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Adv Genet,
1990]
As recognized by T. H. Morgan, the problems of genetics and development are interwoven. Morgan noted that understanding how the genotype of an organism specifies its phenotype would require knowing the fundamental mechanisms of gene action, how genes interact to specify the properties of cells, and how cells interact to specify each adult character. We now have a basic understanding of the primary effects of genes (to encode protein or RNA products). However, little is known about how the genes of a zygote specify a complex pattern of cell divisions, the generation of diverse cell types, and the arrangement of those cells into specific morphological structures. A "favorable material" (as Morgan put it) for investigating these problems would be a simple organism in which development could be analyzed at the level of single genes and single cells. The small free-living soil nematode Caenorhabditis elegans is such an organism...
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Ageing Res Rev,
2013]
We have conducted a comprehensive literature review regarding the effect of vitamin E on lifespan in model organisms including single-cell organisms, rotifers, Caenorhabditis elegans, Drosophila melanogaster and laboratory rodents. We searched Pubmed and ISI Web of knowledge for studies up to 2011 using the terms "tocopherols", "tocotrienols", "lifespan" and "longevity" in the above mentioned model organisms. Twenty-four studies were included in the final analysis. While some studies suggest an increase in lifespan due to vitamin E, other studies did not observe any vitamin E-mediated changes in lifespan in model organisms. Furthermore there are several studies reporting a decrease in lifespan in response to vitamin E supplementation. Different outcomes between studies may be partly related to species-specific differences, differences in vitamin E concentrations and the vitamin E congeners administered. The findings of our literature review suggest that there is no consistent beneficial effect of vitamin E on lifespan in model organisms which is consistent with reports in human intervention studies.
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Hermann, Editeurs des Sciences et des Arts. Paris, France.,
2002]
L'espce Caenorhabditis elegans fut dcrite en 1900 Alger par E. Maupas, qui s'intressait son mode de reproduction hermaphrodite. Plus tard, vers le milieu du vingtime sicle, V. Nigon et ses collaboratuers Lyon tudirent les reorganizations cellulaires accompagnant la fecundation et les premiers clivages. J. Brun isola les preiers mutants morpholgiques.
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Parasite,
1994]
Two genes coding for cuticlin components of Coenorhabditis elegans have been cloned and their structure is described. Recombinant proteins have been produced in E. coli and antibodies raised against them. Nucleic acid and specific antibodies are being used to isolate the homologues from the parasitic species Ascaris lumbricoides and Brugia pahangi.
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Annual Review of Genetics,
1984]
As recognized by T. H. Morgan, the problems of genetics and development are interwoven: understanding how the genotype of an organism specifies its phenotype requires knowing the fundamental mechanism of gene action, how genes interact to specify the properties of cells, and how cells interact to specify each adult character. We now know that the primary effect of a gene is to encode a protein or RNA product. However, little is known about how the genes of a zygote specify a complex pattern of cell divisions, the generation of diverse cell types, and the arrangement of those cells into specific morphological structures. A "favorable material" (as Morgan put it) for investigating these problems would be a simple organism in which development could be analyzed at the level of single genes and single cells. The small free-living soil nematode Caenorhabditis elegans is such an organism. C. elegans is easily grown and handled in the laboratory and is well suited for both genetic and developmental studies. This nematode consists of only about 1,000 (non-germ) cells, and both its anatomy and its development are essentially invariant. The complete anatomy of C. elegans, including the "wiring diagram" of the nervous system, is known at an ultrastructural level. In addition, the developmental origin of every cell is known since the complete cell lineage from the zygote to the adult has been determined. The genetic properties of C. elegans allow researchers to combine the classical Mendelian approach of Morgan and his coworkers with the approach of modern microbial genetics: C. elegans is diploid but microscopic in size (so large numbers of animals can be handled, up to 10*5 on a single petri dish) and has a very rapid life cycle (an egg matures into a fertile adult within two to four days, depending upon temperature; this adult produces 300-400 progeny over the next few days, resulting in an effective organismal doubling time of about 15 hours). Many aspects of the biology of C. elegans have been reviewed. Here we describe how these features have led to an initial understanding of some of the issues concerning genetics and development that Morgan raised fifty years ago. We review the methods underlying and the results derived form four approaches that have been used to study the genetics of nematode development. The first approach, which takes advantage of the genetic diversity generated by evolution, is to compare the development of related species. For example, simple differences in otherwise identical cell lineages may be the result of one or a few mutational events that occurred during the divergence of two species; the nature of these differences can suggest ways in which genes may control development. The second approach is to identify a large set of mutations that affect particular cell lineages; this approach can indicate the number, types, and specificities of genes that affect particular developmental events. The third approach involves the detailed genetic analyses of genes identified by mutations that alter development; such studies can reveal the wild-type functions of those genes and thereby identify genes that play regulatory roles in development. The fourth approach is to examine the interactions among mutations using studies of extragenic suppression and epistasis; this type of analysis can suggest how genes interact during normal development to
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Seminars in Developmental Biology,
1994]
Gastrulation in Caenorhabditis elegans has been described by following the movements of individual nuclei in living embryos by Nomarski microscopy. Gastrulation starts in the 26-cell stage when the two gut precursors, Ea and Ep, move into the blastocoele. The migration of Ea and Ep does not depend on interactions with specific neighboring cells and appears to rely on the earlier fate specification of the E lineage. In particular, the long cell cycle length of Ea and Ep appears important for gastrulation. Later in embryogenesis, the precursors to the germline, muscle and pharynx join the E descendants in the interior. As in other organisms, the movement of gastrulation permit novel cell contacts that are important for the specification of certain cell fates.
