1
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Wang Y, Zhang X, Huang H, Xia Y, Yao Y, Mak AFT, Yung PSH, Chan KM, Wang L, Zhang C, Huang Y, Mak KKL. Osteocalcin expressing cells from tendon sheaths in mice contribute to tendon repair by activating Hedgehog signaling. eLife 2017; 6. [PMID: 29244023 PMCID: PMC5731821 DOI: 10.7554/elife.30474] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Accepted: 12/05/2017] [Indexed: 11/25/2022] Open
Abstract
Both extrinsic and intrinsic tissues contribute to tendon repair, but the origin and molecular functions of extrinsic tissues in tendon repair are not fully understood. Here we show that tendon sheath cells harbor stem/progenitor cell properties and contribute to tendon repair by activating Hedgehog signaling. We found that Osteocalcin (Bglap) can be used as an adult tendon-sheath-specific marker in mice. Lineage tracing experiments show that Bglap-expressing cells in adult sheath tissues possess clonogenic and multipotent properties comparable to those of stem/progenitor cells isolated from tendon fibers. Transplantation of sheath tissues improves tendon repair. Mechanistically, Hh signaling in sheath tissues is necessary and sufficient to promote the proliferation of Mkx-expressing cells in sheath tissues, and its action is mediated through TGFβ/Smad3 signaling. Furthermore, co-localization of GLI1+ and MKX+ cells is also found in human tendinopathy specimens. Our work reveals the molecular function of Hh signaling in extrinsic sheath tissues for tendon repair.
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Affiliation(s)
- Yi Wang
- Developmental and Regenerative Biology, School of Biomedical Sciences, The Chinese University of Hong Kong, Shatin, Hong Kong
| | - Xu Zhang
- Developmental and Regenerative Biology, School of Biomedical Sciences, The Chinese University of Hong Kong, Shatin, Hong Kong
| | - Huihui Huang
- Developmental and Regenerative Biology, School of Biomedical Sciences, The Chinese University of Hong Kong, Shatin, Hong Kong
| | - Yin Xia
- Developmental and Regenerative Biology, School of Biomedical Sciences, The Chinese University of Hong Kong, Shatin, Hong Kong
| | - YiFei Yao
- Division of Biomedical Engineering, The Chinese University of Hong Kong, Shatin, Hong Kong
| | - Arthur Fuk-Tat Mak
- Division of Biomedical Engineering, The Chinese University of Hong Kong, Shatin, Hong Kong
| | - Patrick Shu-Hang Yung
- Department of Orthopaedics and Traumatology, The Chinese University of Hong Kong, Prince of Wales Hospital, Sha Tin, Hong Kong
| | - Kai-Ming Chan
- Department of Orthopaedics and Traumatology, The Chinese University of Hong Kong, Prince of Wales Hospital, Sha Tin, Hong Kong
| | - Li Wang
- Neural, Vascular and Metabolic Biology, School of Biomedical Sciences, The Chinese University of Hong Kong, Shatin, Hong Kong
| | - Chenglin Zhang
- Neural, Vascular and Metabolic Biology, School of Biomedical Sciences, The Chinese University of Hong Kong, Shatin, Hong Kong
| | - Yu Huang
- Neural, Vascular and Metabolic Biology, School of Biomedical Sciences, The Chinese University of Hong Kong, Shatin, Hong Kong
| | - Kingston King-Lun Mak
- Developmental and Regenerative Biology, School of Biomedical Sciences, The Chinese University of Hong Kong, Shatin, Hong Kong
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2
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Stiers PJ, van Gastel N, Moermans K, Stockmans I, Carmeliet G. Regulatory elements driving the expression of skeletal lineage reporters differ during bone development and adulthood. Bone 2017; 105:154-162. [PMID: 28863946 DOI: 10.1016/j.bone.2017.08.029] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/09/2017] [Revised: 08/28/2017] [Accepted: 08/28/2017] [Indexed: 01/06/2023]
Abstract
To improve bone healing or regeneration more insight in the fate and role of the different skeletal cell types is required. Mouse models for fate mapping and lineage tracing of skeletal cells, using stage-specific promoters, have advanced our understanding of bone development, a process that is largely recapitulated during bone repair. However, validation of these models is often only performed during development, whereas proof of the activity and specificity of the used promoters during the bone regenerative process is limited. Here, we show that the regulatory elements of the 6kb collagen type II promoter are not adequate to drive gene expression during bone repair. Similarly, the 2.3kb promoter of collagen type I lacks activity in adult mice, but the 3.2kb promoter is suitable. Furthermore, Cre-mediated fate mapping allows the visualization of progeny, but this label retention may hinder to distinguish these cells from ones with active expression of the marker at later time points. Together, our results show that the lineage-specific regulatory elements driving gene expression during bone development differ from those required later in life and during bone repair, and justify validation of lineage-specific cell tracing and gene silencing strategies during fracture healing and bone regenerative applications.
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Affiliation(s)
- Pieter-Jan Stiers
- Laboratory of Clinical and Experimental Endocrinology, Department of Clinical and Experimental Medicine, KU Leuven, Leuven, Belgium; Prometheus, Division of Skeletal Tissue Engineering, KU Leuven, Leuven, Belgium
| | - Nick van Gastel
- Laboratory of Clinical and Experimental Endocrinology, Department of Clinical and Experimental Medicine, KU Leuven, Leuven, Belgium; Prometheus, Division of Skeletal Tissue Engineering, KU Leuven, Leuven, Belgium
| | - Karen Moermans
- Laboratory of Clinical and Experimental Endocrinology, Department of Clinical and Experimental Medicine, KU Leuven, Leuven, Belgium
| | - Ingrid Stockmans
- Laboratory of Clinical and Experimental Endocrinology, Department of Clinical and Experimental Medicine, KU Leuven, Leuven, Belgium
| | - Geert Carmeliet
- Laboratory of Clinical and Experimental Endocrinology, Department of Clinical and Experimental Medicine, KU Leuven, Leuven, Belgium; Prometheus, Division of Skeletal Tissue Engineering, KU Leuven, Leuven, Belgium.
