chrX-38403681-C-G

Position:

• chrX-38403681-C-G

Variant summary

Our verdict is Pathogenic. Variant got 12 ACMG points: 12P and 0B. PM1 PM2 PM5 PP3_Strong PP5_Moderate

The NM_000531.6(OTC):​c.604C>G​(p.His202Asp) variant causes a missense change. 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 Likely pathogenic (★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. H202P) has been classified as Pathogenic.

• Frequency: Genomes: not found (cov: 22)
• Consequence: OTC NM_000531.6 missense
• Clinical Significance: Likely pathogenic criteria provided, single submitter P:1
• Conservation: PhyloP100: 3.63

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 12 ACMG points.

• PM1: In a hotspot region, there are 13 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 4 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-38403681-C-T is described in ClinVar as [Pathogenic]. Clinvar id is 97267.Status of the report is criteria_provided_single_submitter, 1 stars.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.983
• PP5: Variant X-38403681-C-G is Pathogenic according to our data. Variant chrX-38403681-C-G is described in ClinVar as [Likely_pathogenic]. Clinvar id is 949644.Status of the report is criteria_provided_single_submitter, 1 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
OTC	NM_000531.6	c.604C>G	p.His202Asp	missense_variant	6/10	ENST00000039007.5
OTC	NM_001407092.1	c.604C>G	p.His202Asp	missense_variant	8/12
OTC	XM_017029556.2	c.604C>G	p.His202Asp	missense_variant	6/9

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
OTC	ENST00000039007.5	c.604C>G	p.His202Asp	missense_variant	6/10	1	NM_000531.6	P1
OTC	ENST00000643344.1	c.*354C>G		3_prime_UTR_variant, NMD_transcript_variant	7/11
OTC	ENST00000488812.1			downstream_gene_variant		5

Frequencies

GnomAD3 genomes Cov.: 22

GnomAD4 exome Cov.: 30

GnomAD4 genome Cov.: 22

ClinVar

Significance: Likely pathogenic

Submissions summary: Pathogenic:1

Revision: criteria provided, single submitter

Submissions by phenotype

Ornithine carbamoyltransferase deficiency Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Mar 23, 2023

In summary, the currently available evidence indicates that the variant is pathogenic, but additional data are needed to prove that conclusively. Therefore, this variant has been classified as Likely Pathogenic. This variant disrupts the p.His202 amino acid residue in OTC. Other variant(s) that disrupt this residue have been determined to be pathogenic (PMID: 9266388, 9501271, 17334707, 25433810, 30285816). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. 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. ClinVar contains an entry for this variant (Variation ID: 949644). This missense change has been observed in individual(s) with OTC-related conditions (Invitae). This variant is not present in population databases (gnomAD no frequency). This sequence change replaces histidine, which is basic and polar, with aspartic acid, which is acidic and polar, at codon 202 of the OTC protein (p.His202Asp). -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.91
BayesDel_addAF	Pathogenic	0.60	D
BayesDel_noAF	Pathogenic	0.63
CADD	Pathogenic	27
DANN	Uncertain	0.99
DEOGEN2	Pathogenic	0.97	D
FATHMM_MKL	Uncertain	0.95	D
LIST_S2	Uncertain	0.91	D
M_CAP	Pathogenic	0.79	D
MetaRNN	Pathogenic	0.98	D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Pathogenic	3.2	M
MutationTaster	Benign	1.0	D
PrimateAI	Uncertain	0.77	T
PROVEAN	Pathogenic	-6.8	D
REVEL	Pathogenic	0.91
Sift	Benign	0.069	T
Sift4G	Uncertain	0.0080	D
Polyphen		0.99	D
Vest4		0.91
MutPred		0.84		Gain of relative solvent accessibility (P = 0.1259);
MVP		0.99
MPC		1.4
ClinPred		0.99	D
GERP RS		5.9
Varity_R		0.97
gMVP		0.99

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: rs72558408; hg19: chrX-38262934;