Spatial distribution of two maternal messengers in Paracentrotus lividus during oogenesis and embryogenesis.

Carlo, Marta Di; Romancino, Daniele P.; Montana, Giovanna; Ghersi, Giulio

doi:10.1073/pnas.91.12.5622

Cited by 34 publications

(11 citation statements)

References 34 publications

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“…For instance, orthodenticle-related transcripts that are evenly distributed in the unfertilized eggs and in the early cleavage embryos have recently been identified in Strongylocentrotus purpuratus (18). Zygotic (22) and maternal (35) restricted to the animal region have also been described. Finally, PlHboxl2, for the reasons outlined below, might also be involved in the mechanism of initial specification of the embryonic cells.…”

Section: Discussionmentioning

confidence: 99%

Homeobox-containing gene transiently expressed in a spatially restricted pattern in the early sea urchin embryo.

Bernardo¹,

Russo²,

Oliveri³

et al. 1995

Proc. Natl. Acad. Sci. U.S.A.

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In the sea urchin embryo, the lineage founder cells whose polyclonal progenies will give rise to five different territories are segregated at the sixth division. To investigate the mechanisms by which the fates of embryonic cells are first established, we looked for temporal and spatial expression of homeobox genes in the very early cleavage embryos. We report evidence that PlHboxl2, a paired homeobox-containing gene, is expressed in the embryo from the 4-cell stage. The abundance of the transcripts reaches its maximum when the embryo has been divided into the five polyclonal territoriesnamely at the 64-cell stage-and it abruptly declines at later stages of development. Blastomere dissociation experiments indicate that maximal expression ofPlHboxl2 is dependent on intercellular interactions, thus suggesting that signal transduction mechanisms are responsible for its transcriptional activation in the early cleavage embryo. Spatial expression of PlHboxl2 was determined by whole-mount in situ hybridization. PlHboxl2 transcripts in embryos at the fourth, fifth, and sixth divisions seem to be restricted to the conditionally specified ectodermal lineages. These results suggest a possible role of the PlHboxl2 gene in the early events of cell specification of the presumptive ectodermal territories.In metazoan organisms, commitment of cells to a particular fate or set of fates takes place by three known modes. Syncitial specification is the mechanism used by Drosophila and most insect embryos. Blastomere specification is largely conditional in most invertebrate embryos, and conditional specification is also the major mechanism operating after cellularization in Drosophila. Finally, in most invertebrate embryos the fates of some blastomeres are mostly determined by autonomous specification processes (1, 2). In the sea urchin embryo, specification of cell fates is both cell autonomous and conditional. Only the four micromeres that arise at the vegetal pole at the fourth division appear to be autonomously specified (3). If removed from the embryo and cultured, the micromeres will in fact differentiate in skeletogenic mesenchyme cells, form spicules, and express the cell-lineage marker genes (4-7).Founder cells that are conditionally specified constitute a large fraction of the sea urchin embryo (3). Lithium and phorbol 12-myristate 13-acetate, which are known to affect the inositol phosphate and the protein kinase C second messenger pathways (8-10), respectively, alter cell fate during development. Therefore, signal transduction mechanisms, activated by ligand-receptor interactions, are most probably involved in the specification of adjacent blastomeres. Initial specification of founder cells ends at the sixth cleavage. After segregation of the lineages, the sea urchin embryo at the 64-cell stage can be divided into five polyclonal territories that will differentiate into various structures of the pluteus (11,12).The molecular details of blastomere specification in the sea urchin remain to be elucidated. To clarify ...

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Section: Discussionmentioning

confidence: 99%

Homeobox-containing gene transiently expressed in a spatially restricted pattern in the early sea urchin embryo.

Bernardo¹,

Russo²,

Oliveri³

et al. 1995

Proc. Natl. Acad. Sci. U.S.A.