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3
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Oppenheimer H, Kumar A, Meir H, Schwartz I, Zini A, Haze A, Kandel L, Mattan Y, Liebergall M, Dvir-Ginzberg M. Set7/9 impacts COL2A1 expression through binding and repression of SirT1 histone deacetylation. J Bone Miner Res 2014; 29:348-60. [PMID: 23873758 DOI: 10.1002/jbmr.2052] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/15/2013] [Revised: 07/04/2013] [Accepted: 07/12/2013] [Indexed: 12/12/2022]
Abstract
Type II collagen is a key cartilaginous extracellular protein required for normal endochondral development and cartilage homeostasis. COL2A1 gene expression is positively regulated by the NAD-dependent protein deacetylase Sirtuin 1 (SirT1), through its ability to bind chromatin regions of the COL2A1 promoter and enhancer. Although SirT1/Sox9 binding on the enhancer site of COL2A1 was previously demonstrated, little is known about its functional role on the gene promoter site. Here, we examined the mechanism by which promoter-associated SirT1 governs COL2A1 expression. Human chondrocytes were encapsulated in three-dimensional (3D) alginate beads where they exhibited upregulated COL2A1 mRNA expression and increased levels of SirT1 occupancy on the promoter and enhancer regions, when compared to monolayer controls. Chromatin immunoprecipitation (ChIP) analyses of 3D cultures showed augmented levels of the DNA-binding transcription factor SP1, and the histone methyltransferase Set7/9, on the COL2A1 promoter site. ChIP reChIP assays revealed that SirT1 and Set7/9 form a protein complex on the COL2A1 promoter region of 3D-cultured chondrocytes, which also demonstrated elevated trimethylated lysine 4 on histone 3 (3MeH3K4), a hallmark of Set7/9 methyltransferase activity. Advanced passaging of chondrocytes yielded a decrease in 3MeH3K4 and Set7/9 levels on the COL2A1 promoter and reduced COL2A1 expression, suggesting that the SirT1/Set7/9 complex is preferentially formed on the COL2A1 promoter and required for gene activation. Interestingly, despite SirT1 occupancy, its deacetylation targets (ie, H3K9/14 and H4K16) were found acetylated on the COL2A1 promoter of 3D-cultured chondrocytes. A possible explanation for this phenotype is the enrichment of the histone acetyltransferases P300 and GCN5 on the COL2A1 promoter of3 D-cultured chondrocytes. Our study indicates that Set7/9 prevents the histone deacetylase activity of SirT1, potentiating euchromatin formation on the promoter site of COL2A1 and resulting in morphology-dependent COL2A1 gene transactivation.
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Affiliation(s)
- Hanna Oppenheimer
- Laboratory of Cartilage Biology, Institute of Dental Sciences, Hebrew University of Jerusalem, Jerusalem, Israel
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4
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Elefteriou F, Yang X. Genetic mouse models for bone studies--strengths and limitations. Bone 2011; 49:1242-54. [PMID: 21907838 PMCID: PMC3331798 DOI: 10.1016/j.bone.2011.08.021] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/20/2011] [Revised: 08/15/2011] [Accepted: 08/18/2011] [Indexed: 11/25/2022]
Abstract
Mice have become a preferred model system for bone research because of their genetic and pathophysiological similarities to humans: a relatively short reproductive period, leading to relatively low cost of maintenance and the availability of the entire mouse genome sequence information. The success in producing the first transgenic mouse line that expressed rabbit β-globin protein in mouse erythrocytes three decades ago marked the beginning of the use of genetically engineered mice as model system to study human diseases. Soon afterward the development of cultured pluripotent embryonic stem cells provided the possibility of gene replacement or gene deletion in mice. These technologies have been critical to identify new genes involved in bone development, growth, remodeling, repair, and diseases, but like many other approaches, they have limitations. This review will introduce the approaches that allow the generation of transgenic mice and global or conditional (tissue-specific and inducible) mutant mice. A list of the various promoters used to achieve bone-specific gene deletion or overexpression is included. The limitations of these approaches are discussed, and general guidelines related to the analysis of genetic mouse models are provided.
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Affiliation(s)
- Florent Elefteriou
- Vanderbilt University Medical Center, Department of Medicine, Vanderbilt Center for Bone Biology, 1235H Light Hall, Nashville, TN 37232-0575, USA
| | - Xiangli Yang
- Vanderbilt University Medical Center, Department of Medicine, Vanderbilt Center for Bone Biology, 1235H Light Hall, Nashville, TN 37232-0575, USA
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5
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Ma G, Yu J, Xiao Y, Chan D, Gao B, Hu J, He Y, Guo S, Zhou J, Zhang L, Gao L, Zhang W, Kang Y, Cheah KSE, Feng G, Guo X, Wang Y, Zhou CZ, He L. Indian hedgehog mutations causing brachydactyly type A1 impair Hedgehog signal transduction at multiple levels. Cell Res 2011; 21:1343-57. [PMID: 21537345 DOI: 10.1038/cr.2011.76] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Brachydactyly type A1 (BDA1), the first recorded Mendelian autosomal dominant disorder in humans, is characterized by a shortening or absence of the middle phalanges. Heterozygous missense mutations in the Indian Hedgehog (IHH) gene have been identified as a cause of BDA1; however, the biochemical consequences of these mutations are unclear. In this paper, we analyzed three BDA1 mutations (E95K, D100E, and E131K) in the N-terminal fragment of Indian Hedgehog (IhhN). Structural analysis showed that the E95K mutation changes a negatively charged area to a positively charged area in a calcium-binding groove, and that the D100E mutation changes the local tertiary structure. Furthermore, we showed that the E95K and D100E mutations led to a temperature-sensitive and calcium-dependent instability of IhhN, which might contribute to an enhanced intracellular degradation of the mutant proteins via the lysosome. Notably, all three mutations affected Hh binding to the receptor Patched1 (PTC1), reducing its capacity to induce cellular differentiation. We propose that these are common features of the mutations that cause BDA1, affecting the Hh tertiary structure, intracellular fate, binding to the receptor/partners, and binding to extracellular components. The combination of these features alters signaling capacity and range, but the impact is likely to be variable and mutation-dependent. The potential variation in the signaling range is characterized by an enhanced interaction with heparan sulfate for IHH with the E95K mutation, but not the E131K mutation. Taken together, our results suggest that these IHH mutations affect Hh signaling at multiple levels, causing abnormal bone development and abnormal digit formation.
