The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Hiroshi Kitagawa - One of the best experts on this subject based on the ideXlab platform.
-
the glycosyltransferase extl2 promotes proteoglycan deposition and injurious neuroinflammation following demyelination
Journal of Neuroinflammation, 2020Co-Authors: Manoj Kumar Mishra, Hiroshi Kitagawa, Yifei Dong, Samira Ghorbanigazar, Erin L Stephenson, Khalil S Rawji, Claudia Silva, Stephen Sawcer, Wee V YongAbstract:Chondroitin sulfate proteoglycans (CSPGs) are potent inhibitors of axonal regrowth and remyelination. More recently, they have also been highlighted as a modulator of macrophage infiltration into the central nervous system in experimental autoimmune encephalomyelitis, an inflammatory model of multiple sclerosis. We interrogated results from single nucleotide polymorphisms (SNPs) lying in or close to genes regulating CSPG metabolism in the summary results from two publicly available systematic studies of multiple sclerosis (MS) genetics. A demyelinating injury model in the spinal cord of exostosin-like 2 deficient (EXTL2-/-) mice was used to investigate the effects of dysregulation of EXTL2 on remyelination. Cell cultures of bone marrow-derived macrophages and primary oligodendrocyte precursor cells and neurons were supplemented with purified CSPGs or conditioned media to assess potential mechanisms of action. The strongest evidence for genetic association was seen for SNPs mapping to the region containing the glycosyltransferase exostosin-like 2 (EXTL2), an enzyme that normally suppresses CSPG biosynthesis. Six of these SNPs showed genome-wide significant evidence for association in one of the studies with concordant and nominally significant effects in the second study. We then went on to show that a demyelinating injury to the spinal cord of EXTL2−/− mice resulted in excessive deposition of CSPGs in the lesion area. EXTL2−/− mice had exacerbated axonal damage and myelin disruption relative to wild-type mice, and increased representation of microglia/macrophages within lesions. In tissue culture, activated bone marrow-derived macrophages from EXTL2−/− mice overproduce tumor necrosis factor α (TNFα) and matrix metalloproteinases (MMPs). These results emphasize CSPGs as a prominent modulator of neuroinflammation and they highlight CSPGs accumulating in lesions in promoting axonal injury.
-
extl2 a member of the ext family of tumor suppressors controls glycosaminoglycan biosynthesis in a xylose kinase dependent manner
Journal of Biological Chemistry, 2013Co-Authors: Satomi Nadanaka, Naoko Shoji, Kazuyuki Sugahara, Shaobo Zhou, Shoji Kagiyama, Kazushi Sugihara, Masahide Asano, Hiroshi KitagawaAbstract:Mutant alleles of EXT1 or EXT2, two members of the EXT gene family, are causative agents in hereditary multiple exostoses, and their gene products function together as a polymerase in the biosynthesis of heparan sulfate. EXTL2, one of three EXT-like genes in the human genome that are homologous to EXT1 and EXT2, encodes a transferase that adds not only GlcNAc but also N-acetylgalactosamine to the glycosaminoglycan (GAG)-protein linkage region via an α1,4-linkage. However, both the role of EXTL2 in the biosynthesis of GAGs and the biological significance of EXTL2 remain unclear. Here we show that EXTL2 transfers a GlcNAc residue to the tetrasaccharide linkage region that is phosphorylated by a xylose kinase 1 (FAM20B) and thereby terminates chain elongation. We isolated an oligosaccharide from the mouse liver, which was not detected in EXTL2 knock-out mice. Based on structural analysis by a combination of glycosidase digestion and 500-MHz 1H NMR spectroscopy, the oligosaccharide was found to be GlcNAcα1-4GlcUAβ1–3Galβ1–3Galβ1–4Xyl(2-O-phosphate), which was considered to be a biosynthetic intermediate of an immature GAG chain. Indeed, EXTL2 specifically transferred a GlcNAc residue to a phosphorylated linkage tetrasaccharide, GlcUAβ1–3Galβ1–3Galβ1–4Xyl(2-O-phosphate). Remarkably, the phosphorylated linkage pentasaccharide generated by EXTL2 was not used as an acceptor for heparan sulfate or chondroitin sulfate polymerases. Moreover, production of GAGs was significantly higher in EXTL2 knock-out mice than in wild-type mice. These results indicate that EXTL2 functions to suppress GAG biosynthesis that is enhanced by a xylose kinase and that the EXTL2-dependent mechanism that regulates GAG biosynthesis might be a “quality control system” for proteoglycans.
