FIGURE 14. A feedback loop between the AER and the ZPA.

FIGURE 14

A feedback loop between the AER and the ZPA. Shh is expressed in the ZPA in the posterior mesoderm of the limb bud. FGF4 is expressed in the posterior AER, while FGF8 is expressed throughout the AER. The continued expression of Shh depends on FGF signalling, while the expression of FGF4 requires Shh signals. Together, the ZPA and AER pattern the anterior–posterior and proximal–distal axes of the vertebrate limb.

From: Limb Development

Cover of FGF Signalling in Vertebrate Development
FGF Signalling in Vertebrate Development.
Pownall ME, Isaacs HV.
San Rafael (CA): Morgan & Claypool Life Sciences; 2010.
Copyright © 2010 by Morgan & Claypool Life Sciences.

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