Citation: Erkenbrack, E. M. (2017). Divergence of ectodermal and mesodermal gene regulatory network linkages in early development of sea urchins. Proceedings of the National Academy of Sciences, 113(46), E7202-E7211.
Mechanistic understanding of evolutionary divergence in animal body plans devolves from analysis of those developmental processes that, in forms descendant from a common ancestor, are responsible for their morphological differences. The last common ancestor of the two extant subclasses of sea urchins, i.e., euechinoids and cidaroids, existed well before the Permian/Triassic extinction (252 mya). Subsequent evolutionary divergence of these clades offers in principle a rare opportunity to solve the developmental regulatory events underlying a defined evolutionary divergence process.
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.
© 2016 Eric M Erkenbrack and SpringerNature. All rights reserved.