X-38421026-G-T

Position:

• chrX-38421026-G-T

Variant summary

Our verdict is Pathogenic. Variant got 10 ACMG points: 10P and 0B. PM1 PM2 PM5 PP3_Strong

The NM_000531.6(OTC):​c.1009G>T​(p.Val337Phe) 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 Uncertain significance (★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. V337L) has been classified as Pathogenic.

• Frequency: Genomes: not found (cov: 23)
• Consequence: OTC NM_000531.6 missense
• Clinical Significance: Uncertain significance criteria provided, single submitter P:1 U:1
• Conservation: PhyloP100: 4.03

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 10 ACMG points.

• PM1: In a hotspot region, there are 8 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 1 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-38421026-G-C is described in ClinVar as [Pathogenic]. Clinvar id is 97095.Status of the report is no_assertion_criteria_provided, 0 stars.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.985

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
OTC	NM_000531.6	c.1009G>T	p.Val337Phe	missense_variant	10/10	ENST00000039007.5
OTC	NM_001407092.1	c.1009G>T	p.Val337Phe	missense_variant	12/12

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
OTC	ENST00000039007.5	c.1009G>T	p.Val337Phe	missense_variant	10/10	1	NM_000531.6	P1
OTC	ENST00000643344.1	c.*759G>T		3_prime_UTR_variant, NMD_transcript_variant	11/11

Frequencies

GnomAD3 genomes Cov.: 23

GnomAD4 exome Cov.: 26

GnomAD4 genome Cov.: 23

ClinVar

Significance: Uncertain significance

Submissions summary: Pathogenic:1 Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

Ornithine carbamoyltransferase deficiency Pathogenic:1 Uncertain:1

Uncertain significance, criteria provided, single submitter	clinical testing	Neuberg Centre For Genomic Medicine, NCGM	-	The missense variant in c.1009G>T(p.Val337Phe) in OTC gene has been submitted to ClinVar as Pathogenic, but no details are available for independent assessment. It has not been reported in affected individuals. The p.Val337Phe variant is novel (not in any individuals) in gnomAD Exomes and 1000 Genomes. The variant is predicted to be damaging by both SIFT and PolyPhen2. The amino acid Val at position 337 is changed to a Phe changing protein sequence and it might alter its composition and physico-chemical properties. The residue is conserved across species. The amino acid change p.Val337Phe in OTC is predicted as conserved by GERP++ and PhyloP across 100 vertebrates. For these reasons, this variant has been classified as Uncertain Significance. -
Pathogenic, no assertion criteria provided	clinical testing	Molecular Genetics laboratory, Necker Hospital	-	2 boys with a neonatal form and 1 girl with a paroxysmal form -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.73
BayesDel_addAF	Pathogenic	0.67	D
BayesDel_noAF	Pathogenic	0.72
CADD	Uncertain	26
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	0.96	D
FATHMM_MKL	Uncertain	0.92	D
LIST_S2	Uncertain	0.95	D
M_CAP	Pathogenic	0.82	D
MetaRNN	Pathogenic	0.98	D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Pathogenic	4.0	H
MutationTaster	Benign	1.0	D
PrimateAI	Uncertain	0.67	T
PROVEAN	Uncertain	-3.8	D
REVEL	Pathogenic	0.95
Sift	Uncertain	0.0030	D
Sift4G	Uncertain	0.0050	D
Polyphen		0.99	D
Vest4		0.86
MutPred		0.82		Loss of stability (P = 0.1042);
MVP		1.0
MPC		1.3
ClinPred		0.99	D
GERP RS		4.5
Varity_R		0.97
gMVP		0.97

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.020		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: rs72558487; hg19: chrX-38280279;