Shiurba RA et al. (1991), Nuclear translocation of fibroblast growth fact...

XB-ART-24499

Development 1991 Oct 01;1132:487-93.

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Nuclear translocation of fibroblast growth factor during Xenopus mesoderm induction.

Shiurba RA , Jing N , Sakakura T , Godsave SF .

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Mesoderm induction, the earliest inductive cell-cell interaction in vertebrate embryogenesis, is thought to be mediated by polypeptide growth factors including fibroblast growth factor (FGF). Here we present an immunocytochemical analysis of FGF during mesoderm induction in Xenopus laevis. Antibodies to both basic and acidic FGF were immunoreactive with oocytes and early embryos. Immunostaining was predominantly intracellular and was concentrated in the marginal zone and vegetal pole throughout cleavage and blastula stages. In addition, basic FGF (bFGF) antibodies showed intense nuclear staining in these regions, at and following the mid-blastula transition, when embryonic transcription begins. Acidic FGF (aFGF) also appeared in some nuclei at these stages. Taken together the evidence suggests that FGF is prepositioned in mesoderm-forming regions and is actively involved in mesoderm induction in vivo.

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Species referenced: Xenopus laevis
Genes referenced: fgf1 fgf2 kcnt1
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	Fig. 1. Immunocytochemical localization of bFGF (A,C-G,I) and aFGF (B,J-L,O,P) in Xenopus laevis oocytes and embryos by Immunogold-silver staining. Endogenous cortical pigment always appears dark in the animal hemisphere. (A,E) 4- to 8-cell stage; (E) high power of bFGF in yolk-rich vegetal pole cytoplasm. (B,F) stage 8; (F) high power view of bFGF perinuclear ring. (C) stage 9. (D,G) stage 10; (G) high power view of bFGF in nuclei. (H) stage 10 normal rabbit IgG negative control. (I,J) ovary; (I) bFGF and (J) aFGF associated with oocyte yolk. Previtellogenic oocytes (arrows) are unstained. bFGF is present in follicle cells. (K,L) stage 9, stage 10 aFGF. (M,N) Positive controls, stage 8.5, animal pole; (M) anti-tubulin, (N) anti-mitochondria. (O,P) aFGF stage 10; (O) animal hemisphere, (P) marginal zone.
	Fig. 2. Immunocytochemical staining of mid-blastulae after solid-phase preabsorption of anti-bFGF antibody (R&D). (A) bFGF absorbed, (B) unabsorbed and (C) KLH absorbed.
	Fig. 3. Immunoblots of heparinbinding proteins from extracts of Xenopus laevis eggs and embryos. (Panel A) anti-Xenopus bFGF (Slack), (panel B) antibovine bFGF (R&D) and (Panel C) anti-bovine aFGF (Genzyme) antibodies were tested against the following antigens: bF, recombinant bovine bFGF (50 ng, Boehringer Mannheim); XbF, recombinant Xenopus bFGF (200ng); aF, aFGF purified from bovine brain (50 ng, R&D); heparin-binding proteins affinity purified from extracts of: UFE, unfertilized eggs and B, mid-late blastula stage embryos. Minor bands faintly stained by antibFGF above MT 29X103 were also present in control blots. Arrow at Mr 15 to 16X103 in panel B points to the immunoreactive band in UFE and blastula extracts.