rs72558454

chrX-38408987-C-T

Variant summary

Our verdict is Pathogenic. Variant got 18 ACMG points: 18P and 0B. PM1 PM2 PM5 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. R277L) 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:7
• Conservation: PhyloP100: 3.41

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]

ACMG classification

Verdict is Pathogenic. Variant got 18 ACMG points.

• PM1: In a hotspot region, there are 3 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 6 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 id is 97339.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.
• 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 id is 10999.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
OTC	NM_000531.6	c.829C>T	p.Arg277Trp	missense_variant	8/10	ENST00000039007.5
OTC	NM_001407092.1	c.829C>T	p.Arg277Trp	missense_variant	10/12
OTC	XM_017029556.2	c.829C>T	p.Arg277Trp	missense_variant	8/9

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
OTC	ENST00000039007.5	c.829C>T	p.Arg277Trp	missense_variant	8/10	1	NM_000531.6	P1
OTC	ENST00000643344.1	c.*579C>T		3_prime_UTR_variant, NMD_transcript_variant	9/11

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

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: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00000119

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 23

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:7

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Ornithine carbamoyltransferase deficiency Pathogenic:5

Pathogenic, no assertion criteria provided	literature only	OMIM	Jun 01, 1990	- -
Pathogenic, criteria provided, single submitter	clinical testing	MGZ Medical Genetics Center	Jul 11, 2022	- -
Pathogenic, criteria provided, single submitter	clinical testing	Invitae	Nov 09, 2023	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. -
Pathogenic, criteria provided, single submitter	clinical testing	Genome-Nilou Lab	Nov 07, 2021	- -
Pathogenic, criteria provided, single submitter	clinical testing	Women's Health and Genetics/Laboratory Corporation of America, LabCorp	Feb 03, 2020	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. -

not provided Pathogenic:2

Pathogenic, no assertion criteria provided	literature only	GenMed Metabolism Lab	-	- -
Pathogenic, criteria provided, single submitter	clinical testing	GeneDx	Apr 03, 2019	Not observed in large population cohorts (Lek et al., 2016); In silico analysis, which includes protein predictors and evolutionary conservation, supports a deleterious effect; The majority of missense variants in this gene are considered pathogenic (Stenson et al., 2014); This variant is associated with the following publications: (PMID: 25994866, 21061009, 25026867, 25525159, 21644234, 23278509, 8365726, 7860066, 29581464, 2347583, 30285816, 2037279, 28324312, 33272297) -

Computational scores

Source: dbNSFP v4.3

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
MutationTaster	Benign	1.0	A
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

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

Publications

LitVar

Other links and lift over

dbSNP: rs72558454; hg19: chrX-38268240;