EXT3

Gene Summary

Gene:EXT3; exostoses (multiple) 3
Aliases: EXT2
Location:19p
Summary:-
Databases:OMIM, HGNC, GeneCard, Gene
Source:NCBIAccessed: 16 March, 2015

Cancer Overview

Research Indicators

Publications Per Year (1990-2015)
Graph generated 16 March 2015 using data from PubMed using criteria.

Literature Analysis

Mouse over the terms for more detail; many indicate links which you can click for dedicated pages about the topic.

  • Point Mutation
  • Tumor Suppressor Gene
  • Pedigree
  • Amino Acid Sequence
  • Loss of Heterozygosity
  • Chromosome 8
  • DNA Sequence Analysis
  • Heterozygote
  • Polymerase Chain Reaction
  • Tumor Suppressor Proteins
  • Base Sequence
  • N-Acetylhexosaminyltransferases
  • Chromosome Mapping
  • Sequence Alignment
  • Single-Stranded Conformational Polymorphism
  • Phenotype
  • Chondrosarcoma
  • Adolescents
  • Genetic Linkage
  • Cloning, Molecular
  • Bone Cancer
  • Genetic Markers
  • Chromosome 19
  • Molecular Sequence Data
  • Osteochondroma
  • DNA Mutational Analysis
  • Frameshift Mutation
  • Tissue Distribution
  • Exostoses, Multiple Hereditary
  • Exons
  • DNA Primers
  • Family
  • Sequence Deletion
  • Proteins
  • Chromosome 11
  • Genes, Dominant
  • N-Acetylglucosaminyltransferases
  • Mutation
  • Genetic Heterogeneity
Tag cloud generated 16 March, 2015 using data from PubMed, MeSH and CancerIndex

Specific Cancers (1)

Data table showing topics related to specific cancers and associated disorders. Scope includes mutations and abnormal protein expression.

Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).

Latest Publications: EXT3 (cancer-related)

Vanita V, Sperling K, Sandhu HS, et al.
Novel EXT1 and EXT2 mutations in hereditary multiple exostoses families of Indian origin.
Genet Test Mol Biomarkers. 2009; 13(1):43-9 [PubMed] Related Publications
BACKGROUND: Hereditary multiple exostosis (HME) is an autosomal dominant bone disorder, characterized by short stature and the presence of multiple benign tumors mainly at the ends of long bones. HME is genetically heterogeneous with two known genes on 8q24 (EXT1) and 11p11 (EXT2), and a third minor locus mapped to 19p (EXT3). The majority of EXT1 and EXT2 mutations result in premature protein truncation and loss of function.
MATERIALS AND METHODS: We analyzed two autosomal dominant HME families of Indian origin. Linkage analysis using fluorescently labeled microsatellite markers at the candidate gene regions was performed. Mutation analysis was carried out by bidirectional sequencing of purified PCR products.
RESULTS: We found linkage in one family to EXT1 and in the other family to EXT2. Mutation screening in the EXT1 gene revealed a novel frameshift mutation, a single base deletion in exon 1 (c.142delC). This mutation segregated in all affected members and was absent in the unaffected family members and 60 unrelated controls. In the second family, a previously unreported stop mutation, the substitution c.817C>T, was observed in the EXT2 gene in all affected members and in none of the unaffected family members and 90 unrelated controls.
CONCLUSIONS: Our findings expand the mutation spectrum of EXT1 and EXT2 and highlight the genetic and phenotypic heterogeneity of HME.

Foroughmand AM, Galehdari H, Rasouli M, et al.
Novel mutation in the EXT-1 gene in an Iranian family affected with hereditary multiple exostoses.
Pak J Biol Sci. 2008; 11(7):1037-41 [PubMed] Related Publications
Identification of casual mutations in Hereditary Multiple Exostoses (HME) is important because of similar conditions in which multiple exostoses occur. Therefore mutation analysis can help to confirm the clinical diagnosis and to improve the management of therapy. HME is an inherited disorder of bone growth. HME can be referred to by various names such as Heredity Multiple Exostoses, Hereditary Multiple Osteochondromata, Multiple Carthaginous Exostoses, etc. People who have HME grow exostoses, or bony bumps, on their bones which can vary in size, location and number depending on the individual. HME is inherited in an autosomal dominant manner with an estimated prevalence of 1/50,000 in western countries. At least three loci (EXT1, EXT2 and EXT3) thought to be involved in this skeletal disease. Approximately 90% of affected families possess mutations in the coding regions of EXT1 and EXT2 genes and the majority of these mutations cause loss of function. EXT1 and EXT2 genes encode related members of a putative tumor suppressor family. In this first report from Iran we identified a frame shift mutation (1100-1101 insA) in exon 3 of EXT1 gene in a family being suspicious of HME. This mutation leads to a premature stop codon and previously not described. Additionally, we have found an unreported silent mutation in the exon six of EXT1 gene with uncertain significance.

