12-109553732-C-T

Variant names:

• chr12-109553732-C-T
• rs777939885
• NM_052845.4:c.*3296G>A

Variant summary

Our verdict is Likely benign. The variant received -4 ACMG points: 0P and 4B. BP4_Strong

The NM_052845.4(MMAB):​c.*3296G>A variant causes a 3 prime UTR change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.0000449 in 401,098 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★).

• Frequency:
  • Genomes: 𝑓 0.000079 (0 hom., cov: 33)
  • Exomes 𝑓: 0.000024 (0 hom.)
• Consequence: MMAB NM_052845.4 3_prime_UTR
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: -0.475
• Publications: 0 publications found

Genes affected

MMAB (HGNC:19331): (metabolism of cobalamin associated B) This gene encodes a protein that catalyzes the final step in the conversion of vitamin B(12) into adenosylcobalamin (AdoCbl), a vitamin B12-containing coenzyme for methylmalonyl-CoA mutase. Mutations in the gene are the cause of vitamin B12-dependent methylmalonic aciduria linked to the cblB complementation group. Alternatively spliced transcript variants have been found. [provided by RefSeq, Apr 2011]

MMAB Gene-Disease associations (from GenCC):

• methylmalonic aciduria, cblB type

  Inheritance: AR Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: ClinGen, G2P, Myriad Women’s Health, Labcorp Genetics (formerly Invitae), Orphanet

ACMG classification

Our verdict: Likely_benign. The variant received -4 ACMG points.

• BP4: Computational evidence support a benign effect (BayesDel_noAF=-0.84).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
MMAB	NM_052845.4	c.*3296G>A		3_prime_UTR_variant	Exon 9 of 9	ENST00000545712.7	NP_443077.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
MMAB	ENST00000545712.7	c.*3296G>A		3_prime_UTR_variant	Exon 9 of 9	1	NM_052845.4	ENSP00000445920.1

Frequencies

GnomAD3 genomes AF: 0.0000723 AC: 11 AN: 152124 Hom.: 0 Cov.: 33

Gnomad AFR AF: 0.000193

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.0000655

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: 0.0000294

Gnomad OTH AF: 0.00

GnomAD2 exomes AF: 0.0000214 AC: 2 AN: 93670 AF XY: 0.0000204

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: 0.00

Gnomad NFE exome AF: 0.0000278

Gnomad OTH exome AF: 0.000332

GnomAD4 exome AF: 0.0000241 AC: 6 AN: 248856 Hom.: 0 Cov.: 0 AF XY: 0.0000217 AC XY: 3 AN XY: 138552

African (AFR) AF: 0.00 AC: 0 AN: 6970

American (AMR) AF: 0.0000450 AC: 1 AN: 22224

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 7434

East Asian (EAS) AF: 0.00 AC: 0 AN: 8686

South Asian (SAS) AF: 0.0000203 AC: 1 AN: 49158

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 10212

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 894

European-Non Finnish (NFE) AF: 0.0000304 AC: 4 AN: 131530

Other (OTH) AF: 0.00 AC: 0 AN: 11748

GnomAD4 genome AF: 0.0000788 AC: 12 AN: 152242 Hom.: 0 Cov.: 33 AF XY: 0.0000672 AC XY: 5 AN XY: 74444

African (AFR) AF: 0.000217 AC: 9 AN: 41536

American (AMR) AF: 0.0000654 AC: 1 AN: 15292

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 3472

East Asian (EAS) AF: 0.00 AC: 0 AN: 5178

South Asian (SAS) AF: 0.00 AC: 0 AN: 4824

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 10602

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 294

European-Non Finnish (NFE) AF: 0.0000294 AC: 2 AN: 68024

Other (OTH) AF: 0.00 AC: 0 AN: 2110

Alfa AF: 0.00 Hom.: 0

Bravo AF: 0.0000680

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Methylmalonic aciduria, cblB type Uncertain:1

Jan 12, 2018

Illumina Laboratory Services, Illumina

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This variant was observed in the ICSL laboratory as part of a predisposition screen in an ostensibly healthy population. It had not been previously curated by ICSL or reported in the Human Gene Mutation Database (HGMD: prior to June 1st, 2018), and was therefore a candidate for classification through an automated scoring system. Utilizing variant allele frequency, disease prevalence and penetrance estimates, and inheritance mode, an automated score was calculated to assess if this variant is too frequent to cause the disease. Based on the score, this variant could not be ruled out of causing disease and therefore its association with disease required further investigation. A literature search was performed for the gene, cDNA change, and amino acid change (if applicable). No publications were found based on this search. This variant was therefore classified as a variant of unknown significance for this disease. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_noAF	Benign	-0.84
CADD	Benign	0.25
DANN	Benign	0.67
PhyloP100		-0.47

Splicing

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

Other links and lift over

dbSNP: rs777939885; hg19: chr12-109991537; COSMIC: COSV57170795;