Genetic Variant MMAB:p.Ser174Trp (chr12-109561103-G-C) – ACMG Classification: Likely_pathogenic (7 pts)

Variant summary

Our verdict is Likely pathogenic. The variant received 7 ACMG points: 7P and 0B. PM1PM2PM5PP3

The NM_052845.4(MMAB):c.521C>G(p.Ser174Trp) variant causes a missense, splice region change. The variant allele was found at a frequency of 0.000000686 in 1,457,702 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. 2/3 splice prediction tools predicting alterations to normal splicing. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar. Another variant affecting the same amino acid position, but resulting in a different missense (i.e. S174L) has been classified as Likely pathogenic.

Frequency

Genomes: not found (cov: 30)

Exomes 𝑓: 6.9e-7 ( 0 hom. )

Consequence

MMAB
NM_052845.4 missense, splice_region

Scores

Splicing: ADA: 0.9739

Clinical Significance

Not reported in ClinVar

Conservation

PhyloP100: 7.15

Publications

0 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:

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ACMG classification

Classification was made for transcript

Our verdict: Likely_pathogenic. The variant received 7 ACMG points.

PM1

In a chain Corrinoid adenosyltransferase MMAB (size 217) in uniprot entity MMAB_HUMAN there are 29 pathogenic changes around while only 7 benign (81%) 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 chr12-109561103-G-A is described in ClinVar as Conflicting_classifications_of_pathogenicity. ClinVar VariationId is 445684.

PP3

Splicing predictors support a deleterious effect. Scorers claiming Pathogenic: dbscSNV1_ADA, dbscSNV1_RF. No scorers claiming Uncertain. Scorers claiming Benign: max_spliceai.

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_052845.4. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Sel.	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	MMAB	NM_052845.4	MANE Select	c.521C>G	p.Ser174Trp	missense splice_region	Exon 7 of 9	NP_443077.1
	MMAB	NR_038118.2		n.632C>G		splice_region non_coding_transcript_exon	Exon 8 of 10

Ensembl Transcripts

Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein
MMAB	ENST00000545712.7	TSL:1 MANE Select	c.521C>G	p.Ser174Trp	missense splice_region	Exon 7 of 9	ENSP00000445920.1
MMAB	ENST00000878519.1		c.584C>G	p.Ser195Trp	missense splice_region	Exon 8 of 10	ENSP00000548578.1
MMAB	ENST00000878520.1		c.521C>G	p.Ser174Trp	missense splice_region	Exon 7 of 8	ENSP00000548579.1

Frequencies

GnomAD3 genomes

Cov.:

GnomAD4 exome

AF:

6.86e-7

AC:

AN:

1457702

Hom.:

Cov.:

AF XY:

0.00

AC XY:

AN XY:

725408

show subpopulations

African (AFR)

AF:

0.00

AC:

AN:

33472

American (AMR)

AF:

0.00

AC:

AN:

44712

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

26128

East Asian (EAS)

AF:

0.0000252

AC:

AN:

39688

South Asian (SAS)

AF:

0.00

AC:

AN:

86250

European-Finnish (FIN)

AF:

0.00

AC:

AN:

49464

Middle Eastern (MID)

AF:

0.00

AC:

AN:

5768

European-Non Finnish (NFE)

AF:

0.00

AC:

AN:

1111870

Other (OTH)

AF:

0.00

AC:

AN:

60350

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

GnomAD4 genome

Cov.:

ClinVar

Not reported in ClinVar

Computational scores

Source: dbNSFP v4.9

Name

Calibrated prediction

Score

Prediction

AlphaMissense

Pathogenic

0.71

BayesDel_addAF

Pathogenic

0.52

BayesDel_noAF

Pathogenic

0.51

CADD

Pathogenic

(source)

DANN

Uncertain

0.99

DEOGEN2

Pathogenic

0.84

Eigen

Pathogenic

0.86

Eigen_PC

Pathogenic

0.78

FATHMM_MKL

Uncertain

0.95

LIST_S2

Pathogenic

0.98

M_CAP

Pathogenic

0.65

MetaRNN

Pathogenic

0.96

MetaSVM

Pathogenic

1.1

MutationAssessor

Pathogenic

3.4

PhyloP100

7.2

PrimateAI

Uncertain

0.60

PROVEAN

Pathogenic

-5.3

REVEL

Pathogenic

0.93

Sift

Uncertain

0.0040

Sift4G

Pathogenic

0.0010

Polyphen

1.0

Vest4

0.91

MutPred

0.79

Loss of disorder (P = 0.0135)

MVP

0.99

MPC

0.99

ClinPred

1.0

GERP RS

4.9

Varity_R

0.95

gMVP

0.93

Mutation Taster

=23/77

disease causing

(source)

Splicing

Name

Calibrated prediction

Score

Prediction

dbscSNV1_ADA

Pathogenic

0.97

dbscSNV1_RF

Pathogenic

0.77

SpliceAI score (max)

0.010

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

Variant Effect in Transcripts

RefSeq Transcripts

Ensembl Transcripts

Frequencies

ClinVar

Computational scores

Splicing

Publications

Other links and lift over