... the margin of the bud. Mesenchyme and apical ridge do not expand in concert - the apical ridge extends more anteriorly. We used the fatemaps to investigate the relation-ship between cell lineage and elaboration of Hoxd-13 and Fgf-4 domains. Hoxd-13 and Fgf-4 are initially expressed posteriorly until about...

... limb. Retinoic acid and Sonic Hedgehog (SHH) can act as polarizing signals; when applied anteriorly in the limb bud, they induce mirror-image digit duplications and ectopic Bmp-2 expression in anterior mesenchyme. In addition, the two signals can activate Fgf-4 expression in anterior ridge and HoxD...

...Caroline N. Dealy; Robert A. Kosher ABSTRACT IGF-I, insulin, FGF-2 and FGF-4 have been implicated in the reciprocal interactions between the apical ectodermal ridge (AER) and underlying mesoderm required for outgrowth and patterning of the developing limb. To study further the roles of these growth...

... the expression of FGF-4 and FGF-6 while TGFβ-2 is expressed normally. Early sclerotomal markers, such as Pax-1 reveal no substantial reduction of sclerotome size. At E11.5 the condensing mesenchyme of the rib anlagen is considerably reduced in size in Myf-5 mutant mice. This may be caused by the lack of Myf-5...

..., a period during which Bmp-2 is activated but no shh or Fgf-4 expression could be detected. Our results suggest that there are two independent mechanisms for activating the HoxD complex, one polarising region-dependent and one independent, and that shh expression may not be necessary to maintain outgrowth...

... a defect in maintenance of Shh by the ld mutant AER. Fur-thermore, no Fgf-4 transcripts are detected in the ld mutant AER, whereas Fgf-8 transcripts remain expressed. However, Shh expression can be rescued by heterospecific grafting of ld mutant posterior mesenchyme under a wild-type chicken AER...

... of a number of genes thought to play a role in limb development. Most signifi-cantly, we find that although the AERs of ld limb buds express several AER markers, they do not express detectable levels of fibroblast growth factor 4 (fgf-4), which has been proposed to be the AER signal to the mesoderm. Thus we...

..., in the region immediately underlying that portion of the ridge in which the Fgf-4 gene is expressed. Using an in vitro culture system, we show that the ridge is required for both the induction and maintenance of Evx-1 expression in the distal mesenchyme. We also demonstrate that in the absence of the ridge, FGF...

...Lee Niswander; Gail R. Martin ABSTRACT Fgf-4 , initially isolated as a transforming gene from human tumors, is a member of the Fibroblast Growth Factor (FGF) family. It has previously been shown by northern blot hybridization analysis to be expressed in teratocarcinoma and embryonic stem cells...