Citation: Gao, F., Thompson, J. R., Petsios, E., Erkenbrack, E., Moats, R. A., Bottjer, D. J., & Davidson, E. H. (2015). Juvenile skeletogenesis in anciently diverged sea urchin clades. Developmental biology, 400(1), 148-158.
Placental invasion into the maternal endometrium of the uterus shows substantial similarities to early cancer dissemination into stroma1,2,3,4. These similarities have inspired the hypothesis of antagonistic pleiotropy5,6. According to this hypothesis, trophoblasts evolved the capacity to invade the endometrium, leading to invasive placentation. These mechanisms can become reactivated in cancer cells, leading to a predisposition to metastasis. This implies that cancer malignancy should be limited to placental mammals where invasive placentation first evolved. This prediction, however, is inconsistent with the fact that opossums, with ancestrally non-invasive placenta7,8, get invasive skin cancers9. Here, we explore an alternative scenario in which stromal cells of the uterus evolved to either resist or permit invasion, determining the outcome of placental invasiveness9.
This work provides direct evidence of evolutionary rewiring of gene-regulatory circuitry accompanying divergence of two subclasses of echinoderm, the cidaroid and euechinoid sea urchins. These forms descend from a known common Paleo- zoic ancestor, and their embryos develop differently, offering an opportunity to probe the basic evolutionary process by which clade divergence occurs at the gene-regulatory net- work (GRN) level. We carried out a systematic analysis of the use of particular genes participating in embryonic skeleto- genic cell specification, building on an established euechinoid developmental GRN. This study revealed that the well-known and elegantly configured regulatory circuitry that underlies skeletogenic specification in modern sea urchins is largely a novel evolutionary invention. The results dramatically dis- play extensive regulatory changes in a specific developmental GRN, underlying an incidence of cladistic divergence at the subclass level.
© 2016 Eric M Erkenbrack and Elsevier. All rights reserved.