Expression of Fgf4 during early development of the chick embryo

Fibroblast growth factor 4 (Fgf4) has been implicated as a regulator of mes oderm formation, posteriorisation, neural induction and neural patterning. Much of the evidence for this derives from studies in which exogenous FGF4 is applied to avian embryos. We have therefore examined expression of endog enous Fgf4 mRNA in the developing chick embryo at stages when these process es are occurring. Expression was detected in the primitive streak from the onset of gastrulation. Notably, transient expression of transcripts was fou nd in head process cells at the onset of neural plate formation and regiona lisation. Later, mRNA was detected in the presumptive posterior hindbrain a nd within the ventral midbrain. Fgf4 mRNA was also found in paraxial mesode rm underlying the posterior hindbrain, somites, branchial arches, limb buds and the tail bud. (C) 1999 Elsevier Science Ireland Ltd. All rights reserv ed.