rs920825350

Positions:

• chr4-145646087-A-G

Variant summary

Our verdict is Uncertain significance. Variant got 5 ACMG points: 5P and 0B. PM2 PP3_Moderate PP5

The NM_172250.3(MMAA):​c.664A>G​(p.Arg222Gly) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000342 in 1,461,806 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 Conflicting classifications of pathogenicity (no stars). Synonymous variant affecting the same amino acid position (i.e. R222R) has been classified as Likely benign.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000034 (0 hom.)
• Consequence: MMAA NM_172250.3 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:1 U:2
• Conservation: PhyloP100: 2.44

Genes affected

MMAA (HGNC:18871): (metabolism of cobalamin associated A) The protein encoded by this gene is involved in the translocation of cobalamin into the mitochondrion, where it is used in the final steps of adenosylcobalamin synthesis. Adenosylcobalamin is a coenzyme required for the activity of methylmalonyl-CoA mutase. Defects in this gene are a cause of methylmalonic aciduria. [provided by RefSeq, Jul 2008]

(HGNC:):

ACMG classification

Verdict is Uncertain_significance. Variant got 5 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.894
• PP5: Variant 4-145646087-A-G is Pathogenic according to our data. Variant chr4-145646087-A-G is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 522648.We mark this variant Likely_pathogenic, oryginal submissions are: {Uncertain_significance=2, Likely_pathogenic=1}.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
MMAA	NM_172250.3	c.664A>G	p.Arg222Gly	missense_variant	4/7	ENST00000649156.2
MMAA	NM_001375644.1	c.664A>G	p.Arg222Gly	missense_variant	4/7
MMAA	XM_011531684.4	c.664A>G	p.Arg222Gly	missense_variant	4/7

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
MMAA	ENST00000649156.2	c.664A>G	p.Arg222Gly	missense_variant	4/7		NM_172250.3	P1
	ENST00000504555.1	n.254-3260T>C		intron_variant, non_coding_transcript_variant		5

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD3 exomes AF: 0.00000398 AC: 1 AN: 251422 Hom.: 0 AF XY: 0.00000736 AC XY: 1 AN XY: 135882

Gnomad AFR exome AF: 0.00

Gnomad AMR exome AF: 0.0000289

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad SAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.00

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000342 AC: 5 AN: 1461806 Hom.: 0 Cov.: 31 AF XY: 0.00000413 AC XY: 3 AN XY: 727200

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.0000224

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: 0.00

Gnomad4 OTH exome AF: 0.0000662

GnomAD4 genome Cov.: 32

Bravo AF: 0.00000756

Asia WGS AF: 0.000289 AC: 1 AN: 3478

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:1 Uncertain:2

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Methylmalonic aciduria, cblA type Pathogenic:1 Uncertain:1

Uncertain significance, criteria provided, single submitter	clinical testing	Invitae	Aug 09, 2022	This sequence change replaces arginine, which is basic and polar, with glycine, which is neutral and non-polar, at codon 222 of the MMAA protein (p.Arg222Gly). This variant is present in population databases (no rsID available, gnomAD 0.003%). This variant has not been reported in the literature in individuals affected with MMAA-related conditions. ClinVar contains an entry for this variant (Variation ID: 522648). Advanced modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) performed at Invitae indicates that this missense variant is expected to disrupt MMAA protein function. 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. -
Likely pathogenic, criteria provided, single submitter	clinical testing	Genomic Research Center, Shahid Beheshti University of Medical Sciences	Dec 03, 2017	- -

Inborn genetic diseases Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Ambry Genetics

May 24, 2023

The c.664A>G (p.R222G) alteration is located in exon 4 (coding exon 3) of the MMAA gene. This alteration results from a A to G substitution at nucleotide position 664, causing the arginine (R) at amino acid position 222 to be replaced by a glycine (G). 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	Uncertain	0.54
BayesDel_addAF	Pathogenic	0.37	D
BayesDel_noAF	Pathogenic	0.38
CADD	Uncertain	25
DANN	Pathogenic	1.0
DEOGEN2	Pathogenic	0.81	D;.;D;D;D;D
Eigen	Uncertain	0.68
Eigen_PC	Uncertain	0.63
FATHMM_MKL	Uncertain	0.80	D
M_CAP	Pathogenic	0.45	D
MetaRNN	Pathogenic	0.89	D;D;D;D;D;D
MetaSVM	Pathogenic	0.85	D
MutationAssessor	Pathogenic	2.9	M;.;M;M;M;.
MutationTaster	Benign	1.0	D;D
PrimateAI	Uncertain	0.76	T
Polyphen		1.0	D;.;D;D;D;.
Vest4		0.91, 0.91
MutPred		0.67		Gain of catalytic residue at G219 (P = 0.0615);Gain of catalytic residue at G219 (P = 0.0615);Gain of catalytic residue at G219 (P = 0.0615);Gain of catalytic residue at G219 (P = 0.0615);Gain of catalytic residue at G219 (P = 0.0615);Gain of catalytic residue at G219 (P = 0.0615);
MVP		0.98
MPC		0.62
ClinPred		0.99	D
GERP RS		5.4
Varity_R		0.90
gMVP		0.93

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

Publications

LitVar

Other links and lift over

dbSNP: rs920825350; hg19: chr4-146567239; COSMIC: COSV55580405; COSMIC: COSV55580405;