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Development of the Tetrapod Limb
Limb Anatomy
The Limb Bud
Hox Gene Specification of Limb Skeleton Identity
- From proximal to distal: Hox genes in the limb
Determining What Kind of Limb to Form and Where to Put It
- Specifying the limb fields
- Induction of the early limb bud
Outgrowth: Generating the Proximal-Distal Axis of the Limb
- The apical ectodermal ridge
- Specifying the limb mesoderm: Determining the proximal-distal polarity
- Turing’s model: A reaction-diffusion mechanism of proximal-distal limb development
Specifying the Anterior-Posterior Axis
- Sonic hedgehog defines a zone of polarizing activity
- Specifying digit identity by Sonic hedgehog
- Sonic hedgehog and FGFs: Another positive feedback loop
- Hox genes are part of the regulatory network specifying digit identity
Generating the Dorsal-Ventral Axis
Cell Death and the Formation of Digits and Joints
- Sculpting the autopod
- Forming the joints
Evolution by Altering Limb Signaling Centers