-
biosynthesis of heparan sulfate in ext1 deficient cells
Biochemical Journal, 2010Co-Authors: Megumi Okada, Naoko Shoji, Satomi Nadanaka, Jun'ichi Tamura, Hiroshi KitagawaAbstract:HS (heparan sulfate) is synthesized by HS co-polymerases encoded by the EXT1 and EXT2 genes (exostosin 1 and 2), which are known as causative genes for hereditary multiple exostoses, a dominantly inherited genetic disorder characterized by multiple cartilaginous tumours. It has been thought that the hetero-oligomeric EXT1–EXT2 complex is the biologically relevant form of the polymerase and that targeted deletion of either EXT1 or EXT2 leads to a complete lack of HS synthesis. In the present paper we show, unexpectedly, that two distinct cell lines defective in EXT1 expression indeed produce small but significant amounts of HS chains. The HS chains produced without the aid of EXT1 were shorter than HS chains formed in concert with EXT1 and EXT2. In addition, biosynthesis of HS in EXT1 -defective cells was notably blocked by knockdown of either EXT2 or EXTL2 (EXT-like), but not of EXTL3 . Then, to examine the roles of EXTL2 in the biosynthesis of HS in EXT1 -deficient cells, we focused on the GlcNAc ( N -aetylglucosamine) transferase activity of EXTL2, which is involved in the initiation of HS chains by transferring the first GlcNAc to the linkage region. Although EXT2 alone synthesized no heparan polymers on the synthetic linkage region analogue GlcUAβ1-3Galβ1- O -C 2 H 4 NH-benzyloxycarbonyl, marked polymerization by EXT2 alone was demonstrated on GlcNAcα1-4GlcUAβ1-3Galβ1- O -C 2 H 4 N-benzyloxycarbonyl (where GlcUA is glucuronic acid and Gal is galactose), which was generated by transferring a GlcNAc residue using recombinant EXTL2 on to GlcUAβ1–3Galβ1- O -C 2 H 4 NH-benzyloxycarbonyl. These findings indicate that the transfer of the first GlcNAc residue to the linkage region by EXTL2 is critically required for the biosynthesis of HS in cells deficient in EXT1 .
-
rib 2 a caenorhabditis elegans homolog of the human tumor suppressor ext genes encodes a novel alpha1 4 n acetylglucosaminyltransferase involved in the biosynthetic initiation and elongation of heparan sulfate
Journal of Biological Chemistry, 2001Co-Authors: Hiroshi Kitagawa, Noriyuki Egusa, Jun'ichi Tamura, Marion Kuschegullberg, Ulf Lindahl, Kazuyuki SugaharaAbstract:Abstract The proteins encoded by the EXT1,EXT2, and EXTL2 genes, members of the hereditary multiple exostoses gene family of tumor suppressors, are glycosyltransferases required for the heparan sulfate biosynthesis. Only two homologous genes, rib-1 and rib-2, of the mammalian EXT genes were identified in theCaenorhabditis elegans genome. Although heparan sulfate is found in C. elegans, the involvement of the rib-1 and rib-2 proteins in heparan sulfate biosynthesis remains unclear. In the present study, the substrate specificity of a soluble recombinant form of the rib-2 protein was determined and compared with those of the recombinant forms of the mammalian EXT1, EXT2, and EXTL2 proteins. The present findings revealed that the rib-2 protein was a unique α1,4-N-acetylglucosaminyltransferase involved in the biosynthetic initiation and elongation of heparan sulfate. In contrast, the findings confirmed the previous observations that both the EXT1 and EXT2 proteins were heparan sulfate copolymerases with both α1,4-N-acetylglucosaminyltransferase and β1,4-glucuronyltransferase activities, which are involved only in the elongation step of the heparan sulfate chain, and that the EXTL2 protein was an α1,4-N-acetylglucosaminyltransferase involved only in the initiation of heparan sulfate synthesis. These findings suggest that the biosynthetic mechanism of heparan sulfate inC. elegans is distinct from that reported for the mammalian system.
