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Tetrapod Limb Development

Tetrapod Limb Development. Revisiting Axis specification Limb Formation and Growth Digit Formation. The tetrapod limb. stylopod. zeugopod. autopod. Limb Development in 4 dimensions. Proximal-Distal axis Anterior Posterior axis Dorsal-Lateral axis Time. Limb bud Specification.

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Tetrapod Limb Development

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  1. Tetrapod Limb Development • Revisiting Axis specification • Limb Formation and Growth • Digit Formation

  2. The tetrapod limb stylopod zeugopod autopod

  3. Limb Development in 4 dimensions • Proximal-Distal axis • Anterior Posterior axis • Dorsal-Lateral axis • Time

  4. Limb bud Specification • Limb bud fate mapping • Removal • Transplantation • Cell/Tissue tracking • Limb Field • Limb Bud formation • Hox genes: Hox 6 and Forelimb

  5. Limb Bud: Lateral plate mesoderm

  6. Multilimbs arise from dividing the bud

  7. Induction of limb bud formation • Fgf8 • Wnt2b/8c and Fgf10

  8. Induction of Limb Bud

  9. Forelimb or Hindlimb? • Tbx transcription factors: Tbx5 and Tbx4

  10. Genetic Regulation of early limb formation Hox6 Tbx5 Fgf10 For Forelimb

  11. Proximal-Distal Axis: Anterior ectodermal ridge

  12. AER and Limb bud development • AER major signaling center for forming Limb. • Ensures plasticity of mesenchyme • Maintains factors that determine A-P axis • Contacts A-P/D-V axis specifiers in order to inform cells how to differentiate • AER at distal margin of forming limb bud. • Makes direct contact with mesenchyme underneath (Progress zone-PZ).

  13. AER and Limb development

  14. Role of PZ in Limb growth/specification

  15. Limb Growth

  16. Reaction-diffusion model for proximal-distal limb specification

  17. A-P axis: Sonic Hedgehog • Zone of polarizing activity (ZPA) • Shh expressed in ZPA

  18. A-P axis: Sonic Hedgehog • Zone of polarizing activity (ZPA) • Shh expressed in ZPA

  19. Polydactyly: Shhoverexpression?

  20. Digit formation

  21. D-V axis: third and final axis • Wnt7a • Lim1-dorsal specification regulator

  22. Coordination of the 3 axes

  23. Sculpting the hand • BMPs initiate cell death in interdigital, interior, and anterior-posterior necrotic zones.

  24. Joint Formation

  25. Fgfs and dwarfism

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