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Affiliation(s)
- Gang Ma
- Bio-X Center, Key Laboratory for the Genetics of Developmental and Neuropsychiatric Disorders (Ministry of Education), Shanghai Jiao Tong University, Shanghai 200030, China
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6
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Zhang M, Xin L, Bao E, Hartung J, Yue Z. Variation in the expression of Hsp27, αB-crystallin mRNA and protein in heart and liver of pigs exposed to different transport times. Res Vet Sci 2010; 90:432-8. [PMID: 20659751 DOI: 10.1016/j.rvsc.2010.06.028] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2009] [Revised: 06/17/2010] [Accepted: 06/28/2010] [Indexed: 10/19/2022]
Abstract
Twenty pigs were randomly divided into four groups of five pigs each (not transported - control, 1, 2 and 4h of transportation). A significant increase of ALT, AST and CK in the blood serum and acute parenchyma cell lesions were observed and those were characterized by acute degenerations in the heart and liver. Hsp27 expression levels increased significantly in the heart after 2h and in the liver after 4h of transportation, accompanying with the hsp27 mRNA increasing significantly in the heart and liver after 1h of transportation. αB-crystallin expression levels were fluctuant (not significantly) in the heart and liver during transporting, however, αB-crystallin mRNA increase notably in the heart after 1h and decrease significantly in the liver at 1 and 2h of transportation, respectively. In conclusion, the cellular damage to the heart and liver is highest after 1h of transportation, Hsp27 and αB-crystallin play dissimilar roles and show tissue-specific response in different tissues during transportation.
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Affiliation(s)
- Miao Zhang
- College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210095, China
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7
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Namdari S, Wei L, Moore D, Chen Q. Reduced limb length and worsened osteoarthritis in adult mice after genetic inhibition of p38 MAP kinase activity in cartilage. ACTA ACUST UNITED AC 2009; 58:3520-9. [PMID: 18975318 DOI: 10.1002/art.23999] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
OBJECTIVE MAP kinase p38 is part of an intracellular signaling pathway activated by environmental stress and inflammatory factors. Since in vitro studies show that inhibiting p38 activity leads to a reduction in the release of degenerative metalloproteinase from chondrocytes, we speculated that inactivation of p38 in vivo may be chondroprotective. To test this hypothesis, we examined the morphology of adult mice that express a dominant-negative (DN) p38 MAPK transgene in a cartilage-specific manner. METHODS The in vivo effects of the genetic inhibition of p38 MAPK activity in cartilage were investigated in 1-year-old heterozygous DN p38-transgenic mice (n = 10) using morphologic measurements, microfocal computed tomography scanning, biomechanical testing, and histologic analysis. Results were compared with those in wild-type (WT) littermates (n = 9). RESULTS Adult DN p38 MAPK+/- -transgenic mice exhibited 50% p38 MAPK activity in articular chondrocytes as compared with WT mice. They were significantly shorter in overall body length as well as in the femur and tibia lengths. There were no differences in bone material or mechanical properties between the transgenic and WT mice. Surprisingly, the transgenic mice had higher grades of osteoarthritis of the knee joint. CONCLUSION Genetic inhibition of p38 MAPK activity in cartilage results in shortened limb length and defects in the articular cartilage of the knee joints of adult mice. Our findings demonstrate that chronic life-long reduction of p38 MAPK activity may be harmful to joint health and suggest that the timing of p38 inhibition for chondroprotection in vivo is an important variable that warrants further investigation.
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Affiliation(s)
- Surena Namdari
- Rhode Island Hospital, and Warren Alpert Medical School, Brown University, Providence, Rhode Island, USA
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8
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Kiernan AE, Pelling AL, Leung KKH, Tang ASP, Bell DM, Tease C, Lovell-Badge R, Steel KP, Cheah KSE. Sox2 is required for sensory organ development in the mammalian inner ear. Nature 2005; 434:1031-5. [PMID: 15846349 DOI: 10.1038/nature03487] [Citation(s) in RCA: 409] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2004] [Accepted: 02/07/2005] [Indexed: 11/08/2022]
Abstract
Sensory hair cells and their associated non-sensory supporting cells in the inner ear are fundamental for hearing and balance. They arise from a common progenitor, but little is known about the molecular events specifying this cell lineage. We recently identified two allelic mouse mutants, light coat and circling (Lcc) and yellow submarine (Ysb), that show hearing and balance impairment. Lcc/Lcc mice are completely deaf, whereas Ysb/Ysb mice are severely hearing impaired. We report here that inner ears of Lcc/Lcc mice fail to establish a prosensory domain and neither hair cells nor supporting cells differentiate, resulting in a severe inner ear malformation, whereas the sensory epithelium of Ysb/Ysb mice shows abnormal development with disorganized and fewer hair cells. These phenotypes are due to the absence (in Lcc mutants) or reduced expression (in Ysb mutants) of the transcription factor SOX2, specifically within the developing inner ear. SOX2 continues to be expressed in the inner ears of mice lacking Math1 (also known as Atoh1 and HATH1), a gene essential for hair cell differentiation, whereas Math1 expression is absent in Lcc mutants, suggesting that Sox2 acts upstream of Math1.
