proximal axis - Alternate prepattern model for outgrowth of...

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Proximal/Distal axis: Interactions between the ectoderm (AER) and underlying mesoderm (called the Progress Zone) allow: Outgrowth along the proximal/distal axis Survival of progress zone cells
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AER is required for many aspects of limb development
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Effects of removal of AER AER is required for limb outgrowth.
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The beauty of a peacock’s forelimbs! !
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Original progress zone model AER maintains proliferation and prevents differentiation Cell fate in the limb is determined by the length of time it spends in the progress zone
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Cells are pre-specified Each domain of cells expands over time Thus, AER removal causes death of the more distal cell types
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Unformatted text preview: Alternate prepattern model for outgrowth of the limb: Organization of the A-P axis in the limb The ZPA determines the A/P identity of the digits ZPA r Zone of Polarizing Activity What is responsible for the action of the ZPA? Retinoic acid? Or Sonic hedgehog (Shh), a target of Retinoic acid? 4) Morphogenesis a. coordinating the three axes b. forming digits and joints c. forming cartilages Dorsal-Ventral Axis of the Limb Unlike the other axes, the ectoderm regulates the dorsal-ventral polarity of limb mesoderm cells. Wnt7a is expressed in the dorsal ectoderm of the limb E 15.5- Forelimbs of mice t= tendons p=pads Dorsal ventral...
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This note was uploaded on 09/03/2009 for the course BIO 503 taught by Professor Z.zyang during the Fall '09 term at Nanjing University.

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proximal axis - Alternate prepattern model for outgrowth of...

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