Limits...
How Hox genes can shed light on the place of echinoderms among the deuterostomes.

David B, Mooi R - Evodevo (2014)

Bottom Line: Synthesis of available data helps to explain morphogenesis along the anterior/posterior axis of echinoderms, delineating the origins and fate of that axis during ontogeny.From this, it is easy to distinguish between 'seriality' along echinoderm rays and true A/P axis phenomena such as colinearity within the somatocoels, and the ontogenetic outcomes of the unique translocation and inversion of the anterior Hox class found within the Echinodermata.An up-to-date summary and integration of the disparate lines of research so far produced on the relationship between Hox genes and pattern formation for all deuterostomes allows for development of a phylogeny and scenario for the evolution of deuterostomes in general, and the Echinodermata in particular.

View Article: PubMed Central - HTML - PubMed

Affiliation: UMR CNRS 6282 Biogéosciences, Université de Bourgogne, 21000 Dijon, France.

ABSTRACT

Background: The Hox gene cluster ranks among the greatest of biological discoveries of the past 30 years. Morphogenetic patterning genes are remarkable for the systems they regulate during major ontogenetic events, and for their expressions of molecular, temporal, and spatial colinearity. Recent descriptions of exceptions to these colinearities are suggesting deep phylogenetic signal that can be used to explore origins of entire deuterostome phyla. Among the most enigmatic of these deuterostomes in terms of unique body patterning are the echinoderms. However, there remains no overall synthesis of the correlation between this signal and the variations observable in the presence/absence and expression patterns of Hox genes.

Results: Recent data from Hox cluster analyses shed light on how the bizarre shift from bilateral larvae to radial adults during echinoderm ontogeny can be accomplished by equally radical modifications within the Hox cluster. In order to explore this more fully, a compilation of observations on the genetic patterns among deuterostomes is integrated with the body patterning trajectories seen across the deuterostome clade.

Conclusions: Synthesis of available data helps to explain morphogenesis along the anterior/posterior axis of echinoderms, delineating the origins and fate of that axis during ontogeny. From this, it is easy to distinguish between 'seriality' along echinoderm rays and true A/P axis phenomena such as colinearity within the somatocoels, and the ontogenetic outcomes of the unique translocation and inversion of the anterior Hox class found within the Echinodermata. An up-to-date summary and integration of the disparate lines of research so far produced on the relationship between Hox genes and pattern formation for all deuterostomes allows for development of a phylogeny and scenario for the evolution of deuterostomes in general, and the Echinodermata in particular.

No MeSH data available.


Related in: MedlinePlus

Expression pattern of the Intervening Zone and of related genes among bilaterian Animalia. The IZ (separating Otx and Hox1 domains) corresponds to the midbrain-hindbrain boundary (MHB) in vertebrates, the neck region of urochordates, the anterior part of the second somite in cephalochordates, the deutocerebrum of insects, and to the anterior part of the trunk in annelids. Expression domains of Pax2/5/8 and En are shown (diamonds) only when they are located between those of Otx and Hox1. Expression domains of Pax2/5/8 are still largely unknown in Ambulacraria, hence the two alternative hypotheses shown for this character.
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Figure 5: Expression pattern of the Intervening Zone and of related genes among bilaterian Animalia. The IZ (separating Otx and Hox1 domains) corresponds to the midbrain-hindbrain boundary (MHB) in vertebrates, the neck region of urochordates, the anterior part of the second somite in cephalochordates, the deutocerebrum of insects, and to the anterior part of the trunk in annelids. Expression domains of Pax2/5/8 and En are shown (diamonds) only when they are located between those of Otx and Hox1. Expression domains of Pax2/5/8 are still largely unknown in Ambulacraria, hence the two alternative hypotheses shown for this character.

Mentions: In some clades, there is a gap between the territory of Otx and that of the most anterior Hox, therefore suggesting a tripartite organization, while in other clades the territories abut (Figure 5). When it exists, the intervening zone (IZ) might or might not correspond to the domain of expression of several genes, among them Pax2/5/8, En, or Fgf8.


