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[
BioEssays,
1997]
Axis specification is the first step in defining specific regions of the developing embryo. Embryos exploit asymmetries, either pre-existing in the egg or triggered by external cues, to establish embryonic axes. The axial information is then used to generate regional differences within the embryo. In this review, we discuss experiments in animals which address three questions: whether the unfertilized egg is constructed with pre-determined axes, what cues are used to specify the embryonic axes, and how these cues are interpreted to generate the initial regional differences within the embryo. Based on mapping the data onto an animal phylogeny, we then propose a scenario for how this primary developmental decision occurred in ancestral metazoans.
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[
Curr Biol,
2000]
Researchers have suspected that initial polarization of the Caenorhabditis elegans embryo might be directed by microtubules, but demonstrating this has faced obstacles. A new study has cleverly bypassed these obstacles.
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[
Curr Biol,
2003]
Many cells divide asymmetrically by shifting their division machinery toward a specific region of the cell cortex, but little is known about how this occurs. Three recent papers have implicated activators of heterotrimeric G protein signaling in this process in Caenorhabditis elegans.
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[
Dev Suppl,
1993]
The polarization of the embryonic axes is a key event in embryogenesis, being one of the earliest manifestations of the shape and form of the organism. The acquisition of polarity by individual blastomeres is one of the earliest indicators of commitment to a particular pathway of differentiation. These phenomena have been studied in the development of C. elegans both at the cellular and organismal level. This review summarizes what is known about how polarity is established in the blastomeres of this organism, how the division axes of polarized cells are determined, and how the embryonic axes are set up.
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Dev Cell,
2007]
The par genes were discovered in genetic screens for regulators of cytoplasmic partitioning in the early embryo of C. elegans, and encode six different proteins required for asymmetric cell division by the worm zygote. Some of the PAR proteins are localized asymmetrically and form physical complexes with one another. Strikingly, the PAR proteins have been found to regulate cell polarization in many different contexts in diverse animals, suggesting they form part of an ancient and fundamental mechanism for cell polarization. Although the picture of how the PAR proteins function remains incomplete, cell biology and biochemistry are beginning to explain how PAR proteins polarize cells.
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Philos Trans R Soc Lond B Biol Sci,
2001]
The phylum Nematoda serves as an excellent model system for exploring how development evolves, using a comparative approach to developmental genetics. More than 100 laboratories are studying developmental mechanisms in the nematode Caenorhabditis elegans, and many of the methods that have been developed for C. elegans can be applied to other nematodes. This review summarizes what is known so far about steps in early development that have evolved in the nematodes, and proposes potential experiments that could make use of these data to further our understanding of how development evolves. The promise of such a comparative approach to developmental genetics is to fill a wide gap in our understanding of evolution-a gap spanning from mutations in developmental genes through to their phenotypic results, on which natural selection may act.
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Trends Cell Biol,
2016]
Most current research in cell biology uses just a handful of model systems including yeast, Arabidopsis, Drosophila, Caenorhabditis elegans, zebrafish, mouse, and cultured mammalian cells. And for good reason - for many biological questions, the best system for the question is likely to be found among these models. However, in some cases, and particularly as the questions that engage scientists broaden, the best system for a question may be a little-studied organism. Modern research tools are facilitating a renaissance for unusual and interesting organisms as emerging model systems. As a result, we predict that an ever-expanding breadth of model systems may be a hallmark of future cell biology.
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Dev Dyn,
2000]
Many cells must divide in specific orientations, yet for only a handful of cases do we have some understanding of how cells choose division orientations. We know of only a few cases where division orientations are controlled by specific cell-cell interactions. These cases are of interest, because they tell us something new and seemingly fundamental about how cells can function during development. Here, the evidence that interactions control division orientation in some cells of the early C. elegans embryo is presented, and what is known about how contact can regulate division orientation is discussed. Whether contact-mediated division orientation is a peculiarity of C. elegans or whether it may be more widespread is addressed.
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Genetics,
2020]
Gastrulation is fundamental to the development of multicellular animals. Along with neurulation, gastrulation is one of the major processes of morphogenesis in which cells or whole tissues move from the surface of an embryo to its interior. Cell internalization mechanisms that have been discovered to date in <i>Caenorhabditis elegans</i> gastrulation bear some similarity to internalization mechanisms of other systems including <i>Drosophila</i>, <i>Xenopus</i>, and mouse, suggesting that ancient and conserved mechanisms internalize cells in diverse organisms. <i>C. elegans</i> gastrulation occurs at an early stage, beginning when the embryo is composed of just 26 cells, suggesting some promise for connecting the rich array of developmental mechanisms that establish polarity and pattern in embryos to the force-producing mechanisms that change cell shapes and move cells interiorly. Here, we review our current understanding of <i>C. elegans</i> gastrulation mechanisms. We address how cells determine which direction is the interior and polarize with respect to that direction, how cells change shape by apical constriction and internalize, and how the embryo specifies which cells will internalize and when. We summarize future prospects for using this system to discover some of the general principles by which animal cells change shape and internalize during development.