The Experts below are selected from a list of 294 Experts worldwide ranked by ideXlab platform

Koji Tamura - One of the best experts on this subject based on the ideXlab platform.

  • yap1 transcription regulator in the hippo signaling pathway is required for xenopus Limb Bud regeneration
    Developmental Biology, 2014
    Co-Authors: Shinichi Hayashi, Koji Tamura, Hitoshi Yokoyama
    Abstract:

    Abstract The Hippo signaling pathway is conserved from insects to mammals and is important for multiple processes, including cell proliferation, apoptosis and tissue homeostasis. Hippo signaling is also crucial for regeneration, including intercalary regeneration, of the whole body in the flatworm and of the leg in the cricket. However, its role in vertebrate epimorphic regeneration is unknown. Therefore, to identify principles of regeneration that are conserved among bilaterians, we investigated the role of Hippo signaling in the Limb Bud regeneration of an anuran amphibian, Xenopus laevis. We found that a transcription factor, Yap1, an important downstream effector of Hippo signaling, is upregulated in the regenerating Limb Bud. To evaluate Yap1׳s function in Limb Bud regeneration, we made transgenic animals that expressed a dominant-negative form of Yap under a heat-shock promoter. Overexpression of a dominant-negative form of Yap in tadpoles reduced cell proliferation, induced ectopic apoptosis, perturbed the expression domains of Limb-patterning genes including hoxa13, hoxa11, and shh in the regenerating Limb Bud. Transient expression of a dominant-negative Yap in transgenic tadpoles also caused Limb Bud regeneration defects, and reduced intercalary regeneration. These results indicate that Yap1 has a crucial role in controlling the Limb regenerative capacity in Xenopus, and suggest that the involvement of Hippo signaling in regeneration is conserved between vertebrates and invertebrates. This finding provides molecular evidence that common principles underlie regeneration across phyla, and may contribute to the development of new therapies in regenerative medicine.

  • Morphogenetic change of the Limb Bud in the hand plate formation.
    Journal of experimental zoology. Part B Molecular and developmental evolution, 2010
    Co-Authors: Kosei Sato, Ryohei Seki, Miyuki Noro, Hitoshi Yokoyama, Koji Tamura
    Abstract:

    The vertebrate hand plate is flattened and paddle shaped; that is, it is wide along the anteroposterior (AP) axis (thumb to little finger) and thin along the dorsoventral axis (back of hand to palm). To learn how the hand plate develops its three-dimensional architecture, we observed morphological changes in the distal Limb Bud of the chick embryo at stages 23-27 and the gecko embryo 11-13 days after oviposition. Cell population of the posterior distal Limb Bud expanded more than that of the anterior one in the chick embryo. Taken together with the observation that these two cell populations did not show significant differences in their expansion along the proximodistal axis, we propose that the cell population in the posterior Limb Bud contributes more to the morphogenetic increase along the AP axis, which widens the Limb Bud for the formation of the hand plate. Our observation that more mitoses were oriented anteroposteriorly than dorsoventrally in the chick embryo at around stage 25 suggests that the oriented cell division contributes to the morphogenetic increase along the AP axis.

  • Specification of cell fate along the proximal-distal axis in the developing chick Limb Bud.
    Development (Cambridge England), 2007
    Co-Authors: Kosei Sato, Yutaka Koizumi, Masanori Takahashi, Atsushi Kuroiwa, Koji Tamura
    Abstract:

    Pattern formation along the proximal-distal (PD) axis in the developing Limb Bud serves as a good model for learning how cell fate and regionalization of domains, which are essential processes in morphogenesis during development, are specified by positional information. In the present study, detailed fate maps for the Limb Bud of the chick embryo were constructed in order to gain insights into how cell fate for future structures along the PD axis is specified and subdivided. Our fate map revealed that there is a large overlap between the prospective autopod and zeugopod in the distal Limb Bud at an early stage (stage 19), whereas a Limb Bud at this stage has already regionalized the proximal compartments for the prospective stylopod and zeugopod. A clearer boundary of cell fate specifying the prospective autopod and zeugopod could be seen at stage 23, but cell mixing was still detectable inside the prospective autopod region at this stage. Detailed analysis of HOXA11 AND HOXA13 expression at single cell resolution suggested that the cell mixing is not due to separation of some different cell populations existing in a mosaic. Our findings suggest that a mixable unregionalized cell population is maintained in the distal area of the Limb Bud, while the proximal region starts to be regionalized at the early stage of Limb development.

  • Characteristics of initiation and early events for muscle development in the Xenopus Limb Bud
    Developmental dynamics : an official publication of the American Association of Anatomists, 2005
    Co-Authors: Akira Satoh, Hiroyuki Ide, Kazuhiro Sakamaki, Koji Tamura
    Abstract:

    In Xenopus laevis, Limb Buds start to develop at a later point of the larval stage, prior to metamorphosis. This onset of Limb development in Xenopus is totally different from that in amniotes such as birds and mammals, in which Limb Buds emerge at an early stage of embryogenesis, in parallel with other organogenesis. We investigated Limb myogenesis in Xenopus, focusing on myogenic gene expression, myogenic ability of Limb Bud cells in the early stage, and the origin of myogenic precursor cells in the Limb Bud. The Xenopus early Limb Bud contains myoD/cardiac actin-positive and pax3/pax7-negative cells. Interestingly, results of transplantation experiments have revealed that this early Limb Bud contains myogenic precursor cells. In order to know the contribution of myogenic cells in somites to myogenic precursor cells in the early Limb Bud, we used a Cre-LoxP system for tracing over a long period. The results of fate tracing for myogenic cells in somites of the Xenopus embryo suggested that early-specified myogenic cells in somites do not contribute to Limb muscle in Xenopus. Taken together, the results suggest that Limb muscle development in Xenopus has characteristics of initiation and early events distinct from those of other vertebrate clades.

  • Apical ectodermal ridge induction by the transplantation of En-1-overexpressing ectoderm in chick Limb Bud
    Development growth & differentiation, 1998
    Co-Authors: Mikiko Tanaka, Koji Tamura, Yasuyo Shigetani, Sayaka Sugiyama, Harukazu Nakamura, Hiroyuki Ide
    Abstract:

    In the early chick embryo, the dorsal ventral (DV) boundary organizes the apical ectodermal ridge (AER) structure in the Limb Bud field. Here it is reported that Engrailed-1 (En-1), a homolog of the Drosophila segment polarity gene engrailed expressed in the ventral Limb ectoderm, participates in AER formation at the DV boundary of the Limb Bud. Restricted ectopic expression of En-1 in the dorsal side of the Limb Bud by transplantation of En-1-overexpressing ectoderm induces ectopic AER at the boundary of En-1-positive and -negative cells. The results suggest that En-1 is involved in AER formation at the DV boundary of the Limb Bud.

Rolf Zeller - One of the best experts on this subject based on the ideXlab platform.

  • Dynamic and self-regulatory interactions among gene regulatory networks control vertebrate Limb Bud morphogenesis
    Current topics in developmental biology, 2020
    Co-Authors: Aimée Zuniga, Rolf Zeller
    Abstract:

    Abstract Vertebrate Limb Bud outgrowth and patterning is controlled by two instructive signaling centers, the apical ectodermal ridge (AER) and the polarizing region in the posterior Limb Bud mesenchyme. Molecular analysis of Limb Bud development has identified a self-regulatory signaling system that operates between the AER and mesenchyme and orchestrates the dynamic progression of Limb Bud outgrowth and patterning. The first focus of this review are the gene regulatory networks (GRNs) and interactions that control the positioning of the fore- and hindLimb fields along the primary body axis, establish the initial axis polarity and control the precise positioning of the signaling centers. These early processes are largely controlled by activating and inhibiting interactions among types of transcriptional regulators expressed in specific territories. The second focus deals with the dynamic interactions among the GRNs that control Limb Bud patterning and outgrowth by responding to inputs from the self-regulatory Limb Bud signaling system. The final part describes the GRN interactions regulating digit morphogenesis and the Turing-type system that controls the periodicity of the digit ray pattern. This review highlights the significant progress made toward an integrative analysis and understanding of the morpho-regulatory systems that orchestrate patterning and outgrowth of vertebrate Limb Buds in time and space.

