Genomic inventory and expression of Sox and Fox genes in the cnidarian Nematostella vectensis

Abstract

The Sox and Forkhead (Fox) gene families are comprised of transcription factors that play important roles in a variety of developmental processes, including germ layer specification, gastrulation, cell fate determination, and morphogenesis. Both the Sox and Fox gene families are divided into subgroups based on the amino acid sequence of their respective DNA-binding domains, the high-mobility group (HMG) box (Sox genes) or Forkhead domain (Fox genes). Utilizing the draft genome sequence of the cnidarian Nematostella vectensis, we examined the genomic complement of Sox and Fox genes in this organism to gain insight into the nature of these gene families in a basal metazoan. We identified 14 Sox genes and 15 Fox genes in Nematostella and conducted a Bayesian phylogenetic analysis comparing HMG box and Forkhead domain sequences from Nematostella with diverse taxa. We found that the majority of bilaterian Sox groups have clear Nematostella orthologs, while only a minority of Fox groups are represented, suggesting that the evolutionary pressures driving the diversification of these gene families may be distinct from one another. In addition, we examined the expression of a subset of these genes during development in Nematostella and found that some of these genes are expressed in patterns consistent with roles in germ layer specification and the regulation of cellular behaviors important for gastrulation. The diversity of expression patterns among members of these gene families in Nematostella reinforces the notion that despite their relatively simple morphology, cnidarians possess much of the molecular complexity observed in bilaterian taxa.

Molecular evidence for deep evolutionary roots of bilaterality in animal development

“…This notion is supported by expression of various genes implicated in neural fate specification in the planula apical tuft, a sensory structure at the anterior end of the swimming stage. The apical tuft expresses NvDpp and NvBMP5-8, and their inhibitor (NvNoggin1), and a variety of genes associated with neural tissue including NvGsc, NvNetrin, NvCOE (43), NvAnthox1 (9), NvSoxB1, and NvFoxD.1 (65), some of which are also expressed in the pharynx (NvGsc, NvDpp, NvBMP5-8, NvNoggin1) (Fig. 7).…”

The nervous system of Xenacoelomorpha: a genomic perspective

“…Some of the progeny of these micromeres are internalized at later stages of embryonic development and differentiate into neurons. The differentiation of neurons from these internalized cells is readily accounted for by the expression of a SoxB orthologue, a gene that is early expressed in pro-neural cells in a great variety of taxa, including non-bilaterian taxa such as the cnidarians (Magie et al, 2005;Hejnol and Martindale, 2009). Later on in development, the Hox patterning system plays a clearly important role in providing positional cues to the differentiating neurons.…”

Transgenic analysis of a SoxB gene reveals neural progenitor cells in the cnidarian Nematostella vectensis

“…Marlow et al (2009);Matus et al (2007a)]. Here, we address the developmental origins of neural cell types in anthozoans by employing a transgenic approach based on the putative neural regulator NvSoxB(2) (Magie et al, 2005).…”