The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Veronique Lefebvre - One of the best experts on this subject based on the ideXlab platform.
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the transcription factors sox9 and sox5 sox6 cooperate genome wide through super enhancers to drive chondrogenesis
Nucleic Acids Research, 2015Co-Authors: Chia Feng Liu, Veronique LefebvreAbstract:SOX9 is a transcriptional activator required for chondrogenesis, and SOX5 and SOX6 are closely related DNA-binding proteins that critically enhance its function. We use here genome-wide approaches to gain novel insights into the full spectrum of the target genes and modes of action of this chondrogenic trio. Using the RCS cell line as a faithful model for proliferating/early prehypertrophic growth plate chondrocytes, we uncover that SOX6 and SOX9 bind thousands of genomic sites, frequently and most efficiently near each other. SOX9 recognizes pairs of inverted SOX motifs, whereas SOX6 favors pairs of tandem SOX motifs. The SOX proteins primarily target enhancers. While binding to a small fraction of typical enhancers, they bind multiple sites on almost all super-enhancers (SEs) present in RCS cells. These SEs are predominantly linked to cartilage-specific genes. The SOX proteins effectively work together to activate these SEs and are required for in vivo expression of their associated genes. These genes encode key regulatory factors, including the SOX trio proteins, and all essential cartilage extracellular matrix components. Chst11, Fgfr3, Runx2 and Runx3 are among many other newly identified SOX trio targets. SOX9 and SOX5/SOX6 thus cooperate genome-wide, primarily through SEs, to implement the growth plate chondrocyte differentiation program.
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cis regulatory control of corticospinal system development and evolution
Nature, 2012Co-Authors: Sungbo Shim, Veronique Lefebvre, Kenneth Y Kwan, Nenad SestanAbstract:The co-emergence of a six-layered cerebral neocortex and its corticospinal output system is one of the evolutionary hallmarks of mammals. However, the genetic programs that underlie their development and evolution remain poorly understood. Here we identify a conserved non-exonic element (E4) that acts as a cortex-specific enhancer for the nearby gene Fezf2 (also known as Fezl and Zfp312), which is required for the specification of corticospinal neuron identity and connectivity. We find that SOX4 and SOX11 functionally compete with the repressor SOX5 in the transactivation of E4. Cortex-specific double deletion of SOX4 and Sox11 leads to the loss of Fezf2 expression, failed specification of corticospinal neurons and, independent of Fezf2, a reeler-like inversion of layers. We show evidence supporting the emergence of functional SOX-binding sites in E4 during tetrapod evolution, and their subsequent stabilization in mammals and possibly amniotes. These findings reveal that SOX transcription factors converge onto a cis-acting element of Fezf2 and form critical components of a regulatory network controlling the identity and connectivity of corticospinal neurons.
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synovial joint morphogenesis requires the chondrogenic action of sox5 and sox6 in growth plate and articular cartilage
Developmental Biology, 2010Co-Authors: Patrick Smits, Yu Han, Amber Silvester, Alfredo Penzomendez, Bogdan Dumitriu, Carol A De La Motte, David M Kingsley, Veronique LefebvreAbstract:The mechanisms underlying synovial joint development remain poorly understood. Here we use complete and cell-specific gene inactivation to identify the roles of the redundant chondrogenic transcription factors Sox5 and Sox6 in this process. We show that joint development aborts early in complete mutants (Sox5−/−6−/−). Gdf5 and Wnt9a expression is punctual in articular progenitor cells, but Sox9 downregulation and cell condensation in joint interzones are late. Joint cell differentiation is unsuccessful, regardless of lineage, and cavitation fails. Sox5 and Sox6 restricted expression to chondrocytes in wild-type embryos and continued Erg expression and weak Ihh expression in Sox5−/−6−/− growth plates suggest that growth plate failure contribute to this Sox5−/−6−/− joint morphogenesis block. Sox5/6 inactivation in specified joint cells and chondrocytes (Sox5fl/fl6fl/flCol2Cre) also results in a joint morphogenesis block, whereas Sox5/6 inactivation in specified joint cells only (Sox5fl/fl6fl/flGdf5Cre) results in milder joint defects and normal growth plates. Sox5fl/fl6fl/flGdf5Cre articular chondrocytes remain undifferentiated, as shown by continued Gdf5 expression and pancartilaginous gene downregulation. Along with Prg4 downregulation, these defects likely account for joint tissue overgrowth and incomplete cavitation in adult mice. Together, these data suggest that synovial joint morphogenesis relies on essential roles for Sox5/6 in promoting both growth plate and articular chondrocyte differentiation.
