3-183039064-C-T

Variant summary

Our verdict is Likely pathogenic. Variant got 8 ACMG points: 8P and 0B. PM1 PM2 PP3_Strong

The NM_020166.5(MCCC1):c.1339G>A(p.Ala447Thr) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000124 in 1,614,066 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 (★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. A447S) has been classified as Uncertain significance.

• Frequency:
  • Genomes: 𝑓 0.0000066 (0 hom., cov: 32)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: MCCC1 NM_020166.5 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 7.54

Genes affected

MCCC1 (HGNC:6936): (methylcrotonyl-CoA carboxylase subunit 1) This gene encodes the large subunit of 3-methylcrotonyl-CoA carboxylase. This enzyme functions as a heterodimer and catalyzes the carboxylation of 3-methylcrotonyl-CoA to form 3-methylglutaconyl-CoA. Mutations in this gene are associated with 3-Methylcrotonylglycinuria, an autosomal recessive disorder of leucine catabolism. [provided by RefSeq, Jul 2008]

ACMG classification

Verdict is Likely_pathogenic. Variant got 8 ACMG points.

• PM1: In a hotspot region, there are 2 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 1 benign, 3 uncertain in NM_020166.5
• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.974

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
MCCC1	NM_020166.5	c.1339G>A	p.Ala447Thr	missense_variant	12/19	ENST00000265594.9

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
MCCC1	ENST00000265594.9	c.1339G>A	p.Ala447Thr	missense_variant	12/19	1	NM_020166.5	P1

Frequencies

GnomAD3 genomes AF: 0.00000657 AC: 1 AN: 152176 Hom.: 0 Cov.: 32

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

GnomAD3 exomes AF: 0.00000796 AC: 2 AN: 251396 Hom.: 0 AF XY: 0.00000736 AC XY: 1 AN XY: 135856

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: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.0000176

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1461890 Hom.: 0 Cov.: 32 AF XY: 0.00 AC XY: 0 AN XY: 727248

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: 152176 Hom.: 0 Cov.: 32 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

ExAC AF: 0.00000824 AC: 1

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

3-methylcrotonyl-CoA carboxylase 1 deficiency Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Invitae

Sep 01, 2021

This sequence change replaces alanine with threonine at codon 447 of the MCCC1 protein (p.Ala447Thr). The alanine residue is highly conserved and there is a small physicochemical difference between alanine and threonine. This variant is present in population databases (rs546480708, ExAC 0.001%). This variant has not been reported in the literature in individuals affected with MCCC1-related conditions. Algorithms developed to predict the effect of missense changes on protein structure and function (SIFT, PolyPhen-2, Align-GVGD) all suggest that this variant is likely to be disruptive. 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	Benign	0.29
BayesDel_addAF	Pathogenic	0.44	D
BayesDel_noAF	Pathogenic	0.41
Cadd	Pathogenic	27
Dann	Pathogenic	1.0
DEOGEN2	Pathogenic	0.84	D;D;D;D;D
Eigen	Pathogenic	0.86
Eigen_PC	Pathogenic	0.76
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Pathogenic	0.99	D;D;D;D;D
M_CAP	Pathogenic	0.33	D
MetaRNN	Pathogenic	0.97	D;D;D;D;D
MetaSVM	Pathogenic	1.0	D
MutationAssessor	Pathogenic	3.0	M;.;.;.;.
MutationTaster	Benign	1.0	D;D;D
PrimateAI	Uncertain	0.61	T
PROVEAN	Uncertain	-3.8	D;D;.;.;D
REVEL	Pathogenic	0.85
Sift	Uncertain	0.0010	D;D;.;.;D
Sift4G	Pathogenic	0.0010	D;D;D;D;.
Polyphen		1.0	D;D;.;.;D
Vest4		0.86
MutPred		0.85		Gain of phosphorylation at A447 (P = 0.062);.;.;.;.;
MVP		0.98
MPC		0.60
ClinPred		0.98	D
GERP RS		5.8
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.1
Varity_R		0.73
gMVP		0.89

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: rs546480708; hg19: chr3-182756852; COSMIC: COSV99659580; COSMIC: COSV99659580;