-
the tumor suppressor ext like gene extl2 encodes an alpha1 4 n acetylhexosaminyltransferase that transfers n acetylgalactosamine and n acetylglucosamine to the common glycosaminoglycan protein linkage region the key enzyme for the chain initiation of
Journal of Biological Chemistry, 1999Co-Authors: Hiroshi Kitagawa, Hiromi Shimakawa, Kazuyuki SugaharaAbstract:Abstract We previously demonstrated a unique α-N-acetylgalactosaminyltransferase that transferredN-acetylgalactosamine (GalNAc) to the tetrasaccharide-serine, GlcAβ1–3Galβ1–3Galβ1–4Xylβ1-O-Ser (GlcA represents glucuronic acid), derived from the common glycosaminoglycan-protein linkage region, through an α1,4-linkage. In this study, we purified the enzyme from the serum-free culture medium of a human sarcoma cell line. Peptide sequence analysis of the purified enzyme revealed 100% identity to the multiple exostoses-like geneEXTL2/EXTR2, a member of the hereditary multiple exostoses (EXT) gene family of tumor suppressors. The expression of a soluble recombinant form of the protein produced an active enzyme, which transferred α-GalNAc from UDP-[3H]GalNAc to various acceptor substrates including GlcAβ1–3Galβ1–3Galβ1–4Xylβ1-O-Ser. Interestingly, the enzyme also catalyzed the transfer ofN-acetylglucosamine (GlcNAc) from UDP-[3H]GlcNAc to GlcAβ1–3Galβ1-O-naphthalenemethanol, which was the acceptor substrate for the previously described GlcNAc transferase I involved in the biosynthetic initiation of heparan sulfate. The GlcNAc transferase reaction product was sensitive to the action of heparitinase I, establishing the identity of the enzyme to be α1,4-GlcNAc transferase. These results altogether indicate thatEXTL2/EXTR2 encodes the α1,4-N-acetylhexosaminyltransferase that transfers GalNAc/GlcNAc to the tetrasaccharide representing the common glycosaminoglycan-protein linkage region and that is most likely the critical enzyme that determines and initiates the heparin/heparan sulfate synthesis, separating it from the chondroitin sulfate/dermatan sulfate synthesis.
Kazuyuki Sugahara - One of the best experts on this subject based on the ideXlab platform.
