Genomic organization, gene structure, and developmental expression of three Clustered otx genes in the sea anemone Nematostella vectensis

Abstract

Otx homeodomain transcription factors have been studied in a variety of eumetazoan animals where they have roles in anterior neural development, endomesoderm formation, and the formation of larval ciliated fields. Here, we describe the gene structure and developmental expression of three Otx loci in the starlet sea anemone, Nematostella vectensis (phylum Cnidaria; class Anthozoa). Nematostella's three Otx genes (OtxA, OtxB, and OtxC) are located in a compact genomic cluster spanning 63.6 kb. The homeodomains of all three Otx genes are highly similar to their bilaterian counterparts, but only OtxB exhibits the conserved WSP motif that is located downstream of the homeodomain in many Otx proteins. The genomic organization, in concert with phylogenetic analyses, indicates that two tandem duplications occurred in the lineage leading to Nematostella some time after the Cnidaria diverged from the Bilateria. In situ hybridization reveals that otx is initially expressed by invaginating mesendodermal cells in the gastrula. Later, each of the three otx paralogs is expressed in three discrete larval body regions: in the endoderm of the foot or physa, in an endodermal ring surrounding the pharynx, and in the ectoderm of the tentacles. These data suggest that a single otx locus had already acquired diverse developmental functions in the cnidarian-bilaterian ancestor. Furthermore, following two gene duplications in the line leading to Nematostella, there have been only minor alterations in the spatiotemporal expression of the three Otx paralogs. However, the absence of a conserved protein domain in OtxA and OtxC suggests functional evolution of the protein itself. J. Exp. Zool. (Mol. Dev. Evol.) 308B: 494-506, 2007. r 2007 How to cite this article: Mazza ME, Pang K, Martindale MQ, Finnerty JR. 2007. Genomic organization, gene structure, and developmental expression of three clustered otx genes in the sea anemone Nematostella vectensis. J. Exp. Zool. (Mol. Dev. Evol.) 308B: 494-506.

Evolutionary origins of blastoporal expression and organizer activity of the vertebrate gastrula organizer genelhx1and its ancient metazoan paraloglhx3

“…1A). By comparison with the reported expression patterns of organizer genes in the Nematostella embryo (Fritzenwanker et al, 2004;Matus et al, 2006;Mazza et al, 2007), chd, otx and foxa appear to be coexpressed with lhx1 in the blastoporal region, whereas gsc, nog and follistatin only start to be expressed at later stages in the endoderm.…”

Conserved and novel gene expression between regeneration and asexual fission in Nematostella vectensis

“…During embryogenesis, anthox1 expression is observed initially in both tissue layers before becoming restricted to the ectoderm ). Nv-otxC expression is restricted to the aboral endoderm during embryonic development (Mazza et al 2007).…”

“…For Nv-fox, Nv-otxC, anthox1, anthox1a, anthox7, and anthox8, identical probes to those used during Nematostella embryogenesis were employed Martindale et al 2004;Mazza et al 2007). For anthox6, the probe was extended by 0.3 kb for increased resolution.…”

“…Previous work has identified markers during embryogenesis for oral development (Nv-fox; Martindale et al 2004), aboral development (Nv-otxC; Mazza et al 2007), and the primary, oral-aboral axis (Hox-like genes; Finnerty et al 2004). In order to investigate the basic patterning mechanisms of regeneration and asexual fission in Nematostella, we examined the expression of these conserved developmental patterning genes during Nematostella adult developmental trajectories.…”

BMPs and Chordin regulate patterning of the directive axis in a sea anemone

“…In sharp contrast, two endodermal marker genes of the oral-aboral axis are severely affected in all Morpholino injected embryos: both, the oral endoderm marker twist (20), as well as the aboral endodermal expression of otxC (21) are completely abolished upon knockdown of dpp, bmp5-8, or chd (Fig. 3 Z-IЈ).…”