Origins of Bilateral Symmetry: Hox and Dpp Expression in a Sea Anemone

  title={Origins of Bilateral Symmetry: Hox and Dpp Expression in a Sea Anemone},
  author={John R. Finnerty and Kevin Pang and Patrick M. Burton and David Paulson and Mark Q. Martindale},
  pages={1335 - 1337}
Over 99% of modern animals are members of the evolutionary lineage Bilateria. The evolutionary success of Bilateria is credited partly to the origin of bilateral symmetry. Although animals of the phylum Cnidaria are not within the Bilateria, some representatives, such as the sea anemone Nematostella vectensis, exhibit bilateral symmetry. We show that Nematostella uses homologous genes to achieve bilateral symmetry: Multiple Hox genes are expressed in a staggered fashion along its primary body… 

Characterization of the Hox patterning genes in acoel flatworms

The posterior Hox genes were used to specify and maintain defined anatomical regions within the AP axis of animals since the beginning of bilaterian evolution, and how the morphological transition from radial to bilateral animals took place is concluded.

Hox genes pattern the primary body axis of an anthozoan cnidarian prior to gastrulation

Functional perturbation reveals a previously unrecognized domain of Hox expression in the starlet sea anemone, Nematostella vectensis, and suggests an ancient link between Hox/Wnt patterning of the oral-aboral axis and suggests that these domains are likely established during blastula formation in anthozoan cnidarians.

EvoD/Vo: the origins of BMP signalling in the neuroectoderm

This Review focuses on the origins of nervous system patterning and discusses recent comparative genetic studies, indicating the existence of an ancient molecular mechanism underlying nervous system organization that was probably already present in the bilaterian ancestor.

Early Stages of Animal Mesoderm Evolution

Sequencing of genomes of unicellular eukaryotes Holozoa, basal multicellular Porifera and Cnidaria, and Bilateria showed that the gene repertoire and gene regulatory networks that play a key role in the evolution ofMulticellular animals, in particular in the formation of the mesoderm, have an earlier origin than was expected.

Hox, Wnt, and the evolution of the primary body axis: insights from the early-divergent phyla

The hypothesis that Wnt genes may be the earliest primary body axis patterning mechanism by suggesting that Hox genes were co-opted into this patterning network prior to the last common ancestor of cnidarians and bilaterians is extended.

The radial expression of dorsal-ventral patterning genes in placozoans, Trichoplax adhaerens, argues for an oral-aboral axis

The results suggest that placozoans have an oral-aboral axis similar to cnidarians and that the parahoxozoan ancestor (common ancestor of Placozoa and Cnidaria) was likely radially symmetric.

The early evolution of Hox genes: a battle of belief?

New data from whole genome sequencing and recent progress in phylogeny of basal metazoans allow to provide an answer to the origin of metazoan animals and the early evolution of Hox genes.

Posterior expression of nanos orthologs during embryonic and larval development of the anthozoan Nematostella vectensis.

The isolation of two nanos orthologs in the anthozoan Nematostella vectensis is reported, showing that nanos mRNA is asymmetrically distributed in the fertilized egg and this asymmetry is maintained during embryonic development, indicating that posterior nanos expression during development is a conserved feature among cnidarians.

Early origin of the bilaterian developmental toolkit

  • D. Erwin
  • Biology
    Philosophical Transactions of the Royal Society B: Biological Sciences
  • 2009
It is suggested that placozoans and cnidarians represent a depauperate residue of a once more diverse assemblage of early animals, some of which may be represented in the Ediacaran fauna (c. 585–542 Myr ago).



Localized expression of a dpp/BMP2/4 ortholog in a coral embryo

  • D. HaywardG. Samuel E. Ball
  • Biology
    Proceedings of the National Academy of Sciences of the United States of America
  • 2002
It is shown that a dpp/BMP2/4 ortholog is present in the reef-building scleractinian coral, Acropora millepora, and that it is capable of causing phenotypic effects in Drosophila that mimic those of the endogenous dpp gene.

Conservation of Hox/ParaHox-related genes in the early development of a cnidarian.

Phylogenetic analysis shows that not all cnidarian Hox-like genes have recognizable orthologues in bilaterian groups, but the expression analysis of Cnox1-Pc and Gsx correlates to some extent with the expression pattern of cognate genes of bilaterians, confirming the conservation of genes involved in organizing animal body plans and their putative common ancestral origin.

The evolution of the Hox cluster: insights from outgroups.

Cnidarians Reveal Intermediate Stages in the Evolution of Hox Clusters and Axial Complexity1

The linkage of eve to a Hox gene, a condition previously described in a coral, is found in vertebrates but apparently absent in insects.

The HOX-like gene Cnox2-Pc is expressed at the anterior region in all life cycle stages of the jellyfish Podocoryne carnea

The results suggest that Cnox2-Pc is involved in establishment of an anterior-posterior axis during development in primitive metazoans.

Cnidarian homeoboxes and the zootype

A series of phylogenetic analyses indicate that Cnidaria, thought to be the earliest-evolving animal phylum with the exception of the sponges, lack several HOX genes that are present in Drosophila and vertebrates.

Evolution of Antp-class genes and differential expression of Hydra Hox/paraHox genes in anterior patterning.

The results suggest that the Hydra genes related to anterior Hox/paraHox genes are involved at different stages of apical differentiation, however, the positional information defining the oral/aboral axis in Hydra cannot be correlated strictly to that characterizing the anterior-posterior axis in vertebrates or arthropods.

Combined-method phylogenetic analysis of Hox and ParaHox genes of the metazoa.

ParaHox hypothesis is supported and first confirmation that ind (intermediate neuroblasts defective) is an anterior ParaHox ortholog from protostomes is given, as phylogenetic methods are used to determine Hox-gene orthologies and to infer probable clustering events leading to the current bilaterian Hox complement.

Defining phyla: evolutionary pathways to metazoan body plans

It is concluded that a benthic radiation of animals could have supplied the ancestral lineages of all but a few phyla, is consistent with molecular evidence, accords well with fossil evidence, and accounts for some of the difficulties in phylogenetic analyses of phyla based on morphological criteria.

Conservation of dorsal-ventral patterning in arthropods and chordates.

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  • Biology, Medicine
    Current opinion in genetics & development
  • 1996