  • To BMP or not to BMP during vertebrate Limb Bud development.
    Seminars in cell & developmental biology, 2014
    Co-Authors: Emanuele Pignatti, Rolf Zeller, Aimée Zuniga
    Abstract:

    The analysis of vertebrate Limb Bud development provides insight of general relevance into the signaling networks that underlie the controlled proliferative expansion of large populations of mesenchymal progenitors, cell fate determination and initiation of differentiation. In particular, extensive genetic analysis of mouse and experimental manipulation of chicken Limb Bud development has revealed the self-regulatory feedback signaling systems that interlink the main morphoregulatory signaling pathways including BMPs and their antagonists. It this review, we showcase the key role of BMPs and their antagonists during Limb Bud development. This review provides an understanding of the key morphoregulatory interactions that underlie the highly dynamic changes in BMP activity and signal transduction as Limb Bud development progresses from initiation and setting-up the signaling centers to determination and formation of the chondrogenic primordia for the Limb skeletal elements.

  • shh propagates distal Limb Bud development by enhancing cyp26b1 mediated retinoic acid clearance via aer fgf signalling
    Development, 2011
    Co-Authors: Simone Probst, Rolf Zeller, Conradin Kraemer, Philippe Demougin, Rushikesh Sheth, Gail R Martin, Hidetaka Shiratori, Hiroshi Hamada, Dagmar Iber, Aimée Zuniga
    Abstract:

    The essential roles of SHH in anteroposterior (AP) and AER-FGF signalling in proximodistal (PD) Limb Bud development are well understood. In addition, these morphoregulatory signals are key components of the self-regulatory SHH/GREM1/AER-FGF feedback signalling system that regulates distal progression of Limb Bud development. This study uncovers an additional signalling module required for coordinated progression of Limb Bud axis development. Transcriptome analysis using Shh-deficient mouse Limb Buds revealed that the expression of proximal genes was distally extended from early stages onwards, which pointed to a more prominent involvement of SHH in PD Limb axis development. In particular, retinoic acid (RA) target genes were upregulated proximally, while the expression of the RA-inactivating Cyp26b1 enzyme was downregulated distally, pointing to increased RA activity in Shh-deficient mouse Limb Buds. Further genetic and molecular analysis established that Cyp26b1 expression is regulated by AER-FGF signalling. During initiation of Limb Bud outgrowth, the activation of Cyp26b1 expression creates a distal 'RA-free' domain, as indicated by complementary downregulation of a transcriptional sensor of RA activity. Subsequently, Cyp26b1 expression increases as a consequence of SHH-dependent upregulation of AER-FGF signalling. To better understand the underlying signalling interactions, computational simulations of the spatiotemporal expression patterns and interactions were generated. These simulations predicted the existence of an antagonistic AER-FGF/CYP26B1/RA signalling module, which was verified experimentally. In summary, SHH promotes distal progression of Limb development by enhancing CYP26B1-mediated RA clearance as part of a signalling network linking the SHH/GREM1/AER-FGF feedback loop to the newly identified AER-FGF/CYP26B1/RA module.

  • Vertebrate Limb Bud development : moving towards integrative analysis of organogenesis
    Nature reviews. Genetics, 2009
    Co-Authors: Rolf Zeller, Javier Lopez-rios, Aimée Zuniga
    Abstract:

    The Limb Bud is of paradigmatic value to understanding vertebrate organogenesis. Recent genetic analysis in mice has revealed the existence of a largely self-regulatory Limb Bud signalling system that involves many of the pathways that are known to regulate morphogenesis. These findings contrast with the prevailing view that the main Limb Bud axes develop largely independently of one another. In this Review, we discuss models of Limb development and attempt to integrate the current knowledge of the signalling interactions that govern Limb skeletal development into a systems model. The resulting integrative model provides insights into how the specification and proliferative expansion of the anteroposterior and proximodistal Limb Bud axes are coordinately controlled in time and space.

  • mutual genetic antagonism involving gli3 and dhand prepatterns the vertebrate Limb Bud mesenchyme prior to shh signaling
    Genes & Development, 2002
    Co-Authors: Pascal Te Welscher, Marian Fernandezteran, Marian A Ros, Rolf Zeller
    Abstract:

    The bHLH transcription factor dHAND is required for establishment of SHH signaling by the Limb Bud organizer in posterior mesenchyme, a step crucial to development of vertebrate paired appendages. We show that the transcriptional repressor GLI3 restricts dHAND expression to posterior mesenchyme prior to activation of SHH signaling in mouse Limb Buds. dHAND, in turn, excludes anterior genes such as Gli3 and Alx4 from posterior mesenchyme. Furthermore, genetic interaction of GLI3 and dHAND directs establishment of the SHH/FGF signaling feedback loop by restricting the BMP antagonist GREMLIN posteriorly. These interactions polarize the nascent Limb Bud mesenchyme prior to SHH signaling.