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MESH Headings
- Alleles
- Animals
- Basic Helix-Loop-Helix Transcription Factors
- Cell Differentiation
- DNA-Binding Proteins/deficiency
- DNA-Binding Proteins/genetics
- DNA-Binding Proteins/metabolism
- Ear, Inner/abnormalities
- Ear, Inner/embryology
- Ear, Inner/metabolism
- Ear, Inner/pathology
- Hair Cells, Auditory, Inner/abnormalities
- Hair Cells, Auditory, Inner/metabolism
- Hair Cells, Auditory, Inner/pathology
- Mice
- Mice, Mutant Strains
- Mutation/genetics
- Nerve Tissue Proteins/deficiency
- Nerve Tissue Proteins/genetics
- Nerve Tissue Proteins/metabolism
- Phenotype
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- SOXB1 Transcription Factors
- Trans-Activators/deficiency
- Trans-Activators/genetics
- Trans-Activators/metabolism
- Transcription Factors/deficiency
- Transcription Factors/genetics
- Transcription Factors/metabolism
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Affiliation(s)
- Amy E Kiernan
- MRC Institute of Hearing Research, University of Nottingham, Nottingham NG7 2RD, UK
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9
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Reddi AH. Cartilage morphogenetic proteins: role in joint development, homoeostasis, and regeneration. Ann Rheum Dis 2003; 62 Suppl 2:ii73-8. [PMID: 14532155 PMCID: PMC1766760 DOI: 10.1136/ard.62.suppl_2.ii73] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
BACKGROUND Articular cartilage homoeostasis is critical for joint function. The steady state homoeostasis of articular cartilage is a balance between anabolic morphogens such as cartilage derived morphogenetic proteins (CDMPs) and bone morphogenetic proteins (BMPs) of the BMP family and catabolic cytokines such as interleukin (IL)1, IL17, and tumour necrosis factor alpha. Although bone and articular cartilage are adjacent tissues, there is a profound difference in their regeneration potential. Bone has the highest potential for regeneration. On the other hand, articular cartilage is recalcitrant to repair. OBJECTIVE To examine the hypothesis that the feeble innate regeneration ability of cartilage is due to the preponderance of catabolic cytokines such as IL1 and IL17. RESULTS During a systematic investigation of CDMPs and cytokines IL17B (chondroleukin) was found in bovine articular cartilage. DISCUSSION AND CONCLUSIONS BMP-7 and IL17B are present in articular cartilage and synthesised in chondrocytes as shown by northern blots and real-time reverse transcription-polymerase chain reaction. The coexistence of anabolic morphogens and catabolic cytokines in articular cartilage has important implications for cartilage homoeostasis and regeneration. The networks of signalling systems of morphogens and cytokines determine the net capacity for regenerative morphogenesis of articular cartilage. Finally, the feeble innate capacity for articular cartilage may be improved by targeted therapy by soluble receptors to block catabolic cytokines.
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Affiliation(s)
- A H Reddi
- Centre for Tissue Regeneration and Repair, Department of Orthopaedic Surgery, University of California, Davis School of Medicine, Sacramento, California 95817, USA.
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10
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Osaki M, Tan L, Choy BK, Yoshida Y, Cheah KSE, Auron PE, Goldring MB. The TATA-containing core promoter of the type II collagen gene (COL2A1) is the target of interferon-gamma-mediated inhibition in human chondrocytes: requirement for Stat1 alpha, Jak1 and Jak2. Biochem J 2003; 369:103-15. [PMID: 12223098 PMCID: PMC1223055 DOI: 10.1042/bj20020928] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2002] [Revised: 09/05/2002] [Accepted: 09/11/2002] [Indexed: 01/18/2023]
Abstract
Interferon-gamma (IFN-gamma) inhibits the synthesis of the cartilage-specific extracellular matrix protein type II collagen, and suppresses the expression of the type II collagen gene ( COL2A1 ) at the transcriptional level. To further examine this mechanism, the responses of COL2A1 regulatory sequences to IFN-gamma and the role of components of the Janus kinase/signal transducer and activators of transcription (JAK/STAT) pathway were examined in the immortalized human chondrocyte cell line, C-28/I2. IFN-gamma inhibited the mRNA levels of COL2A1 and aggrecan, but not Sox9, L-Sox5 and Sox6, all of which were expressed by these cells as markers of the differentiated phenotype. IFN-gamma suppressed the expression of luciferase reporter constructs containing sequences of the COL2A1 promoter spanning -6368 to +125 bp in the absence and presence of the intronic enhancer and stimulated activity of the gamma-interferon-activated site (GAS) luciferase reporter vector, associated with induction of Stat1 alpha-binding activity in nuclear extracts. These responses to IFN-gamma were blocked by overexpression of the JAK inhibitor, JAK-binding protein (JAB), or reversed by dominant-negative Stat1 alpha Y701F containing a mutation at Tyr-701, the JAK phosphorylation site. IFN-gamma had no effect on COL2A1 promoter expression in Jak1 (U4A)-, Jak2 (gamma 2A)- and Stat1 alpha (U3A)-deficient cell lines. In the U3A cell line, the response to IFN-gamma was rescued by overexpression of Stat1 alpha, but not by either Stat1 alpha Y701F or Stat1 beta. Functional analysis using deletion constructs showed that the IFN-gamma response was retained in the COL2A1 core promoter region spanning -45 to +11 bp, containing the TATA-box and GC-rich sequences but no Stat1-binding elements. Inhibition of COL2A1 promoter activity by IFN-gamma persisted in the presence of multiple deletions within the -45/+11 bp region. Our results indicate that repression of COL2A1 gene transcription by IFN-gamma requires Jak1, Jak2 and Stat1 alpha and suggest that this response involves indirect interaction of activated Stat1 alpha with the general transcriptional machinery that drives constitutive COL2A1 expression.
