1. Anteroposterior patterning in hemichordates and the origins of the chordate nervous system.
- Author
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Lowe CJ, Wu M, Salic A, Evans L, Lander E, Stange-Thomann N, Gruber CE, Gerhart J, and Kirschner M
- Subjects
- Animals, Biological Evolution, Chordata, Nonvertebrate cytology, Chordata, Nonvertebrate genetics, Ectoderm cytology, Ectoderm metabolism, Embryo, Nonmammalian embryology, Evolution, Molecular, Genes, Homeobox genetics, Invertebrates metabolism, Molecular Sequence Data, Nervous System cytology, Nervous System metabolism, Phylogeny, Sequence Homology, Nucleic Acid, Vertebrates metabolism, Body Patterning genetics, Chordata, Nonvertebrate embryology, Gene Expression Regulation, Developmental genetics, Invertebrates embryology, Nervous System embryology, Vertebrates embryology
- Abstract
The chordate central nervous system has been hypothesized to originate from either a dorsal centralized, or a ventral centralized, or a noncentralized nervous system of a deuterostome ancestor. In an effort to resolve these issues, we examined the hemichordate Saccoglossus kowalevskii and studied the expression of orthologs of genes that are involved in patterning the chordate central nervous system. All 22 orthologs studied are expressed in the ectoderm in an anteroposterior arrangement nearly identical to that found in chordates. Domain topography is conserved between hemichordates and chordates despite the fact that hemichordates have a diffuse nerve net, whereas chordates have a centralized system. We propose that the deuterostome ancestor may have had a diffuse nervous system, which was later centralized during the evolution of the chordate lineage.
- Published
- 2003
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