Aimée Zuniga - One of the best experts on this subject based on the ideXlab platform.

  • Dynamic and self-regulatory interactions among gene regulatory networks control vertebrate Limb Bud morphogenesis
    Current topics in developmental biology, 2020
    Co-Authors: Aimée Zuniga, Rolf Zeller
    Abstract:

    Abstract Vertebrate Limb Bud outgrowth and patterning is controlled by two instructive signaling centers, the apical ectodermal ridge (AER) and the polarizing region in the posterior Limb Bud mesenchyme. Molecular analysis of Limb Bud development has identified a self-regulatory signaling system that operates between the AER and mesenchyme and orchestrates the dynamic progression of Limb Bud outgrowth and patterning. The first focus of this review are the gene regulatory networks (GRNs) and interactions that control the positioning of the fore- and hindLimb fields along the primary body axis, establish the initial axis polarity and control the precise positioning of the signaling centers. These early processes are largely controlled by activating and inhibiting interactions among types of transcriptional regulators expressed in specific territories. The second focus deals with the dynamic interactions among the GRNs that control Limb Bud patterning and outgrowth by responding to inputs from the self-regulatory Limb Bud signaling system. The final part describes the GRN interactions regulating digit morphogenesis and the Turing-type system that controls the periodicity of the digit ray pattern. This review highlights the significant progress made toward an integrative analysis and understanding of the morpho-regulatory systems that orchestrate patterning and outgrowth of vertebrate Limb Buds in time and space.

  • To BMP or not to BMP during vertebrate Limb Bud development.
    Seminars in cell & developmental biology, 2014
    Co-Authors: Emanuele Pignatti, Rolf Zeller, Aimée Zuniga
    Abstract:

    The analysis of vertebrate Limb Bud development provides insight of general relevance into the signaling networks that underlie the controlled proliferative expansion of large populations of mesenchymal progenitors, cell fate determination and initiation of differentiation. In particular, extensive genetic analysis of mouse and experimental manipulation of chicken Limb Bud development has revealed the self-regulatory feedback signaling systems that interlink the main morphoregulatory signaling pathways including BMPs and their antagonists. It this review, we showcase the key role of BMPs and their antagonists during Limb Bud development. This review provides an understanding of the key morphoregulatory interactions that underlie the highly dynamic changes in BMP activity and signal transduction as Limb Bud development progresses from initiation and setting-up the signaling centers to determination and formation of the chondrogenic primordia for the Limb skeletal elements.

  • shh propagates distal Limb Bud development by enhancing cyp26b1 mediated retinoic acid clearance via aer fgf signalling
    Development, 2011
    Co-Authors: Simone Probst, Rolf Zeller, Conradin Kraemer, Philippe Demougin, Rushikesh Sheth, Gail R Martin, Hidetaka Shiratori, Hiroshi Hamada, Dagmar Iber, Aimée Zuniga
    Abstract:

    The essential roles of SHH in anteroposterior (AP) and AER-FGF signalling in proximodistal (PD) Limb Bud development are well understood. In addition, these morphoregulatory signals are key components of the self-regulatory SHH/GREM1/AER-FGF feedback signalling system that regulates distal progression of Limb Bud development. This study uncovers an additional signalling module required for coordinated progression of Limb Bud axis development. Transcriptome analysis using Shh-deficient mouse Limb Buds revealed that the expression of proximal genes was distally extended from early stages onwards, which pointed to a more prominent involvement of SHH in PD Limb axis development. In particular, retinoic acid (RA) target genes were upregulated proximally, while the expression of the RA-inactivating Cyp26b1 enzyme was downregulated distally, pointing to increased RA activity in Shh-deficient mouse Limb Buds. Further genetic and molecular analysis established that Cyp26b1 expression is regulated by AER-FGF signalling. During initiation of Limb Bud outgrowth, the activation of Cyp26b1 expression creates a distal 'RA-free' domain, as indicated by complementary downregulation of a transcriptional sensor of RA activity. Subsequently, Cyp26b1 expression increases as a consequence of SHH-dependent upregulation of AER-FGF signalling. To better understand the underlying signalling interactions, computational simulations of the spatiotemporal expression patterns and interactions were generated. These simulations predicted the existence of an antagonistic AER-FGF/CYP26B1/RA signalling module, which was verified experimentally. In summary, SHH promotes distal progression of Limb development by enhancing CYP26B1-mediated RA clearance as part of a signalling network linking the SHH/GREM1/AER-FGF feedback loop to the newly identified AER-FGF/CYP26B1/RA module.