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the soxd transcription factors sox5 sox6 and sox13 are key cell fate modulators
The International Journal of Biochemistry & Cell Biology, 2010Co-Authors: Veronique LefebvreAbstract:Sox5, Sox6, and Sox13 constitute the group D of sex-determining region (Sry)-related transcription factors. They are highly conserved in the family-specific high-mobility-group (HMG) box DNA-binding domain and in a group-specific coiled-coil domain. The latter mediates SoxD protein dimerization and thereby preferential binding to pairs of DNA recognition sites. The SoxD genes have overlapping expression and cell-autonomously control discrete lineages. Sox5 and Sox6 redundantly enhance chondrogenesis, but retard gliogenesis. Sox5 hinders melanogenesis, promotes neural crest generation, and controls the pace of neurogenesis. Sox6 promotes erythropoiesis, and Sox13 modulates T cell specification and is an autoimmune antigen. SoxD proteins enhance transactivation by Sox9 in chondrocytes, but antagonize Sox9 and other SoxE proteins in oligodendrocytes and melanocytes, and also repress transcription through various mechanisms in several other lineages. While their biological and molecular functions remain incompletely understood, the SoxD proteins have thus already proven that they critically modulate cell fate in major lineages.
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conditional knockout of SOX4 markedly affects b lymphopoiesis in adult mice
Blood, 2009Co-Authors: Baohua Sun, Veronique Lefebvre, Saradhi Mallampati, Yun Gong, Donghai Wang, James M You, Hesham M Amin, Klaus Rajewsky, Xiaoping SunAbstract:Abstract 913 The development of mature B cells from self-renewing pluripotent hematopoietic stem cells (HSCs) involves a complex process that is regulated in a hierarchical order by various proteins, particularly transcription factors. SOX4 is an SRY-related HMG-box-containing transcription factor and is known to be implicated in B cell development. However, SOX4 's role in B cell development has not been systematically investigated. In this project, we used conditional knockout mouse strains to study the effect of SOX4 deletion on B lymphopoiesis in adult mice. To determine when in the B cell developmental process SOX4 is required, we crossed SOX4 -floxed mice with 5 Cre-recombinase-expressing mouse strains that were expected to result in deletion of the floxed SOX4 gene at different developmental stages, as follows: Vav-Cre (HSC stage in early embryos), Mx1-Cre (HSC stage in adults, induced by pIpC injection), MB1-Cre (early progenitor B cell stage), CD19-Cre (pro-B cell stage), and CD21-Cre (mature B cell stage). We demonstrated that deletion of SOX4 caused arrest of B lymphopoiesis at the transition from pre-pro-B cell stage (fraction A) to pro-B cell stage (fraction B); fraction B and later-stage B cells were nearly absent. There was a significant reduction in the number of hematopoietic stem (LSK) cells upon SOX4 deletion, but the number of common lymphocyte progenitors (CLPs) was not significantly changed and that of fraction A cells was only slightly reduced, suggesting that reduction in HSCs was not directly responsible for the B cell deficiency. Deletion of SOX4 in the early embryonic stage (Vav-Cre) and in adults (Mx1-Cre) resulted in similar phenotypes with regard to B lymphopoiesis, except that the number of peritoneal B1 cells was reduced more significantly in Vav-Cre than in Mx1-Cre mice. MB1-Cre yielded results similar to those of Vav-Cre, but B lymphopoiesis arrest was not as dramatic. SOX4f/f CD19-Cre and SOX4f/f CD21-Cre mice produced no significant difference in B cell phenotype compared with SOX4f/+ CD19-Cre and SOX4f/+ CD21-Cre mice, respectively. These data suggest that SOX4 is required for early B cell development at the transition from pre-pro-B cells to pro-B cells and is not required for mature B cell development. To further understand the mechanism by which SOX4 deletion induced pro-B cell deficiency, we performed semi-quantitative RT-PCR on residual pro-B cells and showed that SOX4 deletion did not change the mRNA expression of the well-known genes involved in early B cell development (EBF1, E2A, Rag1, CXCR4, IL7R, EZH2, PAX5, FoxP1, STAT5), indicating that SOX4 might be functioning in early B lymphopoiesis through a novel mechanism. We next studied pro-B cell viability in SOX4 f/+ and SOX4 f/f Vav-Cre mice. We found that, when SOX4 was depleted, bone marrow pro-B cells, but not pre-pro-B cells, underwent remarkable apoptosis, as shown by increased annexin V staining. In accordance, the level of the antiapoptotic protein Bcl2 in SOX4 -deleted pro-B cells was much lower than that in control pro-B cells. Introduction of Bcl2 transgenic gene into the SOX4 conditional knockout mice decreased pro-B cell apoptosis and partially rescued the SOX4 -deficient B cell development. We also observed striking molecular communication between SOX4 and the c-Kit-mediated cell survival signaling pathway; after intraperitoneal injection of the c-Kit inhibitor imatinib, the apoptotic rate was much higher in SOX4 f/+ Vav-Cre mice than in SOX4+/+ mice, suggesting that reduction of SOX4 level sensitized the cells to the inhibitor. Our data suggest that SOX4 deletion markedly decreases pro-B cell viability by modulating Bcl2 and that the c-Kit signaling pathway and SOX4 function is interlinked. We are currently investigating SOX4 transcription program and the mechanism of SOX4 -induced Bcl2 protein reduction in progenitor B cells. Disclosures: No relevant conflicts of interest to declare.
