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Abstract
Cartilage oligomeric matrix protein (COMP) is an extracellular matrix protein expressed in cartilage, ligament, and tendon. The importance of COMP in the matrix of these cells is underscored by the discovery that mutations in COMP cause the skeletal dysplasias, pseudoachondroplasia (PSACH) and multiple epiphyseal dysplasia (EDM1). Here, we present the first report on the analysis of the human COMP promoter region in cartilage, ligament, and tendon cells. A 1.7-kb region of the COMP promoter has been cloned and sequenced and no TATA or CAAT boxes were found. Primer extension identified multiple transcription start sites. All four transcription start sites were utilized in chondrocytes with only three of them utilized in tendon and ligament cells. Differential regulation was observed for different parts of this 1.7-kb region with the 370-bp proximal region conveying the strongest promoter activity. The highest activity was observed in tendon and ligament. Finally, we provide evidence that the DNA binding protein SP1 plays a role in the regulation of COMP expression. These results indicate that COMP expression within these cells is regulated in a unique manner that differs from the expression of other extracellular matrix genes.
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Affiliation(s)
- M Deere
- Department of Pediatrics, University of Texas Medical School at Houston, Houston, TX 77030, USA
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Chen H, Deere M, Hecht JT, Lawler J. Cartilage oligomeric matrix protein is a calcium-binding protein, and a mutation in its type 3 repeats causes conformational changes. J Biol Chem 2000; 275:26538-44. [PMID: 10852928 DOI: 10.1074/jbc.m909780199] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mutations in residues in the type 3 calcium-binding repeats and COOH-terminal globular region of cartilage oligomeric matrix protein (COMP) lead to two skeletal dysplasias, pseudoachondroplasia and multiple epiphyseal dysplasia. It has been hypothesized that these mutations cause COMP to misfold and to be retained in the endoplasmic reticulum. However, this hypothesis is not supported by previous reports that COMP, when purified in the presence of EDTA, shows no obvious difference in electron microscopic appearance in the presence or absence of calcium ions. Since this discrepancy may be due to the removal of calcium during purification, we have expressed wild-type COMP and the most common mutant form found in pseudoachondroplasia, MUT3, using a mammalian expression system and have purified both proteins in the presence of calcium. Both proteins are expressed as pentamers. Direct calcium binding experiments demonstrate that wild-type COMP, when purified in the presence of calcium, is a calcium-binding protein. Rotary shadowing electron microscopy and limited trypsin digestion at various calcium concentrations show that there are conformational changes associated with calcium binding to COMP. Whereas COMP exists in a more compact conformation in the presence of calcium, it shows a more extended conformation when calcium is removed. MUT3, with a single aspartic acid deletion in the type 3 repeats, binds less calcium and presents an intermediate conformation between the calcium-replete and calcium-depleted forms of COMP. In conclusion, we show that a single mutation in the type 3 repeats of COMP causes the mutant protein to misfold. Our data demonstrate the importance of calcium binding to the structure of COMP and provide a plausible explanation for the observation that mutations in the type 3 repeats and COOH-terminal globular region lead to pseudoachondroplasia.
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Affiliation(s)
- H Chen
- Division of Tumor Biology and Angiogenesis, Department of Pathology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts 02215, USA
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Deere M, Sanford T, Francomano CA, Daniels K, Hecht JT. Identification of nine novel mutations in cartilage oligomeric matrix protein in patients with pseudoachondroplasia and multiple epiphyseal dysplasia. Am J Med Genet 1999; 85:486-90. [PMID: 10405447 DOI: 10.1002/(sici)1096-8628(19990827)85:5<486::aid-ajmg10>3.0.co;2-o] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Pseudoachondroplasia (PSACH) and multiple epiphyseal dysplasia (EDM1) are allelic disorders caused by mutations in the gene encoding cartilage oligomeric matrix protein (COMP). PSACH is a dominant condition characterized by disproportionate short stature, joint laxity, and early-onset osteoarthritis. EDM1 is a less severe skeletal dysplasia associated with average to mild short stature, joint pain, and early-onset osteoarthritis. COMP is an extracellular matrix protein present in cartilage, ligament, and tendon tissues. Here, we report on nine novel mutations in COMP causing PSACH and EDM1. Four of these mutations are in exons 13C and 14 where no previous mutations had been reported. One of those mutations was identified in two separate EDM1 families. In addition, we have identified the first case of PSACH resulting from an expansion of the five aspartates in exon 17B. We are also reporting a mutation in a third PSACH family with somatic/germline mosaicism. Therefore, this report increases the range of mutations that cause PSACH and EDM1 and provides additional regions to target for mutational analysis.