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“…Both the mRNA and proteins of the Bep family are prelocalized to the animal side of eggs during oogenesis (Di Carlo et al 1994. Incubation of embryos with a Fab fragment directed against Bep4 protein caused exogastrulation, probably via the Wnt signaling pathway and cadherin (Romancino et al 2001).…”

Section: Introductionmentioning

confidence: 99%

Transient activation of the micro1 homeobox gene family in the sea urchin (Hemicentrotus pulcherrimus) micromere

et al. 2002

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The animal-vegetal (A-V) axis of sea urchin embryos is morphologically evident at the 16-cell stage of development. Mesomeres, macromeres, and micromeres are arrayed along the A-V axis. The vegetal micromere differentiates into the skeletogenic mesenchyme and functions as a signaling center. To date, no zygotic or maternally specified gene with restricted expression in the micromere at the 16-cell stage has been reported. We performed subtraction PCR and dot blot hybridization using poly(A)+ RNA extracted from the micromere (tester) and the mesomere (driver) in order to identify micromere-specific genes. Using a cDNA fragment identified in this screen, we isolated four similar but distinct cDNA clones from a library, which corresponded to a group of genes that we refer to as the micro1 family. The micro1 family encoded putative transcription factors with a homeodomain which had 87-95% identity between family members. The most highly conserved protein was encoded by PlHbox12 from Paracentrotus lividus (71-76% identity among family members). Northern blot hybridization and in situ hybridization demonstrated that micro1 was transiently activated during the early cleavage stages and that the transcript was restricted to the micromere. Thus, the expression domain was complementary to that of PlHbox12 along the A-V axis. The micro1 gene family has at least six loci, including polymorphic alleles, which are probably clustered in the genome. PlHbox12 and micro1 constitute a novel family of paired-like class homeobox genes. Phylogenetic analyses suggest that PlHbox12/micro1 evolved exceptionally rapidly.

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“…Oogenesis in sea urchins is a process that has been studied intensively (Di Carlo et al 1994;Byrne et al 1999;Walker et al 2005;Song et al 2006). Many transcriptional factors that are responsible for the unique transcriptional activity seen in oocytes have been described in the sea urchin Strongylocentrotus purpuratus (Song et al 2006).…”

Section: Introductionmentioning

confidence: 99%

Isolation of oogonia from ovaries of the sea urchin Strongylocentrotus nudus

et al. 2010

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The presence of oogonia in the ovaries of adult females is typical in species with a broadcast spawning reproductive strategy, including invertebrates and lower vertebrates. In sea urchins, difficulties in the study of oogonia arise from the small number of these cells and the lack of specific markers for their identification. Therefore, more reliable methods are needed for identifying and manipulating oogonial cells in quantities sufficient for experimentation. Homologs of the DEAD-box RNA helicase vasa expressed in germline cells have been proposed for use as markers to detect germline cells in diverse species. We have developed a method for the isolation of sea urchin oogonia by using immunocytochemistry with vasa antibodies, together with reverse transcription and the polymerase chain reaction to detect the expression of Sp-vasa and Sp-nanos2 homologs and a morphological approach to identify germline cells in sea urchin ovaries and cell fractions isolated from the ovarian germinal epithelium. This method has allowed us to obtain 15%-18% of small oogonia with 70%-75% purity from the total amount of isolated germ cells. Our findings represent the first methodological basis for obtaining cell populations containing sea urchin oogonia; this method might be useful as a tool for further investigations of the early stages of sea urchin oogenesis.

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Spatial distribution of two maternal messengers in Paracentrotus lividus during oogenesis and embryogenesis.

Cited by 34 publications

References 34 publications

Homeobox-containing gene transiently expressed in a spatially restricted pattern in the early sea urchin embryo.

Homeobox-containing gene transiently expressed in a spatially restricted pattern in the early sea urchin embryo.

Transient activation of the micro1 homeobox gene family in the sea urchin (Hemicentrotus pulcherrimus) micromere

Isolation of oogonia from ovaries of the sea urchin Strongylocentrotus nudus

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