Carlos S Moreno - One of the best experts on this subject based on the ideXlab platform.
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SOX4 regulates invasion of bladder cancer cells via repression of wnt5a
International Journal of Oncology, 2019Co-Authors: Josue D Moran, Hannah H Kim, Carlos S MorenoAbstract:Sry‑Related HMG‑BOX‑4 (SOX4) is a developmental transcription factor that is overexpressed in as many as 23% of bladder cancer patients; however, the role of SOX4 in bladder cancer tumorigenesis is not yet well understood. Given the many roles of SOX4 in embryonic development and the context‑dependent regulation of gene expression, in this study, we sought to determine the role of SOX4 in bladder cancer and to identify SOX4‑regulated genes that may contribute to tumorigenesis. For this purpose, we employed a CRISPR interference (CRISPRi) method to transcriptionally repress SOX4 expression in T24 bladder cancer cell lines, 'rescued' these cell lines with the lentiviral‑mediated expression of SOX4, and performed whole genome expression profiling. The cells in which SOX4 was knocked down (T24‑SOX4‑KD) exhibited decreased invasive capabilities, but no changes in migration or proliferation, whereas rescue experiments with SOX4 lentiviral vector restored the invasive phenotype. Gene expression profiling revealed 173 high confidence SOX4‑regulated genes, including WNT5a as a potential target of repression by SOX4. Treatment of the T24‑SOX4‑KD cells with a WNT5a antagonist restored the invasive phenotype observed in the T24‑scramble control cells and the SOX4 lentiviral‑rescued cells. High WNT5a expression was associated with a decreased invasion and WNT5a expression inversely correlated with SOX4 expression, suggesting that SOX4 can negatively regulate WNT5a levels either directly or indirectly and that WNT5a likely plays a protective role against invasion in bladder cancer cells.
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SOX4 interacts with plakoglobin in a wnt3a dependent manner in prostate cancer cells
BMC Cell Biology, 2011Co-Authors: Yu Heng Lai, Jessica Cheng, Dongmei Cheng, Mattie E Feasel, Kyle Den Beste, Junmin Peng, Asma Nusrat, Carlos S MorenoAbstract:SOX4 is a developmental transcription factor that is required for differentiation and proliferation in multiple tissues. SOX4 is overexpressed in many human malignancies, but the precise role of SOX4 in cancer progression is still not well understood. Thus, the identification of additional SOX4 binding partners is essential for elucidating the mechanism of SOX4-mediated effects in cancer progression. Here, we have adapted a one-step affinity purification method that enables rapid purification of SOX4 complexes via intracellular biotinylation of the amino-terminus of SOX4 to perform large-scale proteomics analysis. We have discovered that junction plakoglobin (JUP) interacts with SOX4 in both the cytosol and the nucleus and the interaction between SOX4 and plakoglobin is significantly increased when prostate and breast cancer cells are stimulated with WNT3A. Interactions between SOX4 and plakoglobin were further enhanced by the nuclear export inhibitor leptomycin B (LMB), suggesting that plakoglobin promotes nuclear export of SOX4. The SOX4-plakoglobin complex affected the expression of Wnt pathway target genes and SOX4 downstream targets, such as AXIN2, DICER1, and DHX9. In addition, SOX4 DNA binding activity to the promoters of DICER1, AXIN2, DHX9 and SOX4 itself was reduced by conditions that promote SOX4-plakoglobin complex formation. Conditions that enhanced SOX4-plakoglobin interactions resulted in reduced transcriptional activity of β-catenin luciferase reporters. These data suggest that this newly identified interaction between SOX4 and plakoglobin is inhibitory and provides new insights into the role of SOX4 in key pathways in cell proliferation, development, and cancer progression.
