EFGF IS EXPRESSED IN THE DORSAL MIDLINE OF XENOPUS-LAEVIS

A detailed study of the expression pattern of embryonic fibroblast gro wth factor (eFGF) during early Xenopus development has been undertaken using whore-mount DIG in situ hybridization. We show that the zygotic expression of eFGF is activated in the mesoderm of the early gastrula and is first visualized as a ring around the blastopore, with signifi cantly higher levels of expression on the dorsal side of the embryo. A s gastrulation proceeds, eFGF transcripts become increasingly abundant in the dorsal blastopore lip. In the early neurula eFGF expression ca n be detected in the extreme posterior of the embryo around the closed blastopore and in the cells of the notochord. This latter result is s ignificant and represents the first report of a Xenopus FGF that is ex pressed in the notochord. In addition, we show that during gastrula an d neurula stages, expression of eFGF closely follows the expression of the Xenopus brachyury (Xbra) gene. During later development eFGF expr ession is localized to the tail-bud region and a stripe at the mid-bra in/hind-brain junction. These data provide further evidence that FGFs play an important role in regulating the expression of brachyury in th e developing mesoderm.