rs1555971000

Positions:

• chrX-38352555-G-A

Variant summary

Our verdict is Uncertain significance. Variant got 3 ACMG points: 4P and 1B. PM2 PP5_Moderate BP4

The NM_001407092.1(OTC):​c.-79-63G>A variant causes a intron change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a benign outcome for this variant. Variant has been reported in ClinVar as Likely pathogenic (★).

• Frequency: Genomes: not found (cov: 23)
• Consequence: OTC NM_001407092.1 intron
• Clinical Significance: Likely pathogenic criteria provided, single submitter P:2
• Conservation: PhyloP100: 3.21

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 Uncertain_significance. Variant got 3 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant X-38352555-G-A is Pathogenic according to our data. Variant chrX-38352555-G-A is described in ClinVar as [Likely_pathogenic]. Clinvar id is 487342.Status of the report is criteria_provided_single_submitter, 1 stars.
• BP4: Computational evidence support a benign effect (BayesDel_noAF=-0.29). . Strength limited to SUPPORTING due to the PP5.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
OTC	NM_001407092.1	c.-79-63G>A		intron_variant
OTC	NM_000531.6			upstream_gene_variant		ENST00000039007.5
OTC	XM_017029556.2			upstream_gene_variant

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
OTC	ENST00000039007.5			upstream_gene_variant		1	NM_000531.6	P1
OTC	ENST00000488812.1			upstream_gene_variant		5
OTC	ENST00000643344.1			upstream_gene_variant

Frequencies

GnomAD3 genomes Cov.: 23

GnomAD4 exome Cov.: 5

GnomAD4 genome Cov.: 23

ClinVar

Significance: Likely pathogenic

Submissions summary: Pathogenic:2

Revision: criteria provided, single submitter

Submissions by phenotype

Ornithine carbamoyltransferase deficiency Pathogenic:2

Likely pathogenic, criteria provided, single submitter	clinical testing	Invitae	Feb 06, 2019	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. Experimental studies have shown that this promoter change causes a reduction of OTC transcription (PMID: 29282796). This variant has been observed in individuals affected with clinical features of OTC deficiency (PMID: 29282796, Invitae). ClinVar contains an entry for this variant (Variation ID: 487342). This variant is not present in population databases (ExAC no frequency). This variant occurs in a non-coding region of the OTC gene. It does not change the encoded amino acid sequence of the OTC protein. -
Likely pathogenic, no assertion criteria provided	research	Caldovic Lab, Children's National Health System	Dec 12, 2017	The patient had clinical and biochemical symptoms of OTC deficiency, and no disease causing sequence variants in the OTC coding sequence and canonical splice sites. Functional testing in cultured cells indicates reduced expression of reporter gene -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_noAF	Benign	-0.29
CADD	Benign	20
DANN	Benign	0.89

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: rs1555971000; hg19: chrX-38211808;