12-109561055-C-T

Variant names:

Variant summary

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

The NM_052845.4(MMAB):c.569G>A(p.Arg190His) variant causes a missense change. The variant allele was found at a frequency of 0.0000174 in 1,610,288 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 Likely pathogenic (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. R190C) has been classified as Likely pathogenic.

Frequency

Genomes: 𝑓 0.0000066 ( 0 hom., cov: 30)

Exomes 𝑓: 0.000019 ( 0 hom. )

Consequence

MMAB
NM_052845.4 missense

Scores

Clinical Significance

Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:6O:1

Conservation

PhyloP100: 5.67

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 chr12-109561056-G-A is described in ClinVar as [Likely_pathogenic]. Clinvar id is 96244.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

PP3

MetaRNN computational evidence supports a deleterious effect, 0.995

PP5

Variant 12-109561055-C-T is Pathogenic according to our data. Variant chr12-109561055-C-T is described in ClinVar as [Likely_pathogenic]. Clinvar id is 203819.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr12-109561055-C-T is described in Lovd as [Likely_pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
MMAB	NM_052845.4 link	c.569G>A	p.Arg190His	missense_variant	Exon 7 of 9	ENST00000545712.7	NP_443077.1	Q96EY8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
MMAB	ENST00000545712.7 link	c.569G>A	p.Arg190His	missense_variant	Exon 7 of 9	1	NM_052845.4	ENSP00000445920.1		Q96EY8

Frequencies

GnomAD3 genomes

AF:

0.00000659

AC:

AN:

151764

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.00

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:

0.0000147

Gnomad OTH

AF:

0.00

GnomAD3 exomes

AF:

0.00000402

AC:

AN:

248806

Hom.:

AF XY:

0.00000741

AC XY:

AN XY:

134988

show subpopulations

Gnomad AFR exome

AF:

0.00

Gnomad AMR exome

AF:

0.00

Gnomad ASJ exome

AF:

0.00

Gnomad EAS exome

AF:

0.00

Gnomad SAS exome

AF:

0.00

Gnomad FIN exome

AF:

0.00

Gnomad NFE exome

AF:

0.00000885

Gnomad OTH exome

AF:

0.00

GnomAD4 exome

AF:

0.0000185

AC:

AN:

1458524

Hom.:

Cov.:

AF XY:

0.0000207

AC XY:

AN XY:

725830

show subpopulations

Gnomad4 AFR exome

AF:

0.00

Gnomad4 AMR exome

AF:

0.00

Gnomad4 ASJ exome

AF:

0.00

Gnomad4 EAS exome

AF:

0.0000252

Gnomad4 SAS exome

AF:

0.00

Gnomad4 FIN exome

AF:

0.00

Gnomad4 NFE exome

AF:

0.0000234

Gnomad4 OTH exome

AF:

0.00

GnomAD4 genome

AF:

0.00000659

AC:

AN:

151764

Hom.:

Cov.:

AF XY:

0.00

AC XY:

AN XY:

74086

show subpopulations

Gnomad4 AFR

AF:

0.00

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:

0.0000147

Gnomad4 OTH

AF:

0.00

Alfa

AF:

0.0000329

Hom.:

Bravo

AF:

0.0000113

TwinsUK

AF:

0.000270

AC:

ALSPAC

AF:

0.00

AC:

ExAC

AF:

0.00000824

AC:

EpiCase

AF:

0.00

EpiControl

AF:

0.000119

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:6Other:1

Revision: criteria provided, multiple submitters, no conflicts

LINK: link

Submissions by phenotype

Methylmalonic aciduria, cblB type

Pathogenic:4Other:1

GeneReviews

Significance: not provided

Review Status: no classification provided

Collection Method: literature only

- -

Feb 03, 2025

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces arginine, which is basic and polar, with histidine, which is basic and polar, at codon 190 of the MMAB protein (p.Arg190His). The frequency data for this variant in the population databases is considered unreliable, as metrics indicate poor data quality at this position in the gnomAD database. This missense change has been observed in individuals with methylmalonic aciduria cobalamin B type (PMID: 16410054). ClinVar contains an entry for this variant (Variation ID: 203819). Invitae Evidence Modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) 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). This variant disrupts the p.Arg190 amino acid residue in MMAB. Other variant(s) that disrupt this residue have been determined to be pathogenic (PMID: 16410054, 19625202, 24059531, 29039164, 29197662). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. For these reasons, this variant has been classified as Pathogenic. -

May 16, 2017

Counsyl

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Jan 05, 2024

Baylor Genetics

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Jun 01, 2021

Baumgartner lab, University Children's Hospital Zurich

Significance: Pathogenic

Review Status: no assertion criteria provided

Collection Method: clinical testing

- -

not provided

Pathogenic:1

Dec 07, 2018

GeneDx

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The R190H variant is a conservative amino acid substitution as these residues share similar properties, and are less likely to impact secondary structure. This change occurs at a residue that is conserved across species. In silico analysis predicts this mutation is probably damaging to the protein structure/function. Mutations at this residue (R190C) and nearby residues (R186Q, R191W, R191Q) have been reported in association with methylmalonic aciduria, supporting the functional importance of this residue and this region of the protein. The R190H mutation in the MMAB gene has been reported previously in association with methylmalonic aciduria (Lerner-Ellis et al., 2006). The R190H mutation was not observed in approximately 6,500 individuals of European and African American ancestry in the NHLBI Exome Sequencing Project, indicating it is not a common benign variant in these populations. We interpret R190H as a disease-causing mutation. This variant has been observed to be maternally inherited. -

Methylmalonic acidemia

Pathogenic:1

Apr 21, 2021

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

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Variant summary: MMAB c.569G>A (p.Arg190His) results in a non-conservative amino acid change located in the Cobalamin adenosyltransferase-like of the encoded protein sequence. Five of five in-silico tools predict a damaging effect of the variant on protein function. The variant allele was found at a frequency of 4e-06 in 248806 control chromosomes. c.569G>A has been reported in the literature in individuals affected with Methylmalonic Acidemia (Lerner-Ellis_2006). In experimental studies, the variant has been shown to result in decreased stability, significantly decreased affinity for AdoCbl, the product of the adenosylation reaction, and therefore completely inactive enzyme (Brasil_2018, Zhang_2006, Zhang_2009). Four clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar after 2014 without evidence for independent evaluation. Three classified as pathogenic/likely pathogenic while one classified as VUS. Based on the evidence outlined above, the variant was classified as pathogenic. -

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

AlphaMissense

Pathogenic

0.70

BayesDel_addAF

Pathogenic

0.56

BayesDel_noAF

Pathogenic

0.57

CADD

Pathogenic

DANN

Pathogenic

1.0

DEOGEN2

Pathogenic

0.86

D;.

Eigen

Pathogenic

0.96

Eigen_PC

Pathogenic

0.81

FATHMM_MKL

Uncertain

0.92

LIST_S2

Uncertain

0.96

D;D

M_CAP

Pathogenic

0.87

MetaRNN

Pathogenic

1.0

D;D

MetaSVM

Pathogenic

1.0

MutationAssessor

Pathogenic

4.8

H;.

PrimateAI

Uncertain

0.69

PROVEAN

Uncertain

-4.4

D;.

REVEL

Pathogenic

0.97

Sift

Uncertain

0.0010

D;.

Sift4G

Pathogenic

0.0010

D;D

Polyphen

1.0

D;.

Vest4

0.95

MutPred

0.99

Loss of MoRF binding (P = 0.0093);.;

MVP

1.0

MPC

0.93

ClinPred

1.0

GERP RS

4.9

RBP_binding_hub_radar

0.0

RBP_regulation_power_radar

1.7

Varity_R

0.97

gMVP

0.95

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