Chen WC, Chi CH, Chuang CC, Jou IM
Three novel EXT1 and EXT2 gene mutations in Taiwanese patients with multiple exostoses.
J Formos Med Assoc. 2006; 105(5):434-7 [PubMed] Related Publications
Multiple osteochondromatosis, also known as hereditary multiple exostoses (HME), is an inherited autosomal dominant disorder characterized by the presence of multiple exostoses on the long bones. These exostoses are benign cartilaginous tumors (enchondromata). Three different exostosis (EXT) loci on chromosomes 8q (exostosin 1, EXT1), 11p (exostosin 2, EXT2) and 19p (exostosin 3, EXT3) have been reported. Recently, the EXT1 and EXT2 genes were identified by positional cloning. Using polymerase chain reaction and direct sequencing, we analyzed the EXT1 and EXT2 genes in three familial cases and one sporadic case of HME in Taiwanese patients. We found three novel mutations (S277X in the EXT1 gene, and G194X and 939+1G>A in the EXT2 gene) and a known mutation (Q172X in the EXT2 gene). Mutation analysis in families with HME allows for genetic counseling and prenatal diagnosis.

Faiyaz-Ul-Haque M, Ahmad W, Zaidi SH, et al.
Novel mutations in the EXT1 gene in two consanguineous families affected with multiple hereditary exostoses (familial osteochondromatosis).
Clin Genet. 2004; 66(2):144-51 [PubMed] Related Publications
Multiple hereditary exostoses (HME) is an autosomal dominant developmental disorder exhibiting multiple osteocartilaginous bone tumors that generally arise near the ends of growing long bones. Here, we report two large consanguineous families from Pakistan, who display the typical features of HME. Affected individuals also show a previously unreported feature--bilateral overriding of single toes. Analysis using microsatellite markers for each of the known EXT loci, EXT1, EXT2, and EXT3 showed linkage to EXT1. In the first family, mutation analysis of the EXT1 gene revealed that affected individuals were heterozygous for an in-frame G-to-C transversion at the conserved splice donor site in intron 1. This mutation is predicted to disrupt splicing of the first intron and produce a frameshift that leads to a premature termination codon. In the second family, an insertion of an A in exon 8 is predicted to produce a frameshift at codon 555 followed by a premature termination, a further 10 codons downstream. In both families, an increased number of affected male subjects were observed. In affected females in family 2, phenotypic variability and incomplete penetrance were noted.

Shi YR, Wu JY, Hsu YA, et al.
Mutation screening of the EXT genes in patients with hereditary multiple exostoses in Taiwan.
Genet Test. 2002; 6(3):237-43 [PubMed] Related Publications
Hereditary multiple exostoses (HME) is an autosomal dominant disorder characterized by growth of benign bone tumors. This genetically heterozygous disease comprises three chromosomal loci: the EXT1 gene on chromosome 8q23-q24, EXT2 on 11p11-p13, and EXT3 on 19p. Both EXT1 and EXT2 have been cloned and defined as a new family of potential tumor suppressor genes in previous work. However, no studies have been conducted in the Taiwanese population. To determine if previous results can also be applied to the Taiwanese, we analyzed 5 Taiwanese probands with clinical features of HME: 1 of them is a sporadic case, and the others are familial cases. Linkage studies were performed in the familial cases before the mutation analysis to determine to which of the three EXT chromosomes these cases could be assigned. Our results showed that one proband is linked to the EXT1 locus and three are linked to the EXT2 locus; the sporadic case was subsequently found to involve EXT1. We then identified four new mutations that have not been found in other races: two in EXT1--frameshift (K218fsX247) and nonsense (Y468X) mutations and two in EXT2-missense (R223P) and nonsense (Y394X) mutations. Our results indicate that in familial cases, linkage analysis can prove useful for preimplantation genetic diagnosis.

Francannet C, Cohen-Tanugi A, Le Merrer M, et al.
Genotype-phenotype correlation in hereditary multiple exostoses.
J Med Genet. 2001; 38(7):430-4 [PubMed] Free Access to Full Article Related Publications
Hereditary multiple exostoses (HME) is a genetically heterogeneous autosomal dominant disorder characterised by the development of bony protuberances mainly located on the long bones. Three HME loci have been mapped to chromosomes 8q24 (EXT1), 11p11-13 (EXT2), and 19p (EXT3). The EXT1 and EXT2 genes encode glycosyltransferases involved in biosynthesis of heparan sulphate proteoglycans. Here we report on a clinical survey and mutation analysis of 42 HME French families and show that EXT1 and EXT2 accounted for more than 90% of HME cases in our series. Among them, 27/42 cases were accounted for by EXT1 (64%, four nonsense, 19 frameshift, three missense, and one splice site mutations) and 9/42 cases were accounted for by EXT2 (21%, four nonsense, two frameshift, two missense, and one splice site mutation). Overall, 31/36 mutations were expected to cause loss of protein function (86%). The most severe forms of the disease and malignant transformation of exostoses to chondrosarcomas were associated with EXT1 mutations. These findings provide the first genotype-phenotype correlation in HME and will, it is hoped, facilitate the clinical management of these patients.

Kivioja A, Ervasti H, Kinnunen J, et al.
Chondrosarcoma in a family with multiple hereditary exostoses.
J Bone Joint Surg Br. 2000; 82(2):261-6 [PubMed] Related Publications
Multiple hereditary exostoses is an autosomal dominant skeletal disorder in which there are numerous cartilage-capped excrescences in areas of actively growing bone. The condition is genetically heterogeneous, and at least three genes, ext1, ext2 and ext3 are involved. The reported risk for malignant transformation to chondrosarcoma has been from 0.6% to 2.8%. We have reviewed six generations of a family with 114 living adult members, 46 of them with multiple exostoses. Four have had operations for chondrosarcoma, giving the risk for malignant transformation as 8.3% in this family. Clinical and radiological examination revealed two additional patients with a suspicion of malignancy, but in whom the histological findings were benign. Reported elsewhere in detail, genetic linkage analysis mapped the causative gene to chromosome 11 and molecular studies revealed a guanine-to-thymine transversion in the ext2 gene. Patients with multiple hereditary exostoses carry a relatively high risk of malignant transformation. They should be informed of this possibility and regularly reviewed.

Stickens D, Brown D, Evans GA
EXT genes are differentially expressed in bone and cartilage during mouse embryogenesis.
Dev Dyn. 2000; 218(3):452-64 [PubMed] Related Publications
Hereditary multiple exostoses (HME) is a genetically heterogeneous disease characterized by the development of bony protuberances at the ends of all long bones. Genetic analyses have revealed HME to be a multigenic disorder linked to three loci on chromosomes 8q24 (EXT1), 11p11-13 (EXT2), and 19p (EXT3). The EXT1 and EXT2 genes have been cloned and defined as glycosyltransferases involved in the synthesis of heparan sulfate. EST database analysis has demonstrated additional gene family members, EXT-like genes (EXTL1, EXTL2, and EXTL3), not associated with a HME locus. The mouse homologs of EXT1 and EXT2 have also been cloned and shown to be 99% and 95% identical to their human counterparts, respectively. Here, we report the identification of the mouse EXTL1 gene and show it is 74% identical to the human EXTL1 gene. Expression studies of all three mouse EXT genes throughout various stages of embryonic development were carried out and whole-mount in situ hybridization in the developing limb buds showed high levels of expression of all three EXT genes. However, in situ hybridization of sectioned embryos revealed remarkable differences in expression profiles of EXT1, EXT2, and EXTL1. The identical expression patterns found for the EXT1 and EXT2 genes support the recent observation that both proteins form a glycosyltransferase complex. We suggest a model for exostoses formation based on the involvement of EXT1 and EXT2 in the Indian hedgehog/parathyroid hormone-related peptide (PTHrP) signaling pathway, an important regulator of the chondrocyte maturation process.

Xu L, Xia J, Jiang H, et al.
Mutation analysis of hereditary multiple exostoses in the Chinese.
Hum Genet. 1999 Jul-Aug; 105(1-2):45-50 [PubMed] Related Publications
Hereditary multiple exostoses (EXT; MIM 133700) is an autosomal dominant bone disorder. It is genetically heterogeneous with at least three chromosomal loci: EXT1 on 8q24.1, EXT2 on 11p11, and EXT3 on 19p. EXT1 and EXT2, the two genes responsible for EXT1 and EXT2, respectively, have been cloned. Recently, three other members of the EXT gene family, named the EXT-like genes (EXTL: EXTL1, EXTL2, and EXTL3), have been isolated. EXT1, EXT2, and the three EXTLs are homologous with one another. We have identified the intron-exon boundaries of EXTL1 and EXTL3 and analyzed EXT1, EXT2, EXTL1, and EXTL3, in 36 Chinese families with EXT, to identify underlying disease-related mutations in the Chinese population. Of the 36 families, five and 12 family groups have mutations in EXT1 and EXT2, respectively. No disease-related mutation has been found in either EXTL1 or EXTL2, although one polymorphism has been detected in EXTL1. Of the 15 different mutations (three families share a common mutation in EXT2), 12 are novel. Most of the mutations are either frameshift or nonsense mutations (12/15). These mutations lead directly or indirectly to premature stop codons, and the mutations generate truncated proteins. This finding is consistent with the hypothesis that the development of EXT is mainly attributable to loss of gene function. Missense mutations are rare in our families, but these mutations may reflect some functionally crucial regions of these proteins. EXT1 is the most frequent single cause of EXT in the Caucasian population in Europe and North America. It accounts for about 40% of cases of EXT. Our study of 36 EXT Chinese families has found that EXT1 seems much less common in the Chinese population, although the frequency of the EXT2 mutation is similar in the Caucasian and Chinese populations. Our findings suggest a possibly different genetic spectrum of this disease in different populations.

