C Elegans Life Cycle

10 Key excerpts on "C Elegans Life Cycle"

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  Behavioral and Department Models

  • Bert Zuckerman(Author)
  • 2012(Publication Date)
  • Academic Press

    (Publisher)

  (From Schierenberg, 1978, reproduced by permission.) 8 Gunter von Ehrenstein and Einhard Schierenberg 2. Life Cycle Caenorhabditis elegans is easily and very inexpensively grown under control-lable laboratory conditions, which is important for a good model. Normally it is kept at 20°C on agar plates with E. coli as food source (Brenner, 1974). Growth and reproduction have been thoroughly analyzed at 16°, 20°, and 25°C, and de-velopmental chronologies for all three temperatures have been described (Byerly etal., 1975, 1976a,b). The life cycle of C. elegans is rapid and takes about 3.5 days (20°C). The eggs are fertilized upon passing the spermatheca and a tough shell forms around the egg, most likely chitinous, as in other nematodes (Christenson, 1950; Fairbairn, 1957; Rogers, 1962; Foor, 1967; Kaulenas and Fairbairn, 1968; Bird, 1971). The eggs start to cleave inside the mother; they are laid at about the 30-cell stage. Embryogenesis is very regular, and a juvenile with about 550 cells (Sulston and Horvitz, 1977) hatches from the egg case. In the period between hatching and the adult stage, the animal feeds and grows not only in size, but also in cell number, passing through four larval stages, L1-L4, and four molts. The times of the molts (at 20°C) are 13, 21.5, 29.5, and 41 hr after hatching, respectively; the sizes are about 350, 470, 640, and 890^m, respectively (Cassada and Russell, 1975). In the same period, the gonad, which contains four nuclei in the LI stage, increases to about 2500 in the mature adult (Hirsh et al., 1976). Other obvious morphological changes are the nongonadal sexual structures of hermaphrodites and males, which are not present in juveniles. Egg laying begins about 50 hr after hatching and each hermaphrodite produces 200-300 progeny (Byerly et al., 1976a). When adverse environmental conditions interfere with normal development, the L2 stage larvae go into a dormant survival stage known as the dauer larva (Cassada and Russell, 1975).

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  Handbook of the Biology of Aging

  • Edward J. Masoro, Steven N. Austad(Authors)
  • 2011(Publication Date)
  • Academic Press

    (Publisher)

  Throughout its relatively brief history, the study of C. elegans has relied on cur-rent methodology in both molecular genet-ics and in computer sciences, the first allowing the breakthroughs and the second allowing the wide dissemination of Chapter 13 Dissecting the Processes of Aging Using the Nematode Caenorhabditis elegans Samuel T. Henderson, Shane L. Rea, and Thomas E. Johnson Genetic variants that live longer than parental strains seem more likely than shorter-lived variants to be altered in primary rate-limiting processes that determine life-span. — Johnson & Wood, 1982 CHAPTER 13 / Dissecting the Processes of Aging Using the Nematode Caenorhabditis elegans 361 the results and rapid access to biological materials and information. These resources continue to be developed with centralized bioinformatics resources (http://www.wormbase.org) and genetic stocks maintained by the C. elegans Genetics Center. B. C. elegans as a Model for Aging C. elegans represents a relative newcomer among model genetic systems used in the study of aging. In fact, the species was not even listed in the Index in the first edition of the Handbook of the Biology of Aging in 1977. However, a full chapter appeared in the next three editions (Johnson, 1990a; Lithgow, 1996; Russell & Jacobson, 1985); but the absence of a chapter in the fifth edition, during a time of massive discover-ies, leaves a huge amount of work to be described and integrated by the authors of this chapter. Prior to 1982, the worm was used as a model for only a few aging studies, especially into altered rates of protein synthesis during aging and effects of drug interventions on longevity (Epstein & Gershon, 1972; Rothstein, 1980). Undoubtedly, the main reason for the prevalence of aging research on C.

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  Neurobehavioral Genetics

  Methods and Applications, Second Edition

  • Byron C. Jones, Pierre Mormede, Byron C. Jones, Pierre Mormede(Authors)
  • 2006(Publication Date)
  • CRC Press

    (Publisher)

