Imaging patterns of calcium transients during neural induction in Xenopus laevis embryos.
Through the injection of f-aequorin (a calcium-sensitive bioluminescent reporter) into the dorsal micromeres of 8-cell stage Xenopus laevis embryos, and the use of a Photon Imaging Microscope, distinct patterns of calcium signalling were visualised during the gastrulation period. We present results to show that localised domains of elevated calcium were observed exclusively in the anterior dorsal part of the ectoderm, and that these transients increased in number and amplitude between stages 9 to 11, just prior to the onset of neural induction. During this time, however, no increase in cytosolic free calcium was observed in the ventral ectoderm, mesoderm or endoderm. The origin and role of these dorsal calcium-signalling patterns were also investigated. Calcium transients require the presence of functional L-type voltage-sensitive calcium channels. Inhibition of channel activation from stages 8 to 14 with the specific antagonist R(+)BayK 8644 led to a complete inhibition of the calcium transients during gastrulation and resulted in severe defects in the subsequent formation of the anterior nervous system. BayK treatment also led to a reduction in the expression of Zic3 and geminin in whole embryos, and of NCAM in noggin-treated animal caps. The possible role of calcium transients in regulating developmental gene expression is discussed.
Leclerc
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Centre de Biologie du Développement, UMR 5547, Université Paul Sabatier, F-31062 Toulouse CEDEX 04, France.
Webb
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Daguzan
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Moreau
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Miller
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D000331:Aequorin / Q000378:metabolism*; D000818:Animals; D016466:CHO Cells; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020746:Calcium Channels, L-Type / Q000378:metabolism*; D020013:Calcium Signaling; D002352:Carrier Proteins; D018797:Cell Cycle Proteins / Q000378:metabolism; D006224:Cricetinae; D017077:Culture Media, Conditioned; D004475:Ectoderm / Q000166:cytology* / Q000378:metabolism; D004533:Egtazic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D047108:Embryonic Development; D004627:Embryonic Induction; D005260:Female; D005775:Gastrula / Q000378:metabolism*; D064248:Geminin; D018507:Gene Expression Regulation, Developmental; D018398:Homeodomain Proteins / Q000378:metabolism; D017403:In Situ Hybridization; D009420:Nervous System / Q000196:embryology*; D019006:Neural Cell Adhesion Molecules / Q000235:genetics / Q000378:metabolism; D009529:Nicardipine / Q000494:pharmacology; D011506:Proteins / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D014157:Transcription Factors / Q000378:metabolism; D029867:Xenopus Proteins; D014982:Xenopus laevis / Q000196:embryology; D000099176:Noggin Protein
D000331:Aequorin; D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D017077:Culture Media, Conditioned; D004533:Egtazic Acid; D064248:Geminin; D018398:Homeodomain Proteins; D019006:Neural Cell Adhesion Molecules; D009529:Nicardipine; D011506:Proteins; D014157:Transcription Factors; D029867:Xenopus Proteins; D000099176:Noggin Protein; C577998:GMNN protein, Xenopus; C109036:Zic3 protein, Xenopus; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid