NM_000531.6:c.867G>A

Variant names:

• chrX-38409025-G-A
• NM_000531.6:c.867G>A

Variant summary

Our verdict is Likely pathogenic. Variant got 7 ACMG points: 7P and 0B. PM2 PP3_Strong PP5

The NM_000531.6(OTC):​c.867G>A​(p.Lys289Lys) variant causes a splice region, synonymous change involving the alteration of a conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a benign outcome for this variant. 3/3 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars).

• Frequency: Genomes: not found (cov: 23)
• Consequence: OTC NM_000531.6 splice_region, synonymous
• Scores: Splicing: ADA: 1.000
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:1 U:1
• Conservation: PhyloP100: 9.45

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]

ENSG00000250349 (HGNC:):

ACMG classification

Verdict is Likely_pathogenic. Variant got 7 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP3: Splicing scoreres supports a deletorius effect: Scorers claiming Pathogenic: dbscSNV1_ADA, dbscSNV1_RF, max_spliceai. No scorers claiming Uncertain. No scorers claiming Benign.
• PP5: Variant X-38409025-G-A is Pathogenic according to our data. Variant chrX-38409025-G-A is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 1686000.We mark this variant Likely_pathogenic, oryginal submissions are: {Uncertain_significance=1, Pathogenic=1}.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
OTC	NM_000531.6	c.867G>A	p.Lys289Lys	splice_region_variant, synonymous_variant	Exon 8 of 10	ENST00000039007.5	NP_000522.3
OTC	NM_001407092.1	c.867G>A	p.Lys289Lys	splice_region_variant, synonymous_variant	Exon 10 of 12		NP_001394021.1
OTC	XM_017029556.2	c.867G>A	p.Lys289Lys	splice_region_variant, synonymous_variant	Exon 8 of 9		XP_016885045.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
OTC	ENST00000039007.5	c.867G>A	p.Lys289Lys	splice_region_variant, synonymous_variant	Exon 8 of 10	1	NM_000531.6	ENSP00000039007.4
ENSG00000250349	ENST00000465127.1	c.172-257096G>A		intron_variant	Intron 3 of 8	5		ENSP00000417050.1
OTC	ENST00000643344.1	n.*617G>A		splice_region_variant, non_coding_transcript_exon_variant	Exon 9 of 11			ENSP00000496606.1
OTC	ENST00000643344.1	n.*617G>A		3_prime_UTR_variant	Exon 9 of 11			ENSP00000496606.1

Frequencies

GnomAD3 genomes Cov.: 23

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 23

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:1 Uncertain:1

Revision: criteria provided, conflicting classifications

Submissions by phenotype

Ornithine carbamoyltransferase deficiency Pathogenic:1 Uncertain:1

May 04, 2022

Mendelics

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Jul 15, 2022

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This variant is not present in population databases (gnomAD no frequency). This sequence change affects codon 289 of the OTC mRNA. It is a 'silent' change, meaning that it does not change the encoded amino acid sequence of the OTC protein. RNA analysis indicates that this variant induces altered splicing and likely results in the loss of 4 amino acid residue(s), but is expected to preserve the integrity of the reading-frame. This variant has been observed in individual(s) with ornithine transcarbamylase deficiency (PMID: 23278509). In at least one individual the variant was observed to be de novo. In summary, the available evidence is currently insufficient to determine the role of this variant in disease. Therefore, it has been classified as a Variant of Uncertain Significance. Variants that disrupt the consensus splice site are a relatively common cause of aberrant splicing (PMID: 17576681, 9536098). Studies have shown that this variant results in the activation of a cryptic splice site in exon 8 (PMID: 23278509). ClinVar contains an entry for this variant (Variation ID: 1686000). -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_noAF	Benign	-0.28
CADD	Benign	22
DANN	Benign	0.88

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	1.0
SpliceAI score (max)		0.83		Details are displayed if max score is > 0.2
DS_DL_spliceai		0.83		Position offset: 0

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

Publications

No publications associated with this variant yet.

Other links and lift over

hg19: chrX-38268278;