-
extl2 a member of the ext family of tumor suppressors controls glycosaminoglycan biosynthesis in a xylose kinase dependent manner
Journal of Biological Chemistry, 2013Co-Authors: Satomi Nadanaka, Naoko Shoji, Kazuyuki Sugahara, Shaobo Zhou, Shoji Kagiyama, Kazushi Sugihara, Masahide Asano, Hiroshi KitagawaAbstract:Mutant alleles of EXT1 or EXT2, two members of the EXT gene family, are causative agents in hereditary multiple exostoses, and their gene products function together as a polymerase in the biosynthesis of heparan sulfate. EXTL2, one of three EXT-like genes in the human genome that are homologous to EXT1 and EXT2, encodes a transferase that adds not only GlcNAc but also N-acetylgalactosamine to the glycosaminoglycan (GAG)-protein linkage region via an α1,4-linkage. However, both the role of EXTL2 in the biosynthesis of GAGs and the biological significance of EXTL2 remain unclear. Here we show that EXTL2 transfers a GlcNAc residue to the tetrasaccharide linkage region that is phosphorylated by a xylose kinase 1 (FAM20B) and thereby terminates chain elongation. We isolated an oligosaccharide from the mouse liver, which was not detected in EXTL2 knock-out mice. Based on structural analysis by a combination of glycosidase digestion and 500-MHz 1H NMR spectroscopy, the oligosaccharide was found to be GlcNAcα1-4GlcUAβ1–3Galβ1–3Galβ1–4Xyl(2-O-phosphate), which was considered to be a biosynthetic intermediate of an immature GAG chain. Indeed, EXTL2 specifically transferred a GlcNAc residue to a phosphorylated linkage tetrasaccharide, GlcUAβ1–3Galβ1–3Galβ1–4Xyl(2-O-phosphate). Remarkably, the phosphorylated linkage pentasaccharide generated by EXTL2 was not used as an acceptor for heparan sulfate or chondroitin sulfate polymerases. Moreover, production of GAGs was significantly higher in EXTL2 knock-out mice than in wild-type mice. These results indicate that EXTL2 functions to suppress GAG biosynthesis that is enhanced by a xylose kinase and that the EXTL2-dependent mechanism that regulates GAG biosynthesis might be a “quality control system” for proteoglycans.
-
rib 2 a caenorhabditis elegans homolog of the human tumor suppressor ext genes encodes a novel alpha1 4 n acetylglucosaminyltransferase involved in the biosynthetic initiation and elongation of heparan sulfate
Journal of Biological Chemistry, 2001Co-Authors: Hiroshi Kitagawa, Noriyuki Egusa, Jun'ichi Tamura, Marion Kuschegullberg, Ulf Lindahl, Kazuyuki SugaharaAbstract:Abstract The proteins encoded by the EXT1,EXT2, and EXTL2 genes, members of the hereditary multiple exostoses gene family of tumor suppressors, are glycosyltransferases required for the heparan sulfate biosynthesis. Only two homologous genes, rib-1 and rib-2, of the mammalian EXT genes were identified in theCaenorhabditis elegans genome. Although heparan sulfate is found in C. elegans, the involvement of the rib-1 and rib-2 proteins in heparan sulfate biosynthesis remains unclear. In the present study, the substrate specificity of a soluble recombinant form of the rib-2 protein was determined and compared with those of the recombinant forms of the mammalian EXT1, EXT2, and EXTL2 proteins. The present findings revealed that the rib-2 protein was a unique α1,4-N-acetylglucosaminyltransferase involved in the biosynthetic initiation and elongation of heparan sulfate. In contrast, the findings confirmed the previous observations that both the EXT1 and EXT2 proteins were heparan sulfate copolymerases with both α1,4-N-acetylglucosaminyltransferase and β1,4-glucuronyltransferase activities, which are involved only in the elongation step of the heparan sulfate chain, and that the EXTL2 protein was an α1,4-N-acetylglucosaminyltransferase involved only in the initiation of heparan sulfate synthesis. These findings suggest that the biosynthetic mechanism of heparan sulfate inC. elegans is distinct from that reported for the mammalian system.
