Comparative transcriptomics reveal distinct patterns of gene expression conservation through vertebrate embryogenesis

Abstract

15Despite the diversity of life, studies of variation across animals often remind us of our deep evolutionary 16 past. Abundant genome sequencing over the last ~25 years reveals remarkable conservation of genes and 17 recent analyses of gene regulatory networks illustrate that not only genes but entire pathways are conserved, 18 reused, and elaborated in the evolution of diversity. Predating these discoveries, 19 th -century embryologists 19 observed that though morphology at birth varies tremendously, certain stages of embryogenesis appear 20 remarkably similar across vertebrates. Specifically, while early and late stages are variable across species, 21 anatomy of mid-stages embryos (the phylotypic stage) is conserved. This model of vertebrate development 22