rs765547005

Variant summary

Our verdict is Likely pathogenic. Variant got 6 ACMG points: 6P and 0B. PM1PM2PP3_Moderate

The NM_052845.4(MMAB):c.656A>G(p.Tyr219Cys) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000993 in 1,611,266 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: 𝑓 0.000046 ( 0 hom., cov: 34)

Exomes 𝑓: 0.0000062 ( 0 hom. )

Consequence

MMAB
NM_052845.4 missense

Scores

Clinical Significance

Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:1U:4O:1

Conservation

PhyloP100: 3.09

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 Likely_pathogenic. Variant got 6 ACMG points.

PM1

In a chain Corrinoid adenosyltransferase MMAB (size 217) in uniprot entity MMAB_HUMAN there are 32 pathogenic changes around while only 10 benign (76%) in NM_052845.4

PM2

Very rare variant in population databases, with high coverage;

PP3

MetaRNN computational evidence supports a deleterious effect, 0.894

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
MMAB	NM_052845.4 linkuse as main transcript	c.656A>G	p.Tyr219Cys	missense_variant	9/9	ENST00000545712.7

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
MMAB	ENST00000545712.7 linkuse as main transcript	c.656A>G	p.Tyr219Cys	missense_variant	9/9	1	NM_052845.4	P1

Frequencies

GnomAD3 genomes

AF:

0.0000460

AC:

AN:

152246

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.000169

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:

0.00

Gnomad OTH

AF:

0.00

GnomAD3 exomes

AF:

0.0000239

AC:

AN:

251446

Hom.:

AF XY:

0.00

AC XY:

AN XY:

135898

show subpopulations

Gnomad AFR exome

AF:

0.000369

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:

0.00

Gnomad OTH exome

AF:

0.00

GnomAD4 exome

AF:

0.00000617

AC:

AN:

1458902

Hom.:

Cov.:

AF XY:

0.00000689

AC XY:

AN XY:

726050

show subpopulations

Gnomad4 AFR exome

AF:

0.000239

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:

9.01e-7

Gnomad4 OTH exome

AF:

0.00

GnomAD4 genome

AF:

0.0000459

AC:

AN:

152364

Hom.:

Cov.:

AF XY:

0.0000537

AC XY:

AN XY:

74510

show subpopulations

Gnomad4 AFR

AF:

0.000168

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:

0.00

Gnomad4 OTH

AF:

0.00

Alfa

AF:

0.0000647

Hom.:

Bravo

AF:

0.0000302

ExAC

AF:

0.0000330

AC:

Asia WGS

AF:

0.000289

AC:

AN:

3478

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:1Uncertain:4Other:1

Revision: criteria provided, conflicting classifications

LINK: link

Submissions by phenotype

Methylmalonic aciduria, cblB type

Pathogenic:1Uncertain:2Other:1

Uncertain significance, criteria provided, single submitter	clinical testing	Counsyl	Jan 04, 2018	- -
Likely pathogenic, criteria provided, single submitter	clinical testing	Invitae	Oct 22, 2023	This sequence change replaces tyrosine, which is neutral and polar, with cysteine, which is neutral and slightly polar, at codon 219 of the MMAB protein (p.Tyr219Cys). This variant is present in population databases (rs765547005, gnomAD 0.03%). This missense change has been observed in individual(s) with clinical features of cobalamin B deficiency (PMID: 16410054; Invitae). In at least one individual the data is consistent with being in trans (on the opposite chromosome) from a pathogenic variant. ClinVar contains an entry for this variant (Variation ID: 219007). 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 not expected to disrupt MMAB protein function. 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. -
not provided, no classification provided	literature only	GeneReviews	-	- -
Uncertain significance, no assertion criteria provided	clinical testing	Natera, Inc.	Sep 16, 2020	- -

not specified

Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

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

Dec 24, 2022

Variant summary: MMAB c.656A>G (p.Tyr219Cys) results in a non-conservative amino acid change located in the Cobalamin adenosyltransferase-like domain (IPR016030) of the encoded protein sequence. Four of five in-silico tools predict a damaging effect of the variant on protein function. The variant allele was found at a frequency of 2.4e-05 in 251446 control chromosomes (gnomAD). c.656A>G has been reported in the literature as a complex genotype in individuals affected with Methylmalonic Aciduria, cblB type: these individuals carried a second pathogenic variant and a benign/VUS variant (Lerner-Ellis_2006). These data indicate that the variant may be associated with disease. To our knowledge, no experimental evidence demonstrating an impact on protein function has been reported. Three ClinVar submitters have assessed the variant since 2014: all three classified the variant as uncertain significance. Based on the evidence outlined above, the variant was classified as VUS-possibly pathogenic. -

not provided

Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

GeneDx

Jul 20, 2017

The Y219C variant has previously been reported in association with methylmalonic acidemia (MMA), cblB type in two individuals who were also heterozygous for two other variants in the MMAB gene; the phase of these variants was not determined (Lerner-Ellis et al., 2006). The Y219C variant is a non-conservative amino acid substitution, which is likely to impact secondary protein structure as these residues differ in polarity, charge, size and/or other properties. This substitution occurs at a position that is conserved in mammals. In silico analysis predicts this variant is probably damaging to the protein structure/function. Therefore, based on the currently available information, it is unclear whether this variant is a pathogenic variant or a rare benign variant. -

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

AlphaMissense

Benign

0.30

BayesDel_addAF

Pathogenic

0.24

BayesDel_noAF

Pathogenic

0.42

Cadd

Uncertain

Dann

Uncertain

1.0

DEOGEN2

Uncertain

0.64

D;.

Eigen

Uncertain

0.47

Eigen_PC

Uncertain

0.43

FATHMM_MKL

Uncertain

0.86

LIST_S2

Uncertain

0.93

D;D

M_CAP

Pathogenic

0.47

MetaRNN

Pathogenic

0.89

D;D

MetaSVM

Pathogenic

0.97

MutationAssessor

Uncertain

2.3

M;.

MutationTaster

Benign

1.0

D;D

PrimateAI

Uncertain

0.70

PROVEAN

Pathogenic

-5.4

D;.

REVEL

Pathogenic

0.91

Sift

Benign

0.032

D;.

Sift4G

Uncertain

0.057

T;D

Polyphen

0.99

D;.

Vest4

0.68

MVP

0.99

MPC

0.78

ClinPred

0.78

GERP RS

5.4

RBP_binding_hub_radar

0.0

RBP_regulation_power_radar

1.7

Varity_R

0.86

gMVP

0.93

Splicing

Name

Calibrated prediction

Score

Prediction

SpliceAI score (max)

0.020

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