Initiation of cyp26a1 Expression in the Zebrafish Anterior Neural Plate by a Novel Cis-Acting Element

AbstractPrimary neurulation is the process by which the neural tube, the central nervous system precursor, is formed from the neural plate. Incomplete neural tube closure occurs frequently, yet underlying causes remain poorly understood. Developmental studies in amniotes and amphibians have identified hingepoint and neural fold formation as key morphogenetic events and hallmarks of primary neurulation, the disruption of which causes neural tube defects. In contrast, the mode of neurulation in teleosts has remained highly debated. Teleosts are thought to have evolved a unique mode of neurulation, whereby the neural plate infolds in absence of hingepoints and neural folds, at least in the hindbrain/trunk where it has been studied. Using high-resolution imaging and time-lapse microscopy, we show here the presence of these morphological landmarks in the zebrafish anterior neural plate. These results reveal similarities between neurulation in teleosts and other vertebrates and hence the suitability of zebrafish to understand human neurulation.

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A gene regulatory network that underlies the derivation of the anterior neural plate from the epiblast

Developmental Biology ◽

10.1016/j.ydbio.2010.05.445 ◽

2010 ◽

Vol 344 (1) ◽

pp. 495

Author(s):

Makiko Iwafuchi-Doi ◽

Tatsuya Takemoto ◽

Yuzo Yoshida ◽

Isao Matsuo ◽

Jun Aruga ◽

...

Keyword(s):

Gene Regulatory Network ◽

Regulatory Network ◽

Neural Plate ◽

Gene Regulatory ◽

Anterior Neural Plate

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Identification of an evolutionarily conserved 110 base-pair cis-acting regulatory sequence that governs Wnt-1 expression in the murine neural plate

Development ◽

10.1242/dev.125.14.2735 ◽

1998 ◽

Vol 125 (14) ◽

pp. 2735-2746 ◽

Cited By ~ 3

Author(s):

D.H. Rowitch ◽

Y. Echelard ◽

P.S. Danielian ◽

K. Gellner ◽

S. Brenner ◽

...

Keyword(s):

Base Pair ◽

Regulatory Element ◽

Regulatory Region ◽

Neural Plate ◽

Homologous Region ◽

Regulatory Sequence ◽

Embryonic Mouse ◽

Cis Acting ◽

Evolutionarily Conserved

The generation of anterior-posterior polarity in the vertebrate brain requires the establishment of regional domains of gene expression at early somite stages. Wnt-1 encodes a signal that is expressed in the developing midbrain and is essential for midbrain and anterior hindbrain development. Previous work identified a 5.5 kilobase region located downstream of the Wnt-1 coding sequence which is necessary and sufficient for Wnt-1 expression in vivo. Using a transgenic mouse reporter assay, we have now identified a 110 base pair regulatory sequence within the 5.5 kilobase enhancer, which is sufficient for expression of a lacZ reporter in the approximate Wnt-1 pattern at neural plate stages. Multimers of this element driving Wnt-1 expression can partially rescue the midbrain-hindbrain phenotype of Wnt-1(−/−) embryos. The possibility that this region represents an evolutionarily conserved regulatory module is suggested by the identification of a highly homologous region located downstream of the wnt-1 gene in the pufferfish (Fugu rubripes). These sequences are capable of appropriate temporal and spatial activation of a reporter gene in the embryonic mouse midbrain; although, later aspects of the Wnt-1 expression pattern are absent. Genetic evidence has implicated Pax transcription factors in the regulation of Wnt-1. Although Pax-2 binds to the 110 base pair murine regulatory element in vitro, the location of the binding sites could not be precisely established and mutation of two putative low affinity sites did not abolish activation of a Wnt-1 reporter transgene in vivo. Thus, it is unlikely that Pax proteins regulate Wnt-1 by direct interactions with this cis-acting regulatory region. Our analysis of the 110 base pair minimal regulatory element suggests that Wnt-1 regulation is complex, involving different regulatory interactions for activation and the later maintenance of transgene expression in the dorsal midbrain and ventral diencephalon, and at the midbrain-hindbrain junction.

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Inductive interactions direct early regionalization of the mouse forebrain

Development ◽

10.1242/dev.124.14.2709 ◽

1997 ◽

Vol 124 (14) ◽

pp. 2709-2718 ◽

Cited By ~ 68

Author(s):

K. Shimamura ◽

J.L. Rubenstein

Keyword(s):

Sonic Hedgehog ◽

Bone Morphogenetic Proteins ◽

Molecular Mechanisms ◽

Neural Plate ◽

Gene Encoding ◽

Prechordal Plate ◽

Optic Vesicles ◽

The Central Nervous System ◽

Anterior Neural Plate ◽

Anterior Posterior

The cellular and molecular mechanisms that regulate regional specification of the forebrain are largely unknown. We studied the expression of transcription factors in neural plate explants to identify tissues, and the molecules produced by these tissues, that regulate medial-lateral and local patterning of the prosencephalic neural plate. Molecular properties of the medial neural plate are regulated by the prechordal plate perhaps through the action of Sonic Hedgehog. By contrast, gene expression in the lateral neural plate is regulated by non-neural ectoderm and bone morphogenetic proteins. This suggests that the forebrain employs the same medial-lateral (ventral-dorsal) patterning mechanisms present in the rest of the central nervous system. We have also found that the anterior neural ridge regulates patterning of the anterior neural plate, perhaps through a mechanism that is distinct from those that regulate general medial-lateral patterning. The anterior neural ridge is essential for expression of BF1, a gene encoding a transcription factor required for regionalization and growth of the telencephalic and optic vesicles. In addition, the anterior neural ridge expresses Fgf8, and recombinant FGF8 protein is capable of inducing BF1, suggesting that FGF8 regulates the development of anterolateral neural plate derivatives. Furthermore, we provide evidence that the neural plate is subdivided into distinct anterior-posterior domains that have different responses to the inductive signals from the prechordal plate, Sonic Hedgehog, the anterior neural ridge and FGF8. In sum, these results suggest that regionalization of the forebrain primordia is established by several distinct patterning mechanisms: (1) anterior-posterior patterning creates transverse zones with differential competence within the neural plate, (2) patterning along the medial-lateral axis generates longitudinally aligned domains and (3) local inductive interactions, such as a signal(s) from the anterior neural ridge, further define the regional organization.

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