-
the tumor suppressor ext like gene extl2 encodes an alpha1 4 n acetylhexosaminyltransferase that transfers n acetylgalactosamine and n acetylglucosamine to the common glycosaminoglycan protein linkage region the key enzyme for the chain initiation of
Journal of Biological Chemistry, 1999Co-Authors: Hiroshi Kitagawa, Hiromi Shimakawa, Kazuyuki SugaharaAbstract:Abstract We previously demonstrated a unique α-N-acetylgalactosaminyltransferase that transferredN-acetylgalactosamine (GalNAc) to the tetrasaccharide-serine, GlcAβ1–3Galβ1–3Galβ1–4Xylβ1-O-Ser (GlcA represents glucuronic acid), derived from the common glycosaminoglycan-protein linkage region, through an α1,4-linkage. In this study, we purified the enzyme from the serum-free culture medium of a human sarcoma cell line. Peptide sequence analysis of the purified enzyme revealed 100% identity to the multiple exostoses-like geneEXTL2/EXTR2, a member of the hereditary multiple exostoses (EXT) gene family of tumor suppressors. The expression of a soluble recombinant form of the protein produced an active enzyme, which transferred α-GalNAc from UDP-[3H]GalNAc to various acceptor substrates including GlcAβ1–3Galβ1–3Galβ1–4Xylβ1-O-Ser. Interestingly, the enzyme also catalyzed the transfer ofN-acetylglucosamine (GlcNAc) from UDP-[3H]GlcNAc to GlcAβ1–3Galβ1-O-naphthalenemethanol, which was the acceptor substrate for the previously described GlcNAc transferase I involved in the biosynthetic initiation of heparan sulfate. The GlcNAc transferase reaction product was sensitive to the action of heparitinase I, establishing the identity of the enzyme to be α1,4-GlcNAc transferase. These results altogether indicate thatEXTL2/EXTR2 encodes the α1,4-N-acetylhexosaminyltransferase that transfers GalNAc/GlcNAc to the tetrasaccharide representing the common glycosaminoglycan-protein linkage region and that is most likely the critical enzyme that determines and initiates the heparin/heparan sulfate synthesis, separating it from the chondroitin sulfate/dermatan sulfate synthesis.
-
the tumor suppressor ext like gene extl2 encodes an α1 4 n acetylhexosaminyltransferase that transfersn acetylgalactosamine and n acetylglucosamine to the common glycosaminoglycan protein linkage region the key enzyme for the chain initiation of hepa
Journal of Biological Chemistry, 1999Co-Authors: Hiroshi Kitagawa, Hiromi Shimakawa, Kazuyuki SugaharaAbstract:Abstract We previously demonstrated a unique α-N-acetylgalactosaminyltransferase that transferredN-acetylgalactosamine (GalNAc) to the tetrasaccharide-serine, GlcAβ1–3Galβ1–3Galβ1–4Xylβ1-O-Ser (GlcA represents glucuronic acid), derived from the common glycosaminoglycan-protein linkage region, through an α1,4-linkage. In this study, we purified the enzyme from the serum-free culture medium of a human sarcoma cell line. Peptide sequence analysis of the purified enzyme revealed 100% identity to the multiple exostoses-like geneEXTL2/EXTR2, a member of the hereditary multiple exostoses (EXT) gene family of tumor suppressors. The expression of a soluble recombinant form of the protein produced an active enzyme, which transferred α-GalNAc from UDP-[3H]GalNAc to various acceptor substrates including GlcAβ1–3Galβ1–3Galβ1–4Xylβ1-O-Ser. Interestingly, the enzyme also catalyzed the transfer ofN-acetylglucosamine (GlcNAc) from UDP-[3H]GlcNAc to GlcAβ1–3Galβ1-O-naphthalenemethanol, which was the acceptor substrate for the previously described GlcNAc transferase I involved in the biosynthetic initiation of heparan sulfate. The GlcNAc transferase reaction product was sensitive to the action of heparitinase I, establishing the identity of the enzyme to be α1,4-GlcNAc transferase. These results altogether indicate thatEXTL2/EXTR2 encodes the α1,4-N-acetylhexosaminyltransferase that transfers GalNAc/GlcNAc to the tetrasaccharide representing the common glycosaminoglycan-protein linkage region and that is most likely the critical enzyme that determines and initiates the heparin/heparan sulfate synthesis, separating it from the chondroitin sulfate/dermatan sulfate synthesis.