  First, we will briefly describe this animal model, which has become increasingly popular for molecular and cellular biology studies, and then we will present a few examples of behavioral studies that are conducted on this organism. We aim to show that this model provides paradigms for questions central to many behaviors, and that they can be addressed at a single cell/single gene resolution. 24.2 C. ELEGANS AS A MODEL ORGANISM 24.2.1 C. ELEGANS H AS A V ERY S IMPLE N ERVOUS S YSTEM The nematode Caenorhabditis elegans is a free-living round worm present in the soils of temperate climates (Wood, 1988; Riddle et al., 1997). For laboratory use, it 354 Neurobehavioral Genetics can be grown easily on petri dishes seeded with Escherichia coli (Figure 24.1). Its length is about 1 mm as an adult and it has 959 somatic cells. Among those, 302 of them are neurons, which can be divided into 116 classes on the basis of their morphology (Figure 24.2). With a laser beam, it is possible to destroy a given neuron in an anaesthetized animal to assess the involvement of this neuron in a behavior or a function. Moreover, the—almost invariant—connectivity of all neurons has been established by 3D reconstruction of serially sectioned animals. At the molecular level, the nervous system of C. elegans shares a common organization with the far-distant vertebrates: its main excitatory transmitter is FIGURE 24.1 C. elegans on a culture plate. Worms of various stages can be seen, including eggs, larvae and adults. Adults are approximately 1 mm long. FIGURE 24.2 The nervous system of C. elegans . Most or all neurons of C. elegans are visualized by expressing a gpc-2::GFP construct. Weakly, staining of muscle cells can be seen. Arrows indicate the ventral nerve cord, a triangle indicates staining in the anterior ganglia, an asterisk indicates the posterior ganglia.

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  Chromosomal Instability and Aging

  Basic Science and Clinical Implications

  • Fuki Hisama, Sherman M. Weissman, George M. Martin(Authors)
  • 2003(Publication Date)
  • CRC Press

    (Publisher)

  20 Genetics of Aging in the Nematode Caenorhabditis elegans Philip S. Hartman Texas Christian University, Fort Worth, Texas, U.S.A. Naoaki Ishii Tokai University School of Medicine, Isehara, Kanagawa, Japan Thomas E. Johnson University of Colorado at Boulder, Boulder, Colorado, U.S.A. I. CAENORHABDITIS ELEGANS AS A MODEL SYSTEM FOR AGING RESEARCH Caenorhabditis elegans is a small nematode worm containing somewhat less than 1000 postmitotic, somatic cells at adulthood. Its invariant, mosaic pattern of de- velopment and self-fertilizing hermaphroditic life style have made it favorite of developmental biologists second only to Drosophila. Details on numerous aspects of its development and other aspects of current studies have been compiled in two books (1,2), and detailed methodologies can be found in the journal Methods in Cell Biology, Vol. 48 (3). Several online sources of information are available, including an informal newsletter, published by the C. elegans Stock Center (http://elegans.swmed.edu/), which also includes access to all nematode publica- tions (4654 at the time of this writing, including 146 cross referenced to aging). Numerous bioinformatics resources are available and can be accessed through the same URL or at http://www.wormbase.org/ and other sites. Biologists identified C. elegans as a good model for studying aging in the 1970s (reviewed in refs. 4–6). However, studies on aging were galvanized with the recognition that a lack of inbreeding depression and significant heritabil- ities makes it possible to identify genetic variants affecting the processes of 493 aging (7). Soon the first single-gene mutation (age-1) leading to longer-than- normal life span was identified (8) and subsequently mapped and shown to behave as a single gene (9). Mutations in age-1 are recessive to the wild type and dramatically lengthen life expectancy by an average of about 40% and maximum life span by about 70% (10).

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  Nematoda

  • Andreas Schmidt-Rhaesa(Author)
  • 2013(Publication Date)
  • De Gruyter

    (Publisher)

  A number of additional scientific milestones have been set with C. elegans . These include the entire cell lineages from the zygote to adult-hood (Sulston and Horvitz 1977, Kimble and Hirsh 1979, Sulston et al. 1983) and the complete wiring diagram of the nervous system (White et al. 1986). Groundbreaking methods like gene silencing by RNA interference (RNAi) (Fire et al. 1998, Ahringer 2006) and visualization of gene expression in vivo with the GFP technique (Chalfie et al. 1994, Boulin et al. 2006) were originally established in this system. The RNAi technology allowed the systematic ana-lysis of gene function by genome-wide RNAi screens. In 2002, 2006 and 2008, researchers working with C. elegans were awarded Nobel prizes in Medicine and Chemistry. 2.4.2.1 Zygote formation and embryogenesis: an overview Although the cellular development of the C. elegans embryo is very similar to the pattern described above for Ascaris (Figs. 2.1, 2.2), the complete cell-by-cell descrip-tion in vivo from first cleavage to hatching (Deppe et al. 1978, Sulston et al. 1983) and the visualization of subcel-lular structures, without any experimental interference, resulted in many new insights. This level of analysis will be treated first. Development in C. elegans is highly reproducible. It is many times faster and the egg is much more trans-parent than in Ascaris . Within about 13 h (at 21°C), a juvenile with exactly 558 cells develops from the unc-leaved egg. Embryogenesis can be subdivided into a “proliferation phase”, where nearly all embryonic cell divisions take place, and a “morphogenesis phase”, where the ball of cells gradually transforms into a worm Fig. 2.7 : Development of partial embryos in Parascaris . Development of embryos after UV-irradiation of blastomeres named in red. Modified from Stevens (1909).

