TY - JOUR
T1 - Axial mesoderm and patterning of the zebrafish embryo1
AU - Halpern, Marnie E.
N1 - Funding Information:
Zebrafish studies were performed in the laboratory of C. B. Kirnmel, with the help and collaboration of colleagues at the University of Oregon and elsewhere. Interactions with members of the labs of J. Eisen, J. Postlethwait, M. Westerfield and J. Weston were critical for aspects of this work. I especially thank K. Hatta, R. Ho, D. Ki-melman (Univ. of Washington), B. Melby, B. Riggleman, (Washington State University), S. Schulte-Merker (Max-Plank Insti-tut fur Entwicklungsbiologie, Tubingen), W. Talbot, B. Thisse, C. Thisse, B. Trevar-row, F. Van Eeden (Tubingen) and C. Walker for their contributions. Molecular analyses of the no tail mutations were carried out in collaboration with the laboratory of C. Niisslein-Volhard, whom I thank for her generous support. The initial characterization of floating head was done in the laboratory of T. Jowett, Newcastle. I thank C.-M. Fan, J. Gall, and C. B. Kimmel for providing helpful comments. M.E.H. was supported by a Centennial Fellowship of the Medical Research Council of Canada and is currently supported by the Pew Scholars Program in Biomedical Research.
PY - 1997
Y1 - 1997
N2 - SYNOPSIS. It has long been recognized that the notochord, a derivative of the gastrula organizer, is important for patterning the vertebrate embryo. Experimental manipulations of amphibian and chick embryos demonstrate the notochord's influence on neural tube and somite differentiation. Recent studies implicate the notochord-derived signal Sonic hedgehog. In zebrafish, genetic strategies have enabled the recovery of mutations that disrupt notochord development. Embryos mutant tor floating head or no tail lack differentiated notochord and, consistent with encoding transcription factors, both genes behave cell autonomously in genetic mosaics: wild-type cells develop into notochord in mutant embryos, whereas mutant cells fail to contribute to wild-type notochord. In floating head mutants, axial mesoderm fated to form notochord respecifies to paraxial mesoderm, differentiating into muscle instead. As a result, fused somites . develop across the trunk midline. In no tail mutants, mesenchymal cells related by lineage to notochord are found in the midline, and although trunk somites are bilaterally paired, they lack Engrailed-expressing muscle pioneer cells. In the presence of wild-type notochord, however, no tail mutant cells can differentiate muscle pioneers, suggesting that induction of muscle pioneers is a normal function of notochord. Notochord is also involved in induction of floor plate at the ventral midline of the vertebrate neural tube; yet In floating head and no tail mutants, floor plate cells develop in the absence of differentiating notochord. Expression of sonic hedgehog by newly-forming axial mesoderm at gastrulation may account for floor plate induction prior to notochord differentiation. Thus, analyses of zebrafish notochordless mutants suggest a role for both early and late signaling by cells of the notochord lineage during embryogenesis.
AB - SYNOPSIS. It has long been recognized that the notochord, a derivative of the gastrula organizer, is important for patterning the vertebrate embryo. Experimental manipulations of amphibian and chick embryos demonstrate the notochord's influence on neural tube and somite differentiation. Recent studies implicate the notochord-derived signal Sonic hedgehog. In zebrafish, genetic strategies have enabled the recovery of mutations that disrupt notochord development. Embryos mutant tor floating head or no tail lack differentiated notochord and, consistent with encoding transcription factors, both genes behave cell autonomously in genetic mosaics: wild-type cells develop into notochord in mutant embryos, whereas mutant cells fail to contribute to wild-type notochord. In floating head mutants, axial mesoderm fated to form notochord respecifies to paraxial mesoderm, differentiating into muscle instead. As a result, fused somites . develop across the trunk midline. In no tail mutants, mesenchymal cells related by lineage to notochord are found in the midline, and although trunk somites are bilaterally paired, they lack Engrailed-expressing muscle pioneer cells. In the presence of wild-type notochord, however, no tail mutant cells can differentiate muscle pioneers, suggesting that induction of muscle pioneers is a normal function of notochord. Notochord is also involved in induction of floor plate at the ventral midline of the vertebrate neural tube; yet In floating head and no tail mutants, floor plate cells develop in the absence of differentiating notochord. Expression of sonic hedgehog by newly-forming axial mesoderm at gastrulation may account for floor plate induction prior to notochord differentiation. Thus, analyses of zebrafish notochordless mutants suggest a role for both early and late signaling by cells of the notochord lineage during embryogenesis.
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U2 - 10.1093/icb/37.3.311
DO - 10.1093/icb/37.3.311
M3 - Article
AN - SCOPUS:33748044341
SN - 0003-1569
VL - 37
SP - 311
EP - 322
JO - American Zoologist
JF - American Zoologist
IS - 3
ER -