rs66724222

Positions:

• chrX-38408988-G-A
• chrX-38408988-G-T

Variant summary

Our verdict is Pathogenic. Variant got 14 ACMG points: 14P and 0B. PM2 PP3_Strong PP5_Very_Strong

The NM_000531.6(OTC):​c.830G>A​(p.Arg277Gln) variant causes a missense change involving the alteration of a conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Pathogenic (★★).

• Frequency:
  • Genomes: not found (cov: 23)
  • Exomes 𝑓: 0.0000018 (0 hom. 0 hem.)
  • Failed GnomAD Quality Control
• Consequence: OTC NM_000531.6 missense
• Clinical Significance: Pathogenic criteria provided, multiple submitters, no conflicts P:6
• Conservation: PhyloP100: 9.46

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 14 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.993
• PP5: Variant X-38408988-G-A is Pathogenic according to our data. 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.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
OTC	NM_000531.6	c.830G>A	p.Arg277Gln	missense_variant	8/10	ENST00000039007.5	NP_000522.3
OTC	NM_001407092.1	c.830G>A	p.Arg277Gln	missense_variant	10/12		NP_001394021.1
OTC	XM_017029556.2	c.830G>A	p.Arg277Gln	missense_variant	8/9		XP_016885045.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
OTC	ENST00000039007.5	c.830G>A	p.Arg277Gln	missense_variant	8/10	1	NM_000531.6	ENSP00000039007	P1
OTC	ENST00000643344.1	c.*580G>A		3_prime_UTR_variant, NMD_transcript_variant	9/11			ENSP00000496606

Frequencies

GnomAD3 genomes Cov.: 23

GnomAD4 exome Data not reliable, filtered out with message: AS_VQSR AF: 0.00000182 AC: 2 AN: 1097982 Hom.: 0 Cov.: 31 AF XY: 0.00 AC XY: 0 AN XY: 363358

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.0000331

Gnomad4 SAS exome AF: 0.0000185

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 23

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:6

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Ornithine carbamoyltransferase deficiency Pathogenic:4

Pathogenic, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	Sep 04, 2023	This variant is not present in population databases (gnomAD no frequency). This sequence change replaces arginine, which is basic and polar, with glutamine, which is neutral and polar, at codon 277 of the OTC protein (p.Arg277Gln). This missense change has been observed in individuals with OTC deficiency (PMID: 7951259, 17922216). ClinVar contains an entry for this variant (Variation ID: 97339). 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. This variant disrupts the p.Arg277 amino acid residue in OTC. Other variant(s) that disrupt this residue have been determined to be pathogenic (PMID: 2037279, 2347583, 7860066, 25026867, 30285816). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. 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	May 23, 2022	Variant summary: OTC c.830G>A (p.Arg277Gln) results in a conservative amino acid change located in the Aspartate/ornithine carbamoyltransferase, Asp/Orn-binding domain of the encoded protein sequence. Four of five in-silico tools predict a damaging effect of the variant on protein function. The variant was absent in 183008 control chromosomes. c.830G>A has been reported in the literature in multiple individuals affected with Ornithine Transcarbamylase Deficiency (example Tuchman_1994b, Morizono_1997, Genet_2000, Mak_2007, Storkanova_2013). These data indicate that the variant is likely to be associated with disease. The variant has been reported to negatively impact the stability of the protein in vitro and to reduce its activity to 7% of the wild-type enzyme (Morizono_1997). Three clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar after 2014 without evidence for independent evaluation. All laboratories classified the variant as pathogenic. Based on the evidence outlined above, the variant was classified as pathogenic. -
Pathogenic, criteria provided, single submitter	clinical testing	Baylor Genetics	Mar 12, 2024	- -

not specified Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

ARUP Laboratories, Molecular Genetics and Genomics, ARUP Laboratories

Oct 18, 2016

- -

not provided Pathogenic:1

Pathogenic, no assertion criteria provided

literature only

GenMed Metabolism Lab

-

- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.65
BayesDel_addAF	Pathogenic	0.72	D
BayesDel_noAF	Pathogenic	0.79
CADD	Pathogenic	29
DANN	Pathogenic	1.0
DEOGEN2	Pathogenic	0.97	D
FATHMM_MKL	Pathogenic	0.99	D
LIST_S2	Pathogenic	0.98	D
M_CAP	Pathogenic	0.93	D
MetaRNN	Pathogenic	0.99	D
MetaSVM	Pathogenic	1.0	D
MutationAssessor	Pathogenic	4.5	H
MutationTaster	Benign	1.0	D
PrimateAI	Uncertain	0.49	T
PROVEAN	Uncertain	-3.9	D
REVEL	Pathogenic	0.96
Sift	Uncertain	0.0030	D
Sift4G	Uncertain	0.0040	D
Polyphen		1.0	D
Vest4		0.97
MutPred		0.92		Loss of MoRF binding (P = 0.0467);
MVP		1.0
MPC		1.3
ClinPred		1.0	D
GERP RS		5.6
Varity_R		0.97
gMVP		0.98

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.080		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: rs66724222; hg19: chrX-38268241;