Genetic Variant EXT1:c.*146G>C (chr8-117799566-C-G) – ACMG Classification: Uncertain_significance (0 pts)

Variant summary

Our verdict is Uncertain significance. The variant received 0 ACMG points: 2P and 2B. PM2BP4_Moderate

The NM_000127.3(EXT1):c.*146G>C variant causes a 3 prime UTR change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000268 in 747,396 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★).

Frequency

Genomes: not found (cov: 32)

Exomes 𝑓: 0.0000027 ( 0 hom. )

Consequence

EXT1
NM_000127.3 3_prime_UTR

Scores

Clinical Significance

Uncertain significance criteria provided, single submitter U:1

Conservation

PhyloP100: 0.485

Publications

0 publications found

Variant links:

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]

EXT1 Gene-Disease associations (from GenCC):

exostoses, multiple, type 1
Inheritance: AD Classification: DEFINITIVE, STRONG Submitted by: Labcorp Genetics (formerly Invitae), G2P, ClinGen
chondrosarcoma
Inheritance: AD Classification: STRONG Submitted by: Genomics England PanelApp
hereditary multiple osteochondromas
Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet

EXT1 links:

Genome browser will be placed here

ACMG classification

Classification was made for transcript

Our verdict: Uncertain_significance. The variant received 0 ACMG points.

PM2

Very rare variant in population databases, with high coverage;

BP4

Computational evidence support a benign effect (BayesDel_noAF=-0.43).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
EXT1	NM_000127.3 link	c.*146G>C		3_prime_UTR_variant	Exon 11 of 11	ENST00000378204.7	NP_000118.2	Q16394

Ensembl

Gene	Transcript	HGVSc	Effect	Exon rank	TSL	MANE	Protein	UniProt
EXT1	ENST00000378204.7 link	c.*146G>C	3_prime_UTR_variant	Exon 11 of 11	1	NM_000127.3	ENSP00000367446.3	Q16394
EXT1	ENST00000684189.1 link	n.1854G>C	non_coding_transcript_exon_variant	Exon 11 of 11
EXT1	ENST00000684443.1 link	n.*21G>C	downstream_gene_variant

Frequencies

GnomAD3 genomes

Cov.:

GnomAD4 exome

AF:

0.00000268

AC:

AN:

747396

Hom.:

Cov.:

AF XY:

0.00000258

AC XY:

AN XY:

387074

show subpopulations

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

African (AFR)

AF:

0.00

AC:

AN:

18298

American (AMR)

AF:

0.00

AC:

AN:

27970

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

18182

East Asian (EAS)

AF:

0.00

AC:

AN:

33504

South Asian (SAS)

AF:

0.0000175

AC:

AN:

57204

European-Finnish (FIN)

AF:

0.00

AC:

AN:

40858

Middle Eastern (MID)

AF:

0.00

AC:

AN:

3446

European-Non Finnish (NFE)

AF:

0.00000195

AC:

AN:

511916

Other (OTH)

AF:

0.00

AC:

AN:

36018

⚠️ The allele balance in gnomAD4 Exomes is highly skewed from 0.5 (p-value = 0.000000), which strongly suggests a high chance of mosaicism in these individuals.

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.325

Heterozygous variant carriers

0.00

0.20

0.40

0.60

0.80

0.95

Allele balance

GnomAD4 genome

Cov.:

Alfa

AF:

0.00

Hom.:

Bravo

AF:

0.00000378

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:1

Revision: criteria provided, single submitter

LINK: link

Submissions by phenotype

Multiple congenital exostosis

Uncertain:1

Jan 13, 2018

Illumina Laboratory Services, Illumina

Significance:Uncertain significance

Review Status:criteria provided, single submitter

Collection Method:clinical testing

This variant was observed in the ICSL laboratory as part of a predisposition screen in an ostensibly healthy population. It had not been previously curated by ICSL or reported in the Human Gene Mutation Database (HGMD: prior to June 1st, 2018), and was therefore a candidate for classification through an automated scoring system. Utilizing variant allele frequency, disease prevalence and penetrance estimates, and inheritance mode, an automated score was calculated to assess if this variant is too frequent to cause the disease. Based on the score, this variant could not be ruled out of causing disease and therefore its association with disease required further investigation. A literature search was performed for the gene, cDNA change, and amino acid change (if applicable). No publications were found based on this search. This variant was therefore classified as a variant of unknown significance for this disease. -

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

BayesDel_noAF

Benign

-0.43

CADD

Benign

(source)

DANN

Benign

0.77

PhyloP100

0.48

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

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8-117799566-C-G

Variant summary

Frequency

Consequence

Scores

Clinical Significance

Conservation

Publications

ACMG classification

Transcripts

RefSeq

Ensembl

Frequencies

Age Distribution

ClinVar

Submissions by phenotype

Computational scores

Splicing

Publications

Other links and lift over