Calcium Signaling and Cell Fate Determination During Neural Induction in Amphibian Embryos
Experiments performed with isolated ectoderm explants from Xenopus laevis embryos suggest that neural determination is a “by default” mechanism, which occurs when bone morphogenetic proteins (BMPs) are antagonized by extracellular antagonists. BMPs are re
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Calcium Signaling and Cell Fate Determination During Neural Induction in Amphibian Embryos
M. Moreau . S. E. Webb . I. Ne´ant . A. L. Miller . C. Leclerc
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Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
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Calcium Is Involved in the Choice Between Neural and Epidermal Fate . . . . . . . . . . . . . . . . . . . . . . . . 4
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Dihydropyridine-Sensitive Ca2+ Channels and Neural Induction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
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Imaging Ca2+ Transients During Neural Induction in Intact Amphibian Embryos . . . . . . . . . . . . . . . Ca2+ Signaling Activity Begins at the Blastula Stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ca2+ Activity Was Found to be Restricted Exclusively to the Dorsal Ectoderm . . . . . . . . . . . . . . . . . . . . . In Intact Embryos, Inhibition of Calcium Signaling Disrupts Neural Induction . . . . . . . . . . . . . . . . . . .
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5 Are There Ca2+-Sensitive Target Genes? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 5.1 Identification of New Ca2+ Target Genes Involved in Neural Induction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 6 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 6.1 How Gene Expression During Neural Induction Might Be Controlled by Ca2+ . . . . . . . . . . . . . . . . . . . . 10
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2009 Springer ScienceþBusiness Media, LLC.
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Calcium signaling and cell fate determination during neural induction in amphibian embryos
Abstract: Experiments performed with isolated ectoderm explants from Xenopus laevis embryos suggest that neural determination is a ‘‘by default’’ mechanism, which occurs when bone morphogenetic proteins (BMPs) are antagonized by extracellular antagonists. BMPs are responsible for the determination of epidermis. However, Ca2+ imaging of intact Xenopus embryos reveals patterns of Ca2+ transients that are generated via the activation of dihydropyridine (DHP)-sensitive Ca2+ channels in the dorsal ectoderm but not in the ventral ectoderm. These increases in the concentration of intracellular Ca2+ ([Ca2+]i) appear to be necessary and sufficient to direct the ectodermal cells toward a neural fate as increasing the [Ca2+]i artificially results in neuralization of the ectoderm. The construction of a subtractive cDNA library between untreated and caffeine-treated (i.e., to increase [Ca2+]i) ectoderms led to the identification of early Ca2+-sensitive target genes expressed in the neural territories. One of these genes, which encodes an arginine methyl transferase, was found to control the expression of the early proneural gene, Zic3. Here, we discuss the possibility of an alternativ
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