Amaya et al (1993)

FGF signalling in the early specification of mesoderm in Xenopus

E. Amaya, P.A. Stein, T.J. Musci and M.W. Kirschner

Development 118:477-87 (1993) (Full Article, 204K)

Abstract

We have examined the role of FGF signalling in the development of muscle and notochord and in

the expression of early mesodermal markers in Xenopus embryos. Disruption of the FGF signalling

pathway by expression of a dominant negative construct of the FGF receptor (XFD) generally

results in gastrulation defects that are later evident in the formation of the trunk and tail, though head

structures are formed nearly normally. These defects are reflected in the loss of notochord and

muscle. Even in embryos that show mild defects and gastrulate properly, muscle formation is

impaired, suggesting that morphogenesis and tissue differentiation each depend on FGF. The XFD

protein inhibits the expression of the immediate early gene brachyury throughout the marginal zone,

including the dorsal side (see Mesoderm Formation ); it does not, however, inhibit the dorsal lip

marker goosecoid, which isexpressed in the first involuting mesoderm at the dorsal side that will

underlie the head. The XFD protein also inhibits Xpo expression, an immediate early marker of

ventral and lateral mesoderm. These results suggest that FGF is involved in the earliest events of

most mesoderm induction that occur before gastrulation and that the early dorsal mesoderm is

already composed of two cell populations that differ in their requirements for FGF.