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Affiliation(s)
- Makoto Osaki
- Beth Israel Deaconess Medical Center, Rheumatology Division, and New England Baptist Bone & Joint Institute, Harvard Institutes of Medicine, Boston, MA 02115, USA
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11
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Dong S, Leung KKH, Pelling AL, Lee PYT, Tang ASP, Heng HHQ, Tsui LC, Tease C, Fisher G, Steel KP, Cheah KSE. Circling, deafness, and yellow coat displayed by yellow submarine (ysb) and light coat and circling (lcc) mice with mutations on chromosome 3. Genomics 2002; 79:777-84. [PMID: 12036291 DOI: 10.1006/geno.2002.6783] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We describe here two mouse mutants, yellow submarine (Ysb) and light coat and circling (Lcc). Ysb arose as the result of insertions of a transgene, pAA2, into the genome. Lcc is an independent, radiation-induced mutation. Both mutants are characterized by recessive circling behavior and deafness, associated with a non-segregating, semi-dominant yellow coat color. Complementation tests showed that Ysb and Lcc are allelic. We attribute the yellow coat in Ysb and Lcc mice to the absence of black awl overhairs, increased agouti zigzag underhairs, and the presence of agouti awls with long subapical yellow pigment. Chromosomal mapping and genomic characterization showed the Ysb and Lcc mutations involve complex chromosomal rearrangements in overlapping regions of mouse chromosome 3, A2/A3-B/C and B-E1, respectively. Ysb and Lcc show for the first time, to our knowledge, the presence of genes in the B-C region of chromosome 3 important for balance and hearing and the pigmentation and specification of coat hair.
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Affiliation(s)
- Shuo Dong
- Department of Biochemistry, University of Hong Kong, 5 Sassoon Road, Hong Kong SAR, China
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12
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Jacenko O, Roberts DW, Campbell MR, McManus PM, Gress CJ, Tao Z. Linking hematopoiesis to endochondral skeletogenesis through analysis of mice transgenic for collagen X. THE AMERICAN JOURNAL OF PATHOLOGY 2002; 160:2019-34. [PMID: 12057907 PMCID: PMC1850848 DOI: 10.1016/s0002-9440(10)61152-2] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Each skeletal element where marrow develops is first defined by a hypertrophic cartilage blueprint. Through programmed tissue substitution, the cartilaginous skeletal model is replaced by trabecular bone and marrow, with accompanying longitudinal tissue growth. During this process of endochondral ossification, hypertrophic cartilage expresses a unique matrix molecule, collagen X. Previously we reported that transgenic mice with dominant interference collagen X mutations develop variable skeleto-hematopoietic abnormalities, manifested as growth plate compressions, diminished trabecular bone, and reduced lymphatic organs (Nature 1993, 365:56). Here, histology and flow cytometry reveal marrow hypoplasia and impaired hematopoiesis in all collagen X transgenic mice. A subset of mice with perinatal lethality manifested the most severe skeletal defects and a reduction of marrow hematopoiesis, highlighted by a lymphocyte decrease. Thymic reduction is accompanied by a paucity of cortical immature T cells, consistent with the marrow's inability to replenish maturing cortical lymphocytes. Diminished spleens exhibit indistinct lymphatic nodules and red pulp depletion; the latter correlates with erythrocyte-filled vascular sinusoids in marrows. All mice display reduced B cells in marrows and spleens, and elevated splenic T cells. These hematopoietic defects underscore an unforeseen link between hypertrophic cartilage, endochondral ossification, and establishment of the marrow microenvironment required for blood cell differentiation.
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Affiliation(s)
- Olena Jacenko
- Department of Animal Biology, University of Pennsylvania School of Veterinary Medicine, Philadelphia, Pennsylvania 19104-6046, USA.
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13
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Chambers MG, Kuffner T, Cowan SK, Cheah KSE, Mason RM. Expression of collagen and aggrecan genes in normal and osteoarthritic murine knee joints. Osteoarthritis Cartilage 2002; 10:51-61. [PMID: 11795983 DOI: 10.1053/joca.2001.0481] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
OBJECTIVE The STR/ort mouse strain develops osteoarthritis (OA) of the medial tibial cartilage whilst CBA mice do not develop this disease. We investigated whether changes occur in the expression of genes encoding major extracellular matrix proteins in the connective tissue of the murine knee joint in OA. DESIGN Expression of the genes encoding collagens II (Col2alpha1), X (Col10alpha1), alpha2(XI) (Col11alpha2) and aggrecan (Agc) was detected in skeletally mature and immature male mice of the CBA and STR/ort strains by in situ hybridization. RESULTS Col2alpha1 was expressed by chondrocytes of the tibial and patella-femoral cartilage and by the meniscal cartilage in all young mice (4-9 weeks) but only in the patella-femoral cartilage in older mice of both strains (36-45 weeks). In contrast Col2alpha1 was expressed by growth plate chondrocytes of both species at all ages. Similarly, Col2alpha1 transcripts were detected in cruciate ligament cells in both strains at all ages. Col10alpha1 transcripts were detected in cruciate ligament cells in both strains at all ages. Col10alpha1 expression was evident in the hypertrophic chondrocytes in the growth plate of young CBA and STR mice, but was not active in these cells in mature animals. However, Col10alpha1 was transcribed in articular chondrocytes of the tibia, meniscal and patella-femoral cartilages of all ages, in normal and osteoarthritic mice. Transcripts were also present in ligament of some mature animals. Col11alpha2 followed a similar pattern of expression in CBA cartilages to Col2alpha1, being active in adult growth plate but generally inactive in adult articular cartilages. Young CBA and STR/ort mice expressed Col11alpha2 in articular cartilage and very strongly throughout the growth plate. Agc expression was detected in all articular cartilages at all ages in both strains. Interestingly, transcripts for all four genes were absent in tibial articular chondrocytes located close to osteoarthritic lesions in STR/ort mice, indicating that these cells are unable to synthesize matrix proteins. Adult STR/ort mice also showed evidence of tissue remodeling around the periphery of the knee joint. Cells in remodeling areas actively transcribed Col2alpha1, Col10alpha1, Col11alpha2 and Agc. CONCLUSION It is unlikely that OA develops in STR/ort mice because of failure to express major proteins in joint tissue. However, once lesions develop in articular cartilage neighbouring chondrocytes fail to express genes encoding several matrix proteins.
