NM_000531.6:c.829C>T

Variant names:

• chrX-38408987-C-T
• rs72558454
• NM_000531.6:c.829C>T

Variant summary

Our verdict is Pathogenic. The variant received 19 ACMG points: 19P and 0B. PM1 PM2 PM5 PP2 PP3_Strong PP5_Very_Strong

The NM_000531.6(OTC):​c.829C>T​(p.Arg277Trp) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000000911 in 1,097,714 control chromosomes in the GnomAD database, with no homozygous occurrence. There are no hemizygote samples in GnomAD. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Pathogenic (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. R277Q) has been classified as Pathogenic.

• Frequency:
  • Genomes: not found (cov: 23)
  • Exomes 𝑓: 9.1e-7 (0 hom. 0 hem.)
• Consequence: OTC NM_000531.6 missense
• Clinical Significance: Pathogenic criteria provided, multiple submitters, no conflicts P:11
• Conservation: PhyloP100: 3.41
• Publications: 25 publications found

Genes affected

OTC (HGNC:8512): (ornithine transcarbamylase) This nuclear gene encodes a mitochondrial matrix enzyme. The encoded protein is involved in the urea cycle which functions to detoxify ammonia into urea for excretion. Mutations in this enzyme lead to ornithine transcarbamylase deficiency, which causes hyperammonemia. [provided by RefSeq, May 2022]

OTC Gene-Disease associations (from GenCC):

• ornithine carbamoyltransferase deficiency

  Inheritance: XL Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: Labcorp Genetics (formerly Invitae), ClinGen, G2P, Laboratory for Molecular Medicine, Orphanet

ENSG00000250349 (HGNC:):

ACMG classification

Our verdict: Pathogenic. The variant received 19 ACMG points.

• PM1: In a hotspot region, there are 3 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 2 benign, 9 uncertain in NM_000531.6
• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chrX-38408988-G-A is described in ClinVar as Pathogenic. ClinVar VariationId is 97339.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.
• PP2: Missense variant in the gene, where a lot of missense mutations are associated with disease in ClinVar. The gene has 266 curated pathogenic missense variants (we use a threshold of 10). The gene has 15 curated benign missense variants. Gene score misZ: 1.3274 (below the threshold of 3.09). Trascript score misZ: NaN (below the threshold of 3.09). GenCC associations: The gene is linked to ornithine carbamoyltransferase deficiency.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.992
• PP5: Variant X-38408987-C-T is Pathogenic according to our data. Variant chrX-38408987-C-T is described in ClinVar as Pathogenic. ClinVar VariationId is 10999.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_000531.6. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	OTC	NM_000531.6	MANE Select	c.829C>T	p.Arg277Trp	missense	Exon 8 of 10	NP_000522.3
	OTC	NM_001407092.1		c.829C>T	p.Arg277Trp	missense	Exon 10 of 12	NP_001394021.1

Ensembl Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	OTC	ENST00000039007.5	TSL:1 MANE Select	c.829C>T	p.Arg277Trp	missense	Exon 8 of 10	ENSP00000039007.4
	ENSG00000250349	ENST00000465127.1	TSL:5	c.172-257134C>T		intron	N/A	ENSP00000417050.1
	OTC	ENST00000713758.1		c.829C>T	p.Arg277Trp	missense	Exon 10 of 12	ENSP00000519059.1

Frequencies

GnomAD3 genomes Cov.: 23

GnomAD4 exome AF: 9.11e-7 AC: 1 AN: 1097714 Hom.: 0 Cov.: 31 AF XY: 0.00 AC XY: 0 AN XY: 363108

African (AFR) AF: 0.00 AC: 0 AN: 26394

American (AMR) AF: 0.00 AC: 0 AN: 35202

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 19375

East Asian (EAS) AF: 0.00 AC: 0 AN: 30190

South Asian (SAS) AF: 0.00 AC: 0 AN: 54133

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 40527

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 4135

European-Non Finnish (NFE) AF: 0.00000119 AC: 1 AN: 841682

Other (OTH) AF: 0.00 AC: 0 AN: 46076

GnomAD4 genome Cov.: 23

Alfa AF: 0.00 Hom.: 0

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:11

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Ornithine carbamoyltransferase deficiency Pathogenic:8

Feb 03, 2020

Women's Health and Genetics/Laboratory Corporation of America, LabCorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Variant summary: OTC c.829C>T (p.Arg277Trp) results in a non-conservative amino acid change located in the Aspartate/ornithine carbamoyltransferase, Asp/Orn-binding domain (IPR006131) of the encoded protein sequence. Five of five in-silico tools predict a damaging effect of the variant on protein function. The variant was absent in 183008 control chromosomes. c.829C>T has been reported in the literature in multiple individuals affected with Ornithine Transcarbamylase Deficiency (example, Finkelstein_1990, Morizono_1997, Bijarnia-Mahay_2018, Kim_2006, Lee_2014, Storkanova_2013, Silvera-Ruiz_2019). These data indicate that the variant is very likely to be associated with disease. At least one publication reports experimental evidence evaluating an impact on protein function. The most pronounced variant effect results in 2%-<30% of normal activity OTC'ase activity with a markedly reduced affinity for L-Ornithine (example, Morizono_1997). One clinical diagnostic laboratory has submitted clinical-significance assessments for this variant to ClinVar after 2014 without evidence for independent evaluation and classified the variant as pathogenic. Based on the evidence outlined above, the variant was classified as pathogenic.

