PCR survey of <i>Xenoturbella bocki</i> Hox genes

Fritzsch, Guido; Böhme, Manja U.; Thorndyke, Mike; Nakano, Hiroaki; Israelsson, Olle; Stach, Thomas; Schlegel, Martin; Hankeln, Thomas; Stadler, Peter F.

doi:10.1002/jez.b.21208

Cited by 27 publications

(19 citation statements)

References 43 publications

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“…Summarizing, and as shown in table 1, we found that, as a general pattern, the number of genes belonging to each family is lower in S. roscoffensis than in X. bocki: 18 bHLHs and 225 GPCRs were present in the former; 33 bHLHs and 258 GPCRs in the latter. This is consistent with, for instance, the number of Hox genes detected: three in acoels [66]; five in xenoturbellids [77]. Here, the complexity of the different families (we refer to the total number of genes per family plus the number of subfamilies present) in these two species is not directly related to the apparent structural complexity of acoel and Xenoturbella neural architectures.…”

Section: A Genomics View Of Xenacoelomorpha Neurogenesissupporting

confidence: 83%

Xenacoelomorpha: a case of independent nervous system centralization?

Gavilán

Perea-Atienza

Martı́nez

2016

Phil. Trans. R. Soc. B

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One contribution of 16 to a discussion meeting issue 'Homology and convergence in nervous system evolution'. Centralized nervous systems (NSs) and complex brains are among the most important innovations in the history of life on our planet. In this context, two related questions have been formulated: How did complex NSs arise in evolution, and how many times did this occur? As a step towards finding an answer, we describe the NS of several representatives of the Xenacoelomorpha, a clade whose members show different degrees of NS complexity. This enigmatic clade is composed of three major taxa: acoels, nemertodermatids and xenoturbellids. Interestingly, while the xenoturbellids seem to have a rather 'simple' NS (a nerve net), members of the most derived group of acoel worms clearly have ganglionic brains. This interesting diversity of NS architectures (with different degrees of compaction) provides a unique system with which to address outstanding questions regarding the evolution of brains and centralized NSs. The recent sequencing of xenacoelomorph genomes gives us a privileged vantage point from which to analyse neural evolution, especially through the study of key gene families involved in neurogenesis and NS function, such as G protein-coupled receptors, helixloop-helix transcription factors and Wnts. We finish our manuscript proposing an adaptive scenario for the origin of centralized NSs (brains).

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Section: A Genomics View Of Xenacoelomorpha Neurogenesissupporting

confidence: 83%

Xenacoelomorpha: a case of independent nervous system centralization?

Gavilán

Perea-Atienza

Martı́nez

2016

Phil. Trans. R. Soc. B

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“…The provisional conclusion is that ophiuroids have a cluster with Hox1 and Hox3 in the anterior class, Hox7 and Hox8 plus at least one other gene in the medial class, and several genes in the posterior class. The GenBank data were also cited by Fritzsch et al [66] in support of the contention that Hox4 was absent in ophiuroids. However, these data are in reference to expression of genes during regeneration of Amphiura filiformis - this is very different from saying that Hox4 is absent from the ophiuroid cluster because there is no reason to assume that Hox4 must reveal its presence during regeneration.…”

Section: Resultssupporting

confidence: 67%

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

David

Mooi

2014

EvoDevo

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BackgroundThe 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.ResultsRecent 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.ConclusionsSynthesis 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.

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“…2004; Hejnol and Martindale 2009; Moreno et al. 2009) while four Hox genes have been reported from X. bocki (Fritzsch et al. 2008; Thomas-Chollier and Martinez 2016).…”

Section: Discussionmentioning

confidence: 99%

Xenacoelomorpha Survey Reveals That All 11 Animal Homeobox Gene Classes Were Present in the First Bilaterians

Brauchle

Bilican

Eyer

et al. 2018

Genome Biology and Evolution

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Homeodomain transcription factors are involved in many developmental processes across animals and have been linked to body plan evolution. Detailed classifications of these proteins identified 11 distinct classes of homeodomain proteins in animal genomes, each harboring specific sequence composition and protein domains. Although humans contain the full set of classes, Drosophila melanogaster and Caenorhabditis elegans each lack one specific class. Furthermore, representative previous analyses in sponges, ctenophores, and cnidarians could not identify several classes in those nonbilaterian metazoan taxa. Consequently, it is currently unknown when certain homeodomain protein classes first evolved during animal evolution. Here, we investigate representatives of the sister group to all remaining bilaterians, the Xenacoelomorpha. We analyzed three acoel, one nemertodermatid, and one Xenoturbella transcriptomes and identified their expressed homeodomain protein content. We report the identification of representatives of all 11 classes of animal homeodomain transcription factors in Xenacoelomorpha and we describe and classify their homeobox genes relative to the established animal homeodomain protein families. Our findings suggest that the genome of the last common ancestor of bilateria contained the full set of these gene classes, supporting the subsequent diversification of bilaterians.

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PCR survey of Xenoturbella bocki Hox genes

Cited by 27 publications

References 43 publications

Xenacoelomorpha: a case of independent nervous system centralization?

Xenacoelomorpha: a case of independent nervous system centralization?

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

Xenacoelomorpha Survey Reveals That All 11 Animal Homeobox Gene Classes Were Present in the First Bilaterians

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