Role of the nanos homolog during sea urchin development

Department of Mathematical and Life Sciences, Graduate School of Science, Hiroshima University, Higashi-Hiroshima, Japan.
Developmental Dynamics (Impact Factor: 2.38). 10/2009; 238(10):2511-21. DOI: 10.1002/dvdy.22074
Source: PubMed


The nanos genes play important roles in the development of primordial germ cells in animal species. In the sea urchin, Hemicentrotus pulcherrimus, small micromere descendants specifically express HpNanos mRNA and this expression continues in the left coelomic pouch, which produces the major component of the adult rudiment. In this study, we showed that morpholino knockdown of HpNanos resulted in a delay of primary mesenchyme cell ingression and a decrease in the number of cells comprising the left coelomic pouch. Knockdown analysis in chimeras and whole embryos revealed the disappearance of small micromere descendants from the archenteron tip. Furthermore, the expression of HpNanos mRNA was induced in other cell lineages in the HpNanos-knockdown and micromere-deleted embryos. Taken together, our results suggest that HpNanos is involved in the inductive interaction of small micromere descendants with other cell lineages, and that HpNanos is required for the survival of small micromere descendants.

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Available from: Hiroshi Ochiai, Oct 13, 2014
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    • "Like other echinoderms, most sea urchins have an indirect development through larval stages following metamorphosis. The sea urchin germ line is known to be segregated after the fifth cleavage of embryo in the form of small micromeres, later included in the adult rudiment of the larvae (Voronina et al., 2008; Fujii et al., 2009; Juliano et al., 2010; Yajima and Wessel, 2011a). The regulation of sea urchin germ line determination evidently displays a combination of inheritance and induction, thus presenting a similarity to both Drosophila and mice. "
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    ABSTRACT: Background: Animal germ cells have specific organelles that are similar to ribonucleoprotein complex called germ plasm, which is accumulated in eggs. Germ plasm is essential for inherited mechanism of germ line segregation in early embryogenesis. Sea urchins have early germ line segregation in early embryogenesis. Nevertheless, organization of plasm-related organelles and their molecular composition are still unclear. Another issue is whether maternally accumulated germ plasm exists in the sea urchin eggs. Results: I analyzed intracellular localization of germ plasm during oogenesis in sea urchin Strongylocentrotus intermedius by using morphological approach and immunocytochemical detection of Vasa, a germ plasm marker. All of ovarian germ cells have germ plasm-related organelles in the form of germ granules, Balbiani bodies and perinuclear nuage found previously in germ cells in other animals. Maternal germ plasm is accumulated in late oogenesis at the cell periphery. Cytoskeletal drug treatment showed an association of Vasa-positive granules with actin filaments in the egg cortex. Conclusions: All of female germ cells of sea urchins have germ plasm-related organelles. Eggs have a maternally accumulated germ plasm associated with cortical cytoskeleton. These findings correlate with early segregation of germ line in sea urchins. This article is protected by copyright. All rights reserved.
    Developmental Dynamics 09/2015; DOI:10.1002/dvdy.24348 · 2.38 Impact Factor
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    • "Nodal signaling also appears to impinge upon the survival of sMics in the right coelomic pouch, which have been proposed to apoptose due to loss of Nanos expression (Fujii et al., 2009; Juliano et al., 2010). By the pluteus stage, the right sMics normally become TUNEL-positive, indicative of apoptosis; inhibition of Nodal prevented this apoptosis whereas elevating Nodal signaling with exogenous Activin induced apoptosis in left side sMics. "
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    ABSTRACT: The formation of the germ line in an embryo marks a fresh round of reproductive potential. The developmental stage and location within the embryo where the primordial germ cells (PGCs) form, however, differs markedly among species. In many animals, the germ line is formed by an inherited mechanism, in which molecules made and selectively partitioned within the oocyte drive the early development of cells that acquire this material to a germ-line fate. In contrast, the germ line of other animals is fated by an inductive mechanism that involves signaling between cells that directs this specialized fate. In this review, we explore the mechanisms of germ-line determination in echinoderms, an early-branching sister group to the chordates. One member of the phylum, sea urchins, appears to use an inherited mechanism of germ-line formation, whereas their relatives, the sea stars, appear to use an inductive mechanism. We first integrate the experimental results currently available for germ-line determination in the sea urchin, for which considerable new information is available, and then broaden the investigation to the lesser-known mechanisms in sea stars and other echinoderms. Even with this limited insight, it appears as sea stars, and perhaps the majority of the echinoderm taxon, rely on inductive mechanisms for germ-line fate determination. This enables a strongly contrasted picture for germ-line determination in this phylum, but one for which transitions between different modes of germ-line determination might now be experimentally addressed. Mol. Reprod. Dev. © 2013 Wiley Periodicals, Inc.
    Molecular Reproduction and Development 07/2014; 81(8). DOI:10.1002/mrd.22223 · 2.53 Impact Factor
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    • "Using sea urchins as a model, nanos has been found to be regulated by transcription, translation, and RNA stability. Moreover, the expression of nanos mRNA is inducible in other cell lineages in the Nanos knockdown and micromere-deleted embryos (Fujii et al., 2009; Juliano et al., 2010), suggesting that the small micromere descendants repress nanos mRNA expression in other cell lineage. It is unclear, however, if the effect is direct or indirect. "
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    ABSTRACT: Nanos is an essential factor of germ line success in all animals tested. This gene encodes a Zn-finger RNA-binding protein that in complex with its partner pumilio, binds to and changes the fate of several known transcripts. We summarize here the documented functions of nanos in several key organisms, and then emphasize echinoderms as a working model for how nanos expression is regulated. Nanos presence outside of the target cells is often detrimental to the animal, and in sea urchins, nanos expression appears to be regulated at every step of transcription, and post-transcriptional activity, making this gene product exciting, every which way. © 2013 Wiley Periodicals, Inc.
    genesis 03/2014; 52(3). DOI:10.1002/dvg.22737 · 2.02 Impact Factor
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