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SOX4 interacts with plakoglobin in a wnt3a dependent manner in prostate cancer cells
BMC Cell Biology, 2011Co-Authors: Yu Heng Lai, Jessica Cheng, Dongmei Cheng, Mattie E Feasel, Junmin Peng, Asma Nusrat, Kyle Den A Beste, Carlos S MorenoAbstract:Background SOX4 is a developmental transcription factor that is required for differentiation and proliferation in multiple tissues. SOX4 is overexpressed in many human malignancies, but the precise role of SOX4 in cancer progression is still not well understood. Thus, the identification of additional SOX4 binding partners is essential for elucidating the mechanism of SOX4-mediated effects in cancer progression.
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genome wide promoter analysis of the SOX4 transcriptional network in prostate cancer cells
Cancer Research, 2009Co-Authors: Christopher D Scharer, Colleen D Mccabe, Mohamed Aliseyed, Michael F Berger, Martha L Bulyk, Carlos S MorenoAbstract:SOX4 is a critical developmental transcription factor in vertebrates and is required for precise differentiation and proliferation in multiple tissues. In addition, SOX4 is overexpressed in many human malignancies, but the exact role of SOX4 in cancer progression is not well understood. Here, we have identified the direct transcriptional targets of SOX4 using a combination of genome-wide localization chromatin immunoprecipitation–chip analysis and transient overexpression followed by expression profiling in a prostate cancer model cell line. We have also used protein-binding microarrays to derive a novel SOX4-specific position-weight matrix and determined that SOX4 binding sites are enriched in SOX4-bound promoter regions. Direct transcriptional targets of SOX4 include several key cellular regulators, such as EGFR, HSP70, Tenascin C, Frizzled-5, Patched-1, and Delta-like 1. We also show that SOX4 targets 23 transcription factors, such as MLL, FOXA1, ZNF281, and NKX3-1. In addition, SOX4 directly regulates expression of three components of the RNA-induced silencing complex, namely Dicer, Argonaute 1, and RNA Helicase A. These data provide new insights into how SOX4 affects developmental signaling pathways and how these changes may influence cancer progression via regulation of gene networks involved in microRNA processing, transcriptional regulation, the TGFβ, Wnt, Hedgehog, and Notch pathways, growth factor signaling, and tumor metastasis. [Cancer Res 2009;69(2):709–17]
Claus C Stolt - One of the best experts on this subject based on the ideXlab platform.
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transcription factors sox5 and sox6 exert direct and indirect influences on oligodendroglial migration in spinal cord and forebrain
Glia, 2016Co-Authors: Tina Baroti, Michael Wegner, Yvonne Zimmermann, Anja Schillinger, Lina Liu, Petra Lommes, Claus C StoltAbstract:Transcription factors of the SoxD protein family have previously been shown to prevent precocious specification and terminal differentiation of oligodendrocyte progenitor cells in the developing spinal cord. Using mice with specific deletion of the SoxD proteins Sox5 and Sox6 in the central nervous system, we now show that SoxD proteins additionally influence migration of oligodendrocyte progenitors in the spinal cord as well as in the forebrain. In mutant mice, emigration of oligodendrocyte progenitors from the ventricular zone and colonization of the mantle zone are significantly delayed probably because of reduced expression of Pdgf receptor alpha and decreased responsiveness toward Pdgf-A as a main migratory cue. In addition to this direct cell-autonomous effect on Pdgf receptor alpha expression, SoxD proteins furthermore promote oligodendroglial migration by keeping the cells in an undifferentiated state and preventing a premature loss of their migratory capacity. This indirect effect becomes particularly important during late embryonic and early postnatal phases of oligodendroglial development. Finally, we show that Sox5 and Sox6 cooperate with Sox9 and Sox10 to activate Pdgf receptor alpha expression and thereby maintain oligodendrocyte progenitors in the immature state. This contrasts with their behavior on myelin genes where they antagonize the function of SoxE proteins. It argues that SoxD proteins can function either as repressors or as co-activators of SoxE proteins thereby modulating their function in a stage-specific manner.
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Sox13 functionally complements the related Sox5 and Sox6 as important developmental modulators in mouse spinal cord oligodendrocytes.
