A conserved gene regulatory network subcircuit drives different developmental fates in the vegetal pole of highly divergent echinoderm embryos

Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA 15213, USA.
Developmental Biology (Impact Factor: 3.64). 11/2009; 340(2):200-8. DOI: 10.1016/j.ydbio.2009.11.020
Source: PubMed

ABSTRACT Comparisons of orthologous developmental gene regulatory networks (GRNs) from different organisms explain how transcriptional regulation can, or cannot, change over time to cause morphological evolution and stasis. Here, we examine a subset of the GRN connections in the central vegetal pole mesoderm of the late sea star blastula and compare them to the GRN for the same embryonic territory of sea urchins. In modern sea urchins, this territory gives rise to skeletogenic mesoderm; in sea stars, it develops into other mesodermal derivatives. Orthologs of many transcription factors that function in the sea urchin skeletogenic mesoderm are co-expressed in the sea star vegetal pole, although this territory does not form a larval skeleton. Systematic perturbation of erg, hex, tbr, and tgif gene function was used to construct a snapshot of the sea star mesoderm GRN. A comparison of this network to the sea urchin skeletogenic mesoderm GRN revealed a conserved, recursively wired subcircuit operating in both organisms. We propose that, while these territories have evolved different functions in sea urchins and sea stars, this subcircuit is part of an ancestral GRN governing echinoderm vegetal pole mesoderm development. The positive regulatory feedback between these transcription factors may explain the conservation of this subcircuit.

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Available from: Veronica F Hinman, Jul 14, 2015
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    • "A related goal is to establish whether this regulatory architecture is deployed whenever gcm/six1 co-expression exists in this species. The coelomic rudiment cells of pluteus larva provide a good candidate for additional study, as mRNAs for both genes have been detected there by WMISH (McCauley et al., 2010; Poustka et al., 2007). Another instance deserving additional investigation arises from the cloning of six1 from an adult coelomocyte cDNA library (Cameron et al., 2000), coupled with the enriched gcm expression in an adult coelomocyte type, the echinochrome-containing red spherule cells (J. "
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    • "These features, and developmental canalization due to the upstream position of such kernels in the body part GRN, explain their exceptional evolutionary conservation. Examples include what may be a pan-bilaterian (i.e., from flies to mice) kernel for heart specification (Davidson, 2006); and an (at least) pan-echinoderm kernel underlying mesoderm specification in both sea urchin and sea star development ((McCauley et al., 2010); these lineages have not shared a common ancestor since the end of the Cambrian). Similarly, a fundamental Box II subcircuit may underlie mesoderm specification in vertebrate embryogenesis (Swiers et al., 2010). "
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    • "The connection between the evolution of developmental GRN to the evolution of diverse body plans is more and more evident as models of GRNs of diverse organisms become available (Davidson and Erwin, 2009; Erwin and Davidson, 2009). It is now apparent that different parts of GRNs evolve at a different pace and some parts are more conserved then others (Hinman et al., 2003; Hinman and Davidson, 2007; Davidson and Erwin, 2009; Erwin and Davidson, 2009; McCauley et al., 2010). Here we focused on one regulatory gene and tried to understand the reasons for its highly conserved developmental role and whether its regulation is as conserved as its role. "
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