X-38369878-G-GT

Variant names:

• chrX-38369878-G-GT
• rs1555972540
• NM_000531.6:c.298+2dupT

Variant summary

Our verdict is Uncertain significance. The variant received 4 ACMG points: 4P and 0B. PVS1_Moderate PM2

The ENST00000039007.5(OTC):​c.298+1_298+2insT variant causes a splice donor, intron change. The variant was absent in control chromosomes in GnomAD project. 1/1 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Uncertain significance (★).

• Frequency: Genomes: not found (cov: 23)
• Consequence: OTC ENST00000039007.5 splice_donor, intron
• Clinical Significance: Uncertain significance criteria provided, single submitter U:1
• Conservation: PhyloP100: 6.27
• Publications: 0 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: Uncertain_significance. The variant received 4 ACMG points.

• PVS1: Splicing +-2 bp (donor or acceptor) variant, product NOT destroyed by NMD, known LOF gene, truncates exone, which is 0.076995306 fraction of the gene. Cryptic splice site detected, with MaxEntScore 3.6, offset of 0 (no position change), new splice context is: cagGTtaag. Cryptic site results in inframe change. If cryptic site found is not functional and variant results in exon loss, it results in frameshift change.
• PM2: Very rare variant in population databases, with high coverage

Variant Effect in Transcripts

ACMG analysis was done for transcript: ENST00000039007.5. 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.298+2dupT		splice_region intron	N/A	NP_000522.3
	OTC	NM_001407092.1		c.298+2dupT		splice_region 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.298+1_298+2insT		splice_donor intron	N/A	ENSP00000039007.4
	ENSG00000250349	ENST00000465127.1	TSL:5	c.172-296243_172-296242insT		intron	N/A	ENSP00000417050.1
	OTC	ENST00000713758.1		c.298+1_298+2insT		splice_donor intron	N/A	ENSP00000519059.1

Frequencies

GnomAD3 genomes Cov.: 23

GnomAD4 exome Cov.: 22

GnomAD4 genome Cov.: 23

ClinVar

ClinVar submissions as Germline

Significance: Uncertain significance

Revision: criteria provided, single submitter

Pathogenic	VUS	Benign	Condition
-	1	-	Ornithine carbamoyltransferase deficiency (1)

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
PhyloP100		6.3

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.91		Details are displayed if max score is > 0.2
DS_DL_spliceai		0.91		Position offset: -1

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

Other links and lift over

dbSNP: rs1555972540; hg19: chrX-38229131;