Feb 28, 2024

All of Us Research Program, National Institutes of Health

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This variant has been reported in multiple individuals with ornithine transcarbamylase deficiency (PMID: 2037279, 18030415, 19893582, 25994866, 31426867, 33272297). It was observed to occur de novo in an affected individual (PMID: 33272297). This variant is absent from large population databases, including the Genome Aggregation Database (http://gnomad.broadinstitute.org/). This variant is predicted to be deleterious by in silico analysis. Functional studies suggest that this variant has a deleterious effect on the protein (PMID: 9175746, 9065786, 10946359).

Nov 07, 2021

Genome-Nilou Lab

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Jun 19, 2024

Revvity Omics, Revvity

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Jun 01, 1990

OMIM

Significance: Pathogenic

Review Status: no assertion criteria provided

Collection Method: literature only

Jul 11, 2022

MGZ Medical Genetics Center

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Jan 30, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces arginine, which is basic and polar, with tryptophan, which is neutral and slightly polar, at codon 277 of the OTC protein (p.Arg277Trp). This variant is not present in population databases (gnomAD no frequency). This missense change has been observed in individual(s) with OTC deficiency (PMID: 2037279, 2347583, 7860066, 25026867, 30285816). ClinVar contains an entry for this variant (Variation ID: 10999). 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 OTC protein function with a positive predictive value of 95%. For these reasons, this variant has been classified as Pathogenic.

May 16, 2024

Color Diagnostics, LLC DBA Color Health

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This missense variant replaces arginine with tryptophan at codon 277 of the OTC protein. Computational prediction suggests that this variant may have deleterious impact on protein structure and function. Functional studies have reported that this variant reduced protein stability and binding affinity to L-ornithine (PMID: 9175746). This variant has been observed in many individuals affected with mild, late-onset ornithine transcarbamylase deficiency (PMID: 2037279, 2347583, 7860066, 9175746, 17041896, 23278509, 25026867, 30285816, 31426867) as well as one male infant with severe disease (PMID: 7860066). It has been shown that this variant segregated with disease in multiple affected families (PMID: 7860066, 23278509) and appeared spontaneously in one proband (PMID: 7860066). This variant has not been identified in the general population by the Genome Aggregation Database (gnomAD). A different missense variant occurring at the same codon, p.Arg277Gln, is known to be disease-causing (ClinVar Variation ID: 97339), indicating that arginine at this position is important for OTC protein function. Based on the available evidence, this variant is classified as Pathogenic.

not provided Pathogenic:3

GenMed Metabolism Lab

Significance: Pathogenic

Review Status: no assertion criteria provided

Collection Method: literature only

May 11, 2024

GeneDx

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Not observed at significant frequency in large population cohorts (gnomAD); In silico analysis supports that this missense variant has a deleterious effect on protein structure/function; This variant is associated with the following publications: (PMID: 25994866, 21061009, 25525159, 21644234, 8365726, 7860066, 29581464, 2347583, 30285816, 2037279, 28324312, 33309754, 32778825, 33190319, 37146589, 23278509, 25026867, 33272297, 34014569)

Nov 01, 2024

CeGaT Center for Human Genetics Tuebingen

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

OTC: PM1, PM2, PM5, PP4:Moderate, PS4:Moderate

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.86
BayesDel_addAF	Pathogenic	0.68	D
BayesDel_noAF	Pathogenic	0.74
CADD	Pathogenic	26
DANN	Pathogenic	1.0
DEOGEN2	Pathogenic	0.99	D
FATHMM_MKL	Uncertain	0.86	D
LIST_S2	Pathogenic	0.99	D
M_CAP	Pathogenic	0.92	D
MetaRNN	Pathogenic	0.99	D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Pathogenic	4.1	H
PhyloP100		3.4
PrimateAI	Uncertain	0.61	T
PROVEAN	Pathogenic	-7.8	D
REVEL	Pathogenic	0.95
Sift	Pathogenic	0.0	D
Sift4G	Pathogenic	0.0	D
Polyphen		1.0	D
Vest4		0.95
MutPred		0.89		Loss of disorder (P = 0.025)
MVP		1.0
MPC		1.2
ClinPred		1.0	D
GERP RS		3.5
Varity_R		0.98
gMVP		0.98
Mutation Taster		=3/97	disease causing (ClinVar)

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.15		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: rs72558454; hg19: chrX-38268240;