chr8-117799792-G-C

Position:

• chr8-117799792-G-C

Variant summary

Our verdict is Uncertain significance. Variant got 3 ACMG points: 3P and 0B. PM2 PP3

The NM_000127.3(EXT1):​c.2161C>G​(p.Gln721Glu) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000205 in 1,461,888 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★★).

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000021 (0 hom.)
• Consequence: EXT1 NM_000127.3 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:2
• Conservation: PhyloP100: 10.0

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 Uncertain_significance. Variant got 3 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.76

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
EXT1	NM_000127.3	c.2161C>G	p.Gln721Glu	missense_variant	11/11	ENST00000378204.7	NP_000118.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
EXT1	ENST00000378204.7	c.2161C>G	p.Gln721Glu	missense_variant	11/11	1	NM_000127.3	ENSP00000367446	P1
EXT1	ENST00000684189.1	n.1628C>G		non_coding_transcript_exon_variant	11/11
EXT1	ENST00000684443.1	n.2287C>G		non_coding_transcript_exon_variant	2/2
EXT1	ENST00000437196.1			downstream_gene_variant		5		ENSP00000407299

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 0.00000205 AC: 3 AN: 1461888 Hom.: 0 Cov.: 32 AF XY: 0.00000413 AC XY: 3 AN XY: 727246

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00000270

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Chondrosarcoma Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Baylor Genetics

Sep 03, 2023

- -

Multiple congenital exostosis Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Labcorp Genetics (formerly Invitae), Labcorp

May 07, 2022

This variant is not present in population databases (gnomAD no frequency). This variant has not been reported in the literature in individuals affected with EXT1-related conditions. Advanced modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) performed at Invitae indicates that this missense variant is not expected to disrupt EXT1 protein function. 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. This sequence change replaces glutamine, which is neutral and polar, with glutamic acid, which is acidic and polar, at codon 721 of the EXT1 protein (p.Gln721Glu). -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.27
BayesDel_addAF	Pathogenic	0.20	D
BayesDel_noAF	Uncertain	0.050
CADD	Pathogenic	26
DANN	Uncertain	0.99
DEOGEN2	Uncertain	0.53	D
Eigen	Uncertain	0.25
Eigen_PC	Uncertain	0.46
FATHMM_MKL	Pathogenic	1.0	D
LIST_S2	Uncertain	0.90	D
M_CAP	Benign	0.063	D
MetaRNN	Pathogenic	0.76	D
MetaSVM	Benign	-0.34	T
MutationAssessor	Benign	1.9	L
MutationTaster	Benign	1.0	D
PrimateAI	Uncertain	0.72	T
PROVEAN	Benign	-1.1	N
REVEL	Uncertain	0.38
Sift	Benign	0.22	T
Sift4G	Benign	0.57	T
Polyphen		0.18	B
Vest4		0.66
MutPred		0.78		Loss of sheet (P = 0.1158);
MVP		0.81
MPC		2.3
ClinPred		0.85	D
GERP RS		6.0
Varity_R		0.44
gMVP		0.68

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.040		Details are displayed if max score is > 0.2

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: chr8-118812031; COSMIC: COSV65477930; COSMIC: COSV65477930;