rs199641732

Positions:

• chr1-45509016-A-G
• chr1-45509016-A-T

Variant summary

Our verdict is Uncertain significance. Variant got 4 ACMG points: 4P and 0B. PM1 PM2

The NM_015506.3(MMACHC):​c.650A>G​(p.Glu217Gly) variant causes a missense change. The variant allele was found at a frequency of 0.000000684 in 1,461,878 control chromosomes in the GnomAD database, with no homozygous occurrence. Variant has been reported in ClinVar as Uncertain significance (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. E217K) has been classified as Uncertain significance.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: MMACHC NM_015506.3 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:5
• Conservation: PhyloP100: 5.44

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]

ACMG classification

Verdict is Uncertain_significance. Variant got 4 ACMG points.

• PM1: In a chain Cyanocobalamin reductase / alkylcobalamin dealkylase (size 281) in uniprot entity MMAC_HUMAN there are 49 pathogenic changes around while only 14 benign (78%) in NM_015506.3
• PM2: Very rare variant in population databases, with high coverage

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
MMACHC	NM_015506.3	c.650A>G	p.Glu217Gly	missense_variant	4/4	ENST00000401061.9	NP_056321.2
MMACHC	NM_001330540.2	c.479A>G	p.Glu160Gly	missense_variant	4/4		NP_001317469.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
MMACHC	ENST00000401061.9	c.650A>G	p.Glu217Gly	missense_variant	4/4	2	NM_015506.3	ENSP00000383840.4
MMACHC	ENST00000616135.1	c.479A>G	p.Glu160Gly	missense_variant	4/5	2		ENSP00000478859.1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1461878 Hom.: 0 Cov.: 32 AF XY: 0.00 AC XY: 0 AN XY: 727242

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: 0.00

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:5

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not provided Uncertain:3

Uncertain significance, criteria provided, single submitter	not provided	Breakthrough Genomics, Breakthrough Genomics	-	- -
Uncertain significance, criteria provided, single submitter	clinical testing	GeneDx	Mar 21, 2017	The E217G variant in the MMACHC gene has not been reported previously as a pathogenic variant, nor as a benign variant, to our knowledge. The E217G variant is not observed in large population cohorts (Lek et al., 2016; 1000 Genomes Consortium et al., 2015; Exome Variant Server). The E217G 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. We interpret E217G as a variant of uncertain significance. -
Uncertain significance, criteria provided, single submitter	clinical testing	Eurofins Ntd Llc (ga)	Mar 19, 2018	- -

Cobalamin C disease Uncertain:2

Uncertain significance, no assertion criteria provided	clinical testing	Natera, Inc.	Aug 03, 2020	- -
Uncertain significance, criteria provided, single submitter	clinical testing	Genome-Nilou Lab	Apr 11, 2023	- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.21
BayesDel_addAF	Pathogenic	0.20	D
BayesDel_noAF	Uncertain	0.040
CADD	Pathogenic	27
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.86	D;T
Eigen	Uncertain	0.52
Eigen_PC	Uncertain	0.57
FATHMM_MKL	Pathogenic	0.98	D
LIST_S2	Uncertain	0.86	D;D
M_CAP	Uncertain	0.21	D
MetaRNN	Uncertain	0.44	T;T
MetaSVM	Pathogenic	0.85	D
MutationAssessor	Uncertain	2.5	M;.
PrimateAI	Benign	0.39	T
PROVEAN	Uncertain	-3.9	D;.
REVEL	Uncertain	0.60
Sift	Benign	0.033	D;.
Sift4G	Uncertain	0.039	D;D
Polyphen		0.94	P;.
Vest4		0.32
MutPred		0.17		Gain of glycosylation at S216 (P = 0.0316);.;
MVP		0.99
MPC		0.034
ClinPred		0.99	D
GERP RS		5.8
Varity_R		0.56
gMVP		0.63

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

Other links and lift over

dbSNP: rs199641732; hg19: chr1-45974688;