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Affiliation(s)
- M Deere
- Department of Pediatrics, University of Texas Medical School at Houston, Houston, Texas 77225-0708, USA
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Deere M, Dieguez JL, Yoon SJ, Hewett-Emmett D, de la Chapelle A, Hecht JT. Genomic characterization of human DSPG3. Genome Res 1999; 9:449-56. [PMID: 10330124 PMCID: PMC310783] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/1998] [Accepted: 03/15/1999] [Indexed: 02/12/2023]
Abstract
DSPG3, the human homolog to chick PG-Lb, is a mejrkp6of the small leucine-rich repeat proteoglycan (SLRP) family, including decorin, biglycan, fibromodulin, and lumican. In contrast to the tissue distribution of the other SLRPs, DSPG3 is predominantly expressed in cartilage. In this study, we have determined that the human DSPG3 gene is composed of seven exons: Exon 2 of DSPG3 includes the start codon, exons 4-7 code for the leucine-rich repeats, exons 3 and 7 contain the potential glycosaminoglycan attachment sites, and exon 7 contains the potential N-glycosylation sites and the stop codon. We have identified two polymorphic variations, an insertion/deletion composed of 19 nucleotides in intron 1 and a tetranucleotide (TATT)n repeat in intron 5. Analysis of 1.6 kb of upstream promoter sequence of DSPG3 reveals three TATA boxes, one of which is 20 nucleotides before the transcription start site. The transcription start site precedes the translation start site by 98 nucleotides. There are 14 potential binding sites for SOX9, a transcription factor present in cartilage, in the promoter, and in the first intron of DSPG3. We have examined the evolution of the SLRP gene family and found that gene products clustered together in the evolutionary tree are encoded by genes with similarities in genomic structure. Hence, it appears that the majority of the introns in the SLRP genes were inserted after the differentiation of the SLRP genes from an ancestral gene that was most likely composed of 2-3 exons.
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Affiliation(s)
- M Deere
- Graduate School of Biomedical Sciences, Program in Human and Molecular Genetics, University of Texas, Health Science Center, Houston, Texas 77030, USA
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Deere M, Sanford T, Ferguson HL, Daniels K, Hecht JT. Identification of twelve mutations in cartilage oligomeric matrix protein (COMP) in patients with pseudoachondroplasia. Am J Med Genet 1998; 80:510-3. [PMID: 9880218 DOI: 10.1002/(sici)1096-8628(19981228)80:5<510::aid-ajmg14>3.0.co;2-f] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Pseudoachondroplasia (PSACH) is an autosomal dominant dwarfing condition characterized by disproportionate short stature, joint laxity, and early-onset osteoarthrosis. PSACH is caused by mutations in the gene encoding cartilage oligomeric matrix protein (COMP). We are reporting on mutations in COMP in 12 patients with PSACH, including ten novel mutations. Eleven of the mutations are in exons 17A, 17B, and 18A, which encode the calcium-binding domains, and one mutation is in exon 19, which encodes part of the carboxy-terminal globular domain. Two of the mutations identified are the common delGAC(1430-1444) in exon 17B, which accounts for 36% of identified PSACH mutations. This report increases the range of mutations in COMP that cause PSACH and provides additional evidence for the importance of the calcium-binding domains and the globular domain to the function of COMP.