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Affiliation(s)
- M G Chambers
- Cell & Molecular Biology Section, Division of Biomedical Sciences, Imperial College School of Medicine, London, England
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Affiliation(s)
- M T Sáenz-Robles
- Department of Biological Sciences. University of Pittsburgh, Pittsburgh, PA 15260, USA
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Selleri L, Depew MJ, Jacobs Y, Chanda SK, Tsang KY, Cheah KS, Rubenstein JL, O'Gorman S, Cleary ML. Requirement for Pbx1 in skeletal patterning and programming chondrocyte proliferation and differentiation. Development 2001; 128:3543-57. [PMID: 11566859 DOI: 10.1242/dev.128.18.3543] [Citation(s) in RCA: 204] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Pbx1 and a subset of homeodomain proteins collaboratively bind DNA as higher-order molecular complexes with unknown consequences for mammalian development. Pbx1 contributions were investigated through characterization of Pbx1-deficient mice. Pbx1 mutants died at embryonic day 15/16 with severe hypoplasia or aplasia of multiple organs and widespread patterning defects of the axial and appendicular skeleton. An obligatory role for Pbx1 in limb axis patterning was apparent from malformations of proximal skeletal elements, but distal structures were unaffected. In addition to multiple rib and vertebral malformations, neural crest cell-derived skeletal structures of the second branchial arch were morphologically transformed into elements reminiscent of first arch-derived cartilages. Although the skeletal malformations did not phenocopy single or compound Hox gene defects, they were restricted to domains specified by Hox proteins bearing Pbx dimerization motifs and unaccompanied by alterations in Hox gene expression. In affected domains of limbs and ribs, chondrocyte proliferation was markedly diminished and there was a notable increase of hypertrophic chondrocytes, accompanied by premature ossification of bone. The pattern of expression of genes known to regulate chondrocyte differentiation was not perturbed in Pbx1-deficient cartilage at early days of embryonic skeletogenesis, however precocious expression of Col1a1, a marker of bone formation, was found. These studies demonstrate a role for Pbx1 in multiple developmental programs and reveal a novel function in co-ordinating the extent and/or timing of proliferation with terminal differentiation. This impacts on the rate of endochondral ossification and bone formation and suggests a mechanistic basis for most of the observed skeletal malformations.
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Affiliation(s)
- L Selleri
- Department of Pathology, Stanford University School of Medicine, Stanford, CA 94305, USA.
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Chan VS, Cohen ES, Weissensteiner T, Cheah KS, Bodmer HC. Chondrocyte antigen expression, immune response and susceptibility to arthritis. Int Immunol 2001; 13:421-9. [PMID: 11282981 DOI: 10.1093/intimm/13.4.421] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The association of HLA-B27 with certain forms of arthritis implies a role for MHC class I-restricted T cells in the arthritic process. Our aim was to study CD8(+) T cell responses towards specific antigens localized in joint tissue. Known determinants were introduced into chondrocytes of transgenic (TG) mice, under the control of the cis-regulatory sequences of the human type II collagen gene (COL2A1). Two Escherichia coli beta-galactosidase (beta-gal)-expressing lines were derived (CIIL73 and CIIL64) as well as two lines (CIINP) expressing influenza A virus nucleoprotein (NP). Expression of the antigens could be demonstrated in cartilaginous tissues. The TG lines showed variable degrees of responsiveness towards the transgene-introduced antigens; whilst 75% of CIIL73 mice had an impaired cytotoxic T lymphocyte (CTL) response towards beta-gal, the response in CIIL64 mice was essentially normal. However, both lines displayed normal proliferative and antibody responses to beta-gal. A reduced CTL response was seen to NP in the CIINP lines in approximately 65% of the animals. In spite of the persistence of T cell responses to the transgene antigens in these lines, induction of CTL responses alone has so far failed to induce clinical signs of arthritis. Interestingly, some animals expressing beta-gal were susceptible to arthritis following challenge with type II collagen alone, whilst their non-TG littermates and TG mice from other lines remained unaffected. As beta-gal is expressed by E. coli, a component of the normal gut flora, this suggests a possible role for gut-derived immune responses. We believe these lines could form the basis of a model for studying links between intestinal inflammation and arthritis.
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Affiliation(s)
- V S Chan
- The Edward Jenner Institute for Vaccine Research, Compton, Newbury, Berkshire RG20 7NN, UK
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Wai AW, Ng LJ, Watanabe H, Yamada Y, Tam PP, Cheah KS. Disrupted expression of matrix genes in the growth plate of the mouse cartilage matrix deficiency (cmd) mutant. DEVELOPMENTAL GENETICS 2000; 22:349-58. [PMID: 9664687 DOI: 10.1002/(sici)1520-6408(1998)22:4<349::aid-dvg5>3.0.co;2-6] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Chondrodysplasia in the autosomal recessive cartilage matrix deficiency (cmd) mutant is caused by lack of the proteoglycan aggrecan arising from a mutation in the gene. Homozygous cmd/cmd mice are characterized by disorganisation of chondrocytes in the growth plate, disproportionate dwarfism, cleft palate, and perinatal lethality. We have studied the impact of the aggrecan deficiency on the expression of other matrix genes during the differentiation of chondrocytes in the growth plate of cmd/cmd 18.5 day fetuses. Compared with the wild-type, there are significant differences in the growth plates of cmd mutants in the combinations of co-expression of genes encoding the glycoprotein link protein, proteoglycan syndecan 3, collagens alpha 1 (X) [Col10a1], alpha 2(XI) [Col11a2], and the alternative transcripts of alpha 1 (II) [Col2a1 type IIA form], and alpha 1 (IX) [Col9a1 long and short forms]. The discordance of gene expression in cmd chondrocytes may be additional factors contributing to the disrupted cellular architecture of the growth plate resulting from the primary absence of aggrecan.
