Genetic Variant EXT1:p.Arg440Leu (chr8-117822563-C-A) – ACMG Classification: Uncertain_significance (4 pts)

Variant summary

Our verdict is Uncertain significance. The variant received 4 ACMG points: 4P and 0B. PM2PP3_Moderate

The NM_000127.3(EXT1):c.1319G>T(p.Arg440Leu) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.000000684 in 1,461,020 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar. Another variant affecting the same amino acid position, but resulting in a different missense (i.e. R440P) has been classified as Uncertain significance.

Frequency

Genomes: not found (cov: 32)

Exomes 𝑓: 6.8e-7 ( 0 hom. )

Consequence

EXT1
NM_000127.3 missense

Scores

Clinical Significance

Not reported in ClinVar

Conservation

PhyloP100: 7.87

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:

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ACMG classification

Classification was made for transcript

Our verdict: Uncertain_significance. The variant received 4 ACMG points.

PM2

Very rare variant in population databases, with high coverage;

PP3

MetaRNN computational evidence supports a deleterious effect, 0.9

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
EXT1	NM_000127.3 link	c.1319G>T	p.Arg440Leu	missense_variant	Exon 5 of 11	ENST00000378204.7	NP_000118.2	Q16394

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
EXT1	ENST00000378204.7 link	c.1319G>T	p.Arg440Leu	missense_variant	Exon 5 of 11	1	NM_000127.3	ENSP00000367446.3		Q16394

Frequencies

GnomAD3 genomes

Cov.:

GnomAD4 exome

AF:

6.84e-7

AC:

AN:

1461020

Hom.:

Cov.:

AF XY:

0.00

AC XY:

AN XY:

726854

show subpopulations

African (AFR)

AF:

0.00

AC:

AN:

33464

American (AMR)

AF:

0.00

AC:

AN:

44722

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

26126

East Asian (EAS)

AF:

0.00

AC:

AN:

39662

South Asian (SAS)

AF:

0.00

AC:

AN:

86250

European-Finnish (FIN)

AF:

0.00

AC:

AN:

53004

Middle Eastern (MID)

AF:

0.00

AC:

AN:

5762

European-Non Finnish (NFE)

AF:

9.00e-7

AC:

AN:

1111656

Other (OTH)

AF:

0.00

AC:

AN:

60374

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.625

Heterozygous variant carriers

0.00

0.20

0.40

0.60

0.80

0.95

Allele balance

Age Distribution

Exome Het

Variant carriers

<30

30-35

35-40

40-45

45-50

50-55

55-60

60-65

65-70

70-75

75-80

>80

Age

GnomAD4 genome

Cov.:

ClinVar

Not reported in ClinVar

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

AlphaMissense

Pathogenic

0.92

BayesDel_addAF

Pathogenic

0.52

BayesDel_noAF

Pathogenic

0.51

CADD

Pathogenic

(source)

DANN

Uncertain

1.0

DEOGEN2

Pathogenic

0.85

Eigen

Pathogenic

0.74

Eigen_PC

Pathogenic

0.78

FATHMM_MKL

Pathogenic

0.99

LIST_S2

Uncertain

0.94

M_CAP

Pathogenic

0.42

MetaRNN

Pathogenic

0.90

MetaSVM

Pathogenic

0.96

MutationAssessor

Uncertain

2.8

PhyloP100

7.9

PrimateAI

Uncertain

0.67

PROVEAN

Pathogenic

-4.9

REVEL

Pathogenic

0.87

Sift

Uncertain

0.0080

Sift4G

Uncertain

0.023

Polyphen

0.94

Vest4

0.92

MutPred

0.55

Loss of MoRF binding (P = 0.0198);

MVP

0.97

MPC

1.1

ClinPred

1.0

GERP RS

5.9

Varity_R

0.51

gMVP

0.94

Mutation Taster

=11/89

disease causing

(source)

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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Variant summary

Frequency

Consequence

Scores

Clinical Significance

Conservation

Publications

ACMG classification

Transcripts

RefSeq

Ensembl

Frequencies

Age Distribution

ClinVar

Computational scores

Splicing

Publications

Other links and lift over