NM_207122.2:c.666C>G

Variant names:

• chr11-44114224-C-G
• rs121918281
• NM_207122.2:c.666C>G

Variant summary

Our verdict is Pathogenic. The variant received 18 ACMG points: 18P and 0B. PVS1 PM2 PP5_Very_Strong

The NM_207122.2(EXT2):​c.666C>G​(p.Tyr222*) variant causes a stop gained change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.000000684 in 1,461,832 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 Pathogenic (★★). Variant results in nonsense mediated mRNA decay.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 6.8e-7 (0 hom.)
• Consequence: EXT2 NM_207122.2 stop_gained
• Clinical Significance: Pathogenic criteria provided, multiple submitters, no conflicts P:4
• Conservation: PhyloP100: 1.26
• Publications: 2 publications found

Genes affected

EXT2 (HGNC:3513): (exostosin glycosyltransferase 2) This gene encodes one of two glycosyltransferases involved in the chain elongation step of heparan sulfate biosynthesis. Mutations in this gene cause the type II form of multiple exostoses. Alternatively spliced transcript variants encoding different isoforms have been noted for this gene. [provided by RefSeq, Jul 2008]

EXT2 Gene-Disease associations (from GenCC):

• exostoses, multiple, type 2

  Inheritance: AD Classification: DEFINITIVE, STRONG Submitted by: Genomics England PanelApp, Labcorp Genetics (formerly Invitae), ClinGen, Ambry Genetics, G2P
• seizures-scoliosis-macrocephaly syndrome

  Inheritance: AR Classification: STRONG, SUPPORTIVE, LIMITED Submitted by: Ambry Genetics, Labcorp Genetics (formerly Invitae), Orphanet
• hereditary multiple osteochondromas

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet

ACMG classification

Our verdict: Pathogenic. The variant received 18 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 11-44114224-C-G is Pathogenic according to our data. Variant chr11-44114224-C-G is described in ClinVar as Pathogenic. ClinVar VariationId is 2475.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_207122.2. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	EXT2	NM_207122.2	MANE Select	c.666C>G	p.Tyr222*	stop_gained	Exon 4 of 14	NP_997005.1
	EXT2	NM_000401.3		c.765C>G	p.Tyr255*	stop_gained	Exon 4 of 14	NP_000392.3
	EXT2	NM_001178083.3		c.666C>G	p.Tyr222*	stop_gained	Exon 4 of 15	NP_001171554.1

Ensembl Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	EXT2	ENST00000533608.7	TSL:1 MANE Select	c.666C>G	p.Tyr222*	stop_gained	Exon 4 of 14	ENSP00000431173.2
	EXT2	ENST00000358681.8	TSL:1	c.666C>G	p.Tyr222*	stop_gained	Exon 4 of 15	ENSP00000351509.4
	EXT2	ENST00000343631.4	TSL:1	c.666C>G	p.Tyr222*	stop_gained	Exon 5 of 15	ENSP00000342656.3

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 6.84e-7 AC: 1 AN: 1461832 Hom.: 0 Cov.: 31 AF XY: 0.00000138 AC XY: 1 AN XY: 727220

African (AFR) AF: 0.00 AC: 0 AN: 33470

American (AMR) AF: 0.00 AC: 0 AN: 44722

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26136

East Asian (EAS) AF: 0.00 AC: 0 AN: 39696

South Asian (SAS) AF: 0.00 AC: 0 AN: 86258

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53412

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5764

European-Non Finnish (NFE) AF: 8.99e-7 AC: 1 AN: 1111980

Other (OTH) AF: 0.00 AC: 0 AN: 60394

GnomAD4 genome Cov.: 32

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:4

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Exostoses, multiple, type 2;C4225248:Seizures-scoliosis-macrocephaly syndrome Pathogenic:1

Jan 08, 2024

Fulgent Genetics, Fulgent Genetics

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Exostoses, multiple, type 2 Pathogenic:1

Sep 01, 1997

OMIM

Significance: Pathogenic

Review Status: no assertion criteria provided

Collection Method: literature only

not provided Pathogenic:1

Oct 28, 2024

GeneDx

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Nonsense variant predicted to result in protein truncation or nonsense mediated decay in a gene for which loss of function is a known mechanism of disease; Not observed at significant frequency in large population cohorts (gnomAD); This variant is associated with the following publications: (PMID: 25525159, 30334991, 9326317)

EXT2-related disorder Pathogenic:1

Nov 27, 2023

PreventionGenetics, part of Exact Sciences

Significance: Pathogenic

Review Status: no assertion criteria provided

Collection Method: clinical testing

The EXT2 c.666C>G variant is predicted to result in premature protein termination (p.Tyr222*). This variant has been reported in several affected members of a family with hereditary multiple osteochondromas (Family 2, Philippe et al. 1997. PubMed ID: 9326317), and also in an individual from an unrelated family with hereditary multiple osteochondromas (Li et al. 2018. PubMed ID: 30334991. This variant has not been reported in a large population database (http://gnomad.broadinstitute.org), indicating this variant is rare. Nonsense variants in EXT2 are expected to be pathogenic. This variant is interpreted as pathogenic.

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.63	D
BayesDel_noAF	Pathogenic	0.62
CADD	Pathogenic	37
DANN	Uncertain	1.0
Eigen	Uncertain	0.58
Eigen_PC	Uncertain	0.42
FATHMM_MKL	Uncertain	0.94	D
PhyloP100		1.3
Vest4		0.90
GERP RS		2.4
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.7
Mutation Taster		=0/200	disease causing (ClinVar)

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.020		Details are displayed if max score is > 0.2

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

Other links and lift over

dbSNP: rs121918281; hg19: chr11-44135774;