XB-ART-13715Int J Dev Biol November 1, 1998; 42 (8): 1101-7.
Expression and functions of FGF-3 in Xenopus development.
We have analyzed the expression pattern of the Xenopus FGF-3 gene during early development and examined its biological activity in three different bioassays using Xenopus embryos. We show that from the early gastrula stage there is a domain of expression around the blastopore which becomes a posterior domain as the blastopore closes. An anterior ectodermal domain becomes detectable from mid-gastrula stages in the prospective hind-brain, and there are several later domains of expression: the midbrain-hindbrain junction, the otocyst, the pharyngeal pouches and the tailbud region. By using double whole-mount in situ hybridizations we show that the XFGF-3 expression in the brain is dynamically regulated both in time and space during development. The anterior domain of early neurula stage embryos corresponds to the prospective rhombomeres 3-5. By the time the neural tube is closed, XFGF-3 expression is restricted to r4 and later a new domain of expression is established at the midbrain/hindbrain junction. In addition, we show that, despite its difference in receptor specificity, XFGF-3 can induce the formation of mesoderm from animal caps similarly to other FGFs. It also displays a posteriorizing activity on whole embryos similar to other FGFs. Although the absence of maternal expression makes it unlikely that XFGF-3 is involved in mesoderm induction in vivo, its posterior domain of expression during gastrulation and its posteriorizing activity suggests that it participates in the maintenance of mesodermal gene expression and in the FGF mediated patterning of the anteroposterior axis during gastrulation.
PubMed ID: 9879707
Article link: Int J Dev Biol
Species referenced: Xenopus
Genes referenced: egr2 en2 fgf3 hoxb1 st13
Article Images: [+] show captions
|Figure 1. XFGF3 expression in the developing Xenopus embryo. (A) Vegetal view of an early gastrula stage embryo (st. 10.5): dorsal to the top. A faint staining IS detected in a complete ring around the blastopore with higher levels of expression visible dorsally. dl, dorsal blastopore lip. (B) Dorsovegetal view of a late gastrula stage embryo (st. 12.5) showing the periblastoporal expression of XFGF-3. Higher levels of XFGF-3 mRNA are present in the lateral and ventral aspects of the blastopore. Arrowheads point to the anterior stripe of expression that begins to be vIsible at this stage on each side of the neural plate. yp, yolk plug. (C-E) Early neurula stage embryos. (C,E) Dorsal views of a st13 and st 14 embryos, respectively (anterior to the left). Expression in the neural plate has become more prominent by this stage. A faint staining IS detected either side of the midline extending up to the anterior stripe (black arrowhead In C and D).(D) Posterior view of a st. 13 embryo showing XFGF-3 expression around the closed blastopore (bp). (F) Dorsal view of a cleared embryo at the end of the neurula stage (st. 20). The anterior stripe of XFGF-3 expression has become much narrower and has converged towards the midline, (G) Posterior view of a stage 20 embryo showing a strong expression in region lateral to the closed blastopore (bp) extending for some distance along the developing aXIS, (H,I) Tailbud stage embryo (St. 32). (H) Side view of the head region of a cleared embryo showing expression In the branchial arches (bra), in the OtiC vesicle (otv) and at the level of the midbrain/hindbrain junction (mhj). (I) Side view of the posterior region of a cleared embryo showing XFGF-3 expresslon in the tailbud in the chordoneural hinge (cnh) and in the postenor wall (pw) of the neurenteric canal. (J-L) Double whole-mount in situ hybridizations showing XFGF-3 and Krox 20 expression (blue and orange staining. respectively). (J) Early neurula stage embryo (st, 14). Krox 20 and XFGF-3 expression are found to overlap at the level of the prospectIVe rhombomere 3 of the hindbrain. At this stage Krox20 expression In the prospective rhombomere 5 IS only barely detectable (arrowhead), (K) Stage 15 embryo, XFGF-3 at this stage IS expressed in rhombomeres 3-5. (L) Stage 20 embryo. By the end of neurulation the domain of XFGF-3 expression has narrowed, being restricted to the prospectIVe rhombomere 4 (M) Double whole-mount In Situ hybridization showing XFGF-3 and HoxB1 (orange staining) expression In a stage 17 embryo. HoxB1 band of expression identity the prospective rhombomere 4. (N,O) Double whole-mount in situ hybridization showing En-2 (orange staining and XFGF-3 expression. (N) Neurula stage embryo (st. 16). Throughout neurulation the band of XFGF-3 expression lies posterior to that of En-2. (O) Side view of a tailbud stage embryo (Sf. 30). By tailbud stages XFGF-3 expression in the hindbrain has disappeared while a new domain of expressIon has arisen at the isthmus (arrowhead) that overlaps wIth that of En-2|
|Fig. 2. Effects of XFGF-3 overexpression. (A,C) Whole animal caps after three days In culture. (B,D) Sections of such animal caps. (A. B) Controls; (B,C) Induced animal caps from embryos that had been injected with 28 pg of XFGF-3 mRNA. epi, epidermis: ms, mesenchyme: mst mesothelium. mus, muscle. (E) Induced animal cap from an embryo injected with 14 pg of XFGF-3 mRNA showing a proctodeum like structure (prc), (F) High magnificatIOn of the same animal cap. (G)Top embryo is a control while the bottom six embryos have been injected with 35pg of XFGF-3 mRNA at the 2-cell stage. (H) Top embryo IS a control while the bottom six embryos have been Injected with 70pg mRNA at the 2-cell stage. (I,J) PBS or XFGF-3 soaked beads were implanted close to the left optiC vesicle of late neurula stage embryos. (I) The presence of the PBS bead (arrowhead) did not have any effect on the development of the eye of control embryos. (J) XFGF-3 beads affected the differentiation of the pigmented epithelium of the eye. Black arrowheads Point to the wide region of the pigmented epithelium where pigmentation IS absent. White arrowhead paints to the position of the implanted XFGF-3 bead. (K) Transverse section at the level of the trunk of a stage 40 embryo which had an XFGF-3 bead Implanted posteriorly at the early neural plate stage. The presence of the XFGF-3 bead has induced the formation of an ectopic otic vesicle (arrowhead),Sc spinal cord: nt, notochord. (L) Higher magnification view of the same specimen.|
|fgf3 (ibroblast growth factor 3) gene expression in the posterior axial mesoderm around the the closed blastopore (bp), referred to as the circumblastorporal collar, in a X. laevis embryo, NF stage 14,|