We have investigated the temporal and the causal basis of blood tissue specification in the chick embryo. Earlier workers have shown that the prospective blood-forming area is specified in a horseshoe-shaped area at the posterior side of the embryo. We found that cultured explants from the posterior marginal zone at stages XI to XIII (consisting of the posterior marginal zone and part of Koller's sickle) have a high propensity to form haemoglobin (Hb), which could be inhibited at stage XI by adding antibody against basic fibroblast growth factor (bFGF) to the neutral culture medium; this treatment had no effect from stage XII onwards. The same result was found when whole embryos were cultured with an antiserum raised against bFGF, or with heparin. In another series of experiments, we found that cultured pieces from the inner-core of stage XIII epiblasts (with or without hypoblast tissue) were able to form Hb, whereas inner-core pieces from the pre-hypoblast stages, namely stages X and XI, did not form Hb. The capacity to form Hb, however, could be conferred upon the inner-core pieces from stage X epiblasts if bFGF at a concentration of 75–150 ng/ml was added to the culture medium. Furthermore, and most pertinently, the capacity to form Hb could be conferred on stage X inner-core pieces when they were co-cultured with hypoblast from a stage XIII embryo in a sandwich explant. Thus the inductive role of the hypoblast appears to be mediated via bFGF.(ABSTRACT TRUNCATED AT 250 WORDS)

REFERENCES

Azar
Y.
,
Eyal-Giladi
H.
(
1979
)
Marginal zone cells- the primitive streak-inducing component of the primary hypoblast in the chick.
J. Embryol. Exp. Morph
52
,
79
88
Beddington
R. S. P.
,
Smith
J. C.
(
1993
)
Control of vertebrate gastrulation: inducing signals and responding genes.
Current Opinion in Genetics and Development
3
,
655
661
Eyal-Giladi
H.
,
Debby
A.
,
Harel
N.
(
1992
)
The posterior section of the chick's area pellucida and its involvement in hypoblast and primitive streak formation.
Development
116
,
819
830
Eyal-Giladi
H.
,
Kochav
S.
(
1976
)
From cleavage to primitive streak formation: A complementary normal table and a new look at the first stages of the development of the chick. I. General morphology.
Dev. Biol
49
,
321
337
Flamme
I.
,
Risau
W.
(
1992
)
Induction of vasculogenesis and hemopoiesis in vitro.
Development
116
,
435
439
Gordon-Thomson
C.
,
Salm
N.
,
Fabian
B. C.
(
1991
)
Fibroblast growth factor can neutralize the inhibitory effect of heparin on erythropoiesis but not on primitive streak formation in chick embryos.
South African Journal of Science
87
,
227
233
Green
J. B. A.
,
Howes
G.
,
Symes
K.
,
Cooke
J.
,
Smith
J. C.
(
1990
)
The biological effects of XTC-MIF: quantitative comparison with Xenopus bFGF.
Development
108
,
173
183
Green
J. B. A.
,
New
H. V.
,
Smith
J. C.
(
1992
)
Responses of embryonic Xenopus cells to activin and FGF are separated by multiple dose thresholds and correspond to distinct axes of the mesoderm.
Cell
71
,
731
739
Hamburger
V.
,
Hamilton
H. L.
(
1951
)
A series of normal stages in the development of the chick embryo.
J. Morphol
88
,
49
92
Jessell
T. M.
,
Melton
D. A.
(
1992
)
Diffusible factors in vertebrate embryonic induction.
Cell
68
,
257
270
Kessel
J.
,
Fabian
B. C.
(
1985
)
Graded morphogenetic patterns during the development of the extraembryonic blood system and coelom of the chick blastoderm: A scanning electron microscope and light microscope study.
Amer. J. Anat
173
,
99
112
Kessel
J.
,
Fabian
B. C.
(
1986
)
The pluripotency of the extraembryonic mesodermal cells of the early chick blastoderm: Effects of the AP and AOV environments.
Dev. Biol
116
,
319
327
Kessel
J.
,
Fabian
B. C.
(
1987
)
Inhibitory and stimulatory influences on mesodermal erythropoiesis in the early chick blastoderm.
Development
101
,
45
49
Khaner
O.
,
Mitrani
E.
,
Eyal-Giladi
H.
(
1985
)
Developmental potencies of area opaca and marginal zone areas of early chick blastoderms.
J. Embryol. Exp. Morph
89
,
235
241
Kimelman
D.
,
Christian
J. L.
,
Moon
R. T.
(
1992
)
Synergistic principles of development: overlapping patterning systems in Xenopus mesoderm induction.
Development
116
,
1
9
Mitrani
E.
,
Gruenbaum
Y.
,
Shohat
H.
,
Ziv
T.
(
1990
)
Fibroblast growth factor during mesoderm induction in the early chick embryo.
Development
109
,
387
393
Mitrani
E.
,
Ziv
T.
,
Thomsen
G.
,
Shimoni
Y.
,
Melton
D. A.
,
Bril
A.
(
1990
)
Activin can induce the formation of axial structures and is expressed in the hypoblast of the chick.
Cell
63
,
495
501
New
D. A. T.
(
1955
)
A new technique for the cultivation of the chick embryo in vitro.
J. Embryol. Exp. Morph
3
,
320
331
O'Brien
B. R. A.
(
1960
)
The presence of haemoglobin within the nucleus of the embryonic chick erythroblast.
Exp. Cell Res
21
,
226
228
Ruiz i Altaba
A.
,
Melton
D. A.
(
1989
)
Interaction between peptide growth factors and homeobox genes in the establishment of antero-posterior polarity in frog embryos.
Nature
341
,
33
38
Slack
J. M. W.
,
Darlington
B. G.
,
Heath
J. K.
,
Godsave
S. F.
(
1987
)
Mesoderm induction in early Xenopus embryos by heparin-binding growth factors.
Nature
326
,
197
200
Stern
C. D.
(
1990
)
The marginal zone and its contribution to the hypoblast and primitive streak of the chick embryo.
Development
109
,
667
682
Stern
C. D.
,
Hatada
Y.
,
Selleck
M. A. J.
,
Storey
K. G.
(
1992
)
Relationships between mesoderm induction and the embryonic axes in chick and frog embryos.
Development
1992
,
151
156
Wilt
F. H.
(
1965
)
Erythropoiesis in the chick embryo: The role of endoderm.
Science
147
,
1588
1590
Wilt
F. H.
(
1974
)
The beginnings of erythropoiesis in the yolk sac of the chick embryo.
Ann. N.Y. Acad. Sci
241
,
99
112
Zagris
N.
(
1982
)
Hypoblast induction of multiple area vasculosae, and stabilization of the area opaca vasculosa in young chick blastoderm.
J. Embryol. Exp. Morph
68
,
115
126
Ziv
T.
,
Shimoni
Y.
,
Mitrani
E.
(
1992
)
Activin can generate ectopic axial structures in chick blastoderm explants.
Development
115
,
689
694
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