The effects of cyclopamine on the ontogeny of fibroblast growth factor 8 mRNA expression during embryonic development of the chick limb

The formation of the vertebrate limb is a complex and tightly regulated developmental process. Outgrowth and patterning of the limb depends on two signaling centers in the limb bud, the Apical Ectodermal Ridge (AER) and the Zone of Polarizing Activity (ZPA). Outgrowth of the limb is controlled by the AER, which expresses the signals for Fibroblast Growth Factors, particularly Fibroblast Growth Factor 8 (FGF‐8). Anterior/posterior patterning of the limb is controlled by the ZPA, which expresses Sonic Hedge Hog (Shh). Previous studies have shown that both FGF‐8 and Shh signaling are crucial for limb development and outgrowth, as well as the expression of each other. In zebrafish, Shh mutants demonstrated a reduction in FGF signaling as well as a truncated limb. The aim of this study was to determine the mRNA expression pattern of FGF‐8 during limb development of the chicken (E 3–15) and the effect of cyclopamine, an inhibitor of Shh, on FGF‐8 mRNA expression using RT‐PCR. Although FGF‐8 expression was maintained in both the treated and untreated embryos throughout limb development, chicks exposed to cyclopamine demonstrated truncated limbs, consistent with previous data. Our data suggests that FGF‐8 expression is not affected by cyclopamine treatment. Future studies will investigate expression patterns of other genes, like BTRC, DLX‐5 and DLX‐6 that are involved in chick limb development after cyclopamine treatment. Sources for this research were provided by Lander University.