heterozygotes, 0 homozygotes). (SP) 0309 - Multiple alternative amino acid changes at the same position have been observed in gnomAD (v3) (highest allele count: 3 heterozygotes, 0 homozygotes). (I) 0501 - Missense variant consistently predicted to be damaging by multiple in silico tools or highly conserved with a major amino acid change. (SP) 0600 - Variant is located in the annotated cobalamin adenosyltransferase domain (DECIPHER). (I) 0801 - This variant has very strong previous evidence of pathogenicity in unrelated individuals. It has been reported in multiple individuals with methylmalonic aciduria cblB type (PMID: 16410054) and regarded as pathogenic in ClinVar. It is usually associated with early onset (GeneReviews). (SP) 1002 - This variant has moderate functional evidence supporting abnormal protein function. Site directed mutagenesis was used to introduce the human homologue substitution p.(Arg119Trp) in Thermoplasma acidophilum, which was shown to result in no enzyme activity (PMID: 15044458). (SP) 1205 - This variant has been shown to be maternally inherited. Mother was tested by Fulgent laboratory. (I) Legend: (SP) - Supporting pathogenic, (I) - Information, (SB) - Supporting benign -
not provided, no classification provided	literature only	GeneReviews	-	- -
Likely pathogenic, criteria provided, single submitter	clinical testing	MGZ Medical Genetics Center	Apr 05, 2022	- -
Pathogenic, criteria provided, single submitter	research	UNC Molecular Genetics Laboratory, University of North Carolina at Chapel Hill	-	The MMAB c.556C>T (p.R186W) variant is frequently observed in individuals with methylmalonic aciduria (MMA) and is associated with an early onset of disease symptoms (PMID: 16410054, 20301409). -
Pathogenic, criteria provided, single submitter	clinical testing	Baylor Genetics	Mar 27, 2024	- -

not provided

Pathogenic:3

Pathogenic, criteria provided, single submitter	clinical testing	GeneDx	Mar 24, 2022	In silico analysis, which includes protein predictors and evolutionary conservation, supports a deleterious effect; This variant is associated with the following publications: (PMID: 21048060, 34915869, 31260114, 20696242, 16410054, 12471062, 18251506, 19625202, 16439175, 17957493, 31525265) -
Pathogenic, criteria provided, single submitter	clinical testing	AiLife Diagnostics, AiLife Diagnostics	Jul 09, 2020	- -
Pathogenic, criteria provided, single submitter	clinical testing	Eurofins Ntd Llc (ga)	Apr 23, 2018	- -

Inborn genetic diseases

Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Ambry Genetics

Jun 04, 2021

The c.556C>T (p.R186W) alteration is located in exon 7 (coding exon 7) of the MMAB gene. This alteration results from a C to T substitution at nucleotide position 556, causing the arginine (R) at amino acid position 186 to be replaced by a tryptophan (W). This mutation has been reported in the compound heterozygous and homozygous states in multiple individuals with methylmalonic aciduria cblB complementation type (O'Shea, 2012; Nizon, 2013; Brasil, 2018). This mutation significantly disrupts the affinity between MMAB and adenosylcobalamin (Dobson, 2002; Zhang, 2006; Lerner-Ellis, 2006; Zhang, 2009). Based on the available evidence, this alteration is classified as pathogenic. -

MMAB-related disorder

Pathogenic:1

Pathogenic, no assertion criteria provided

clinical testing

PreventionGenetics, part of Exact Sciences

Jul 23, 2024

The MMAB c.556C>T variant is predicted to result in the amino acid substitution p.Arg186Trp. This variant has been reported to be one of the most common causes of autosomal recessive methylmalonic acidemia, cblB type (e.g., Dobson et al. 2002. PubMed ID: 12471062; Lerner-Ellis et al. 2006. PubMed ID: 16410054; Forny et al. 2019. PubMed ID: 31260114). A different substitution at the same amino acid (p.Arg186Gln) has also been reported as a pathogenic MMAB variant (e.g., Lerner-Ellis et al. 2006. PubMedID: 16410054). The p.Arg186 amino acid is one of four invariant residues that make up the surface of the cob(I)alamin adenosyltransferase enzyme cobalamin binding cleft, and is thought to potentially interact with cobalamin (Schubert and Hill. 2006. PubMed ID: 17176040). Functional studies also indicate that the p.Arg186Trp substitution may affect normal enzyme oligomerization (Brasil et al. 2018. PubMed ID: 29197662). This variant is reported in 0.025% of alleles in individuals of European (Non-Finnish) descent in gnomAD. In summary, we classify the c.556C>T (p.Arg186Trp) variant as pathogenic. -

Methylmalonic acidemia

Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Women's Health and Genetics/Laboratory Corporation of America, LabCorp

Feb 02, 2017

Variant summary: The MMAB c.556C>T (p.Arg186Trp) variant located in the Adenosycobalamin biosnthesis domain (via InterPro) causes an alteration of a non-conserved nucleotide, which 4/4 in silico tools (SNPs&GO not captured due to low reliability index) predict a damaging outcome. The variant of interest was found in 17/120070 control chromosomes at a frequency of 0.0001416, which does not exceed the estimated maximal expected allele frequency of a pathogenic MMAB variant (0.0013944). Multiple publications cite the variant in affected individuals as homozygotes and compound heterozygotes and has been indicated to be a known common disease mutation (Lerner-Ellis_2006). In addition, multiple clinical diagnostic laboratories/reputable databases classified this variant as pathogenic. Taken together, this variant is classified as pathogenic. -

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

AlphaMissense

Pathogenic

0.64

BayesDel_addAF

Pathogenic

0.32

BayesDel_noAF

Pathogenic

0.54

CADD

Pathogenic

DANN

Uncertain

1.0

DEOGEN2

Pathogenic

0.86

D;.

Eigen

Uncertain

0.53

Eigen_PC

Uncertain

0.31

FATHMM_MKL

Uncertain

0.78

LIST_S2

Pathogenic

0.99

D;D

M_CAP

Pathogenic

0.83

MetaRNN

Pathogenic

0.99

D;D

MetaSVM

Pathogenic

1.0

MutationAssessor

Pathogenic

4.8

H;.

MutationTaster

Benign

1.0

A;A

PrimateAI

Uncertain

0.72

PROVEAN

Pathogenic

-7.5

D;.

REVEL

Pathogenic

0.85

Sift

Pathogenic

0.0

D;.

Sift4G

Pathogenic

0.0

D;D

Polyphen

1.0

D;.

Vest4

0.98

MVP

1.0

MPC

0.85

ClinPred

1.0

GERP RS

3.0

RBP_binding_hub_radar

0.0

RBP_regulation_power_radar

1.1

Varity_R

0.97

gMVP

0.97

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