  • Vertebrate Limb Bud development : moving towards integrative analysis of organogenesis
    Nature reviews. Genetics, 2009
    Co-Authors: Rolf Zeller, Javier Lopez-rios, Aimée Zuniga
    Abstract:

    The Limb Bud is of paradigmatic value to understanding vertebrate organogenesis. Recent genetic analysis in mice has revealed the existence of a largely self-regulatory Limb Bud signalling system that involves many of the pathways that are known to regulate morphogenesis. These findings contrast with the prevailing view that the main Limb Bud axes develop largely independently of one another. In this Review, we discuss models of Limb development and attempt to integrate the current knowledge of the signalling interactions that govern Limb skeletal development into a systems model. The resulting integrative model provides insights into how the specification and proliferative expansion of the anteroposterior and proximodistal Limb Bud axes are coordinately controlled in time and space.

  • gli3 xt and formin ld participate in the positioning of the polarising region and control of posterior Limb Bud identity
    Development, 1999
    Co-Authors: Aimée Zuniga, Rolf Zeller
    Abstract:

    During initiation of Limb-Bud outgrowth in vertebrate embryos, the polarising region (Limb-Bud organizer) is established upon activation of the Sonic Hedgehog (SHH) signaling molecule at the posterior Limb-Bud margin. Another hallmark of establishing anteroposterior Limb-Bud identities is the colinear activation of HoxD genes located at the 5′ end of the cluster (5′HoxD genes). The unique and shared functions of Gli3 and formin in these determinative events were genetically analyzed using single and double homozygous Extra-toes (Xt; disrupting Gli3) and Limb deformity (ld; disrupting formin) mouse embryos. Analysis of the Limb skeletal phenotypes reveals genetic interaction of the two genes. In addition to loss of digit identity and varying degrees of polydactyly, proximal skeletal elements are severely shortened in Xt;ld double homozygous Limbs. The underlying molecular defects affect both establishment of the polarising region and posterior Limb-Bud identity. In particular, the synergism between Gli3- and formin-mediated mesenchyme-AER interactions positions the SHH signaling center at the posterior Limb-Bud margin. The present study shows that establishment and positioning of the polarising region is regulated both by restriction of Shh through Gli3 and its positive feedback regulation through formin. Concurrently, Gli3 functions independently of formin during initial posterior nesting of 5′HoxD domains, whereas their subsequent distal restriction and anterior expansion depends on genetic interaction of Gli3 and formin.

Hiroyuki Ide - One of the best experts on this subject based on the ideXlab platform.

  • Characteristics of initiation and early events for muscle development in the Xenopus Limb Bud
    Developmental dynamics : an official publication of the American Association of Anatomists, 2005
    Co-Authors: Akira Satoh, Hiroyuki Ide, Kazuhiro Sakamaki, Koji Tamura
    Abstract:

    In Xenopus laevis, Limb Buds start to develop at a later point of the larval stage, prior to metamorphosis. This onset of Limb development in Xenopus is totally different from that in amniotes such as birds and mammals, in which Limb Buds emerge at an early stage of embryogenesis, in parallel with other organogenesis. We investigated Limb myogenesis in Xenopus, focusing on myogenic gene expression, myogenic ability of Limb Bud cells in the early stage, and the origin of myogenic precursor cells in the Limb Bud. The Xenopus early Limb Bud contains myoD/cardiac actin-positive and pax3/pax7-negative cells. Interestingly, results of transplantation experiments have revealed that this early Limb Bud contains myogenic precursor cells. In order to know the contribution of myogenic cells in somites to myogenic precursor cells in the early Limb Bud, we used a Cre-LoxP system for tracing over a long period. The results of fate tracing for myogenic cells in somites of the Xenopus embryo suggested that early-specified myogenic cells in somites do not contribute to Limb muscle in Xenopus. Taken together, the results suggest that Limb muscle development in Xenopus has characteristics of initiation and early events distinct from those of other vertebrate clades.

