- Developmental milestones punctuate gene expression in the Caenorhabditis embryo
The complex process by which a metazoan develops from a single cell to a multi-cellular differentiated organism is typically organized by biologists into stages. For example, in the chordate embryo, the gastrula, the neurula and the tail-bud constitute characteristic processes. A debate runs through the history of embryology questioning whether such stages hint at the modularity of embryonic development1-3, or rather, that stages exist in the mind of the biologist, and not in the larva4 or embryo. It thus remains unclear which position accurately reflects the nature of development on a molecular, gene regulatory level. Here we demonstrate that development of five Caenorhabditis species proceeds through multiple distinct stages in which the transcriptome is resistant to differences in species-specific developmental timings. By comparing the complete protein-coding transcriptomes of individually staged embryos across ten morphological markers, we found that time-invariant stages occur throughout development, including a stage we identify as the nematode phylotypic stage. Between such stages, embryos follow transitory states characterized by an acceleration of transcriptional activity. Therefore, on a molecular level, development cannot be viewed as a single process continuously proceeding through time, but rather as a succession of discontinuous stages, or milestones. Comparing the nematode developmental transcriptome with that of the chordate we report on the macro evolution of a milestone by duplication and diversification. This modular view of development by milestones will allow for a more complete understanding of how the functional organization of the embryo has influenced the evolution of animal morphology and diversity.
- Developmental milestones punctuate gene expression in the Caenorhabditis embryo
The complex process by which a metazoan develops from a single cell to a multi-cellular differentiated organism is typically organized by biologists into stages. For example, in the chordate embryo, the gastrula, the neurula and the tail-bud constitute characteristic processes. A debate runs through the history of embryology questioning whether such stages hint at the modularity of embryonic development1-3, or rather, that stages exist in the mind of the biologist, and not in the larva4 or embryo. It thus remains unclear which position accurately reflects the nature of development on a molecular, gene regulatory level. Here we demonstrate that development of five Caenorhabditis species proceeds through multiple distinct stages in which the transcriptome is resistant to differences in species-specific developmental timings. By comparing the complete protein-coding transcriptomes of individually staged embryos across ten morphological markers, we found that time-invariant stages occur throughout development, including a stage we identify as the nematode phylotypic stage. Between such stages, embryos follow transitory states characterized by an acceleration of transcriptional activity. Therefore, on a molecular level, development cannot be viewed as a single process continuously proceeding through time, but rather as a succession of discontinuous stages, or milestones. Comparing the nematode developmental transcriptome with that of the chordate we report on the macro evolution of a milestone by duplication and diversification. This modular view of development by milestones will allow for a more complete understanding of how the functional organization of the embryo has influenced the evolution of animal morphology and diversity.
- Developmental milestones punctuate gene expression in the Caenorhabditis embryo
The complex process by which a metazoan develops from a single cell to a multi-cellular differentiated organism is typically organized by biologists into stages. For example, in the chordate embryo, the gastrula, the neurula and the tail-bud constitute characteristic processes. A debate runs through the history of embryology questioning whether such stages hint at the modularity of embryonic development1-3, or rather, that stages exist in the mind of the biologist, and not in the larva4 or embryo. It thus remains unclear which position accurately reflects the nature of development on a molecular, gene regulatory level. Here we demonstrate that development of five Caenorhabditis species proceeds through multiple distinct stages in which the transcriptome is resistant to differences in species-specific developmental timings. By comparing the complete protein-coding transcriptomes of individually staged embryos across ten morphological markers, we found that time-invariant stages occur throughout development, including a stage we identify as the nematode phylotypic stage. Between such stages, embryos follow transitory states characterized by an acceleration of transcriptional activity. Therefore, on a molecular level, development cannot be viewed as a single process continuously proceeding through time, but rather as a succession of discontinuous stages, or milestones. Comparing the nematode developmental transcriptome with that of the chordate we report on the macro evolution of a milestone by duplication and diversification. This modular view of development by milestones will allow for a more complete understanding of how the functional organization of the embryo has influenced the evolution of animal morphology and diversity.
- Developmental milestones punctuate gene expression in the Caenorhabditis embryo
The complex process by which a metazoan develops from a single cell to a multi-cellular differentiated organism is typically organized by biologists into stages. For example, in the chordate embryo, the gastrula, the neurula and the tail-bud constitute characteristic processes. A debate runs through the history of embryology questioning whether such stages hint at the modularity of embryonic development1-3, or rather, that stages exist in the mind of the biologist, and not in the larva4 or embryo. It thus remains unclear which position accurately reflects the nature of development on a molecular, gene regulatory level. Here we demonstrate that development of five Caenorhabditis species proceeds through multiple distinct stages in which the transcriptome is resistant to differences in species-specific developmental timings. By comparing the complete protein-coding transcriptomes of individually staged embryos across ten morphological markers, we found that time-invariant stages occur throughout development, including a stage we identify as the nematode phylotypic stage. Between such stages, embryos follow transitory states characterized by an acceleration of transcriptional activity. Therefore, on a molecular level, development cannot be viewed as a single process continuously proceeding through time, but rather as a succession of discontinuous stages, or milestones. Comparing the nematode developmental transcriptome with that of the chordate we report on the macro evolution of a milestone by duplication and diversification. This modular view of development by milestones will allow for a more complete understanding of how the functional organization of the embryo has influenced the evolution of animal morphology and diversity.
- Developmental milestones punctuate gene expression in the Caenorhabditis embryo
The complex process by which a metazoan develops from a single cell to a multi-cellular differentiated organism is typically organized by biologists into stages. For example, in the chordate embryo, the gastrula, the neurula and the tail-bud constitute characteristic processes. A debate runs through the history of embryology questioning whether such stages hint at the modularity of embryonic development1-3, or rather, that stages exist in the mind of the biologist, and not in the larva4 or embryo. It thus remains unclear which position accurately reflects the nature of development on a molecular, gene regulatory level. Here we demonstrate that development of five Caenorhabditis species proceeds through multiple distinct stages in which the transcriptome is resistant to differences in species-specific developmental timings. By comparing the complete protein-coding transcriptomes of individually staged embryos across ten morphological markers, we found that time-invariant stages occur throughout development, including a stage we identify as the nematode phylotypic stage. Between such stages, embryos follow transitory states characterized by an acceleration of transcriptional activity. Therefore, on a molecular level, development cannot be viewed as a single process continuously proceeding through time, but rather as a succession of discontinuous stages, or milestones. Comparing the nematode developmental transcriptome with that of the chordate we report on the macro evolution of a milestone by duplication and diversification. This modular view of development by milestones will allow for a more complete understanding of how the functional organization of the embryo has influenced the evolution of animal morphology and diversity.
- Genome-wide analysis of developmental and sex-regulated gene expression profiles in C. elegans
We have constructed DNA microarrays containing 17,871 genes, representing about 94% of the 18,967 genes currently annotated in the Caenorhabditis elegans genome. These DNA microarrays can be used as a tool to define a nearly complete molecular profile of gene expression levels associated with different developmental stages, growth conditions, or worm strains. Here, we used these full-genome DNA microarrays to show the relative levels of gene expression for nearly every gene during development, from eggs through adulthood. These expression data can help reveal when a gene may act during development. We also compared gene expression in males to that of hermaphrodites and found a total of 2,171 sex-regulated genes (P < 0.05). The sex-regulated genes provide a global view of the differences between the sexes at a molecular level and identify many genes likely to be involved in sex-specific differentiation and behavior. Set of arrays organized by shared biological context, such as organism, tumors types, processes, etc. Keywords: Logical Set