Michael J. Wagner - One of the best experts on this subject based on the ideXlab platform.
-
evaluation of locus heterogeneity and ext1 mutations in 34 families with hereditary multiple exostoses
Human Mutation, 1998Co-Authors: Wendy H. Raskind, Nicola H Chapman, Ellen M Wijsman, Linda J. Sandell, Dan E. Wells, Mark Matsushita, Ernest U Conrad, Michael J. Wagner, James R. HouckAbstract: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. Hum Mutat 11:231–239, 1998. © 1998 Wiley-Liss, Inc.
-
identification of novel mutations in the human ext1 tumor suppressor gene
Human Genetics, 1997Co-Authors: Dan E. Wells, April Hill, Nicholas Brown, Michael J. WagnerAbstract: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.
-
hereditary multiple exostoses ext mutational studies of familial ext1 cases and ext associated malignancies
American Journal of Human Genetics, 1997Co-Authors: Jacqueline T. Hecht, Mark F Hansen, Deborah Hogue, Susan H. Blanton, Wendy H. Raskind, Louise C. Strong, Michael J. Wagner, Dan E. WellsAbstract:Abstract 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.
-
hereditary multiple exostosis and chondrosarcoma linkage to chromosome ii and loss of heterozygosity for ext linked markers on chromosomes ii and 8
American Journal of Human Genetics, 1995Co-Authors: Jacqueline T. Hecht, Deborah Hogue, Marc F Hansen, Susan H. Blanton, Louise C. Strong, Michael J. WagnerAbstract: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 shortandem-repeat markers from chromosomes 8, 11, and 19. Loss of heterozygosity (LOH) in the tumor was observed from 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 who had EXT, were similarly analyzed. One tumor from an individual withmore » 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. 23 refs., 3 figs., 2 tabs.« less
Dan E. Wells - One of the best experts on this subject based on the ideXlab platform.
-
evaluation of locus heterogeneity and ext1 mutations in 34 families with hereditary multiple exostoses
Human Mutation, 1998Co-Authors: Wendy H. Raskind, Nicola H Chapman, Ellen M Wijsman, Linda J. Sandell, Dan E. Wells, Mark Matsushita, Ernest U Conrad, Michael J. Wagner, James R. HouckAbstract: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. Hum Mutat 11:231–239, 1998. © 1998 Wiley-Liss, Inc.
-
mutation screening of the ext1 and ext2 genes in patients with hereditary multiple exostoses
American Journal of Human Genetics, 1997Co-Authors: Christophe Philippe, Mark E Emerton, A Hamish, R. W. Simpson, Daniel E. Porter, Dan E. Wells, Anthony P MonacoAbstract:Summary 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.
-
identification of novel mutations in the human ext1 tumor suppressor gene
Human Genetics, 1997Co-Authors: Dan E. Wells, April Hill, Nicholas Brown, Michael J. WagnerAbstract: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.
-
hereditary multiple exostoses ext mutational studies of familial ext1 cases and ext associated malignancies
American Journal of Human Genetics, 1997Co-Authors: Jacqueline T. Hecht, Mark F Hansen, Deborah Hogue, Susan H. Blanton, Wendy H. Raskind, Louise C. Strong, Michael J. Wagner, Dan E. WellsAbstract:Abstract 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.
Luigi D Notarangelo - One of the best experts on this subject based on the ideXlab platform.
-
expanding the spectrum of skeletal dysplasia with immunodeficiency a commentary on identification of biallelic EXTL3 mutations in a novel type of spondylo epi metaphyseal dysplasia
Journal of Human Genetics, 2017Co-Authors: Luigi D NotarangeloAbstract:Expanding the spectrum of skeletal dysplasia with immunodeficiency: a commentary on identification of biallelic EXTL3 mutations in a novel type of spondylo-epi-metaphyseal dysplasia
