X-38401404-C-T

Variant names:

• chrX-38401404-C-T
• rs72556280
• NM_000531.6:c.516C>T

Variant summary

Our verdict is Likely benign. The variant received -1 ACMG points: 2P and 3B. PM2 BP4_Moderate BP7

The NM_000531.6(OTC):​c.516C>T​(p.Ile172Ile) variant causes a synonymous change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000000914 in 1,094,164 control chromosomes in the GnomAD database, with no homozygous occurrence. There are no hemizygote samples in GnomAD. In-silico tool predicts a benign outcome for this variant. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar. Synonymous variant affecting the same amino acid position (i.e. I172I) has been classified as Likely benign.

• Frequency:
  • Genomes: not found (cov: 23)
  • Exomes 𝑓: 9.1e-7 (0 hom. 0 hem.)
• Consequence: OTC NM_000531.6 synonymous
• Clinical Significance: Not reported in ClinVar
• Conservation: PhyloP100: 0.520
• 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: Likely_benign. The variant received -1 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (BayesDel_noAF=-0.35).
• BP7: Synonymous conserved (PhyloP=0.52 with no splicing effect.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
OTC	NM_000531.6	c.516C>T	p.Ile172Ile	synonymous_variant	Exon 5 of 10	ENST00000039007.5	NP_000522.3
OTC	NM_001407092.1	c.516C>T	p.Ile172Ile	synonymous_variant	Exon 7 of 12		NP_001394021.1
OTC	XM_017029556.2	c.516C>T	p.Ile172Ile	synonymous_variant	Exon 5 of 9		XP_016885045.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
OTC	ENST00000039007.5	c.516C>T	p.Ile172Ile	synonymous_variant	Exon 5 of 10	1	NM_000531.6	ENSP00000039007.4
ENSG00000250349	ENST00000465127.1	c.172-264717C>T		intron_variant	Intron 3 of 8	5		ENSP00000417050.1

Frequencies

GnomAD3 genomes Cov.: 23

GnomAD4 exome AF: 9.14e-7 AC: 1 AN: 1094164 Hom.: 0 Cov.: 28 AF XY: 0.00 AC XY: 0 AN XY: 359664

⚠️ The allele balance in gnomAD version 4 Exomes is significantly skewed from the expected value of 0.5.

African (AFR) AF: 0.00 AC: 0 AN: 26327

American (AMR) AF: 0.00 AC: 0 AN: 35205

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 19359

East Asian (EAS) AF: 0.00 AC: 0 AN: 30175

South Asian (SAS) AF: 0.00 AC: 0 AN: 54044

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 40521

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 4123

European-Non Finnish (NFE) AF: 0.00000119 AC: 1 AN: 838456

Other (OTH) AF: 0.00 AC: 0 AN: 45954

⚠️ The allele balance in gnomAD4 Exomes is highly skewed from 0.5 (p-value = 0), which strongly suggests a high chance of mosaicism in these individuals.

GnomAD4 genome Cov.: 23

ClinVar

Not reported in ClinVar

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_noAF	Benign	-0.35
CADD	Benign	7.3
DANN	Benign	0.75
PhyloP100		0.52

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

Other links and lift over

dbSNP: rs72556280; hg19: chrX-38260657; COSMIC: COSV50002398;