The vertebrate phylotypic stage and an early bilaterian-related stage in mouse embryogenesis defined by genomic information

摘要: Embryos of taxonomically different vertebrates are thought to pass through a stage in which they resemble one another morphologically. This "vertebrate phylotypic stage" may represent the basic vertebrate body plan that was established common ancestor vertebrates. However, much controversy remains about when appears, and whether it even exists. To overcome limitations studies based on morphological comparison, we explored comprehensive quantitative method for defining constrained using expressed sequence tag (EST) data, gene ontologies (GO), available genomes various animals. If strong developmental constraints occur during embryos, then genes conserved among would be highly at this stage. We novel evaluating ancestral nature mouse embryonic stages does not depend comparative morphology. The numerical "ancestor index" revealed indeed has period day 8.0–8.5, time appearance pharyngeal arch somites. During period, prominently expresses GO-determined shared Similar analyses existence bilaterian-related bilaterians markedly cleavage-to-gastrulation period. associated with identified by our essential embryogenesis. Our results demonstrate mid-embryonic is constrained, supporting Furthermore, candidate preceded putative bilaterian ancestor-related These only support hourglass model, but also highlight hierarchical aspect embryogenesis proposed von Baer. Identification tissues animals powerful tool examine hypothesis, understand kinds events sets evolutionarily how limit possible variations animal plans.