Regulation of limb development in frogs

Fibroblast growth factor (FGF) is a naturally occurring protein in the bodies of birds and mammals that is present in the limb developmental process. Connective tissue cells and embryonic skin cells in the forming limb secrete FGF. It works with secreted collagen and other extracellular matrix molecules that act as packing tissue to give shape to the body, This growth factor is a signal, which is responsible for keeping prospective limb cells undifferentiated, and dividing rapidly (Xiaoling and Weinstein, 1999). In order to learn whether this protein is also used in amphibians, I attempted to induce the growth of additional limbs in embryonic Xenopus laevis, the South African Clawed Frog (Figure 5). This experiment has been done successfully in chick embryos. It has also been recently noted that FGF is present in salamanders and frog limbs. Implantation of the growth factor into the early embryonic stages of the frog should induce signals from around the site to the proliferating tissue to initiate the formation of a limb bud.