chrX-38408949-C-T

Position:

• chrX-38408949-C-T

Variant summary

Our verdict is Likely pathogenic. Variant got 8 ACMG points: 8P and 0B. PS1_Moderate PM2 PP3_Strong

The NM_000531.6(OTC):​c.791C>T​(p.Thr264Ile) 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 nucleotide change resulting in same amino acid change has been previously reported as Likely pathogenicin UniProt.

• 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: 5.68

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 Likely_pathogenic. Variant got 8 ACMG points.

• PS1: Transcript NM_000531.6 (OTC) is affected with MISSENSE_VARIANT having same AA change as one Pathogenic present in UniProt
• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.994

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
OTC	NM_000531.6	c.791C>T	p.Thr264Ile	missense_variant	8/10	ENST00000039007.5	NP_000522.3
OTC	NM_001407092.1	c.791C>T	p.Thr264Ile	missense_variant	10/12		NP_001394021.1
OTC	XM_017029556.2	c.791C>T	p.Thr264Ile	missense_variant	8/9		XP_016885045.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
OTC	ENST00000039007.5	c.791C>T	p.Thr264Ile	missense_variant	8/10	1	NM_000531.6	ENSP00000039007	P1
OTC	ENST00000643344.1	c.*541C>T		3_prime_UTR_variant, NMD_transcript_variant	9/11			ENSP00000496606

Frequencies

GnomAD3 genomes Cov.: 23

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 23

ClinVar

Significance: Uncertain significance

Submissions summary: Pathogenic:1 Uncertain:1

Revision: criteria provided, single submitter

Submissions by phenotype

not provided Pathogenic:1

Pathogenic, no assertion criteria provided

literature only

GenMed Metabolism Lab

-

- -

not specified Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

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

Sep 02, 2021

Variant summary: OTC c.791C>T (p.Thr264Ile) 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 183176 control chromosomes. The available data on variant occurrences in the general population are insufficient to allow any conclusion about variant significance. c.791C>T has been reported in the literature in at-least one Japanese individual affected with Ornithine Transcarbamylase Deficiency and has been subsequently cited by others (Shimadzu_1998, Kido_2021, Caldovic_2015). These data do not allow any conclusion about variant significance. To our knowledge, no experimental evidence demonstrating an impact on protein function has been reported. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar after 2014. Based on the evidence outlined above, the variant was classified as uncertain significance. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.91
BayesDel_addAF	Pathogenic	0.65	D
BayesDel_noAF	Pathogenic	0.70
CADD	Pathogenic	26
DANN	Pathogenic	1.0
DEOGEN2	Pathogenic	0.96	D
FATHMM_MKL	Uncertain	0.96	D
LIST_S2	Pathogenic	1.0	D
M_CAP	Pathogenic	0.89	D
MetaRNN	Pathogenic	0.99	D
MetaSVM	Pathogenic	1.1	D
MutationAssessor	Uncertain	2.1	M
MutationTaster	Benign	1.0	D
PrimateAI	Uncertain	0.71	T
PROVEAN	Uncertain	-4.1	D
REVEL	Pathogenic	0.94
Sift	Uncertain	0.0010	D
Sift4G	Uncertain	0.0090	D
Polyphen		1.0	D
Vest4		0.98
MutPred		0.95		Gain of helix (P = 0.0696);
MVP		1.0
MPC		1.2
ClinPred		1.0	D
GERP RS		5.6
Varity_R		0.93
gMVP		0.96

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: rs67156896; hg19: chrX-38268202;