8-117837105-T-G

Position:

• chr8-117837105-T-G

Variant summary

Our verdict is Uncertain significance. Variant got 5 ACMG points: 5P and 0B. PM2 PP3 PP5_Moderate

The NM_000127.3(EXT1):​c.1056+3A>C variant causes a splice donor region, intron change involving the alteration of a conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a benign outcome for this variant. Variant has been reported in ClinVar as Pathogenic (★).

• Frequency: Genomes: not found (cov: 32)
• Consequence: EXT1 NM_000127.3 splice_donor_region, intron
• Scores: Splicing: ADA: 0.9994
• Clinical Significance: Pathogenic criteria provided, single submitter P:1
• Conservation: PhyloP100: 7.75

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 5 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP3: Splicing scoreres supports a deletorius effect: Scorers claiming Pathogenic: dbscSNV1_ADA, dbscSNV1_RF. Scorers claiming Uncertain: max_spliceai. No scorers claiming Benign.
• PP5: Variant 8-117837105-T-G is Pathogenic according to our data. Variant chr8-117837105-T-G is described in ClinVar as [Pathogenic]. Clinvar id is 456060.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.1056+3A>C		splice_donor_region_variant, intron_variant		ENST00000378204.7

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
EXT1	ENST00000378204.7	c.1056+3A>C		splice_donor_region_variant, intron_variant		1	NM_000127.3	P1
EXT1	ENST00000436216.2	c.424+3A>C		splice_donor_region_variant, intron_variant, NMD_transcript_variant		3
EXT1	ENST00000437196.1	c.74-1554A>C		intron_variant, NMD_transcript_variant		5
EXT1	ENST00000684189.1	n.523+3A>C		splice_donor_region_variant, intron_variant, non_coding_transcript_variant

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 30

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

May 17, 2017

This variant is not present in population databases (ExAC no frequency). For these reasons, this variant has been classified as Pathogenic. Nucleotide substitutions within the consensus splice site are relatively common causes of aberrant splicing (PMID: 17576681, 9536098). Algorithms developed to predict the effect of nucleotide changes on RNA splicing suggest that this variant may alter RNA splicing, but this prediction has not been confirmed by published transcriptional studies. This variant has been reported in an individual affected with multiple osteochondromas (PMID: 19810120). Family studies have also indicated that this variant segregates with multiple osteochondromas in a family (Invitae). This sequence change falls in intron 2 of the EXT1 gene. It does not directly change the encoded amino acid sequence of the EXT1 protein, but it affects a nucleotide within the consensus splice site of the intron. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_noAF	Benign	-0.25
CADD	Benign	22
DANN	Benign	0.96
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		2.8

Splicing

Name	Calibrated prediction	Score	Prediction
dbscSNV1_ADA	Pathogenic	1.0
dbscSNV1_RF	Pathogenic	0.97
SpliceAI score (max)		0.48		Details are displayed if max score is > 0.2
DS_DL_spliceai		0.48		Position offset: 3

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Publications

LitVar

Other links and lift over

dbSNP: rs1554580140; hg19: chr8-118849344;