rs1161394470

chr1-45508812-G-A

Variant summary

Our verdict is Likely pathogenic. Variant got 6 ACMG points: 6P and 0B. PM1 PM2 PP3_Moderate

The NM_015506.3(MMACHC):c.446G>A(p.Cys149Tyr) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000124 in 1,613,916 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 Uncertain significance (★★).

• Frequency:
  • Genomes: 𝑓 0.0000066 (0 hom., 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:2
• Conservation: PhyloP100: 9.35

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 Likely_pathogenic. Variant got 6 ACMG points.

• PM1: In a hotspot region, there are 7 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 2 benign, 4 uncertain in NM_015506.3
• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.918

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
MMACHC	NM_015506.3	c.446G>A	p.Cys149Tyr	missense_variant	4/4	ENST00000401061.9
MMACHC	NM_001330540.2	c.275G>A	p.Cys92Tyr	missense_variant	4/4

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
MMACHC	ENST00000401061.9	c.446G>A	p.Cys149Tyr	missense_variant	4/4	2	NM_015506.3	P1
MMACHC	ENST00000616135.1	c.275G>A	p.Cys92Tyr	missense_variant	4/5	2

Frequencies

GnomAD3 genomes AF: 0.00000657 AC: 1 AN: 152190 Hom.: 0 Cov.: 32

Gnomad AFR AF: 0.0000241

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: 0.00

Gnomad OTH AF: 0.00

GnomAD3 exomes AF: 0.00000402 AC: 1 AN: 249004 Hom.: 0 AF XY: 0.00000740 AC XY: 1 AN XY: 135096

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 SAS exome AF: 0.0000327

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1461726 Hom.: 0 Cov.: 31 AF XY: 0.00000138 AC XY: 1 AN XY: 727150

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.0000116

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome AF: 0.00000657 AC: 1 AN: 152190 Hom.: 0 Cov.: 32 AF XY: 0.0000135 AC XY: 1 AN XY: 74342

Gnomad4 AFR AF: 0.0000241

Gnomad4 AMR AF: 0.00

Gnomad4 ASJ AF: 0.00

Gnomad4 EAS AF: 0.00

Gnomad4 SAS AF: 0.00

Gnomad4 FIN AF: 0.00

Gnomad4 NFE AF: 0.00

Gnomad4 OTH AF: 0.00

Bravo AF: 0.00000378

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Cobalamin C disease Uncertain:2

Uncertain significance, criteria provided, single submitter	clinical testing	Genome-Nilou Lab	Jul 14, 2021	- -
Uncertain significance, criteria provided, single submitter	clinical testing	Invitae	Aug 27, 2021	This sequence change replaces cysteine with tyrosine at codon 149 of the MMACHC protein (p.Cys149Tyr). The cysteine residue is highly conserved and there is a large physicochemical difference between cysteine and tyrosine. This variant is not present in population databases (ExAC no frequency). This variant has not been reported in the literature in individuals affected with MMACHC-related conditions. Algorithms developed to predict the effect of missense changes on protein structure and function are either unavailable or do not agree on the potential impact of this missense change (SIFT: "Deleterious"; PolyPhen-2: "Probably Damaging"; Align-GVGD: "Class C15"). In summary, the available evidence is currently insufficient to determine the role of this variant in disease. Therefore, it has been classified as a Variant of Uncertain Significance. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.98
BayesDel_addAF	Pathogenic	0.49	D
BayesDel_noAF	Pathogenic	0.56
Cadd	Uncertain	24
Dann	Uncertain	1.0
DEOGEN2	Pathogenic	0.89	D;T
Eigen	Pathogenic	0.89
Eigen_PC	Pathogenic	0.86
FATHMM_MKL	Pathogenic	0.98	D
LIST_S2	Uncertain	0.92	D;D
M_CAP	Pathogenic	0.59	D
MetaRNN	Pathogenic	0.92	D;D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Pathogenic	3.2	M;.
MutationTaster	Benign	1.0	D
PrimateAI	Uncertain	0.73	T
PROVEAN	Pathogenic	-7.6	D;.
REVEL	Pathogenic	0.94
Sift	Uncertain	0.0030	D;.
Sift4G	Uncertain	0.0020	D;D
Polyphen		0.98	D;.
Vest4		0.88
MutPred		0.62		Gain of MoRF binding (P = 0.0739);.;
MVP		0.97
MPC		0.073
ClinPred		0.99	D
GERP RS		5.6
Varity_R		0.96
gMVP		0.98

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.050		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: rs1161394470; hg19: chr1-45974484;