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Affiliation(s)
- M Deere
- Department of Pediatrics, University of Texas Medical School at Houston, 77225-0708, USA
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Hecht JT, Deere M, Putnam E, Cole W, Vertel B, Chen H, Lawler J. Characterization of cartilage oligomeric matrix protein (COMP) in human normal and pseudoachondroplasia musculoskeletal tissues. Matrix Biol 1998; 17:269-78. [PMID: 9749943 DOI: 10.1016/s0945-053x(98)90080-4] [Citation(s) in RCA: 95] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Cartilage oligomeric matrix protein (COMP), the fifth member of the -thrombospondin gene family, is an extracellular matrix calcium-binding protein. The importance of COMP is underscored by the finding that mutations in COMP cause the human dwarfing condition, pseudoachondroplasia (PSACH). Here, we report the results of human tissue distribution and cell secretion studies of human COMP. COMP is expressed and secreted by cultured monolayer chondrocyte, tendon and ligament cells, and COMP secretion is not restricted to a differentiated chondrocyte phenotype. Whereas COMP is retained in the endoplasmic reticulum that accumulates within PSACH chondrocytes in vivo, COMP is not retained intracellularly in the dedifferentiated PSACH chondrocytes in cultures. These results lend further support to the hypothesis that retention of COMP is related to the terminal PSACH chondrocyte phenotype, processing of proteins related to extracellular matrix formation, and maintenance in cartilage.
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Affiliation(s)
- J T Hecht
- Department of Pediatrics, University of Texas Medical School at Houston, 77225, USA
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Ferguson HL, Deere M, Evans R, Rotta J, Hall JG, Hecht JT. Mosaicism in pseudoachondroplasia. Am J Med Genet 1997; 70:287-91. [PMID: 9188668] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Pseudoachondroplasia (PSACH) is a spondylo-epi-metaphyseal dysplasia characterized by disproportionate short stature, generalized ligamentous laxity, and precocious osteoarthritis. PSACH is caused by mutations in the cartilage oligomeric matrix protein (COMP) gene, which codes for a noncollagenous protein expressed in the territorial matrix of chondrocytes. Autosomal dominant inheritance has been demonstrated in many families; however, autosomal recessive inheritance has been suggested in some severe familial cases. Alternatively, germline/somatic mosaicism has been proposed and is credible, since it has been shown that dominantly inherited and sporadic cases of PSACH are caused by the same genetic defect. Here, we present evidence demonstrating somatic mosaicism in two PSACH families that were originally considered to represent autosomal recessive inheritance. The results of this study suggest that autosomal recessive inheritance is unlikely and all cases of PSACH should be studied for mutations in COMP.
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Affiliation(s)
- H L Ferguson
- Department of Pediatrics, University of Texas Medical School at Houston, 77225-0708, USA
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Deere M, Johnson J, Garza S, Harrison WR, Yoon SJ, Elder FF, Kucherlapati R, Hook M, Hecht JT. Characterization of human DSPG3, a small dermatan sulfate proteoglycan. Genomics 1996; 38:399-404. [PMID: 8975717 DOI: 10.1006/geno.1996.0643] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
PG-Lb is a small dermatan sulfate proteoglycan that has been previously characterized in chicken. In the developing limb, chick PG-Lb appears to be exclusively expressed in the zone of flattened chondrocytes. We have cloned and sequenced the human homolog to chick PG-Lb from two human chondrocyte cDNA libraries and a human chondrocyte RNA sample. The human homolog has been named DSPG3, as it is the third member of the small dermatan sulfate proteoglycan family to be identified and characterized along with biglycan (PG-I) and decorin (PG-II). DSPG3 maps to chromosome 12q21 and is composed of 1515 nucleotides of cDNA that code for a 322-amino-acid protein. The protein contains three potential glycosaminoglycan attachment sites, two N-glycosylation sites, a poly- glutamic acid stretch, and six cysteines. By Northern analysis, we have demonstrated that DSPG3 is expressed in cartilage, as well as ligament and placental tissues.