Journal of neurochemistry, 2015Co-Authors: Tina Baroti, Michael Wegner, Anja Schillinger, Claus C StoltAbstract:The role of transcription factor Sox13, which together with Sox5 and Sox6 belongs to the SoxD family, is only poorly characterized in central nervous system development. Therefore, we analysed whether Sox13 expression and function overlaps with or differs from that of its close relatives Sox5 and Sox6. In the developing mouse spinal cord, we found Sox13 predominantly expressed in neuroepithelial precursors, oligodendroglial and astroglial cells. The substantially overlapping expression with Sox5 and Sox6 in oligodendroglial cells prompted us to study potential roles during specification, lineage progression and differentiation of oligodendrocytes. In contrast to Sox5 and Sox6, Sox13 expression continues after differentiation and even increases in myelinating oligodendrocytes. Sox13 deletion did not interfere with oligodendroglial development, which was normal in Sox13-deficient mice. However, the premature differentiation of oligodendrocyte precursors triggered by loss of Sox6 was slightly more prominent in Sox6/Sox13 double-deficient mice. Sox13 can bind to the same sites in myelin gene promoters as Sox5 and Sox6 in vitro. Reporter gene assays furthermore reveal a similar antagonizing effect on Sox10-dependent transactivation of myelin gene promoters as previously shown for Sox5 and Sox6. This argues that Sox13 is functionally redundant with the other SoxD proteins and complements Sox5 and Sox6 in their role as important modulators of oligodendrocyte development. The transcription factor Sox13 is co-expressed with the related Sox5 and Sox6 in cells of the oligodendroglial lineage. By itself, it has little impact on oligodendrocyte development but supports Sox5 and Sox6 during the process as a functionally redundant transcription factor.
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from stem cells to neurons and glia a soxist s view of neural development
Trends in Neurosciences, 2005Co-Authors: Michael Wegner, Claus C StoltAbstract:During nervous system development, neural stem cells give rise to many different types of neurons and glia over an extended period. Little is known about the intrinsic factors that regulate stem-cell maintenance, decide whether neurons or glia are generated, or control terminal differentiation. Transcription factors of the Sox family provide important clues about the control of these events. In the central nervous system (CNS), Sox1, Sox2 and Sox3 are required for stem-cell maintenance, and their effects are counteracted by Sox21. Sox9, by contrast, alters the potential of stem cells from neurogenic to gliogenic, whereas Sox10 is essential for terminal oligodendrocyte differentiation. In the peripheral nervous system (PNS) the same Sox proteins have different functions, uncovering important developmental differences between the CNS and PNS.
Benoit De Crombrugghe - One of the best experts on this subject based on the ideXlab platform.
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the transcription factors l sox5 and sox6 are essential for cartilage formation
Developmental Cell, 2001Co-Authors: Patrick Smits, Richard R Behringer, Jennifer Mandel, Zhaoping Zhang, Jian Ming Deng, Benoit De Crombrugghe, Ping Li, Veronique LefebvreAbstract:Abstract L-Sox5 and Sox6 are highly identical Sry-related transcription factors coexpressed in cartilage. Whereas Sox5 and Sox6 single null mice are born with mild skeletal abnormalities, Sox5; Sox6 double null fetuses die with a severe, generalized chondrodysplasia. In these double mutants, chondroblasts poorly differentiate. They express the genes for all essential cartilage extracellular matrix components at low or undetectable levels and initiate proliferation after a long delay. All cartilages are thus extracellular matrix deficient and remain rudimentary. While chondroblasts in the center of cartilages ultimately activate prehypertrophic chondrocyte markers, epiphyseal chondroblasts ectopically activate hypertrophic chondrocyte markers. Thick intramembranous bone collars develop, but the formation of cartilage growth plates and endochondral bones is disrupted. L-Sox5 and Sox6 are thus redundant, potent enhancers of chondroblast functions, thereby essential for endochondral skeleton formation.
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L-Sox5, Sox6 and Sox9 control essential steps of the chondrocyte differentiation pathway.
Osteoarthritis and Cartilage, 2001Co-Authors: Veronique Lefebvre, Richard R Behringer, Benoit De CrombruggheAbstract:Abstract Objective This work was carried out to identify transcription factors controlling the differentiation of mesenchymal cells into chondrocytes. Design We delineated a cartilage-specific enhancer in the collagen type 2 gene (Col2a1) and identified transcription factors responsible for the activity of this enhancer in chondrocytes. We then analyzed the ability of these transcription factors to activate specific genes of the chondrocyte differentiation program and control cartilage formation in vivo . Results A 48-bp sequence in the first intron of Col2a1 drove gene expression specifically in cartilage in transgenic mouse embryos. The transcription factors L-Sox5, Sox6, and Sox9 bound and cooperatively activated this enhancer in vitro. They belong to the Sry-related family of HMG box DNA-binding proteins, which includes many members implicated in cell fate determination in various lineages. L-Sox5, Sox6, and Sox9 were coexpressed in all precartilaginous condensations in mouse embryos and continued to be expressed in chondrocytes until the cells underwent final hypertrophy. Whereas L-Sox5 and Sox6 are highly homologous proteins, they are totally different from Sox9 outside the HMG box domain. The three proteins cooperatively activated the Col2a1- and aggrecan genes in cultured cells. Heterozygous mutations in SOX9 in humans lead to campomelic dysplasia, a severe and generalized skeletal malformation syndrome. Embryonic cells with a homozygous Sox9 mutation were unable to form cartilage in vivo and activate essential chondrocyte marker genes. Preliminary data indicated that the mutation of Sox5 and Sox6 in the mouse led to severe skeletal malformations. Conclusions L-Sox5, Sox6, and Sox9 play essential roles in chondrocyte differentiation and, thereby, in cartilage formation. Their discovery will help to understand further the molecular mechanisms controlling chondrogenesis in vivo , uncover genetic mechanisms underlying cartilage diseases, and develop novel strategies for cartilage repair.
