Induction of Secondary Embryos by Intra‐ and Interspecific Grafts of Center Cells under the blastopore in Horseshoe Crabs

Itow, Tomio; Kenmochi, Shigeki; Mochizuki, Taeko

doi:10.1111/j.1440-169x.1991.00251.x

Cited by 21 publications

(16 citation statements)

References 9 publications

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“…In a seminal, but rarely cited paper, Itow et al elegantly transplanted a small number of center cells of early gastrulae in Limulus and were able to induce duplication of the embryonic axes. (23) This finding suggests Spemann-type organizer capabilities for this group of cells in chelicerates.…”

Section: From Techniques To Biological Questions: Evolution Of Axial mentioning

confidence: 91%

Mity model: Tetranychus urticae, a candidate for chelicerate model organism

et al. 2007

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Chelicerates (scorpions, horseshoe crabs, spiders, mites and ticks) are the second largest group of arthropods and are of immense importance for fundamental and applied science. They occupy a basal phylogenetic position within the phylum Arthropoda, and are of crucial significance for understanding the evolution of various arthropod lineages. Chelicerates are vectors of human diseases, such as ticks, and major agricultural pests, such as spider mites, thus this group is also of importance for both medicine and agriculture. The developmental genetics of chelicerates is poorly understood and a challenge for the future progress for many aspects of chelicerate biology is the development of a model organism for this group. Toward this end, we are developing a chelicerate genetic model: the two-spotted spider mite Tetranychus urticae. T. urticae has the smallest genome of any arthropod determined so far (75 Mbp, 60% of the size of the Drosophila genome), undergoes rapid development and is easy to maintain in the laboratory. These features make T. urticae a promising reference organism for the economically important, poorly studied and species-rich chelicerate lineage.

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Section: From Techniques To Biological Questions: Evolution Of Axial mentioning

confidence: 91%

Mity model: Tetranychus urticae, a candidate for chelicerate model organism

et al. 2007

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“…Like the spiders, the development of the horseshoe crab (Itow et al, 1991) and some insects (Sander, 1976) seems to be regulative. Probably in these arthropod species, the axial pattern formation largely relies on cellcell interactions.…”

Section: Regulative Development Of the Early Spider Embryomentioning

confidence: 99%

Early patterning of the spider embryo: a cluster of mesenchymal cells at the cumulus produces Dpp signals received by germ disc epithelial cells

Akiyama-Oda¹,

Oda²

2003

Development

138

242

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In early embryogenesis of spiders, the cumulus is characteristically observed as a cellular thickening that arises from the center of the germ disc and moves centrifugally. This cumulus movement breaks the radial symmetry of the germ disc morphology, correlating with the development of the dorsal region of the embryo. Classical experiments on spider embryos have shown that a cumulus has the capacity to induce a secondary axis when transplanted ectopically. In this study, we have examined the house spider, Achaearanea tepidariorum, on the basis of knowledge from Drosophila to characterize the cumulus at the cellular and molecular level. In the cumulus, a cluster of about 10 mesenchymal cells, designated the cumulus mesenchymal (CM) cells, is situated beneath the epithelium, where the CM cells migrate to the rim of the germ disc. Germ disc epithelial cells near the migrating CM cells extend cytoneme-like projections from their basal side onto the surface of the CM cells. Molecular cloning and whole-mount in situ hybridization showed that the CM cells expressed a spider homolog of Drosophila decapentaplegic (dpp), which encodes a secreted protein that functions as a dorsal morphogen in the Drosophila embryo. Furthermore, the spider Dpp signal appeared to induce graded levels of the phosphorylated Mothers against dpp (Mad) protein in the nuclei of germ disc epithelial cells. Adding data from spider homologs of fork head, orthodenticle and caudal, we suggest that, in contrast to the Drosophila embryo, the progressive mesenchymalepithelial cell interactions involving the Dpp-Mad signaling cascade generate dorsoventral polarity in accordance with the anteroposterior axis formation in the spider embryo. Our findings support the idea that the cumulus plays a central role in the axial pattern formation of the spider embryo.Movie and supplemental figure available online

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“…S2 in the supplementary material) or experimentally in spiders, horseshoe crabs and short-germ insects (Holm, 1952;Sekiguchi, 1957;Seitz, 1970;Sander, 1976;Itow et al, 1991). These may indicate the existence of different modes of axis specification from that of Drosophila.…”

Section: Introductionmentioning

confidence: 99%

Axis specification in the spider embryo:dppis required for radial-to-axial symmetry transformation andsogfor ventral patterning

2006

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The mechanism by which Decapentaplegic (Dpp) and its antagonist Short gastrulation (Sog) specify the dorsoventral pattern in Drosophila embryos has been proposed to have a common origin with the mechanism that organizes the body axis in the vertebrate embryo. However, Drosophila Sog makes only minor contributions to the development of ventral structures that hypothetically correspond to the vertebrate dorsum where the axial notochord forms. In this study, we isolated a homologue of the Drosophila sog gene in the spider Achaearanea tepidariorum, and characterized its expression and function. Expression of sog mRNA initially appeared in a radially symmetrical pattern and later became confined to the ventral midline area, which runs axially through the germ band. RNA interference-mediated depletion of the spider sog gene led to a nearly complete loss of ventral structures, including the axial ventral midline and the central nervous system. This defect appeared to be the consequence of dorsalization of the ventral region of the germ band. By contrast, the extra-embryonic area formed normally. Furthermore, we showed that embryos depleted for a spider homologue of dpp failed to break the radial symmetry, displaying evenly high levels of sog expression except in the posterior terminal area. These results suggest that dpp is required for radial-to-axial symmetry transformation of the spider embryo and sog is required for ventral patterning. We propose that the mechanism of spider ventral specification largely differs from that of the fly. Interestingly, ventral specification in the spider is similar to the process in vertebrates in which the antagonism of Dpp/BMP signaling plays a central role in dorsal specification.

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Induction of Secondary Embryos by Intra‐ and Interspecific Grafts of Center Cells under the blastopore in Horseshoe Crabs

Cited by 21 publications

References 9 publications

Mity model: Tetranychus urticae, a candidate for chelicerate model organism

Mity model: Tetranychus urticae, a candidate for chelicerate model organism

Early patterning of the spider embryo: a cluster of mesenchymal cells at the cumulus produces Dpp signals received by germ disc epithelial cells

Axis specification in the spider embryo:dppis required for radial-to-axial symmetry transformation andsogfor ventral patterning

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