How Hox genes can shed light on the place of echinoderms among the deuterostomes.

David B, Mooi R - Evodevo (2014)

Expression pattern of the Intervening Zone and of related genes among bilaterian Animalia. The IZ (separating Otx and Hox1 domains) corresponds to the midbrain-hindbrain boundary (MHB) in vertebrates, the neck region of urochordates, the anterior part of the second somite in cephalochordates, the deutocerebrum of insects, and to the anterior part of the trunk in annelids. Expression domains of Pax2/5/8 and En are shown (diamonds) only when they are located between those of Otx and Hox1. Expression domains of Pax2/5/8 are still largely unknown in Ambulacraria, hence the two alternative hypotheses shown for this character.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4066700&req=5

Figure 5: Expression pattern of the Intervening Zone and of related genes among bilaterian Animalia. The IZ (separating Otx and Hox1 domains) corresponds to the midbrain-hindbrain boundary (MHB) in vertebrates, the neck region of urochordates, the anterior part of the second somite in cephalochordates, the deutocerebrum of insects, and to the anterior part of the trunk in annelids. Expression domains of Pax2/5/8 and En are shown (diamonds) only when they are located between those of Otx and Hox1. Expression domains of Pax2/5/8 are still largely unknown in Ambulacraria, hence the two alternative hypotheses shown for this character.
Mentions: In some clades, there is a gap between the territory of Otx and that of the most anterior Hox, therefore suggesting a tripartite organization, while in other clades the territories abut (Figure 5). When it exists, the intervening zone (IZ) might or might not correspond to the domain of expression of several genes, among them Pax2/5/8, En, or Fgf8.

Bottom Line: Synthesis of available data helps to explain morphogenesis along the anterior/posterior axis of echinoderms, delineating the origins and fate of that axis during ontogeny.From this, it is easy to distinguish between 'seriality' along echinoderm rays and true A/P axis phenomena such as colinearity within the somatocoels, and the ontogenetic outcomes of the unique translocation and inversion of the anterior Hox class found within the Echinodermata.An up-to-date summary and integration of the disparate lines of research so far produced on the relationship between Hox genes and pattern formation for all deuterostomes allows for development of a phylogeny and scenario for the evolution of deuterostomes in general, and the Echinodermata in particular.

View Article: PubMed Central - HTML - PubMed

Affiliation: UMR CNRS 6282 Biogéosciences, Université de Bourgogne, 21000 Dijon, France.

ABSTRACT

Background: The Hox gene cluster ranks among the greatest of biological discoveries of the past 30 years. Morphogenetic patterning genes are remarkable for the systems they regulate during major ontogenetic events, and for their expressions of molecular, temporal, and spatial colinearity. Recent descriptions of exceptions to these colinearities are suggesting deep phylogenetic signal that can be used to explore origins of entire deuterostome phyla. Among the most enigmatic of these deuterostomes in terms of unique body patterning are the echinoderms. However, there remains no overall synthesis of the correlation between this signal and the variations observable in the presence/absence and expression patterns of Hox genes.

Results: Recent data from Hox cluster analyses shed light on how the bizarre shift from bilateral larvae to radial adults during echinoderm ontogeny can be accomplished by equally radical modifications within the Hox cluster. In order to explore this more fully, a compilation of observations on the genetic patterns among deuterostomes is integrated with the body patterning trajectories seen across the deuterostome clade.

Conclusions: Synthesis of available data helps to explain morphogenesis along the anterior/posterior axis of echinoderms, delineating the origins and fate of that axis during ontogeny. From this, it is easy to distinguish between 'seriality' along echinoderm rays and true A/P axis phenomena such as colinearity within the somatocoels, and the ontogenetic outcomes of the unique translocation and inversion of the anterior Hox class found within the Echinodermata. An up-to-date summary and integration of the disparate lines of research so far produced on the relationship between Hox genes and pattern formation for all deuterostomes allows for development of a phylogeny and scenario for the evolution of deuterostomes in general, and the Echinodermata in particular.

No MeSH data available.


Related in: MedlinePlus