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The transcription factors L-Sox5 and Sox6 are essential for cartilage formation
Developmental cell, 2001Co-Authors: Patrick Smits, Richard R Behringer, Jennifer Mandel, Zhaoping Zhang, Jian Ming Deng, Benoit De Crombrugghe, Veronique LefebvreAbstract:Cartilages form the primary skeleton of vertebrate embryos, ensure its rapid growth, and provide mandatory templates upon which definitive bone is progressively laid down. Chondrogenesis is effected by a single cell type, the chondrocyte, which is of mesenchymal origin. Chondrocytes sequentially fulfill the different functions of cartilages by undergoing multiple steps of differentiation. Our main interest over recent years has been to identify transcription factors that specifically control the chondrocyte differentiation pathway. We found that L-Sox5, Sox6, and Sox9 were able to bind and activate a cartilage-specific enhancer of collagen type 2 gene (Col2a1) and were specifically co-expressed with Col2a1 during chondrogenesis in vivo. These data, supported by the notion that many Sox factors control cell fate determination in various lineages, strongly suggested that L-Sox5, Sox6, and Sox9 act as master chondrogenic transcription factors. This hypothesis was tested and confirmed by assessing the consequences of the null mutation of their genes on mouse embryo development. We review here these studies, with a special emphasis on LSoxS and Sox6. Akiyama and collaborators address the role of Sox9 in an accompanying review.
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transcriptional mechanisms of chondrocyte differentiation
Matrix Biology, 2000Co-Authors: Benoit De Crombrugghe, Richard R Behringer, Veronique Lefebvre, Shunichi Murakami, Wendong HuangAbstract:With the goal of identifying master transcription factors that control the genetic program of differentiation of mesenchymal cells into chondrocytes, we first delineated a 48-bp chondrocyte-specific enhancer element in the gene for proalpha1(II) collagen (Col2a1), an early and abundant marker of chondrocytes. Our experiments have demonstrated that the HMG-box-containing transcription factor, Sox9 which binds and activates this enhancer element, is required for chondrocyte differentiation and for expression of a series of chondrocyte-specific marker genes including Col2a1, Col9a2, Col11a2 and Aggrecan. In the absence of Sox9 the block in differentiation occurs at the stage of mesenchymal condensation, suggesting the hypothesis that Sox9 might also control expression of cell surface proteins needed for mesenchymal condensation. Since Sox9 also contains a potent transcription activation domain, it is a typical transcription factor. Two other members of the Sox family, L-Sox5 and Sox6, also bind to the 48-bp Col2a1 enhancer and together with Sox9 activate this enhancer as well as the endogenous Col2a1 and aggrecan genes. L-Sox5 and Sox6 have a high degree of sequence identity to each other and are likely to have redundant functions. Except for the HMG-box, L-Sox5 and Sox6 have no similarity to Sox9 and, hence, are likely to have a complementary function to that of Sox9. Our experiments suggest the hypothesis that, like Sox9, Sox5 and Sox6 might also be needed for chondrocyte differentiation. Other experiments, have provided evidence that the Sox9 polypeptide and the Sox9 gene are targets of signaling molecules that are known to control discrete steps of chondrogenesis in the growth plate of endochondral bones. Protein kinase A (PKA) phosphorylation of Sox9 increases its DNA binding and transcriptional activity. Since PKA-phosphorylated-Sox9 is found in the prehypertrophic zone of the growth plate, the same location where the gene for the receptor of the parathyroid hormone-related peptide (PTHrP) is expressed and since PTHrP signaling is mediated by cyclic AMP, we have hypothesized that Sox9 is a target for PTHrP signaling. Other experiments have also shown that fibroblast growth factors (FGFs) increase the expression of Sox9 in chondrocytes in culture and that this activation is mediated by the mitogen-activated protein kinase pathway. These results favor the hypothesis that in achondroplasia, a disease caused by activating mutations in FGF receptor 3, there might also be an abnormally high Sox9 expression.
