NM_015506.3:c.33G>T

Variant names:

• chr1-45500365-G-T
• rs770446383
• NM_015506.3:c.33G>T

Variant summary

Our verdict is Uncertain significance. The variant received 3 ACMG points: 5P and 2B. PM1 PM2 PP2 BP4_Moderate

The NM_015506.3(MMACHC):​c.33G>T​(p.Lys11Asn) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.0000116 in 1,461,854 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 14/22 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★). Synonymous variant affecting the same amino acid position (i.e. K11K) has been classified as Likely benign.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.000012 (0 hom.)
• Consequence: MMACHC NM_015506.3 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 2.56
• Publications: 0 publications found

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: Labcorp Genetics (formerly Invitae), Ambry Genetics, Myriad Women’s Health, ClinGen, G2P, Orphanet

ACMG classification

Our verdict: Uncertain_significance. The variant received 3 ACMG points.

• PM1: In a chain Cyanocobalamin reductase / alkylcobalamin dealkylase (size 281) in uniprot entity MMAC_HUMAN there are 38 pathogenic changes around while only 16 benign (70%) in NM_015506.3
• PM2: Very rare variant in population databases, with high coverage
• 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.
• BP4: Computational evidence support a benign effect (MetaRNN=0.21762988).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
MMACHC	NM_015506.3	c.33G>T	p.Lys11Asn	missense_variant	Exon 1 of 4	ENST00000401061.9	NP_056321.2
MMACHC	NM_001330540.2	c.-190G>T		5_prime_UTR_variant	Exon 1 of 4		NP_001317469.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
MMACHC	ENST00000401061.9	c.33G>T	p.Lys11Asn	missense_variant	Exon 1 of 4	2	NM_015506.3	ENSP00000383840.4
MMACHC	ENST00000616135.1	c.-139G>T		5_prime_UTR_variant	Exon 1 of 5	2		ENSP00000478859.1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD2 exomes AF: 0.00000801 AC: 2 AN: 249576 AF XY: 0.00000739

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: 0.0000464

Gnomad NFE exome AF: 0.00000883

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.0000116 AC: 17 AN: 1461854 Hom.: 0 Cov.: 30 AF XY: 0.00000825 AC XY: 6 AN XY: 727230

African (AFR) AF: 0.00 AC: 0 AN: 33480

American (AMR) AF: 0.00 AC: 0 AN: 44724

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26136

East Asian (EAS) AF: 0.00 AC: 0 AN: 39698

South Asian (SAS) AF: 0.00 AC: 0 AN: 86256

European-Finnish (FIN) AF: 0.0000374 AC: 2 AN: 53420

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5742

European-Non Finnish (NFE) AF: 0.0000135 AC: 15 AN: 1112010

Other (OTH) AF: 0.00 AC: 0 AN: 60388

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Inborn genetic diseases Uncertain:1

May 17, 2023

Ambry Genetics

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The c.33G>T (p.K11N) alteration is located in exon 1 (coding exon 1) of the MMACHC gene. This alteration results from a G to T substitution at nucleotide position 33, causing the lysine (K) at amino acid position 11 to be replaced by an asparagine (N). Based on insufficient or conflicting evidence, the clinical significance of this alteration remains unclear. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.23
BayesDel_addAF	Benign	-0.0050	T
BayesDel_noAF	Benign	-0.24
CADD	Benign	21
DANN	Uncertain	0.99
DEOGEN2	Benign	0.088	T
Eigen	Benign	-0.24
Eigen_PC	Benign	-0.081
FATHMM_MKL	Benign	0.72	D
LIST_S2	Benign	0.69	T
M_CAP	Uncertain	0.22	D
MetaRNN	Benign	0.22	T
MetaSVM	Uncertain	0.39	D
MutationAssessor	Benign	1.5	L
PhyloP100		2.6
PrimateAI	Uncertain	0.55	T
PROVEAN	Benign	-0.94	N
REVEL	Benign	0.26
Sift	Benign	0.32	T
Sift4G	Benign	0.55	T
Polyphen		0.25	B
Vest4		0.24
MutPred		0.30		Loss of ubiquitination at K11 (P = 0.0098);
MVP		0.93
MPC		0.015
ClinPred		0.41	T
GERP RS		4.9
PromoterAI		-0.18	Neutral
Varity_R		0.22
gMVP		0.56
Mutation Taster		=70/30	polymorphism

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

Other links and lift over

dbSNP: rs770446383; hg19: chr1-45966037;