Getting a handle on embryo limb development: Molecular interactions driving limb outgrowth and patterning

- Limb develops along proximal-distal-PD, anterior-posterior-AP & dorsal-ventral axes.
- The Integrated Space-Time model for coordinated PD/AP limb patterning is proposed.
- Limb molecular clock gene hairy2 is a crucial component of limb development.
- Feedback signaling module with self-terminating property terminates limb outgrowth.