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A new long form of Sox5 (L-Sox5), Sox6 and Sox9 are coexpressed in chondrogenesis and cooperatively activate the type II collagen gene
The EMBO journal, 1998Co-Authors: Veronique Lefebvre, Benoit De CrombruggheAbstract:Transcripts for a new form of Sox5, called L-Sox5, and Sox6 are coexpressed with Sox9 in all chondrogenic sites of mouse embryos. A coiled-coil domain located in the N-terminal part of L-Sox5, and absent in Sox5, showed >90% identity with a similar domain in Sox6 and mediated homodimerization and heterodimerization with Sox6. Dimerization of L-Sox5/Sox6 greatly increased efficiency of binding of the two Sox proteins to DNA containing adjacent HMG sites. L-Sox5, Sox6 and Sox9 cooperatively activated expression of the chondrocyte differentiation marker Col2a1 in 10T1/2 and MC615 cells. A 48 bp chondrocyte-specific enhancer in this gene, which contains several HMG-like sites that are necessary for enhancer activity, bound the three Sox proteins and was cooperatively activated by the three Sox proteins in non-chondrogenic cells. Our data suggest that L-Sox5/Sox6 and Sox9, which belong to two different classes of Sox transcription factors, cooperate with each other in expression of Col2a1 and possibly other genes of the chondrocytic program.
Patrick Smits - One of the best experts on this subject based on the ideXlab platform.
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synovial joint morphogenesis requires the chondrogenic action of sox5 and sox6 in growth plate and articular cartilage
Developmental Biology, 2010Co-Authors: Patrick Smits, Yu Han, Amber Silvester, Alfredo Penzomendez, Bogdan Dumitriu, Carol A De La Motte, David M Kingsley, Veronique LefebvreAbstract:The mechanisms underlying synovial joint development remain poorly understood. Here we use complete and cell-specific gene inactivation to identify the roles of the redundant chondrogenic transcription factors Sox5 and Sox6 in this process. We show that joint development aborts early in complete mutants (Sox5−/−6−/−). Gdf5 and Wnt9a expression is punctual in articular progenitor cells, but Sox9 downregulation and cell condensation in joint interzones are late. Joint cell differentiation is unsuccessful, regardless of lineage, and cavitation fails. Sox5 and Sox6 restricted expression to chondrocytes in wild-type embryos and continued Erg expression and weak Ihh expression in Sox5−/−6−/− growth plates suggest that growth plate failure contribute to this Sox5−/−6−/− joint morphogenesis block. Sox5/6 inactivation in specified joint cells and chondrocytes (Sox5fl/fl6fl/flCol2Cre) also results in a joint morphogenesis block, whereas Sox5/6 inactivation in specified joint cells only (Sox5fl/fl6fl/flGdf5Cre) results in milder joint defects and normal growth plates. Sox5fl/fl6fl/flGdf5Cre articular chondrocytes remain undifferentiated, as shown by continued Gdf5 expression and pancartilaginous gene downregulation. Along with Prg4 downregulation, these defects likely account for joint tissue overgrowth and incomplete cavitation in adult mice. Together, these data suggest that synovial joint morphogenesis relies on essential roles for Sox5/6 in promoting both growth plate and articular chondrocyte differentiation.
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generation of mice harboring a sox6 conditional null allele
Genesis, 2006Co-Authors: Bogdan Dumitriu, Patrick Smits, Veronique LefebvreAbstract:SOX4 belongs to the family of Sry-related HMG box transcription factors, which specify cell fate and differentiation in many lineages. SOX4 is widely expressed in the embryo and controls such processes as neuronal tissue, lymphocyte, heart, and bone development. SOX4-null mice die at embryonic day 14 from heart malformation. This early lethality has therefore limited studies on SOX4 functions. We show here that we have generated mice harboring a SOX4 conditional null allele (SOX4fl+) by flanking the entire coding region with loxP sites. SOX4fl+/fl+ mice are indistinguishable from wildtype mice and produce the wildtype SOX4 protein at a normal level. SOX4fl+ is efficiently converted into a null allele (SOX4fl-) by Cre recombinase in somatic and germ-line cells, and SOX4fl-/fl- embryos die from the same heart defects as SOX4-/- mice. This SOX4 conditional null allele will thus be a valuable tool to further uncovering SOX4 functions in various processes in vivo.
