rs556977618

Positions:

• chr1-45507550-G-A
• chr1-45507550-G-T

Variant summary

Our verdict is Pathogenic. Variant got 10 ACMG points: 10P and 0B. PM2 PP5_Very_Strong

The NM_015506.3(MMACHC):​c.276G>A​(p.Glu92=) variant causes a splice region, synonymous change. The variant allele was found at a frequency of 0.00000248 in 1,614,052 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 2/3 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Likely pathogenic (★★).

• Frequency:
  • Genomes: 𝑓 0.0000066 (0 hom., cov: 31)
  • Exomes 𝑓: 0.0000021 (0 hom.)
• Consequence: MMACHC NM_015506.3 splice_region, synonymous
• Scores: Splicing: ADA: 0.9993
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:3
• Conservation: PhyloP100: 6.33

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 Pathogenic. Variant got 10 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 1-45507550-G-A is Pathogenic according to our data. Variant chr1-45507550-G-A is described in ClinVar as [Likely_pathogenic]. Clinvar id is 161118.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
MMACHC	NM_015506.3	c.276G>A	p.Glu92=	splice_region_variant, synonymous_variant	2/4	ENST00000401061.9	NP_056321.2
MMACHC	NM_001330540.2	c.105G>A	p.Glu35=	splice_region_variant, synonymous_variant	2/4		NP_001317469.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
MMACHC	ENST00000401061.9	c.276G>A	p.Glu92=	splice_region_variant, synonymous_variant	2/4	2	NM_015506.3	ENSP00000383840	P1
MMACHC	ENST00000616135.1	c.105G>A	p.Glu35=	splice_region_variant, synonymous_variant	2/5	2		ENSP00000478859

Frequencies

GnomAD3 genomes AF: 0.00000657 AC: 1 AN: 152188 Hom.: 0 Cov.: 31

Gnomad AFR AF: 0.00

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: 0.0000147

Gnomad OTH AF: 0.00

GnomAD4 exome AF: 0.00000205 AC: 3 AN: 1461864 Hom.: 0 Cov.: 32 AF XY: 0.00000138 AC XY: 1 AN XY: 727228

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: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00000270

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome AF: 0.00000657 AC: 1 AN: 152188 Hom.: 0 Cov.: 31 AF XY: 0.0000135 AC XY: 1 AN XY: 74342

Gnomad4 AFR AF: 0.00

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: 0.0000147

Gnomad4 OTH AF: 0.00

Alfa AF: 0.0000191 Hom.: 0

Bravo AF: 0.0000151

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:3

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Cobalamin C disease Pathogenic:3

Pathogenic, criteria provided, single submitter	clinical testing	Baylor Genetics	Mar 28, 2024	- -
Pathogenic, no assertion criteria provided	literature only	OMIM	Aug 01, 2013	- -
Likely pathogenic, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	Dec 01, 2023	This sequence change affects codon 92 of the MMACHC mRNA. It is a 'silent' change, meaning that it does not change the encoded amino acid sequence of the MMACHC protein. This variant also falls at the last nucleotide of exon 2, which is part of the consensus splice site for this exon. This variant is not present in population databases (gnomAD no frequency). This variant has been observed in individual(s) with MMACHC-related conditions (PMID: 23837176). ClinVar contains an entry for this variant (Variation ID: 161118). Variants that disrupt the consensus splice site are a relatively common cause of aberrant splicing (PMID: 17576681, 9536098). Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may disrupt the consensus splice site. This variant disrupts the c.276G nucleotide in the MMACHC gene. Other variant(s) that disrupt this nucleotide have been determined to be pathogenic (PMID: 20652818, 23837176, 25894566). This suggests that this nucleotide is clinically significant, and that variants that disrupt this position are likely to be disease-causing. In summary, the currently available evidence indicates that the variant is pathogenic, but additional data are needed to prove that conclusively. Therefore, this variant has been classified as Likely Pathogenic. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_noAF	Benign	-0.30
CADD	Benign	20
DANN	Benign	0.87

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.99
SpliceAI score (max)		0.24		Details are displayed if max score is > 0.2
DS_DL_spliceai		0.24		Position offset: 0

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Publications

LitVar

Other links and lift over

dbSNP: rs556977618; hg19: chr1-45973222;