Organization of Hox genes in ascidians: Present, past, and future

Ikuta, Tetsuro; Saiga, Hidetoshi

doi:10.1002/dvdy.20374

Cited by 41 publications

(31 citation statements)

References 76 publications

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“…It has been proposed that Hox genes were organized into a cluster in the ancestor of deuterostomes and that the Hox gene cluster became disorganized in echinoderm and urochordate lineages (Cameron et al, 2006;Ikuta and Saiga, 2005;Lemons and McGinnis, 2006;Seo et al, 2004). It is an indisputable fact that ascidian Hox genes are no longer all clustered and that the colinearity is residual.…”

Section: Discussionmentioning

confidence: 99%

“…Conversely, for Ci-Hox 1, 2, 3, 4 and 5, no morphological defects were detected in the knockdown experiments. Furthermore, the expression of GABAergic and cholinergic neuronal marker genes was unaffected in larvae injected with MOs against Ci-Hox1, 3 and 5, despite the fact that 3,5,10 and 12 are coordinately expressed in the larval CNS (Ikuta and Saiga, 2005;Ikuta and Saiga, 2007;Ikuta et al, 2004). These results suggest that the roles of Hox genes are limited in ascidian larval development.…”

Section: Introductionmentioning

confidence: 94%

“…3,5,10 and 12 exhibit limited spatially coordinated expression in the larval neural tube, as do CiHox10, 12 and 13 in post-larval gut development (Ikuta et al, 2004). Based on these observations, a scenario for the evolution of the ascidian body plan has been proposed, in which ascidians must have acquired their simple body plan and rapid embryogenesis together with extensive genomic rearrangement and gene loss, including disintegration of the Hox gene cluster and loss of some Hox gene members (Ikuta and Saiga, 2005). To fully evaluate the scenario, an in-depth functional analysis of the ascidian Hox genes needs to be performed.…”

Section: Introductionmentioning

confidence: 99%

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Limited functions of Hox genes in the larval development of the ascidian Ciona intestinalis

2010

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SUMMARYIn animals, region specific morphological characters along the anteroposterior axis are controlled by a number of developmental genes, including Hox genes encoding homeodomain transcription factors. Although Hox genes have been regarded to play a key role in the evolution of morphological diversity, as well as in the establishment of the body plan, little is known about the function of Hox genes in invertebrates, except for in insects and nematodes. The present study addresses the role of Hox genes in body patterning during the larval development of the ascidian Ciona intestinalis conducting knockdown experiments of the seven Hox genes expressed during embryogenesis. Experimental results have demonstrated that Ci-Hox12 plays an important role in tail development through the maintenance of expression of Ci-Fgf8/17/18 and Ci-Wnt5 in the tail tip epidermis. Additionally, it has been shown that Ci-Hox10 is involved in the development of GABAergic neurons in the dorsal visceral ganglion. Surprisingly, knockdown of Ci-Hox1, Ci-Hox2, Ci-Hox3, Ci-Hox4 and Ci-Hox5 did not give rise to any consistent morphological defects in the larvae. Furthermore, expression of neuronal marker genes was not affected in larvae injected with MOs against Ci-Hox1, Ci-Hox3 or Ci-Hox5. In conclusion, we suggest that the contribution of Hox genes to the larval development of the ascidian C. intestinalis might be limited, despite the fact that Ci-Hox10 and Ci-Hox12 play important roles in neuronal and tail development.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

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Limited functions of Hox genes in the larval development of the ascidian Ciona intestinalis

2010

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“…Urochordata: For Ciona intestinalis (Ikuta et al, 2004;Spagnuolo et al, 2003) and O. dioica (Seo et al, 2004), information was available from genome sequencing, reviewed in (Ikuta and Saiga, 2005 Fig. 2.…”

Section: Appendixmentioning

confidence: 99%

“…Given the likely position of Xenoturbella as one of the most basal deuterostomes, the analysis of its Hox gene complement is of utmost importance for our understanding of the evolution of Hox gene clusters (see e.g., Garcia-Fernández, 2005;Ikuta and Saiga, 2005;Lemons and McGinnis, 2006;Prohaska et al, 2006 for recent reviews). Here we report therefore on a polymerase chain reaction (PCR) survey of Hox homeobox fragments in X. bocki.…”

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confidence: 99%

PCR survey of Xenoturbella bocki Hox genes

Fritzsch¹,

Böhme²,

Thorndyke³

et al. 2007

J Exp Zool Pt B

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Xenoturbella bocki has recently been identified as one of the most basal deuterostomes, although an even more basal phylogenetic position cannot be ruled out. Here we report on a polymerase chain reaction survey of partial Hox homeobox sequences of X. bocki. Surprisingly, we did not find evidence for more than five Hox genes, one clear labial/PG1 ortholog, one posterior gene most similar to the PG9/10 genes of Ambulacraria, and three central group genes whose precise assignment to a specific paralog group remains open. We furthermore report on a re-evaluation of the available published evidence of Hox genes in other basal deuterostomes.

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Evolutionary perspectives from development of mesodermal components in the lamprey

Kusakabe¹,

Kuratani²

2007

Developmental Dynamics

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Lampreys, a jawless vertebrate species, lack not only jaws but also several other organs, including ventral migratory muscles shared by gnathostomes. In the lamprey embryo, the mesoderm consists primarily of unsegmented head mesoderm, segmented somites, and yet uncharacterized lateral plate mesoderm, as in gnathostomes. Although the adult lamprey possesses segmented myotomes in the head, the head mesoderm of this animal is primarily unsegmented, similar to that in gnathostomes. In the trunk, the large part of lamprey somites is destined to form myotomes, and the Pax3/7 gene expression domain in the lateral part of somites is suggested to represent a dermomyotome homologue. Lamprey myotomes are not segregated by a horizontal myoseptum, which has been regarded as consistent with the apparent absence of a migratory population of hypaxial muscles shared by gnathostomes. However, recent analysis suggests that lampreys have established the gene regulatory cascade necessary for the ventrally migrating myoblasts, which functions in part during the development of the primordial hypobranchial muscle. There have also been new insights on the developmental cascade of lamprey cartilages, in which the Sox family of transcription factors plays major roles, as in gnathostomes. Thus, mesoderm development in lampreys may represent the ancestral state of gene regulatory mechanisms required for the evolution of the complex and diverse body plan of gnathostomes. Developmental Dynamics 236:2410 -2420, 2007.

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Organization of Hox genes in ascidians: Present, past, and future

Cited by 41 publications

References 76 publications

Limited functions of Hox genes in the larval development of the ascidian Ciona intestinalis

Limited functions of Hox genes in the larval development of the ascidian Ciona intestinalis

PCR survey of Xenoturbella bocki Hox genes

Evolutionary perspectives from development of mesodermal components in the lamprey

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