• Share

Ancestral state reconstruction by comparative analysis of a GRN kernel operating in echinoderms
Citation: Erkenbrack, E. M., Ako-Asare, K., Miller, E., Tekelenburg, S., Thompson, J. R., & Romano, L. (2016). Ancestral state reconstruction by comparative analysis of a GRN kernel operating in echinoderms. Development Genes and Evolution, 226(1), 37-45.
Diverse sampling of organisms across the five ma- jor classes in the phylum Echinodermata is beginning to reveal much about the structure and function of gene regulatory net- works (GRNs) in development and evolution. Sea urchins are the most studied clade within this phylum, and recent work suggests there has been dramatic rewiring at the top of the skeletogenic GRN along the lineage leading to extant mem- bers of the euechinoid sea urchins. Such rewiring likely ac- counts for some of the observed developmental differences between the two major subclasses of sea urchins—cidaroids and euechinoids. To address effects of topmost rewiring on downstream GRN events, we cloned four downstream regu- latory genes within the skeletogenic GRN and surveyed their spatiotemporal expression patterns in the cidaroid Eucidaris tribuloides. We performed phylogenetic analyses with homo- logs from other non-vertebrate deuterostomes and character- ized their spatiotemporal expression by quantitative polymer- ase chain reaction (qPCR) and whole-mount in situ hybridi- zation (WMISH). Our data suggest the erg–hex–tgif subcircuit, a putative GRN kernel, exhibits a mesoderm- specific expression pattern early in Eucidaris development that is directly downstream of the initial mesodermal GRN circuitry. Comparative analysis of the expression of this subcircuit in four echinoderm taxa allowed robust ancestral state reconstruction, supporting hypotheses that its ancestral function was to stabilize the mesodermal regulatory state and that it has been co-opted and deployed as a unit in mesodermal subdomains in distantly diverged echinoderms. Importantly, our study supports the notion that GRN kernels exhibit struc- tural and functional modularity, locking down and stabilizing clade-specific, embryonic regulatory states.

More Publications

Decidualization of Human Endometrial Stromal Fibroblasts is a Multiphasic Process Involving Distinct Transcriptional Programs

Decidual stromal cells differentiate from endometrial stromal fibroblasts (ESFs) under the influence of progesterone and cyclic adenosine monophosphate (cAMP) and are essential for implantation and the maintenance of pregnancy. They evolved in the stem lineage of placental (eutherian) mammals coincidental with the evolution of implantation. Here we use the well-established in vitro decidualization protocol to compare early (3 days) and late (8 days) gene transcription patterns in immortalized human ESF. We document extensive, dynamic changes in the early and late decidual cell transcriptomes. The data suggest the existence of an early signal transducer and activator of transcription (STAT) pathway dominated state and a later nuclear factor kB (NFKB) pathway regulated state. Transcription factor expression in both phases is characterized by putative or known progesterone receptor (PGR) target genes, suggesting that both phases are under progesterone control. Decidualization leads to proliferative quiescence, which is reversible by progesterone withdrawal after 3 days but to a lesser extent after 8 days of decidualization. In contrast, progesterone withdrawal induces cell death at comparable levels after short or long exposure to progestins and cAMP. We conclude that decidualization is characterized by a biphasic gene expression dynamic that likely corresponds to different phases in the establishment of the fetal–maternal interface.

A Conserved Role for VEGF Signaling in Specification of Homologous Mesenchymal Cell Types Positioned at Spatially Distinct Developmental Addresses in Early Development of Sea Urchins

Comparative studies of early development in echinoderms are revealing the tempo and mode of alterations to developmental gene regulatory networks and to the cell types they specify. In euechinoid sea urchins, skeletogenic mesenchyme (SM) ingresses prior to gastrulation at the vegetal pole and aligns into a ring-like array with two bilateral pockets of cells, the sites where spiculogenesis will later occur. In cidaroid sea urchins, the anciently diverged sister clade to euechinoid sea urchins, a homologous SM cell type ingresses later in development, after gastrulation has commenced, and consequently at a distinct developmental address. Thus, a heterochronic shift of ingression of the SM cell type occurred in one of the echinoid lineages. In euechinoids, speci cation and migration of SM are facilitated by vascular endothelial growth factor (VEGF) signaling. We describe spatiotemporal expression of vegf and vegfr and experimental manipulations target- ing VEGF signaling in the cidaroid Eucidaris tribuloides.
© 2016 Eric M Erkenbrack and SpringerNature. All rights reserved.