Before limb development begins, FGF10 expression becomes restricted to the proliferating mesenchymal cells of the lateral plate mesoderm, which form the limb bud and become limb mesenchyme.
•
WNT2B and WNT8C stabilize this FGF10 expression in the forelimb and hindlimb, respectively.
•
FGF10 = Initially, Tbx proteins induce secretion of FGF10 by cells in the lateral plate mesoderm.
•
#Placement of FGF10-containing beads beneath chick ectodermal cells results in the formation a limb bud, AER, ZPA and, subsequently, an entire limb.
•
#Knocking out Tbx4 or Tbx5 knockout prevents FGF10 expression in the lateral plate mesoderm in mice.The Hox pathway may affect Tbx expression, which in turn affects FGF10 expression.
FGF10 |
This FGF10 expression stimulates WNT3 expression in the above ectodermal cells – resulting in formation of the apical ectodermal ridge (AER) as well as inducing FGF8 expression.
•
Also induces the mesenchymal cells to secrete FGF10, which acts through WNT3A to sustain the AER’s expression of FGF8.
•
Later, FGF10 expression is restricted to the developing limb mesenchyme, where it is stabilized by WNT8C or WNT2B.