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Wiley Interdiscip Rev Dev Biol,
2013]
The transcriptional regulatory hierarchy that controls development of the Caenorhabditis elegans endoderm begins with the maternally provided SKN-1 transcription factor, which determines the fate of the EMS blastomere of the four-cell embryo. EMS divides to produce the posterior E blastomere (the clonal progenitor of the intestine) and the anterior MS blastomere, a major contributor to mesoderm. This segregation of lineage fates is controlled by an intercellular signal from the neighboring P2 blastomere and centers on the HMG protein POP-1. POP-1 would normally repress the endoderm program in both E and MS but two consequences of the P2-to-EMS signal are that POP-1 is exported from the E-cell nucleus and the remaining POP-1 is converted to an endoderm activator by complexing with SYS-1, a highly diverged -catenin. In the single E cell, a pair of genes encoding small redundant GATA-type transcription factors, END-1 and END-3, are transcribed under the combined control of SKN-1, the POP-1/SYS-1 complex, as well as the redundant pair of MED-1/2 GATA factors, themselves direct zygotic targets of SKN-1 in the EMS cell. With the expression of END-1/END-3, the endoderm is specified. END-1 and END-3 then activate transcription of a further set of GATA-type transcription factors that drive intestine differentiation and function. One of these factors, ELT-2, appears predominant; a second factor, ELT-7, is partially redundant with ELT-2. The mature intestine expresses several thousand genes, apparently all controlled, at least in part, by cis-acting GATA-type motifs.
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Curr Opin Chem Biol,
2014]
The site specific, co-translational introduction of unnatural amino acids into proteins produced in cells has been facilitated by the development of the pyrrolysyl-tRNA synthetase/tRNACUA pair. This pair can now be used to direct the site-specific incorporation of designer amino acids in E. coli, yeast, mammalian cells, and animals (the worm, C. elegans and the fly, D. melanogaster). Developments in encoding components of rapid bioorthogonal reactions are providing new opportunities for labelling and visualising proteins. A new method called stochastic orthogonal recoding of translation with chemoselective modification (SORT-M) leverages advances in genetic code expansion and bioorthogonal chemistry to label proteomes with diverse chemistry at diverse codons in E. coli, mammalian cells, and in spatially and temporally defined sets of cells in the fly. Proteomes in targeted sets of cells have been visualised by SORT-M and proteins in targeted cells have been identified by SORT-M.
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Mol Reprod Dev,
2015]
Developmental robustness is the ability of an embryo to develop normally despite many sources of variation, from differences in the environment to stochastic cell-to-cell differences in gene expression. The nematode Caenorhabditis elegans exhibits an additional level of robustness: Unlike most other animals, the embryonic pattern of cell divisions is nearly identical from animal to animal. The endoderm (gut) lineage is an ideal model for studying such robustness as the juvenile gut has a simple anatomy, consisting of 20 cells that are derived from a single cell, E, and the gene regulatory network that controls E specification shares features with developmental regulatory networks in many other systems, including genetic redundancy, parallel pathways, and feed-forward loops. Early studies were initially concerned with identifying the genes in the network, whereas recent work has focused on understanding how the endoderm produces a robust developmental output in the face of many sources of variation. Genetic control exists at three levels of endoderm development: Progenitor specification, cell divisions within the developing gut, and maintenance of gut differentiation. Recent findings show that specification genes regulate all three of these aspects of gut development, and that mutant embryos can experience a "partial" specification state in which some, but not all, E descendants adopt a gut fate. Ongoing studies using newer quantitative and genome-wide methods promise further insights into how developmental gene-regulatory networks buffer variation. Mol. Reprod. Dev. 2015. 2015 Wiley Periodicals, Inc.
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FEBS Lett,
1992]
The Caenorhabditis elegans and Artemia T4 globin sequences are highly homologous with other invertebrate globins. The intron/exon patterns of their genes display a single intron in the E and G helices respectively. Precoding introns in multirepeat globins are inserted in homologous positions. Comparison of the intron/exon patterns in the known globin gene sequences demonstrates that they are more diverse than first expected but nevertheless can be derived from an ancestral pattern having 3 introns and 4 exons.