12-109554288-C-T

Variant names:

• chr12-109554288-C-T
• rs139886832
• NM_052845.4:c.*2740G>A

Variant summary

Our verdict is Likely benign. The variant received -5 ACMG points: 0P and 5B. BP4_Strong BS1_Supporting

The NM_052845.4(MMAB):​c.*2740G>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 0.000207 in 454,028 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 0.00035 (0 hom., cov: 32)
  • Exomes 𝑓: 0.00013 (0 hom.)
• Consequence: MMAB NM_052845.4 3_prime_UTR
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: -0.288
• 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 -5 ACMG points.

• BP4: Computational evidence support a benign effect (BayesDel_noAF=-0.85).
• BS1: Variant frequency is greater than expected in population afr. GnomAd4 allele frequency = 0.000355 (54/152230) while in subpopulation AFR AF = 0.000891 (37/41532). AF 95% confidence interval is 0.000664. There are 0 homozygotes in GnomAd4. There are 28 alleles in the male GnomAd4 subpopulation. Median coverage is 32. This position passed quality control check. Existence of Clinvar submissions makes me limit the strength of this signal to Supporting

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
MMAB	NM_052845.4	c.*2740G>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.*2740G>A		3_prime_UTR_variant	Exon 9 of 9	1	NM_052845.4	ENSP00000445920.1

Frequencies

GnomAD3 genomes AF: 0.000355 AC: 54 AN: 152112 Hom.: 0 Cov.: 32

Gnomad AFR AF: 0.000894

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.000393

Gnomad ASJ AF: 0.00

Gnomad EAS AF: 0.00

Gnomad SAS AF: 0.000415

Gnomad FIN AF: 0.0000943

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.0000735

Gnomad OTH AF: 0.00144

GnomAD2 exomes AF: 0.000222 AC: 29 AN: 130484 AF XY: 0.000211

Gnomad AFR exome AF: 0.000493

Gnomad AMR exome AF: 0.000616

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.000141

Gnomad OTH exome AF: 0.000749

GnomAD4 exome AF: 0.000133 AC: 40 AN: 301798 Hom.: 0 Cov.: 0 AF XY: 0.000116 AC XY: 20 AN XY: 171998

African (AFR) AF: 0.000468 AC: 4 AN: 8554

American (AMR) AF: 0.000660 AC: 18 AN: 27274

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 10786

East Asian (EAS) AF: 0.00 AC: 0 AN: 9210

South Asian (SAS) AF: 0.0000503 AC: 3 AN: 59650

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 12366

Middle Eastern (MID) AF: 0.00435 AC: 5 AN: 1150

European-Non Finnish (NFE) AF: 0.0000378 AC: 6 AN: 158766

Other (OTH) AF: 0.000285 AC: 4 AN: 14042

GnomAD4 genome AF: 0.000355 AC: 54 AN: 152230 Hom.: 0 Cov.: 32 AF XY: 0.000376 AC XY: 28 AN XY: 74416

African (AFR) AF: 0.000891 AC: 37 AN: 41532

American (AMR) AF: 0.000392 AC: 6 AN: 15304

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

East Asian (EAS) AF: 0.00 AC: 0 AN: 5182

South Asian (SAS) AF: 0.000415 AC: 2 AN: 4818

European-Finnish (FIN) AF: 0.0000943 AC: 1 AN: 10608

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

European-Non Finnish (NFE) AF: 0.0000735 AC: 5 AN: 67996

Other (OTH) AF: 0.00142 AC: 3 AN: 2112

Alfa AF: 0.0000434 Hom.: 0

Bravo AF: 0.000385

Asia WGS AF: 0.000289 AC: 1 AN: 3478

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	-0.85
CADD	Benign	2.4
DANN	Benign	0.47
PhyloP100		-0.29
Mutation Taster		=100/0	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: rs139886832; hg19: chr12-109992093;