chr8-117822480-AG-A

Position:

• chr8-117822480-AG-A

Variant summary

Our verdict is Pathogenic. Variant got 12 ACMG points: 12P and 0B. PVS1 PM2 PP5_Moderate

The NM_000127.3(EXT1):​c.1401del​(p.Tyr468ThrfsTer5) variant causes a frameshift change. The variant was absent in control chromosomes in GnomAD project. Variant has been reported in ClinVar as Pathogenic (★). Variant results in nonsense mediated mRNA decay.

• Frequency: Genomes: not found (cov: 32)
• Consequence: EXT1 NM_000127.3 frameshift
• Clinical Significance: Pathogenic criteria provided, single submitter P:1
• Conservation: PhyloP100: 5.03

Genes affected

EXT1 (HGNC:3512): (exostosin glycosyltransferase 1) This gene encodes an endoplasmic reticulum-resident type II transmembrane glycosyltransferase involved in the chain elongation step of heparan sulfate biosynthesis. Mutations in this gene cause the type I form of multiple exostoses. [provided by RefSeq, Jul 2008]

ACMG classification

Verdict is Pathogenic. Variant got 12 ACMG points.

• PVS1: Loss of function variant, product undergoes nonsense mediated mRNA decay. LoF is a known mechanism of disease.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 8-117822480-AG-A is Pathogenic according to our data. Variant chr8-117822480-AG-A is described in ClinVar as [Pathogenic]. Clinvar id is 456061.Status of the report is criteria_provided_single_submitter, 1 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
EXT1	NM_000127.3	c.1401del	p.Tyr468ThrfsTer5	frameshift_variant	5/11	ENST00000378204.7

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
EXT1	ENST00000378204.7	c.1401del	p.Tyr468ThrfsTer5	frameshift_variant	5/11	1	NM_000127.3	P1
EXT1	ENST00000684189.1	n.868del		non_coding_transcript_exon_variant	5/11
EXT1	ENST00000436216.2	c.*202del		3_prime_UTR_variant, NMD_transcript_variant	6/6	3
EXT1	ENST00000437196.1	c.*292del		3_prime_UTR_variant, NMD_transcript_variant	4/10	5

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 32

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:1

Revision: criteria provided, single submitter

Submissions by phenotype

Multiple congenital exostosis Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

Aug 07, 2017

This sequence change creates a premature translational stop signal (p.Tyr468Thrfs*5) in the EXT1 gene. It is expected to result in an absent or disrupted protein product. This variant is not present in population databases (ExAC no frequency). This variant has not been reported in the literature in individuals with EXT1-related disease. However, a different variant (c.1402del) that results in the same protein effect (p.Tyr468Thrfs*5) has been reported in individuals affected with multiple osteochondromas (PMID: 19810120, 21520333). Loss-of-function variants in EXT1 are known to be pathogenic (PMID: 10679937, 11391482, 19810120). For these reasons, this variant has been classified as Pathogenic. -

Computational scores

Source: dbNSFP v4.3

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.010		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: rs1554579004; hg19: chr8-118834719;