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Affiliation(s)
- A W Wai
- Department of Biochemistry, University of Hong Kong, China
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18
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Haigh JJ, Gerber HP, Ferrara N, Wagner EF. Conditional inactivation of VEGF-A in areas of collagen2a1 expression results in embryonic lethality in the heterozygous state. Development 2000; 127:1445-53. [PMID: 10704390 DOI: 10.1242/dev.127.7.1445] [Citation(s) in RCA: 135] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
VEGF-A has been implicated in regulating the initial angiogenic invasion events that are essential for endochondral bone formation. VEGF-A mRNA expression was indeed found in the sclerotome of the developing somite and in the limb-bud mesenchyme at E10.5 in mouse development but declined during chondrogenesis and became upregulated in hypertrophic chondrocytes prior to angiogenic invasion. To determine the functional importance of VEGF-A expression in the developing chondrogenic tissues, VEGF-A was conditionally inactivated during early embryonic development using Collagen2a1-Cre transgenic lines. Deletion of a single VEGF-A allele in Collagen2a1-Cre-expressing cells results in embryonic lethality around E10.5. This lethality is characterized by aberrant development of the dorsal aorta and intersomitic blood vessels, along with defects in the developing endocardial and myocardial layers of the heart. A small percentage of VEGF(Flox)/+, Collagen2a1-Cre fetuses survive until E17.5, show aberrant endochondral bone formation and develop a heart phenotype resembling a dilated form of ischemic cardiomyopathy. These results provide insights into the function of VEGF-A in heart and endochondral bone formation and underscore the importance of tightly controlled levels of VEGF-A during development.
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Affiliation(s)
- J J Haigh
- Research Institute of Molecular Pathology (IMP), Dr Bohr-Gasse 7, A-1030 Vienna, Austria
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Steimberg N, Viengchareun S, Biehlmann F, Guénal I, Mignotte B, Adolphe M, Thenet S. SV40 large T antigen expression driven by col2a1 regulatory sequences immortalizes articular chondrocytes but does not allow stabilization of type II collagen expression. Exp Cell Res 1999; 249:248-59. [PMID: 10366424 DOI: 10.1006/excr.1999.4478] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Immortalization of chondrocytes by SV40 T Ag has often been reported to trigger the loss of expression of type II collagen, one of the main differentiation markers, although some immortalized chondrocyte lines maintaining a differentiated phenotype have also been described. Here, we show using transient cotransfections in differentiated chondrocytes that, in contrast to c-src, neither SV40 T Ag, nor c-myc, decreases col2a1 transcriptional activity. Then, we report the possibility of immortalizing rabbit articular chondrocytes by expression of SV40 T Ag controlled by the col2a1 promoter and enhancer (pCol2SV). This strategy allows one to select within a population of differentiated chondrocytes those which are able to maintain functional regulation of the col2a1 gene through long-term culture. In precrisis pCol2SV-transfected chondrocytes, all-trans-retinoic acid, a down-regulator of col2a1 expression, induced apoptosis, strongly suggesting the strict control of T Ag expression by col2a1 regulatory sequences. Some pCol2SV-transfected chondrocytes were definitively immortalized, after a short crisis period. However, type II collagen synthesis was restricted to a small proportion of cells, which went on to decrease with subculture, while the proportion of cells expressing T Ag was not affected. In these postcrisis cells, T Ag remained at least partially under the control of functional col2a1 regulatory elements as assessed by all-trans-retinoic acid down-regulation.
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Affiliation(s)
- N Steimberg
- Ecole Pratique des Hautes Etudes, Laboratoire de Pharmacologie Cellulaire, Centre de Recherches Biomédicales des Cordeliers, 15 rue de l'Ecole de Médecine, Paris, 75006, France
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20
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Abstract
Cartilage morphogenesis is a prerequisite for skeletal development and maintenance. The morphogenesis of cartilage determines the shape of bones, and joints including articular cartilage, ligaments, and tendon. This article reviews the recent advances in cartilage-derived morphogenetic proteins (CDMPs) and related bone morphogenetic proteins (BMPs). Cartilage-derived morphogenetic proteins (CDMPs) are related to BMPs and are critical for cartilage and joint morphogenesis. Cartilage morphogenesis is a multistep cascade that includes factors for initiation, promotion, and maintenance of cartilage phenotype. The extracellular matrix of cartilage consists of a constellation of macromolecules such as collagens, proteoglycans, and glycoproteins. Morphogens bind to extracellular matrix components and assemble a morphogenetic scaffold. Recent advances in CDMPs may aid in articular cartilage repair and regeneration.
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Affiliation(s)
- A H Reddi
- Department of Orthopaedic Surgery, University of California Davis, School of Medicine, Sacramento 95817, USA.