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Sox5 and Sox6 are needed to develop and maintain source, columnar, and hypertrophic chondrocytes in the cartilage growth plate
The Journal of cell biology, 2004Co-Authors: Patrick Smits, Srijeet Mitra, Veronique LefebvreAbstract:Sox5 and Sox6 encode Sry-related transcription factors that redundantly promote early chondroblast differentiation. Using mouse embryos with three or four null alleles of Sox5 and Sox6, we show that they are also essential and redundant in major steps of growth plate chondrocyte differentiation. Sox5 and Sox6 promote the development of a highly proliferating pool of chondroblasts between the epiphyses and metaphyses of future long bones. This pool is the likely cellular source of growth plates. Sox5 and Sox6 permit formation of growth plate columnar zones by keeping chondroblasts proliferating and by delaying chondrocyte prehypertrophy. They allow induction of chondrocyte hypertrophy and permit formation of prehypertrophic and hypertrophic zones by delaying chondrocyte terminal differentiation induced by ossification fronts. They act, at least in part, by down-regulating Ihh signaling, Fgfr3, and Runx2 and by up-regulating Bmp6. In conclusion, Sox5 and Sox6 are needed for the establishment of multilayered growth plates, and thereby for proper and timely development of endochondral bones.
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Sox5 and Sox6 are required for notochord extracellular matrix sheath formation, notochord cell survival and development of the nucleus pulposus of intervertebral discs
Development (Cambridge England), 2003Co-Authors: Patrick Smits, Veronique LefebvreAbstract:The notochord has major roles in vertebral column formation: indirectly by inducing sclerotome cell differentiation; and directly by forming the nucleus pulposus of intervertebral discs. Sox5 and Sox6 encode Sry-related HMG box transcription factors that act redundantly to promote chondroblast differentiation in all cartilages of the mouse embryo. We show that Sox5 and Sox6 are expressed in the notochord cell lineage and required for notochord late development. In Sox5(-/-)/Sox6(-/-) embryos, the notochord formed a typical rod-like structure. It fulfilled its inductive functions, as indicated by expression of sonic hedgehog and sclerotome specification. However, the notochord failed to become surrounded with an extracellular matrix sheath. This phenotype was associated with a downregulation of extracellular matrix genes, including the genes for collagen 2, aggrecan and perlecan in both notochord cells and surrounding chondrocytic cells of presumptive inner annuli and vertebral bodies. The mutant notochord then underwent an aberrant, fatal dismantling after sclerotome cell migration. Its cells became removed first from intervertebral spaces and then from vertebral bodies, and it progressively underwent apoptosis. Meanwhile, the development of inner annuli and vertebral bodies was dramatically impaired. Consequently, the vertebral column of Sox5(-/-)/Sox6(-/-) fetuses consisted of a very deficient cartilage and was devoid of nuclei pulposi. In Sox5(-/-)/Sox6(+/-) and more severely in Sox5(+/-)/Sox6(-/-) embryos, the notochord sheath was thinner, but cells survived. By birth, nuclei pulposi were rudimentary, and its cells poorly swelled and still expressing sonic hedgehog. Hence, Sox5 and Sox6 are required for notochord extracellular matrix sheath formation, notochord cell survival and formation of nuclei pulposi. Through these roles and essential roles in cartilage formation, they are central transcriptional regulators of vertebral column development.
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the transcription factors l sox5 and sox6 are essential for cartilage formation
Developmental Cell, 2001Co-Authors: Patrick Smits, Richard R Behringer, Jennifer Mandel, Zhaoping Zhang, Jian Ming Deng, Benoit De Crombrugghe, Ping Li, Veronique LefebvreAbstract:Abstract L-Sox5 and Sox6 are highly identical Sry-related transcription factors coexpressed in cartilage. Whereas Sox5 and Sox6 single null mice are born with mild skeletal abnormalities, Sox5; Sox6 double null fetuses die with a severe, generalized chondrodysplasia. In these double mutants, chondroblasts poorly differentiate. They express the genes for all essential cartilage extracellular matrix components at low or undetectable levels and initiate proliferation after a long delay. All cartilages are thus extracellular matrix deficient and remain rudimentary. While chondroblasts in the center of cartilages ultimately activate prehypertrophic chondrocyte markers, epiphyseal chondroblasts ectopically activate hypertrophic chondrocyte markers. Thick intramembranous bone collars develop, but the formation of cartilage growth plates and endochondral bones is disrupted. L-Sox5 and Sox6 are thus redundant, potent enhancers of chondroblast functions, thereby essential for endochondral skeleton formation.