  • Apical ectodermal ridge induction by the transplantation of En-1-overexpressing ectoderm in chick Limb Bud
    Development growth & differentiation, 1998
    Co-Authors: Mikiko Tanaka, Koji Tamura, Yasuyo Shigetani, Sayaka Sugiyama, Harukazu Nakamura, Hiroyuki Ide
    Abstract:

    In the early chick embryo, the dorsal ventral (DV) boundary organizes the apical ectodermal ridge (AER) structure in the Limb Bud field. Here it is reported that Engrailed-1 (En-1), a homolog of the Drosophila segment polarity gene engrailed expressed in the ventral Limb ectoderm, participates in AER formation at the DV boundary of the Limb Bud. Restricted ectopic expression of En-1 in the dorsal side of the Limb Bud by transplantation of En-1-overexpressing ectoderm induces ectopic AER at the boundary of En-1-positive and -negative cells. The results suggest that En-1 is involved in AER formation at the DV boundary of the Limb Bud.

  • Pattern formation in dissociated Limb Bud mesenchyme in vitro and in vivo
    Wound repair and regeneration : official publication of the Wound Healing Society [and] the European Tissue Repair Society, 1998
    Co-Authors: Hiroyuki Ide, Koji Tamura, Hitoshi Yokoyama, Tetsuya Endo, Minoru Omi, Nauyoki Wada
    Abstract:

    A fundamental process in Limb Bud development is the formation of position-dependent cartilage pattern. Cells of the distal mesenchyme maintain positional values as the expression pattern of transcription factors, for example, hox genes, which induce position-related cell differentiation and cell surface differences. Cultured, dissociated Limb Bud mesenchymal cells segregate from each other, and eventually form cartilage nodules. This sorting out is position-dependent, not cell-type dependent, suggesting that the positional values may be involved. Positional valves were found to be retained in Limb Bud recombinants. In the chick system, the expression of HoxA13 and HoxD12 was present in the distal half of stage 20 recombinants, whereas these markers were expressed throughout the stages 25 recombinants. In the Xenopus system, multiple digit formation was introduced in Limb recombinants, and a position-related relationship between regeneration potency and the multiple digit formation could be established. This determination of multiple digit formation with different stages of Limb mesenchyme may be useful in understanding mechanisms of the loss of vertebrate Limb regeneration potency.

  • MRC-5 cells induce the AER prior to the duplicated pattern formation in chick Limb Bud.
    Developmental biology, 1995
    Co-Authors: Sayuri Yonei, Koji Tamura, Kojune Ohsugi, Hiroyuki Ide
    Abstract:

    We have previously shown that MRC-5 cells induce the duplication of the chick Limb Bud following the implantation into the anterior Limb Bud only during pre-Limb-Bud stages. We now report the process of duplicated pattern formation caused by MRC-5 cells. The duplicated patterns are also formed following the implantation into the center of the Limb Bud and an excess apical ectodermal ridge (AER) with Msx2 expression is induced prior to these duplicated pattern formulations. Only after the implantation into the anterior leg Bud, the shh gene is expressed additionally in the anterior leg Bud and the mirror-symmetric duplication along the anteroposterior (A-P) axis is formed. The map of the polarizing activity in stage 21 embryo suggests that the high polarizing activity of the normal flank region is responsible for the changes in the A-P polarity when MRC-5 cells are grafted into the anterior leg Bud. These results indicate that MRC-5 cells induce the AER and that the excess AER produces the duplicated cartilage pattern of the Limb Bud.

  • Sorting out of Limb Bud cells in monolayer culture.
    The International journal of developmental biology, 1994
    Co-Authors: N Wada, Hiroyuki Ide
    Abstract:

    To examine differences in the surface properties of Limb Bud cells, we mixed cells from the progress zone at different stages or from different positions along proximodistal axis of chick and quail wing Limb Buds. To identify the origin of cells, a chick-specific antibody was used in a mixed culture of chick and quail cells, or cells from one of the stages were labeled with a fluorescent dye, PKH-26. Within 18 hours in mixed culture, cells segregated from each other and formed patches of various sizes. The process zone cells at early developmental stages mixed homogeneously with the cells from proximal region of old Limb Buds and the progress zone cells at late stages mixed homogeneously with the cells from distal region of the old Limb Buds. These results suggest that surface properties of cells in progress zone change during Limb Bud development and vary along the proximodistal and anteroposterior axes of the Limb Bud and that these differences in surface property may correspond to the positional values for Limb pattern formation.

Clifford J. Tabin - One of the best experts on this subject based on the ideXlab platform.

  • wnt5a jnk and fgf mapk pathways regulate the cellular events shaping the vertebrate Limb Bud
    Current Biology, 2010
    Co-Authors: Jerome Gros, Claudio Vinegoni, Paolo Fumene Feruglio, Ralph Weissleder, Clifford J. Tabin
    Abstract:

    Summary Background The vertebrate Limb is a classical model for understanding patterning of three-dimensional structures during embryonic development. Although decades of research have elucidated the tissue and molecular interactions within the Limb Bud required for patterning and morphogenesis of the Limb, the cellular and molecular events that shape the Limb Bud itself have remained largely unknown. Results We show that the mesenchymal cells of the early Limb Bud are not disorganized within the ectoderm as previously thought but are instead highly organized and polarized. Using time-lapse video microscopy, we demonstrate that cells move and divide according to this orientation. The combination of oriented cell divisions and movements drives the proximal-distal elongation of the Limb Bud necessary to set the stage for subsequent morphogenesis. These cellular events are regulated by the combined activities of the WNT and FGF pathways. We show that WNT5A/JNK is necessary for the proper orientation of cell movements and cell division. In contrast, the FGF/MAPK signaling pathway, emanating from the apical ectodermal ridge, does not regulate cell orientation in the Limb Bud but instead establishes a gradient of cell velocity enabling continuous rearrangement of the cells at the distal tip of the Limb. Conclusions Together, these data shed light on the cellular basis of vertebrate Limb Bud morphogenesis and uncover new layers to the sequential signaling pathways acting during vertebrate Limb development.

  • A cellular lineage analysis of the chick Limb Bud.
    Developmental biology, 2007
    Co-Authors: Richard V. Pearse, Paul Scherz, J.k. Campbell, Clifford J. Tabin
    Abstract:

    The chick Limb Bud has been used as a model system for studying pattern formation and tissue development for more than 50 years. However, the lineal relationships among the different cell types and the migrational boundaries of individual cells within the Limb mesenchyme have not been explored. We have used a retroviral lineage analysis system to track the fate of single Limb Bud mesenchymal cells at different times in early Limb development. We find that progenitor cells labeled at stage 19-22 can give rise to multiple cell types including clones containing cells of all five of the major lateral plate mesoderm-derived tissues (cartilage, perichondrium, tendon, muscle connective tissue, and dermis). There is a bias, however, such that clones are more likely to contain the cell types of spatially adjacent tissues such as cartilage/perichondrium and tendon/muscle connective tissue. It has been recently proposed that distinct proximodistal segments are established early in Limb development; however our analysis suggests that there is not a strict barrier to cellular migration along the proximodistal axis in the early stage 19-22 Limb Buds. Finally, our data indicate the presence of a dorsal/ventral boundary established by stage 16 that is inhibitory to cellular mixing. This boundary is demarcated by the expression of the LIM-homeodomain factor lmx1b.

  • Expression of Cre Recombinase in the developing mouse Limb Bud driven by a Prxl enhancer.
    Genesis (New York N.Y. : 2000), 2002
    Co-Authors: Malcolm Logan, Andras Nagy, Corrinne G Lobe, James F. Martin, Eric N. Olson, Clifford J. Tabin
    Abstract:

    Summary: We have used a Prx1 Limb enhancer to drive expression of Cre Recombinase in transgenic mice. This regulatory element leads to Cre expression throughout the early Limb Bud mesenchyme and in a subset of craniofacial mesenchyme. Crossing a murine line carrying this transgene to a reporter mouse harboring a floxed Cre-reporter cassette revealed that recombinase activity is first observed in the earliest Limb Bud at 9.5 dpc. By early to mid Bud stages at 10.5 dpc recombination is essentially complete in all mesenchymal cells in the Limb. Expression of the Cre recombinase was never detected in the Limb Bud ectoderm. The use of Prx1–Cre mice should facilitate analysis of gene function in the developing Limb. genesis 33:77–80, 2002. © 2002 Wiley-Liss, Inc.

  • analysis of hox gene expression in the chick Limb Bud
    Development, 1996
    Co-Authors: Craig E Nelson, Bruce A Morgan, Ann C Burke, Ed Laufer, E Dimambro, Lewis C Murtaugh, E Gonzales, Lino Tessarollo, Luis F Parada, Clifford J. Tabin
    Abstract:

    The vertebrate Hox genes have been shown to be important for patterning the primary and secondary axes of the developing vertebrate embryo. The function of these genes along the primary axis of the embryo has been generally interpreted in the context of positional specification and homeotic transformation of axial structures. The way in which these genes are expressed and function during the development of the secondary axes, particularly the Limb, is less clear. In order to provide a reference for understanding the role of the Hox genes in Limb patterning, we isolated clones of 23 Hox genes expressed during Limb development, characterized their expression patterns and analyzed their regulation by the signalling centers which pattern the Limb. The expression patterns of the Abd-B-related Hoxa and Hoxd genes have previously been partially characterized; however, our study reveals that these genes are expressed in patterns more dynamic and complex than generally appreciated, only transiently approximating simple, concentric, nested domains. Detailed analysis of these patterns suggests that the expression of each of the Hoxa and Hoxd genes is regulated in up to three independent phases. Each of these phases appears to be associated with the specification and patterning of one of the proximodistal segments of the Limb (upper arm, lower arm and hand). Interestingly, in the last of these phases, the expression of the Hoxd genes violates the general rule of spatial and temporal colinearity of Hox gene expression with gene order along the chromosome. In contrast to the Abd-B-related Hoxa and Hoxd genes, which are expressed in both the fore and hind Limbs, different sets of Hoxc genes are expressed in the two Limbs. There is a correlation between the relative position of these genes along the chromosome and the axial level of the Limb Bud in which they are expressed. The more 3′ genes are expressed in the fore Limb Bud while the 5′ genes are expressed in the hind Limb Bud; intermediate genes are transcribed in both Limbs. However, there is no clear correlation between the relative position of the genes along the chromosome and their expression domains within the Limb. With the exception of Hoxc-11, which is transcribed in a posterior portion of the hind Limb, Hoxc gene expression is restricted to the anterior/proximal portion of the Limb Bud. Importantly, comparison of the distributions of Hoxc-6 RNA and protein products reveals posttranscriptional regulation of this gene, suggesting that caution must be exercised in interpreting the functional significance of the RNA distribution of any of the vertebrate Hox genes. To understand the genesis of the complex patterns of Hox gene expression in the Limb Bud, we examined the propagation of Hox gene expression relative to cell proliferation. We find that shifts in Hox gene expression cannot be attributed to passive expansion due to cell proliferation. Rather, phase-specific Hox gene expression patterns appear to result from a context-dependent response of the Limb mesoderm to Sonic hedgehog. Sonic hedgehog (the patterning signal from the Zone of Polarizing Activity) is known to be able to activate Hoxd gene expression in the Limb. Although we find that Sonic hedgehog is capable of initiating and polarizing Hoxd gene expression during both of the latter two phases of Hox gene expression, the specific patterns induced are not determined by the signal, but depend upon the temporal context of the mesoderm receiving the signal. Misexpression of Sonic hedgehog also reveals that Hoxb-9, which is normally excluded from the posterior mesenchyme of the leg, is negatively regulated by Sonic hedgehog and that Hoxc-11, which is expressed in the posterior portion of the leg, is not affected by Sonic hedgehog and hence is not required to pattern the skeletal elements of the lower leg.

  • The initiation of the Limb Bud: Growth factors, Hox genes, and retinoids
    Cell, 1995
    Co-Authors: Clifford J. Tabin
    Abstract:

    Department of Genetics Harvard Medical School Boston, Massachusetts 02115 The undifferentiated vertebrate Limb Bud is a self- organizing system. If transplanted to a favorable ectopic location, the Limb Bud is capable of developing into a mor- phologically normal Limb (Harrison, 1918), and the ante- rior-posterior polarity of the transplanted Limb is deter- mined by the graft rather than the host environment. Great progress has recently been made in understanding the molecular steps by which pattern emerges within an undif- ferentiated Limb Bud (for recent reviews see Johnson et al., 1994; Tickle and Eichele, 1994). But what first initiates the formation of the Limb Bud? And what molecular steps provide the information necessary for polarized self- organization? Two recent papers (Charit~ et al., 1994; Cohn et al., 1995 [this issue of