dbSNP rs121918243: MMACHC:p.Arg161Gln (chr1-45508848-G-A) – ACMG Classification: Pathogenic (18 pts)

Variant summary

Our verdict is Pathogenic. The variant received 18 ACMG points: 18P and 0B. PS3PM1PM5PP2PP3PP5_Very_Strong

The NM_015506.3(MMACHC):c.482G>A(p.Arg161Gln) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.0000551 in 1,614,044 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 (★★). ClinVar reports functional evidence for this variant: "SCV000699401: "In the functional studies mutant R161Q has a decreased ability to bind incoming CNCbl, which results in a decreased ability to reductively decyanate the CNCbl to the cob(II)alamin form used in the metabolic pathway (PS3)."" and additional evidence is available in ClinVar. Another variant affecting the same amino acid position, but resulting in a different missense (i.e. R161G) has been classified as Likely pathogenic.

Frequency

Genomes: 𝑓 0.000072 ( 0 hom., cov: 32)

Exomes 𝑓: 0.000053 ( 0 hom. )

Consequence

MMACHC
NM_015506.3 missense

Scores

Clinical Significance

Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:22O:1

Conservation

PhyloP100: 9.36

Publications

100 publications found

Variant links:

Genes affected

MMACHC (HGNC:24525): (metabolism of cobalamin associated C) The exact function of the protein encoded by this gene is not known, however, its C-terminal region shows similarity to TonB, a bacterial protein involved in energy transduction for cobalamin (vitamin B12) uptake. Hence, it is postulated that this protein may have a role in the binding and intracellular trafficking of cobalamin. Mutations in this gene are associated with methylmalonic aciduria and homocystinuria type cblC. [provided by RefSeq, Oct 2009]

MMACHC Gene-Disease associations (from GenCC):

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

MMACHC links:

Genome browser will be placed here

ACMG classification

Classification was made for transcript

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

PS3

PS3 evidence extracted from ClinVar submissions: SCV000699401: "In the functional studies mutant R161Q has a decreased ability to bind incoming CNCbl, which results in a decreased ability to reductively decyanate the CNCbl to the cob(II)alamin form used in the metabolic pathway (PS3)."; SCV000762779: Experimental studies have shown that this missense change affects MMACHC function (PMID: 19700356, 20219402, 25809485).; SCV005416550: "Well-established in vitro or in vivo functional studies supportive of a damaging effect on the gene or gene product."; SCV000321902: Published functional studies demonstrate reduced protein stability (Gherasim et al., 2015; Froese et al., 2009); SCV000604240: Functional characterization of the variant protein indicates lower thermostability compared to wild type and impaired binding and stabilization of vitamin B12 (Froese 2010, Gherasim 2015).

PM1

In a hotspot region, there are 6 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 1 benign, 9 uncertain in NM_015506.3

PM5

Other missense variant is known to change same aminoacid residue: Variant chr1-45508847-C-G is described in ClinVar as Pathogenic/Likely_pathogenic. ClinVar VariationId is 813351.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

PP2

Missense variant in the gene, where a lot of missense mutations are associated with disease in ClinVar. The gene has 28 curated pathogenic missense variants (we use a threshold of 10). The gene has 7 curated benign missense variants. Gene score misZ: -1.0759 (below the threshold of 3.09). Trascript score misZ: -0.13772 (below the threshold of 3.09). GenCC associations: The gene is linked to methylmalonic aciduria and homocystinuria type cblC.

PP3

MetaRNN computational evidence supports a deleterious effect, 0.762

PP5

Variant 1-45508848-G-A is Pathogenic according to our data. Variant chr1-45508848-G-A is described in ClinVar as Pathogenic/Likely_pathogenic. ClinVar VariationId is 1425.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_015506.3. 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
	MMACHC	NM_015506.3	MANE Select	c.482G>A	p.Arg161Gln	missense	Exon 4 of 4	NP_056321.2	Q9Y4U1
	MMACHC	NM_001330540.2		c.311G>A	p.Arg104Gln	missense	Exon 4 of 4	NP_001317469.1	A0A0C4DGU2

Ensembl Transcripts

Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
MMACHC	ENST00000401061.9	TSL:2 MANE Select	c.482G>A	p.Arg161Gln	missense	Exon 4 of 4	ENSP00000383840.4	Q9Y4U1
MMACHC	ENST00000616135.1	TSL:2	c.311G>A	p.Arg104Gln	missense	Exon 4 of 5	ENSP00000478859.1	A0A0C4DGU2
MMACHC	ENST00000933807.1		c.287G>A	p.Arg96Gln	missense	Exon 3 of 3	ENSP00000603866.1

Frequencies

GnomAD3 genomes

AF:

0.0000723

AC:

AN:

152174

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.0000966

Gnomad AMI

AF:

0.00

Gnomad AMR

AF:

0.000196

Gnomad ASJ

AF:

0.00

Gnomad EAS

AF:

0.00

Gnomad SAS

AF:

0.000207

Gnomad FIN

AF:

0.00

Gnomad MID

AF:

0.00

Gnomad NFE

AF:

0.0000441

Gnomad OTH

AF:

0.00

GnomAD2 exomes

AF:

0.000172

AC:

AN:

249432

AF XY:

0.000140

show subpopulations

Gnomad AFR exome

AF:

0.000194

Gnomad AMR exome

AF:

0.00113

Gnomad ASJ exome

AF:

0.00

Gnomad EAS exome

AF:

0.0000556

Gnomad FIN exome

AF:

0.00

Gnomad NFE exome

AF:

0.00

Gnomad OTH exome

AF:

0.00

GnomAD4 exome

AF:

0.0000534

AC:

AN:

1461870

Hom.:

Cov.:

AF XY:

0.0000523

AC XY:

AN XY:

727234

show subpopulations

African (AFR)

AF:

0.000179

AC:

AN:

33480

American (AMR)

AF:

0.00101

AC:

AN:

44716

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

26132

East Asian (EAS)

AF:

0.0000756

AC:

AN:

39700

South Asian (SAS)

AF:

0.0000116

AC:

AN:

86254

European-Finnish (FIN)

AF:

0.0000374

AC:

AN:

53420

Middle Eastern (MID)

AF:

0.00

AC:

AN:

5768

European-Non Finnish (NFE)

AF:

0.0000162

AC:

AN:

1112006

Other (OTH)

AF:

0.0000497

AC:

AN:

60394

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.504

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:

0.0000723

AC:

AN:

152174

Hom.:

Cov.:

AF XY:

0.0000538

AC XY:

AN XY:

74346

show subpopulations

African (AFR)

AF:

0.0000966

AC:

AN:

41426

American (AMR)

AF:

0.000196

AC:

AN:

15282

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

3472

East Asian (EAS)

AF:

0.00

AC:

AN:

5200

South Asian (SAS)

AF:

0.000207

AC:

AN:

4836

European-Finnish (FIN)

AF:

0.00

AC:

AN:

10616

Middle Eastern (MID)

AF:

0.00

AC:

AN:

316

European-Non Finnish (NFE)

AF:

0.0000441

AC:

AN:

68026

Other (OTH)

AF:

0.00

AC:

AN:

2090

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.520

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:

0.0000986

Hom.:

Bravo

AF:

0.000140

ESP6500AA

AF:

0.000250

AC:

ESP6500EA

AF:

0.00

AC:

ExAC

AF:

0.000149

AC:

EpiCase

AF:

0.0000545

EpiControl

AF:

0.0000593

ClinVar

ClinVar submissions

Significance:Pathogenic/Likely pathogenic

Revision:criteria provided, multiple submitters, no conflicts

View on ClinVar

Pathogenic

VUS

Benign

Condition

Cobalamin C disease (13)

not provided (5)

Inborn genetic diseases (1)

Methylmalonic acidemia with homocystinuria cblC (1)

Methylmalonic aciduria due to methylmalonyl-CoA mutase deficiency (1)

MMACHC-related disorder (1)

Disorders of Intracellular Cobalamin Metabolism (1)

Computational scores

Source: dbNSFP v4.9

Name

Calibrated prediction

Score

Prediction

AlphaMissense

Pathogenic

0.76

BayesDel_addAF

Pathogenic

0.28

BayesDel_noAF

Pathogenic

0.58

CADD

Pathogenic

(source)

DANN

Pathogenic

1.0

DEOGEN2

Pathogenic

0.90

Eigen

Pathogenic

0.98

Eigen_PC

Pathogenic

0.94

FATHMM_MKL

Pathogenic

0.98

LIST_S2

Uncertain

0.86

M_CAP

Pathogenic

0.34

MetaRNN

Pathogenic

0.76

MetaSVM

Pathogenic

1.1

MutationAssessor

Pathogenic

3.0

PhyloP100

9.4

PrimateAI

Uncertain

0.65

PROVEAN

Uncertain

-3.7

REVEL

Pathogenic

0.96

Sift

Pathogenic

0.0

Sift4G

Pathogenic

0.0

Polyphen

1.0

Vest4

0.93

MVP

0.98

MPC

0.067

ClinPred

0.76

GERP RS

5.7

Varity_R

0.96

gMVP

0.98

Mutation Taster

=12/88

disease causing (ClinVar)

(source)

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

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Variant summary

Frequency

Consequence

Scores

Clinical Significance

Conservation

Publications

ACMG classification

Variant Effect in Transcripts

RefSeq Transcripts

Ensembl Transcripts

Frequencies

Age Distribution

Age Distribution

ClinVar

Computational scores

Splicing

Publications

Other links and lift over