X-38401429-G-T

Variant names:

• chrX-38401429-G-T
• rs72556288
• NM_000531.6:c.540+1G>T

Variant summary

Our verdict is Pathogenic. The variant received 18 ACMG points: 18P and 0B. PVS1 PM2 PP5_Very_Strong

The NM_000531.6(OTC):​c.540+1G>T variant causes a splice donor, intron 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. 3/3 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Pathogenic (★★).

• Frequency: Genomes: not found (cov: 23)
• Consequence: OTC NM_000531.6 splice_donor, intron
• Scores: Splicing: ADA: 1.000
• Clinical Significance: Pathogenic criteria provided, multiple submitters, no conflicts P:2
• Conservation: PhyloP100: 9.30
• Publications: 2 publications found

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]

OTC Gene-Disease associations (from GenCC):

• ornithine carbamoyltransferase deficiency

  Inheritance: XL Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: Labcorp Genetics (formerly Invitae), ClinGen, G2P, Laboratory for Molecular Medicine, Orphanet

ENSG00000250349 (HGNC:):

ACMG classification

Our verdict: Pathogenic. The variant received 18 ACMG points.

• PVS1: Splicing +-2 bp (donor or acceptor) variant, LoF is a know mechanism of disease, No cryptic splice site detected. Exon removal results in frameshift change.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant X-38401429-G-T is Pathogenic according to our data. Variant chrX-38401429-G-T is described in ClinVar as Pathogenic. ClinVar VariationId is 449675.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_000531.6. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	OTC	NM_000531.6	MANE Select	c.540+1G>T		splice_donor intron	N/A	NP_000522.3
	OTC	NM_001407092.1		c.540+1G>T		splice_donor intron	N/A	NP_001394021.1

Ensembl Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	OTC	ENST00000039007.5	TSL:1 MANE Select	c.540+1G>T		splice_donor intron	N/A	ENSP00000039007.4
	ENSG00000250349	ENST00000465127.1	TSL:5	c.172-264692G>T		intron	N/A	ENSP00000417050.1
	OTC	ENST00000713758.1		c.540+1G>T		splice_donor intron	N/A	ENSP00000519059.1

Frequencies

GnomAD3 genomes Cov.: 23

GnomAD4 exome Cov.: 28

GnomAD4 genome Cov.: 23

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Ornithine carbamoyltransferase deficiency Pathogenic:1

Aug 22, 2021

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This variant is not present in population databases (ExAC no frequency). Disruption of this splice site has been observed in individual(s) with ornithine transcarbamylase deficiency (PMID: 8566955, 31426867). ClinVar contains an entry for this variant (Variation ID: 449675). Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may disrupt the consensus splice site. For these reasons, this variant has been classified as Pathogenic. This sequence change affects a donor splice site in intron 5 of the OTC gene. It is expected to disrupt RNA splicing. Variants that disrupt the donor or acceptor splice site typically lead to a loss of protein function (PMID: 16199547), and loss-of-function variants in OTC are known to be pathogenic (PMID: 10946359, 16786505).

not provided Pathogenic:1

Feb 02, 2016

GeneDx

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The c.540+1G>T pathogenic variant in the OTC gene has not been reported previously as a pathogenic variant nor as a benign variant, to our knowledge. This splice site variant destroys the canonical splice donor site in intron 5; it is predicted to cause abnormal gene splicing, either leading to an abnormal message that is subject to nonsense-mediated mRNA decay, or to an abnormal protein product if the message is used for protein translation. Other pathogenic variants (540+1G>C, 540+2T>A, 540+2T>C, 540+2T>G) disrupting this canonical splice site have been reported in the Human Gene Mutation Database in association with OTC deficiency (Stenson et al., 2014). The c.540+1G>T variant was not observed in approximately 6500 individuals of European and African American ancestry in the NHLBI Exome Sequencing Project, indicating it is not a common benign variant in these populations. We interpret c.540+1G>T as a pathogenic variant

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.74	D
BayesDel_noAF	Pathogenic	0.34
CADD	Pathogenic	33
DANN	Uncertain	1.0
FATHMM_MKL	Pathogenic	1.0	D
PhyloP100		9.3
GERP RS		5.8
Mutation Taster		=0/100	disease causing (ClinVar)

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.95
SpliceAI score (max)		1.0		Details are displayed if max score is > 0.2
DS_DL_spliceai		1.0		Position offset: -1

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Other links and lift over

dbSNP: rs72556288; hg19: chrX-38260682;