Morphogenetic Interaction of Presumptive Neural and Mesodermal Cells Mixed in Different Ratios

Toivonen, Sulo; Saxén, Lauri

doi:10.1126/science.159.3814.539

Cited by 82 publications

(15 citation statements)

References 2 publications

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“…Since we find expression of xRAR-39 mRNA mainly in the cell layers adjacent to the anterior neural anlagen, the effect of RA on neural transformation might be mediated by the subjacent mesoderm. This notion is in agreement with many findings suggesting that the regional specification of the nervous system is directed by the underlying mesoderm (Eyal-Giladi 1954;Toivonen and Saxen 1968;Nieuwkoop 1973Nieuwkoop , 1985. Alternatively, xRAR-39 might be expressed in the anterior part of the neural plate before it is specified.…”

Section: The Effects Of Exogenous Ra On Embryogenesis Might Be Mediatsupporting

confidence: 79%

A retinoic acid receptor expressed in the early development of Xenopus laevis.

Ellinger‐Ziegelbauer

Dreyer²

1991

Genes Dev.

102

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We have isolated cDNAs coding for a putative retinoic acid receptor (RAR) of the 7-type from a Xenopus laevis neurula cDNA library. By transient cotransfection of COS cells with an expression vector and a reporter plasmid, this cDNA is shown to direct the synthesis of a retinoic acid-dependent transcription factor. In embryos of X. laevis, transcription of the corresponding gene is greatly enhanced during gastrulation and early neurulation. Two distinct areas with high abundance of RAR 7 mRNA are located at the anterior and at the posterior end of the neurula. The two maxima have emerged by the end of gastrulation and they become more pronounced during neurulation. At tailbud and early tadpole stages, the RAR transcripts are found mainly in the head mesenchyme and in the tailbud. The expression of this RAR is region-specific but not germ-layer-specific. The strong and stage-specific activation of zygotic transcription of this RAR gene, and the specific localization of the mRNA are consistent with the temporal and spatial pattern of retinoic acid sensitivity of X. laevis embryos. Therefore it is likely that the gene product mediates the effects of endogenous and of exogenous retinoic acid on early embryogenesis of Xenopus. The significance of these findings for the specification of the anteroposterior axis is discussed.[Key Words: Xenopus-, retinoic acid receptor; anteroposterior axis; in situ hybridization]

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Section: The Effects Of Exogenous Ra On Embryogenesis Might Be Mediatsupporting

confidence: 79%

A retinoic acid receptor expressed in the early development of Xenopus laevis.

Ellinger‐Ziegelbauer

Dreyer²

1991

Genes Dev.

102

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“…We believe that in these experiments, Xlim-1͞3m-generated anterior neural tissue may be posteriorized by the surrounding Xbraexpressing cells in the ventral equatorial zone in a situation akin to posterior dominance seen in earlier transplantation experiments (12), or in cell mixing experiments with anterior neural plate and posterior axial mesoderm (60).…”

Section: Discussionmentioning

confidence: 63%

Role of the Xlim-1 and Xbra genes in anteroposterior patterning of neural tissue by the head and trunk organizer

Taira

Saint-Jeannet

Dawid

1997

Proc. Natl. Acad. Sci. U.S.A.

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Anteroposterior patterning of neural tissue is thought to be directed by the axial mesoderm which is functionally divided into head and trunk organizer. The LIM class homeobox gene Xlim-1 is expressed in the entire axial mesoderm, whereas the distinct transcription factor Xbra is expressed in the notochord but not in the prechordal mesoderm. mRNA injection experiments showed that Xenopus animal explants (caps) expressing an activated form of Xlim-1 (a LIM domain mutant named 3m) induce anterior neural markers whereas caps coexpressing Xlim-1͞3m and Xbra induce posterior neural markers. These data indicate that, in terms of neural inducing ability, Xlim-1͞3m-expressing caps correspond to the head organizer and Xlim-1͞3m plus Xbracoexpressing caps to the trunk organizer. Thus the expression domains of Xlim-1 and Xbra correlate with, and possibly define, the functional domains of the organizer. In animal caps Xlim-1͞3m initiates expression of a neuralizing factor, chordin, whereas Xbra activates embryonic fibroblast growth factor (eFGF) expression, as reported previously; these factors could mediate the neural inducing and patterning effects that were observed. A dominant-negative FGF receptor (XFD) inhibits posteriorization by Xbra in a dose-dependent manner, supporting the suggestion that eFGF or a related factor has posteriorizing inf luence.

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“…It is evident what their conclusion was, though it was not the correct one. Interestingly, it was Toivonen and Saxén [58] who finally resolved the controversy between their and our hypothesis by combining disaggregated forebrain tissue from an early neurula with increasing amounts of chordamesoderm and actually observing the transformation of potential forebrain tissue into hindbrain and spinal cord. This proved the existence of the third, transforming inductive action.…”

Section: Reviewsmentioning

confidence: 99%

Short historical survey of pattern formation in the endo-mesoderm and the neural anlage in the vertebrates: the role of vertical and planar inductive actions

Nieuwkoop

1997

CMLS, Cell. mol. life sci.

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After some introductory remarks about vertical versus horizontal inductive interactions and about planar versus homoiogenetic induction, the author discusses: a) the historical development of the more recently studied endo-mesoderm induction in the Urodeles and in the anuran Xenopus laevis, b) the possible causal relationship between endo-mesoderm induction and the initiation of the gastrulation process, and c) the older history of the regional neural induction as initially studied in the Urodeles and only recently analysed in the anuran Xenopus laevis. The essential vertical interaction in the neural induction process both in urodelian and in anuran amphibians is emphasized.

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Morphogenetic Interaction of Presumptive Neural and Mesodermal Cells Mixed in Different Ratios

Cited by 82 publications

References 2 publications

A retinoic acid receptor expressed in the early development of Xenopus laevis.

A retinoic acid receptor expressed in the early development of Xenopus laevis.

Role of the Xlim-1 and Xbra genes in anteroposterior patterning of neural tissue by the head and trunk organizer

Short historical survey of pattern formation in the endo-mesoderm and the neural anlage in the vertebrates: the role of vertical and planar inductive actions

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