期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2016
卷号：113
期号：46
页码：E7202-E7211
DOI：10.1073/pnas.1612820113
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceSea urchins (echinoids) consist of two subclasses, cidaroids and euechinoids. Research on gene regulatory networks (GRNs) in the early development of three euechinoids indicates that little appreciable change has occurred to their linkages since they diverged [~]90 million years ago (mya). I asked whether this conservation extends to all echinoids. I systematically analyzed the spatiotemporal expression and function of regulatory genes segregating euechinoid ectoderm and mesoderm in a cidaroid. I report marked divergence of GRN architecture in early embryonic specification of the oral-aboral axis in echinoids. Although I found evidence for diverged regulation of both mesodermal and ectodermal genes, comparative analyses indicated that, since these two clades diverged 268 mya, mesodermal GRNs have undergone significantly more alterations than ectodermal GRNs. Developmental gene regulatory networks (GRNs) are assemblages of gene regulatory interactions that direct ontogeny of animal body plans. Studies of GRNs operating in the early development of euechinoid sea urchins have revealed that little appreciable change has occurred since their divergence [~]90 million years ago (mya). These observations suggest that strong conservation of GRN architecture was maintained in early development of the sea urchin lineage. Testing whether this holds for all sea urchins necessitates comparative analyses of echinoid taxa that diverged deeper in geological time. Recent studies highlighted extensive divergence of skeletogenic mesoderm specification in the sister clade of euechinoids, the cidaroids, suggesting that comparative analyses of cidaroid GRN architecture may confer a greater understanding of the evolutionary dynamics of developmental GRNs. Here I report spatiotemporal patterning of 55 regulatory genes and perturbation analyses of key regulatory genes involved in euechinoid oral-aboral patterning of nonskeletogenic mesodermal and ectodermal domains in early development of the cidaroid Eucidaris tribuloides. These results indicate that developmental GRNs directing mesodermal and ectodermal specification have undergone marked alterations since the divergence of cidaroids and euechinoids. Notably, statistical and clustering analyses of echinoid temporal gene expression datasets indicate that regulation of mesodermal genes has diverged more markedly than regulation of ectodermal genes. Although research on indirect-developing euechinoid sea urchins suggests strong conservation of GRN circuitry during early embryogenesis, this study indicates that since the divergence of cidaroids and euechinoids, developmental GRNs have undergone significant, cell type-biased alterations.