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Leung KK, Ng LJ, Ho KK, Tam PP, Cheah KS. Different cis-regulatory DNA elements mediate developmental stage- and tissue-specific expression of the human COL2A1 gene in transgenic mice. J Biophys Biochem Cytol 1998; 141:1291-300. [PMID: 9628886 PMCID: PMC2132792 DOI: 10.1083/jcb.141.6.1291] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Expression of the type II collagen gene (human COL2A1, mouse Col2a1) heralds the differentiation of chondrocytes. It is also expressed in progenitor cells of some nonchondrogenic tissues during embryogenesis. DNA sequences in the 5' flanking region and intron 1 are known to control tissue-specific expression in vitro, but the regulation of COL2A1 expression in vivo is not clearly understood. We have tested the regulatory activity of DNA sequences from COL2A1 on the expression of a lacZ reporter gene in transgenic mice. We have found that type II collagen characteristic expression of the transgene requires the enhancer activity of a 309-bp fragment (+2, 388 to +2,696) in intron 1 in conjunction with 6.1-kb 5' sequences. Different regulatory elements were found in the 1.6-kb region (+701 to +2,387) of intron 1 which only needs 90-bp 5' sequences for tissue-specific expression in different components of the developing cartilaginous skeleton. Distinct positive and negative regulatory elements act together to control tissue-specific transgene expression in the developing midbrain neuroepithelium. Positive elements affecting expression in the midbrain were found in the region from -90 to -1,500 and from +701 to +2,387, whereas negatively acting elements were detected in the regions from -1,500 to -6,100 and +2,388 to +2,855.
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Affiliation(s)
- K K Leung
- Department of Biochemistry, The University of Hong Kong, Hong Kong
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22
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Furth PA, Li M, Hennighausen L. Studying development of disease through temporally controlled gene expression in the salivary gland. Ann N Y Acad Sci 1998; 842:181-7. [PMID: 9599308 DOI: 10.1111/j.1749-6632.1998.tb09646.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Multistep tumorigenesis proceeds through activation of oncogenes and inactivation of tumor suppressor genes. Initiating oncoproteins induce secondary changes that maintain transformation in the absence of original stimuli. Time-dependent reversal of SV40 T antigen (TAg)-induced hyperplasia was studied using temporally controlled gene expression. Targeting TAg expression to the submandibular salivary gland of transgenic mice produces focal hyperplasias at age two weeks, which extend through large areas of the gland by four months. At twelve months, fibrosis and tumor foci accompany hyperplasia. Hyperplasia reverses when TAg expression in discontinued at four months but not at seven months. Secondary changes that maintain transformation appear to be time dependent. The system can be used to identify genetic events resulting in phenotypic reversal at four months and to expose factors preventing its occurrence at seven months. Expression of other proteins can be targeted to the salivary gland, and temporally controlled gene deletions can also be made using this system.
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Affiliation(s)
- P A Furth
- Department of Medicine, University of Maryland Medical School, Baltimore 21201, USA.
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Miosge N, Hesse D, Götz W, Theuring F, Herken R. Localization of large-T oncoprotein during the embryonic and fetal development of transgenic mice. TERATOLOGY 1996; 54:278-83. [PMID: 9098921 DOI: 10.1002/(sici)1096-9926(199612)54:6<278::aid-tera2>3.0.co;2-v] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Oncoproteins are not only involved in the development of tumors but also play a role in physiological regulation in embryonic growth and differentiation. The mechanisms by which regulation is accomplished in embryonic stages differ from postnatal or adult stages. Oncoproteins responsible for tumors in the adult, i.e., products of proto-oncogenes, are prevented from causing tumors in the embryo. If oncogenes are introduced artificially into the embryo. will they be governed by the embryonic regulation described above? To answer this question we used transgenic mice in which the hybrid construct MSV-SV40-Large-T, composed of the Simian-Virus-Oncogene. Large-T with its SV40-promotor and the Moloney Murine Sarcoma Virus (MSV)-enhancer, had been integrated. Under the influence of large-T expression, these animals develop either brain or endocrine pancreas tumors. In the present investigation, we localised large-T expression during development of mouse embryos and fetuses. Interestingly, we saw large-T positive reactions in organ anlagen other than those that later develop tumors. We found large-T antigens in cartilage anlagen, e.g., in ribs and vertebrae, particularly in fetuses of days 14 to 17, and also in a variety of epithelial cells such as in the lung or the choroid plexus. Our results indicate that, as for proto-oncogene products, the effect of an artificially introduced transgenic oncogene product can also be regulated by embryonic cells.
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Affiliation(s)
- N Miosge
- Zentrum Anatomie, Abt. Histologie, Universität Göttingen, Germany
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Reddi AH. Cartilage morphogenesis: role of bone and cartilage morphogenetic proteins, homeobox genes and extracellular matrix. Matrix Biol 1995; 14:599-606. [PMID: 9057810 DOI: 10.1016/s0945-053x(05)80024-1] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Cartilage morphogenesis is one of the central topics in skeletal development. Cartilage geometry determines the future architecture of bones, joints and associated ligaments and tendons. Recent progress in this area has come from purification, cloning and expression of genes encoding bone and cartilage morphogenetic proteins (BMPs and CDMPs). BMPs initiate de novo cartilage and bone differentiation. BMPs are a family of pleiotropic signals for progenitor cell migration by chemotaxis, proliferation, and differentiation. Very recently another class of related morphogenetic proteins, CDMPs have been isolated and cloned. CDMPs may be critical for mesenchymal condensation prior to overt cartilage differentiation, the first step in morphogenesis of both cartilage and bone. The cartilage morphogenetic cascade is a cellular and molecular continuum driven by regulatory signalling molecules such as BMPs and CDMPs and their receptors, homeobox genes, transcription factors, and finally the synthesis and supramolecular assembly of structural macromolecules of the extracellular matrix. BMPs and CDMPs bind to heparin, heparan sulfates, and collagens I and IV. Thus there is a symbiosis of regulatory and structural macromolecules in the morphogenesis of cartilage. An avalanche of recent advances from seemingly disparate areas bodes well for the complete elucidation of the molecular basis of morphogenesis of cartilage, the architectural blue-print for the skeleton.
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Affiliation(s)
- A H Reddi
- Department of Orthopaedic Surgery, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
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