McCormick C, Leduc Y, Martindale D, et al.
The putative tumour suppressor EXT1 alters the expression of cell-surface heparan sulfate.
Nat Genet. 1998; 19(2):158-61 [PubMed] Related Publications
Hereditary multiple exostoses (HME) is an autosomal dominant disorder characterized by the formation of cartilage-capped tumours (exostoses) that develop from the growth plate of endochondral bone. This condition can lead to skeletal abnormalities, short stature and malignant transformation of exostoses to chondrosarcomas or osteosarcomas. Linkage analyses have identified three different genes for HME, EXT1 on 8q24.1, EXT2 on 11p11-13 and EXT3 on 19p (refs 6-9). Most HME cases have been attributed to missense or frameshift mutations in these tumour-supressor genes, whose functions have remained obscure. Here, we show that EXT1 is an ER-resident type II transmembrane glycoprotein whose expression in cells results in the alteration of the synthesis and display of cell surface heparan sulfate glycosaminoglycans (GAGs). Two EXT1 variants containing aetiologic missense mutations failed to alter cell-surface glycosaminoglycans, despite retaining their ER-localization.

Bridge JA, Nelson M, Orndal C, et al.
Clonal karyotypic abnormalities of the hereditary multiple exostoses chromosomal loci 8q24.1 (EXT1) and 11p11-12 (EXT2) in patients with sporadic and hereditary osteochondromas.
Cancer. 1998; 82(9):1657-63 [PubMed] Related Publications
BACKGROUND: Osteochondroma most frequently arises sporadically and as a solitary lesion, but also may arise as multiple lesions characterizing the autosomal dominant disorder hereditary multiple exostoses (HME) and the contiguous gene syndromes Langer-Giedion and DEFECT-11 syndromes. HME is genetically heterogeneous with association of three loci including 8q24.1 (EXT1), 11p11-12 (EXT2), and 19p (EXT3). Constitutional chromosomal microdeletions of 8q24.1 and 11p11-12 are features of the Langer-Giedion and DEFECT-11 syndromes, respectively. Cytogenetic studies of osteochondroma are rare.
METHODS: Cytogenetic analysis was performed on 34 osteochondroma specimens from 22 patients with sporadic lesions and 4 patients with HME utilizing standard methodologies. Fluorescence in situ hybridization with chromosome specific probes was performed on three cases to define structural rearrangements further.
RESULTS: Clonal abnormalities were detected in ten cases. Notably, deletion of 11p11-13 was observed in one case (a sporadic tumor) and loss or rearrangement of 8q22-24.1 in eight cases (seven sporadic and one hereditary tumor).
CONCLUSIONS: These findings: 1) confirm previous observations of 8q24.1 karyotypic anomalies in sporadic osteochondroma, 2) reveal the presence of somatic chromosomal anomalies in hereditary osteochondromata, 3) suggest that similar to hereditary lesions, sporadic osteochondromas also are genetically heterogeneic (involvement of both 8q24.1 and 11p11-12), and 4) support the hypothesis that loss or mutation of EXT1 and EXT2, two putative tumor suppressor genes, may be important in the pathogenesis of sporadic as well as hereditary osteochondromata.

Wuyts W, Van Hul W, De Boulle K, et al.
Mutations in the EXT1 and EXT2 genes in hereditary multiple exostoses.
Am J Hum Genet. 1998; 62(2):346-54 [PubMed] Free Access to Full Article Related Publications
Hereditary multiple exostoses (EXT; MIM 133700) is an autosomal dominant bone disorder characterized by the presence of multiple benign cartilage-capped tumors (exostoses). Besides suffering complications caused by the pressure of these exostoses on the surrounding tissues, EXT patients are at an increased risk for malignant chondrosarcoma, which may develop from an exostosis. EXT is genetically heterogeneous, and three loci have been identified so far: EXT1, on chromosome 8q23-q24; EXT2, on 11p11-p12; and EXT3, on the short arm of chromosome 19. The EXT1 and EXT2 genes were cloned recently, and they were shown to be homologous. We have now analyzed the EXT1 and EXT2 genes, in 26 EXT families originating from nine countries, to identify the underlying disease-causing mutation. Of the 26 families, 10 families had an EXT1 mutation, and 10 had an EXT2 mutation. Twelve of these mutations have never been described before. In addition, we have reviewed all EXT1 and EXT2 mutations reported so far, to determine the nature, frequency, and distribution of mutations that cause EXT. From this analysis, we conclude that mutations in either the EXT1 or the EXT2 gene are responsible for the majority of EXT cases. Most of the mutations in EXT1 and EXT2 cause premature termination of the EXT proteins, whereas missense mutations are rare. The development is thus mainly due to loss of function of the EXT genes, consistent with the hypothesis that the EXT genes have a tumor- suppressor function.

Raskind WH, Conrad EU, Matsushita M, et al.
Evaluation of locus heterogeneity and EXT1 mutations in 34 families with hereditary multiple exostoses.
Hum Mutat. 1998; 11(3):231-9 [PubMed] Related Publications
Hereditary multiple exostoses (EXT) is an autosomal dominant disorder characterized by growth of benign bone tumors. Three chromosomal loci have been implicated in this genetically heterogeneous disease: EXT1 at 8q24, EXT2 at 11p13, and EXT3 on 19p. EXT1 and EXT2 were recently cloned. We evaluated 34 families with EXT to estimate the proportion of disease attributable to EXT1, EXT2, and EXT3 and to investigate the spectrum of EXT1 mutations. Linkage analyses combined with heterogeneity testing provides strong evidence in favor of linkage of disease to both chromosomes 8 and 11, but does not support evidence of linkage to chromosome 19 in this data set. The 11 EXT1 exons were PCR-amplified and sequenced in all 11 isolated cases and in 20 of the 23 familial cases. Twelve different novel EXT1 mutations were detected, including 5 frame-shift deletions or insertions, 1 codon deletion, and 6 single base-pair substitutions distributed across 8 of the exons. Only 2 of the mutations were detected in more than one family. Three mutations affect sites in which alterations were previously reported. Nonchain-terminating missense mutations were identified in codons 280 and 340, both coding for conserved arginine residues. These residues may be crucial to the function of this protein. Although the prevalence of EXT has been estimated to be approximately 1/50,000 individuals, the disease has been reported to occur much more frequently in the Chamorro natives on Guam. Our detection of an EXT1 mutation in one Chamorro subject will allow investigation of a possible founder effect in this population. Combined mutational and heterogeneity analyses in this set of families with multiple exostoses suggest that 66% of our total sample, including 45% of isolated and 77% of familial cases, are attributable to abnormalities in EXT1.

Saito T, Seki N, Yamauchi M, et al.
Structure, chromosomal location, and expression profile of EXTR1 and EXTR2, new members of the multiple exostoses gene family.
Biochem Biophys Res Commun. 1998; 243(1):61-6 [PubMed] Related Publications
Hereditary multiple exostoses (EXT) is an autosomal dominant disorder that is characterized by the appearance of multiple outgrowths of the long bones (exostoses) at their epiphyses. Genetical heterogeneities have segregated at least on chromosome 8, 11, and 19 and been designated EXT1, EXT2, and EXT3, respectively. Recently, the responsible genes for EXT1 and EXT2 have been isolated and appeared to define a structurally related gene family. In the present study, we have identified novel genes which share significant sequence homologies with the EXT genes. The predicted protein products of the novel EXT-related genes, EXTR and EXTR2 (for EXT-related genes 1 and 2), consist of 919 and 330 amino acid residues, respectively. These genes were transcribed ubiquitously in various tissues. Based on PCR-assisted analyses of both a human/rodent mono-chromosomal hybrid cell panel and a radiation hybrid mapping panel, EXTR1 was localized to the chromosome 8p21 region, where loss of heterozygosity has been frequently observed in various tumors, and EXTR2 was assigned to the chromosome 1p21 region, where osteopetrosis, a dominant hereditary disease of bone, has been mapped by genetic linkage analysis, implying that the protein products of these two EXT-related genes, as well as of the EXT genes, have potential tumor suppressor activity.

Philippe C, Porter DE, Emerton ME, et al.
Mutation screening of the EXT1 and EXT2 genes in patients with hereditary multiple exostoses.
Am J Hum Genet. 1997; 61(3):520-8 [PubMed] Free Access to Full Article Related Publications
Hereditary multiple exostoses (HME), the most frequent of all skeletal dysplasias, is an autosomal dominant disorder characterized by the presence of multiple exostoses localized mainly at the end of long bones. HME is genetically heterogeneous, with at least three loci, on 8q24.1 (EXT1), 11p11-p13 (EXT2), and 19p (EXT3). Both the EXT1 and EXT2 genes have been cloned recently and define a new family of potential tumor suppressor genes. This is the first study in which mutation screening has been performed for both the EXT1 and EXT2 genes prior to any linkage analysis. We have screened 17 probands with the HME phenotype, for alterations in all translated exons and flanking intronic sequences, in the EXT1 and EXT2 genes, by conformation-sensitive gel electrophoresis. We found the disease-causing mutation in 12 families (70%), 7 (41%) of which have EXT1 mutations and 5 (29%) EXT2 mutations. Together with the previously described 1-bp deletion in exon 6, which is present in 2 of our families, we report five new mutations in EXT1. Two are missense mutations in exon 2 (G339D and R340C), and the other three alterations (a nonsense mutation, a frameshift, and a splicing mutation) are likely to result in truncated nonfunctional proteins. Four new mutations are described in EXT2. A missense mutation (D227N) was found in 2 different families; the other three alterations (two nonsense mutations and one frameshift mutation) lead directly or indirectly to premature stop codons. The missense mutations in EXT1 and EXT2 may pinpoint crucial domains in both proteins and therefore give clues for the understanding of the pathophysiology of this skeletal disorder.

Wells DE, Hill A, Lin X, et al.
Identification of novel mutations in the human EXT1 tumor suppressor gene.
Hum Genet. 1997; 99(5):612-5 [PubMed] Related Publications
Hereditary multiple exostoses (EXT) is a genetically heterogeneous bone disorder caused by genes segregating on human chromosomes 8, 11, and 19 and designated EXT1, EXT2 and EXT3, respectively. Recently, the EXT1 gene has been isolated and partially characterized and appears to encode a tumor suppressor gene. We have identified six mutations in the human EXT1 gene from six unrelated multiple exostoses families segregating for the EXT gene on chromosome 8. One of the mutations we detected is the same 1-bp deletion in exon 6 that was previously reported in two independent EXT families. The other five mutations, in exons 1, 6, 9, and the splice junction at the 3' end of exon 2, are novel. In each case, the mutation is likely to result in a truncated or nonfunctional EXT1 protein. These results corroborate and extend the previous report of mutations in this gene in two EXT families, and provide additional support for the EXT1 gene as the cause of hereditary multiple exostoses in families showing linkage to chromosome 8.

Legeai-Mallet L, Margaritte-Jeannin P, Lemdani M, et al.
An extension of the admixture test for the study of genetic heterogeneity in hereditary multiple exostoses.
Hum Genet. 1997; 99(3):298-302 [PubMed] Related Publications
Hereditary multiple exostoses (EXT) is an autosomal dominant disorder characterized by the presence of multiple cartilage-capped exostoses in the juxta-epiphyseal regions of the long bones. EXT is heterogeneous with at least three different locations currently having been identified on chromosomes 8, 11 and 19. We have tested a series of 29 EXT families for possible linkage to the three disease loci and estimated the probability of linkage of the disease to each locus in our series, by using an extension of the admixture test, which makes modelling of heterogeneous monogenic disease feasible. The maximum likelihood was obtained for proportions of 44%, 28% and 28% of families being linked to chromosome 8, 11 and 19, respectively. The a posteriori probability of linkage of the disease to EXT1, EXT2 and EXT3 was greater than 80% for 8/29, 5/29 and 3/29 families, respectively, and did not give evidence of a fourth locus for the disease. The present approach can be generalized to the investigation of genetic heterogeneity in other monogenic diseases, as it simultaneously estimates the location of each disease gene and the proportion of families linked to each locus.

Hecht JT, Hogue D, Wang Y, et al.
Hereditary multiple exostoses (EXT): mutational studies of familial EXT1 cases and EXT-associated malignancies.
Am J Hum Genet. 1997; 60(1):80-6 [PubMed] Free Access to Full Article Related Publications
Hereditary multiple exostoses (EXT) is an autosomal dominant disorder characterized by the formation of cartilage-capped prominences that develop from the growth centers of the long bones. EXT is genetically heterogeneous, with three loci, currently identified on chromosomes 8q24.1, 11p13, and 19q. The EXT1 gene, located on chromosome 8q24.1, has been cloned and is encoded by a 3.4-kb cDNA. Five mutations in the EXT1 gene have been identified--four germ-line mutations, including two unrelated families with the same mutation, and one somatic mutation in a patient with chondrosarcoma. Four of the mutations identified resulted in frameshifts and premature termination codons, while the fifth mutation resulted in a substitution of leucine for arginine. Loss of heterozygosity (LOH) analysis of chondrosarcomas and chondroblastomas revealed multiple LOH events at loci on chromosomes 3q, 8q, 10q, and 19q. One sporadic chondrosarcoma demonstrated LOH for EXT1 and EXT3, while a second underwent LOH for EXT2 and chromosome 10. A third chondrosarcoma underwent LOH for EXT1 and chromosome 3q. These results agree with previous findings that mutations at EXT1 and multiple genetic events that include LOH at other loci may be required for the development of chondrosarcoma.

Wuyts W, Van Hul W, Wauters J, et al.
Positional cloning of a gene involved in hereditary multiple exostoses.
Hum Mol Genet. 1996; 5(10):1547-57 [PubMed] Related Publications
Hereditary multiple exostosis (EXT) is an autosomal dominant condition mainly characterized by the presence of multiple exostoses on the long bones. These exostoses are benign cartilaginous tumors (enchondromata). Three different EXT loci on chromosomes 8q (EXT1), 11p (EXT2) and 19p (EXT3) have been reported, and recently the EXT1 gene was identified by positional cloning. To isolate the EXT2 gene, we constructed a contig of yeast artificial chromosomes (YAC) and P1 clones covering the complete EXT2 candidate region on chromosome 11p11-p12. One of the transcribed sequences isolated from this region corresponds to a novel gene with homology to the EXT1 gene, and harbours inactivating mutations in different patients with hereditary multiple exostoses. This indicates that this gene is the EXT2 gene. EXT2 has an open reading frame encoding 718 amino acids with an overall homology of 30.9% with EXT1, suggesting that a family of related genes might be responsible for the development of EXT.

Blanton SH, Hogue D, Wagner M, et al.
Hereditary multiple exostoses: confirmation of linkage to chromosomes 8 and 11.
Am J Med Genet. 1996; 62(2):150-9 [PubMed] Related Publications
Hereditary multiple exostoses (EXT) is an autosomal dominant disorder characterized by the formation of cartilage capped prominences that develop from the epiphyses of the long bones. EXT is heterogeneous with three different locations currently identified on chromosomes 8, 11, and 19. Recently, we identified and studied 12 large multigenerational EXT families. Linkage analyses demonstrates that 6 of these families map to 8q24 and 6 to 11p. None of the families map to the chromosome 19 locus. The results suggest that there are two major loci, on chromosomes 8 and 11, involved in the cause of EXT. The locus on chromosome 19 remains to be confirmed.

Wuyts W, Ramlakhan S, Van Hul W, et al.
Refinement of the multiple exostoses locus (EXT2) to a 3-cM interval on chromosome 11.
Am J Hum Genet. 1995; 57(2):382-7 [PubMed] Free Access to Full Article Related Publications
Hereditary multiple exostoses (EXT) is an autosomal dominant skeletal disorder characterized by the formation of multiple exostoses on the long bones. EXT is genetically heterogeneous, with at least three loci involved: one (EXT1) in the Langer-Giedion region on 8q23-q24, a second (EXT2) in the pericentromeric region of chromosome 11, and a third (EXT3) on chromosome 19p. In this study, linkage analysis in seven extended EXT families, all linked to the EXT2 locus, refined the localization of the EXT2 gene to a 3-cM region flanked by D11S1355 and D11S1361/D11S554. This implies that the EXT2 gene is located at the short arm of chromosome 11, in band 11p11-p12. The refined localization of EXT2 excludes a number of putative candidate genes located in the pericentromeric region of chromosome 11 and facilitates the process of isolating the EXT2 gene.

Raskind WH, Conrad EU, Chansky H, Matsushita M
Loss of heterozygosity in chondrosarcomas for markers linked to hereditary multiple exostoses loci on chromosomes 8 and 11.
Am J Hum Genet. 1995; 56(5):1132-9 [PubMed] Free Access to Full Article Related Publications
Hereditary multiple exostoses (EXT; MIM 133700) is an autosomal dominant condition characterized by growth of multiple benign cartilage-capped tumors. EXT greatly increases the relative risk to develop chondrosarcoma, although most chondrosarcomas are sporadic. This observation suggests that, like the genes responsible for retinoblastoma and other dominantly inherited cancer susceptibility disorders, the genes that cause EXT may have tumor-suppressor function and may play a role in the pathogenesis of the related sporadic tumors. To investigate this hypothesis, we evaluated chondrosarcomas for loss of constitutional heterozygosity (LOH) at polymorphic loci linked to three recently identified genomic regions containing genes involved in EXT. LOH for markers linked to EXT1 on chromosome 8 was detected in a chondrosarcoma that arose in a man with EXT. Four of 17 sporadic tumors showed LOH for markers linked to EXT1, and 7 showed LOH for markers linked to EXT2 on chromosome 11. In all, LOH was observed for markers linked to EXT1 or EXT2 in 44% of the 18 tumors, whereas heterozygosity was retained for markers on 19p linked to EXT3. These findings support the hypothesis that genes on 8q and the pericentromeric region of 11 have tumor-suppressor function and play a role in the development of chondrosarcomas.