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Affiliation(s)
- M Deere
- Graduate School of Biological Sciences, The University of Texas Medical School, Houston 77225, USA
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Hecht JT, Nelson LD, Crowder E, Wang Y, Elder FF, Harrison WR, Francomano CA, Prange CK, Lennon GG, Deere M. Mutations in exon 17B of cartilage oligomeric matrix protein (COMP) cause pseudoachondroplasia. Nat Genet 1995; 10:325-9. [PMID: 7670471 DOI: 10.1038/ng0795-325] [Citation(s) in RCA: 308] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Pseudoachondroplasia (PSACH) is a well characterized dwarfing condition mapping to chromosome 19p12-13.1. Cartilage oligomeric matrix protein (COMP), a cartilage specific protein, maps to the same location within a contig that spans the PSACH locus. Using single strand conformation polymorphism (SSCP) analysis and nucleotide sequencing we have identified COMP mutations in eight familial and isolated PSACH cases. All mutations involve either a single base-pair change or a three base-pair deletion in exon 17B. Six mutations delete or change a well conserved aspartic acid residue within the calcium-binding type 3 repeats. These results demonstrate that mutations in the COMP gene cause pseudochondroplasia.
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Affiliation(s)
- J T Hecht
- Department of Pediatrics, University of Texas Medical School at Houston 77225, USA
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Deere M, Blanton SH, Scott CI, Langer LO, Pauli RM, Hecht JT. Genetic heterogeneity in multiple epiphyseal dysplasia. Am J Hum Genet 1995; 56:698-704. [PMID: 7887425 PMCID: PMC1801152] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Multiple epiphyseal dysplasia (MED) comprises a group of hereditary chondrodysplasias in which there are major anatomic abnormalities of the long tubular bones. The Fairbank and Ribbing types are the most frequently cited types of MED. They are primarily defined radiographically and are autosomal dominant conditions. Recently, MED in one family was shown to map to the pericentromeric region of chromosome 19 and is probably allelic to pseudoachondroplasia. We have tested linkage with six short tandem repeat markers from chromosome 19 to autosomal dominant MED in one four-generation family and to MED in a unique family with three of seven siblings affected and with unaffected parents. Autosomal dominant MED in family 1 was linked with a maximum LOD score, at D19S212, of 3.22 at a recombination fraction (theta) of .00. Linkage to chromosome 19 was excluded with MED in the other family, under both autosomal recessive and autosomal dominant, with either reduced-penetrance or germ line-mosaicism models. Linkage to candidate genes COL9A1, COL9A2, and COL11A2 was tested and excluded for both genetic models in this family. COL11A1 was excluded under a recessive model. We have confirmed linkage of autosomal dominant Fairbank MED to chromosome 19 and have demonstrated that MED is genetically heterogeneous.
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Affiliation(s)
- M Deere
- Department of Pediatrics, University of Texas Medical School, Houston 77225
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Abstract
Pseudoachondroplasia (PSACH) is an autosomal dominant dwarfing condition associated with disproportionate short stature, marked joint deformities, and early onset osteoarthritis. Previous linkage studies have excluded linkage to cartilage and noncartilagenous extracellular matrix candidate genes. Here, we report mapping the pseudoachondroplasia gene to chromosome 19. Maximum lod scores of 4.70, 4.15, and 4.86 at theta = 0.00 were found for D19S212, D19S215, and D19S49, respectively. Multipoint analysis suggests the following order: D19S253-D19S199-(D19S212/PSACH/D19S215)-++ +D19S222-D19S49.
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Affiliation(s)
- J T Hecht
- Department of Pediatrics, University of Texas Medical School, Houston 77225
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Kreis W, Chan K, Budman DR, Schulman P, Allen S, Weiselberg L, Lichtman S, Henderson V, Freeman J, Deere M. Effect of tetrahydrouridine on the clinical pharmacology of 1-beta-D-arabinofuranosylcytosine when both drugs are coinfused over three hours. Cancer Res 1988; 48:1337-42. [PMID: 3342412] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
When 1-beta-D-arabinofuranosylcytosine (ara-C), 25 mg/m2, is infused over 3 h together with tetrahydrouridine (THU) at 10 to 350 mg/m2 to heavily pretreated patients with solid tumors, Michaelis-Menten type kinetic values are observed with leveling off of delta area under the curve, delta ara-C levels at 3 h, and delta total body clearance after 150 mg/m2 of THU. When the ara-C dose was increased to 50, 75, and 100 mg/m2 coinfusion of 250 or 350 mg/m2 of THU significantly increased plasma ara-C at peak and area under the curve. In contrast, total body clearance and volume of distribution decreased significantly. At 100 mg/m2 of ara-C coinfused with high doses of THU, i.e., at 350 mg/m2, the pharmacokinetics of plasma ara-C was changed from a biphasic decay of plasma ara-C at peaks (control) to a curve similar or identical to a monophasic curve, indicating that THU not only inhibits deamination but also changes the distribution of ara-C. This combination provides plasma ara-C levels (greater than or equal to 10 microM) comparable to high dose ara-C at 1 g/m2. Such plasma ara-C levels are considered to be sufficient for saturation of the kinases catalyzing the production of 1-beta-D-arabinofuranosylcytosine 5'-triphosphate. This reduced ara-C dose necessary to achieve saturation of kinases also reduces plasma 1-beta-D-arabinofuranosyluracil levels substantially. Toxicity of this combination was predominantly confined to bone marrow and gastrointestinal toxicity.
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Affiliation(s)
- W Kreis
- Department of Medicine, North Shore University Hospital, Cornell University Medical College, Manhasset, New York
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Kreis W, Chaudhri F, Chan K, Allen S, Budman DR, Schulman P, Weiselberg L, Freeman J, Deere M, Vinciguerra V. Pharmacokinetics of low-dose 1-beta-D-arabinofuranosylcytosine given by continuous intravenous infusion over twenty-one days. Cancer Res 1985; 45:6498-501. [PMID: 3864533] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The pharmacokinetic parameters of low dose 1-beta-D-arabinofuranosylcytosine (ara-C) infusions were studied in 11 patients, 6 males and 5 females, with a mean age of 68.5 +/- 13.8 (SD) years. The drug was infused to 4 patients with pre-leukemia (refractory anemia with excess blasts), 5 patients with acute myelogenous leukemia, and 2 patients with secondary leukemia due to chemotherapy, at a dosage of 20 mg/m2/day over 21 days. The patients' blood and urine were analyzed for ara-C content by radioimmunoassay. Mean steady state plasma levels of 7.7 +/- 4.7 ng/ml (31.7 +/- 19.3 nM) (n = 189) and a range 0.6 (2.5 nM) (lower limit of assay) to 29.7 ng/ml (122.1 nM), with significant inter- and intra-patient variations, were reached within about 2.7 h. The plasma levels of ara-C decreased rapidly, with a t1/2 alpha of about 12 min following discontinuation of the infusion, followed by a very slow t 1/2 beta of about 19 h. Other parameters (mean values of 10 or 11 patients) were: area under the curve, 182.1 +/- 64.8 ng X day/ml; total body clearance, 188.7 +/- 54.8 liters/h; renal clearance, 3.1 +/- 1.4 liters/h; volume of distribution at steady state, 53,913 +/- 17,626 liters; and recovery of ara-C in urine, 1.43 +/- 0.69% (n = 226) of daily administered ara-C. A linear relationship was observed with administered dose when the mean plasma levels of our study were compared with the ones reported for conventional ara-C infusions. Plasma clearance was comparable to that observed in conventional dose, when the observed values were extrapolated to the dose administered in this study.
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