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Development, Vol 126, Issue 17 3769-3779, Copyright © 1999 by Company of Biologists
JOURNAL ARTICLES |
F Ristoratore, M Carl, K Deschet, L Richard-Parpaillon, D Boujard, J Wittbrodt, D Chourrout, F Bourrat and JS Joly
Laboratoire de Genetique des Poissons, INRA, France. ristorat@jouy. inra.fr
In vertebrates, the engrailed genes are expressed at early neurula stage in a narrow stripe encompassing the midbrain-hindbrain boundary (MHB), a region from which a peculiar structure, the isthmus, is formed. Knock-out experiments in mice demonstrated that these genes are essential for the development of this structure and of its derivatives. In contrast, little is known about the effect of an overexpression of engrailed genes in vertebrate development. Here we report the isolation of Ol-eng2, a medaka fish (Oryzias latipes) engrailed gene. We have monitored the effects of its widespread expression following mRNA injections in 1- and 2-cell medaka and Xenopus embryos. We found that the ectopic expression of Ol-eng2 predominantly results in an altered development of the anterior brain, including an inhibition of optic vesicle formation. No change in the patterns of mesencephalic and telencephalic markers were observed. In contrast, expressions of markers of the diencephalon were strongly repressed in injected embryos. Furthermore, the endogenous Ol-eng2, Pax2, Wnt1 and Fgf8, which are essential components of the MHB genetic cascade, were ectopically expressed in this region. Therefore, we propose that Ol-eng2 induces de novo formation of an isthmus-like structure, which correlates with the development of ectopic midbrain structures, including optic tectum. A competence of the diencephalon to change to a midbrain fate has been demonstrated in isthmic graft experiments. Our data demonstrate that this change can be mimicked by ectopic engrailed expression alone.
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E. Matsunaga, I. Araki, and H. Nakamura Role of Pax3/7 in the tectum regionalization Development, October 15, 2001; 128(20): 4069 - 4077. [Abstract] [Full Text] [PDF]
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A Liu and A. Joyner EN and GBX2 play essential roles downstream of FGF8 in patterning the mouse mid/hindbrain region Development, January 1, 2001; 128(2): 181 - 191. [Abstract] [PDF]
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A Louvi and M Wassef Ectopic engrailed 1 expression in the dorsal midline causes cell death, abnormal differentiation of circumventricular organs and errors in axonal pathfinding Development, January 9, 2000; 127(18): 4061 - 4071. [Abstract] [PDF]
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M Carl and J Wittbrodt Graded interference with FGF signalling reveals its dorsoventral asymmetry at the mid-hindbrain boundary Development, January 12, 1999; 126(24): 5659 - 5667. [Abstract] [PDF]
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