Developmental milestones punctuate gene expression in the Caenorhabditis embryo

ABSTRACT: 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 larva”4 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. 150 microarrays, across 10 morphological markers of C. remanei, C. briggsae, C. brenneri, C. elegans and C. japonica wildtype embryos. For each of the two timecourse independent triplicates were generated.

ORGANISM(S): Caenorhabditis brenneri

SUBMITTER: Itai Yanai 

PROVIDER: E-GEOD-31422 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress