Organogensis

VI.1 COORDINATORS
VI.2 PARTICIPANTS
VI.3 SUMMARY
VI.4 INTRODUCTION
VI.5 SPECIFIC AIMS
VI.6 BACKGROUND AND SIGNIFICANCE
VI.7 THEORETICAL FRAMEWORK
VI.8 PRELIMINARY RESULTS
VI.9 RESEARCH DESIGN AND METHODS

• VI.9.ii Limb Development
  • VI.9.ii.a Overview
  • VI.9.ii.b Computational Approach
  • VI.9.ii.c Subprojects
    • VI.9.ii.c.1 Subproject 1 — Role of fibronectin in precartilage condensations
      • VI.9.ii.c.1.i Experiments
      • VI.9.ii.c.1.ii CPM simulation of condensation
    • VI.9.ii.c.2 Subproject 2 — Activator-inhibitor interactions in skeletal pattern formation
      • VI.9.ii.c.2.i Overview
      • VI.9.ii.c.2.ii Background and significance
      • VI.9.ii.c.2.iii Hypothesis
      • VI.9.ii.c.2.iv Models
        • VI.9.ii.c.2.iv.a Cellular automata simulation of reaction-diffusion plus haptotaxis
    • VI.9.ii.c.3 Subproject 3 —Viscoelasticity of limb bud tissues
    • VI.9.ii.c.4 Subproject 4 — The Genetic Control of Limb Development
      • VI.9.ii.c.4.i Introduction
      • VI.9.ii.c.4.ii Goal
      • VI.9.ii.c.4.iii Animal and Tissue Models
      • VI.9.ii.c.4.iv Experimental Approach
    • VI.9.ii.c.5 Subproject 5 — Complete model for avian chondrogenesis
      • VI.9.ii.c.5.i Overview
      • VI.9.ii.c.5.ii Background
      • VI.9.ii.c.5.iii Hypothesis
      • VI.9.ii.c.5.iv Model and preliminary results
      • VI.9.ii.c.5.v Plan
• [ Complete VI.9 Outline ]

VI.10 RELATIONSHIP TO CYTOSKELETON (PROJECT 2) AND BIOLOGICAL NETWORKS (PROJECT 1)
VI.11 TIMELINE

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VI.9.ii Limb Development:

VI.9.ii.a Overview:

We will concentrate on several aspects of limb development:

1. Subproject 1 - Adhesive interactions involved in mediating precartilage mesenchymal condensations. We will concentrate on cell-fibronectin interactions, and overexpress one or more fibronectin functional domains by transfection of mRNA. We will assay morphological effects by qualitative and quantitative analysis of condensation formation in vitro.
2. Subproject 2 - Activator-inhibitor interactions in skeletal pattern formation. We will draw on ongoing work in the Newman laboratory on the activating role for chondrogenesis of members of the TGF-ß family of growth factors (Leonard et al., 1991; Downie and Newman, 1994, 1995) and the role of FGF receptor 2 in mediating lateral inhibition (Moftah et al., 2002).
3. Subproject 3 - Measurement of the viscoelastic properties of limb bud mesenchyme. The Forgacs laboratory will extend their development of instrumentation and theory for such measurements (Foty et al., 1994, 1996; Forgacs et al., 1998).
4. Subproject 4 - Genes and signaling molecules involved in limb development. The CRBM will use expression profiling and analysis of transgenic animals to identify and characterize genes that specify amphibian limb regeneration and its relationship to embryonic development.
5. Subproject 5 - Finally, we will attempt to build a complete model for chondrogenesis during limb formation.

VI.9.ii.b Computational Approach:

Our computer simulations of limb development will employ the CompuCell software we have developed to implement condensation formation, activator-inhibitor interactions and shape regulation of the developing limb bud. We will integrate computation and experiment extensively. In particular, the parameter choices for the various fields in the CPM depend on experimental data: the fibronectin transfection experiments and tissue viscosity experiments we describe below, will provide inputs for the haptotactic module of the model describing mesenchymal condensation. Ongoing work on the kinetics of fibronectin gene expression response to TGF-β and FGF-2 and FGF-8 assayed by quantitative PCR will help specify parameters for the reaction-diffusion pattern formation module. We have already implemented some of this plan: see section VI.9.ii.d for a brief description and pictures of simulation results.