12-109561047-C-T

Variant names:

Variant summary

Our verdict is Pathogenic. The variant received 18 ACMG points: 18P and 0B. PM1PM2PM5PP3_StrongPP5_Very_Strong

The NM_052845.4(MMAB):c.577G>A(p.Glu193Lys) variant causes a missense change. The variant allele was found at a frequency of 0.0000125 in 1,599,550 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. E193Q) has been classified as Likely pathogenic.

Frequency

Genomes: 𝑓 0.000013 ( 0 hom., cov: 30)

Exomes 𝑓: 0.000012 ( 0 hom. )

Consequence

MMAB
NM_052845.4 missense

Scores

Clinical Significance

Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:3U:1

Conservation

PhyloP100: 5.67

Publications

13 publications found

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 Gene-Disease associations (from GenCC):

methylmalonic aciduria, cblB type
Inheritance: AR Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: ClinGen, G2P, Myriad Women’s Health, Labcorp Genetics (formerly Invitae), Orphanet

MMAB links:

Genome browser will be placed here

ACMG classification

Classification was made for transcript

Our verdict: Pathogenic. The variant received 18 ACMG points.

PM1

In a hotspot region, there are 16 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 9 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 chr12-109561047-C-G is described in ClinVar as Likely_pathogenic. ClinVar VariationId is 522406.Status of the report is no_assertion_criteria_provided, 0 stars.

PP3

MetaRNN computational evidence supports a deleterious effect, 0.993

PP5

Variant 12-109561047-C-T is Pathogenic according to our data. Variant chr12-109561047-C-T is described in ClinVar as Pathogenic/Likely_pathogenic. ClinVar VariationId is 554009.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
MMAB	NM_052845.4 link	c.577G>A	p.Glu193Lys	missense_variant	Exon 7 of 9	ENST00000545712.7	NP_443077.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
MMAB	ENST00000545712.7 link	c.577G>A	p.Glu193Lys	missense_variant	Exon 7 of 9	1	NM_052845.4	ENSP00000445920.1

Frequencies

GnomAD3 genomes

AF:

0.0000132

AC:

AN:

151344

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:

0.0000295

Gnomad OTH

AF:

0.00

GnomAD2 exomes

AF:

0.00000805

AC:

AN:

248570

AF XY:

0.0000148

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 FIN exome

AF:

0.00

Gnomad NFE exome

AF:

0.00

Gnomad OTH exome

AF:

0.00

GnomAD4 exome

AF:

0.0000124

AC:

AN:

1448206

Hom.:

Cov.:

AF XY:

0.0000194

AC XY:

AN XY:

720598

show subpopulations

African (AFR)

AF:

0.00

AC:

AN:

33212

American (AMR)

AF:

0.00

AC:

AN:

44412

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

25788

East Asian (EAS)

AF:

0.00

AC:

AN:

39108

South Asian (SAS)

AF:

0.0000348

AC:

AN:

86160

European-Finnish (FIN)

AF:

0.00

AC:

AN:

48602

Middle Eastern (MID)

AF:

0.00

AC:

AN:

5714

European-Non Finnish (NFE)

AF:

0.0000136

AC:

AN:

1105504

Other (OTH)

AF:

0.00

AC:

AN:

59706

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.461

Heterozygous variant carriers

0.00

0.20

0.40

0.60

0.80

0.95

Allele balance

Age Distribution

Exome Het

Variant carriers

<30

30-35

35-40

40-45

45-50

50-55

55-60

60-65

65-70

70-75

75-80

>80

Age

GnomAD4 genome

AF:

0.0000132

AC:

AN:

151344

Hom.:

Cov.:

AF XY:

0.00

AC XY:

AN XY:

73858

show subpopulations

African (AFR)

AF:

0.00

AC:

AN:

41204

American (AMR)

AF:

0.00

AC:

AN:

15212

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

3462

East Asian (EAS)

AF:

0.00

AC:

AN:

5096

South Asian (SAS)

AF:

0.00

AC:

AN:

4752

European-Finnish (FIN)

AF:

0.00

AC:

AN:

10490

Middle Eastern (MID)

AF:

0.00

AC:

AN:

316

European-Non Finnish (NFE)

AF:

0.0000295

AC:

AN:

67824

Other (OTH)

AF:

0.00

AC:

AN:

2078

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.525

Heterozygous variant carriers

0.00

0.20

0.40

0.60

0.80

0.95

Allele balance

Age Distribution

Genome Het

Variant carriers

<30

30-35

35-40

40-45

45-50

50-55

55-60

60-65

65-70

70-75

75-80

>80

Age

Alfa

AF:

0.0000203

Hom.:

Bravo

AF:

0.0000151

ExAC

AF:

0.0000247

AC:

EpiCase

AF:

0.0000545

EpiControl

AF:

0.00

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:3Uncertain:1

Revision: criteria provided, multiple submitters, no conflicts

LINK: link

Submissions by phenotype

Methylmalonic aciduria, cblB type

Pathogenic:3Uncertain:1

Jan 10, 2024

Baylor Genetics

Significance:Likely 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

- -

Sep 22, 2017

Counsyl

Significance:Uncertain significance

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. -

Dec 19, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance:Pathogenic

Review Status:criteria provided, single submitter

Collection Method:clinical testing

This sequence change replaces glutamic acid, which is acidic and polar, with lysine, which is basic and polar, at codon 193 of the MMAB protein (p.Glu193Lys). 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 individual(s) with methylmalonic aciduria (PMID: 12471062, 25760844, 31622506, 33453710, 34796408). 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: 554009). 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, 34757128). For these reasons, this variant has been classified as Pathogenic. -

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

AlphaMissense

Pathogenic

0.85

BayesDel_addAF

Pathogenic

0.57

BayesDel_noAF

Pathogenic

0.58

CADD

Pathogenic

(source)

DANN

Pathogenic

1.0

DEOGEN2

Pathogenic

0.86

D;.

Eigen

Pathogenic

0.98

Eigen_PC

Pathogenic

0.83

FATHMM_MKL

Uncertain

0.92

LIST_S2

Uncertain

0.94

D;D

M_CAP

Pathogenic

0.81

MetaRNN

Pathogenic

0.99

D;D

MetaSVM

Pathogenic

1.1

MutationAssessor

Pathogenic

4.8

H;.

PhyloP100

5.7

PrimateAI

Uncertain

0.72

PROVEAN

Uncertain

-3.7

D;.

REVEL

Pathogenic

0.96

Sift

Pathogenic

0.0

D;.

Sift4G

Pathogenic

0.0

D;D

Polyphen

1.0

D;.

Vest4

0.94

MutPred

0.95

Gain of catalytic residue at E193 (P = 0.0037);.;

MVP

1.0

MPC

0.89

ClinPred

1.0

GERP RS

4.9

RBP_binding_hub_radar

0.0

RBP_regulation_power_radar

1.7

Varity_R

0.98

gMVP

0.99

Mutation Taster

=8/92

disease causing

(source)

Splicing

Name

Calibrated prediction

Score

Prediction

Splicevardb

2.0

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

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Variant summary

Frequency

Consequence

Scores

Clinical Significance

Conservation

Publications

ACMG classification

Transcripts

RefSeq

Ensembl

Frequencies

Age Distribution

Age Distribution

ClinVar

Submissions by phenotype

Computational scores

Splicing

Publications

Other links and lift over