Hecht JT, Hogue D, Strong LC, et al.
Hereditary multiple exostosis and chondrosarcoma: linkage to chromosome II and loss of heterozygosity for EXT-linked markers on chromosomes II and 8.
Am J Hum Genet. 1995; 56(5):1125-31 [PubMed] Free Access to Full Article Related Publications
Hereditary multiple exostosis (EXT) is an autosomal dominant disorder characterized by bony exostoses at the ends of the long bones. Linkage studies have recently suggested that there are three chromosomal locations for EXT genes, 8q24.1 (EXT1), the pericentric region of 11 (EXT2), and 19p (EXT3). As part of a larger study to determine the frequencies of the three EXT types in the United States, we have ascertained a large multigenerational family with EXT and one family member with a chondrosarcoma. This family demonstrated linkage of the disease to chromosome 11 markers. The constitutional and tumor DNAs from the affected family member were compared using short-tandem-repeat markers from chromosomes 8, 11, and 19. Loss of heterozygosity (LOH) in the tumor was observed for chromosome 8 and 11 markers, but chromosome 19 markers were intact. An apparent deletion of the marker D11S903 was observed in constitutional DNA from all affected individuals and in the tumor sample. These results indicate that the EXT2 gene maps to the region containing marker D11S903, which is flanked by markers D11S1355 and D11S1361. Additional constitutional and chondrosarcoma DNA pairs from six unrelated individuals, two of whom had EXT, were similarly analyzed. One tumor from an individual with EXT demonstrated LOH for chromosome 8 markers, and a person with a sporadic chondrosarcoma was found to have tumor-specific LOH and a homozygous deletion of chromosome 11 markers. These findings suggest that EXT genes may be tumor-suppressor genes and that the initiation of tumor development may follow a multistep model.

Le Merrer M, Legeai-Mallet L, Jeannin PM, et al.
A gene for hereditary multiple exostoses maps to chromosome 19p.
Hum Mol Genet. 1994; 3(5):717-22 [PubMed] Related Publications
Hereditary multiple exostoses (EXT) is an autosomal dominant bony disorder characterized by the formation of cartilage-capped juxta-epiphyseal prominences on the long bones. Recently, a disease gene (EXT 1) has been mapped to chromosome 8q23-q24 by linkage analysis in informative families. Here, we report on the genetic mapping of a second locus (EXT 2) to the short arm of chromosome 19 by linkage to a microsatellite DNA marker at the D19S221 locus, which gives additional support to the view that EXT is a genetically heterogeneous condition.

Wang ZQ, Grigoriadis AE, Möhle-Steinlein U, Wagner EF
A novel target cell for c-fos-induced oncogenesis: development of chondrogenic tumours in embryonic stem cell chimeras.
EMBO J. 1991; 10(9):2437-50 [PubMed] Free Access to Full Article Related Publications
Embryonic stem (ES) cells were used to investigate the target cell specificity and consequences of c-fos when expressed ectopically during embryonic development. Chimeric mice generated with different ES cell clones selected for high exogenous c-fos expression were not affected during embryonic development; however, a high frequency of cartilage tumours developed as early as 3-4 weeks of age apparently independent of the extent of chimerism. The tumours originated from cartilagenous tissues and contained many chondrocytes. Expression of exogenous c-fos RNA and Fos protein was observed during development but was highest in tumour tissues, predominantly in differentiating chondrocytes. A number of primary and clonal tumour-derived cell lines were established which expressed high levels of c-fos, c-jun as well as the cartilage-specific gene type II collagen and which gave rise to cartilage tumours in vivo, some of which also contained bone. Interestingly, the levels of c-Fos and c-Jun appeared to be coordinately regulated in the cell lines as well as in chimeric tissues. Thus, we demonstrate that chondrogenic cells and earlier progenitors are specially transformed by Fos/Jun and therefore represent a novel mesenchymal target cell for c-fos overexpression.

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