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  Movement Disorders

  Genetics and Models

  • Mark S. LeDoux(Author)
  • 2014(Publication Date)
  • Academic Press

    (Publisher)

  Caenorhabditis elegans , toward the investigation of evolutionarily conserved functional relationships among organisms represents a rapid route toward a comprehensive understanding of cellular malfunction.

  6.1. Caenorhabditis elegans : Why the Worm?

  Starting in the early 1960s, Sydney Brenner championed the establishment of the nematode C. elegans as a model system for the investigation of embryonic and neuronal development (Wood, 1988 ). Brenner’s vision was centered on the premise that the simplicity of C. elegans anatomy and genetics, coupled with an ease of culturing, manipulation, and rapid generation time (3  days from fertilized egg to adult), would render it experimentally accessible for discerning more-complex issues of development (Brenner, 1974 ). Notably, although males can result from rare chromosomal nondisjunction events, C. elegans is primarily found as a hermaphrodite. The ability of this animal to self-fertilize is especially advantageous for purposes of laboratory propagation and in designing genetic crosses. Literally hundreds of isogenic animals can be obtained from a single worm in the course of several days, making expansion of stocks simple. Moreover, these microscopic worms (∼1  mm as an adult) can be stored frozen, much like bacterial and yeast cultures, and revived to replenish stocks even after several years in storage.

  In late 1998, C. elegans ushered in the genomic era for metazoan species, as it became the first animal to have its complete genome sequence released (

  The C. elegans Sequencing Consortium, 1998

  ). This milestone enabled rapid and comprehensive molecular analyses to be coupled to powerful traditional genetic resources within the context of a multicellular organism. These collectively augment existing and unique resources for this animal, such as a defined neuronal connectivity and fully mapped cell lineage (Bargmann, 1998

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  Biotechnology in Healthcare, Volume 2

  Applications and Initiatives

  • Debmalya Barh(Author)
  • 2022(Publication Date)
  • Academic Press

    (Publisher)

  Drosophila research has advanced our understanding of numerous human diseases' cellular and molecular mechanisms and how they are useful for translation research.

  2. Caenorhabditis elegans models for translational research

  Before diving into the translation significance of research performed using C. elegans, it will be good to know about the organism. C. elegans is a nonparasitic, transparent nematode worm whose life cycle starts with an egg, goes through several larval stages, and is finally an adult. It has an overall lifespan of 2–3weeks. An adult C. elegans has nearly 1000 somatic cells and is about 1mm in length. Although the size of this animal is small, it possesses many complex organ systems, such as the digestive system, nervous system, reproductive system, and muscular system. C. elegans exist in two sexes: a hermaphrodite and a male. A hermaphrodite worm can produce many progenies, while in the presence of a male, cross-fertilization happens. In the laboratory, C. elegans can be easily cultivated in large numbers on agar plates supplemented with the nonpathogenic bacterium Escherichia coli (Lewis and Fleming, 1995 ). In cases of food scarcity, the worm enters a “dauer” stage and can be maintained as such for months as a frozen stock at − 80°C (Apfeld and Alper, 2018 ).

  Ever since the 1970s, when Sydney Brenner pioneered the use of C. elegans for development and neurobiology research, C. elegans has been used to study human biology (Ellis and Horvitz, 1986 ). Brenner shared the 2002 Nobel Prize in Physiology or Medicine with H. Robert Horvitz and John Sulston for decoding the genetics of programmed cell death and animal development, including nervous system formation (Marx, 2002 ). Since Brenner's initial experiments, research performed with C. elegans has advanced our knowledge about many human pathologies such as aging, cancer, cell death, dystonia, Parkinson disease, and stroke (Chege and McColl, 2014 ; Klass, 1983 ; Markaki and Tavernarakis, 2020 ). Translational research using C. elegans continues to this day and is enhanced by the availability of resources and information shared by a highly collaborative worm research community; see Table 3.1 for a list of C. elegans resources. In the following sections, we will describe how C. elegans

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  Handbook of Developmental Neurotoxicology

  • William Slikker Jr., Merle G. Paule, Cheng Wang, William Slikker, Jr.(Authors)
  • 2018(Publication Date)
  • Academic Press

    (Publisher)

  9

  Historically the nematode was exploited for its short generation time, straight-forward Mendelian genetics, and simple anatomy. It possesses nerves, muscles, gut, gonad, and a cuticle. The adult is about a millimeter long, and in the laboratory feeds on bacteria either in liquid or, more commonly, on agar plates. Adults are either self-fertilizing XX hermaphrodites (which allows propagation of severely defective strains) or XO males (which allows mating and genetic manipulation). At any given temperature, wild-type development is invariant. At 20°C the wild-type animal has a 3-day generation time; each hermaphrodite can produce 300 isogenic offspring. The excellent genetics,2 superb catalogue of known neuronal/muscular mutations, well-defined behaviors, characterized cell lineage, and neural anatomy,1 contributed to its early success as a model organism. C. elegans is transparent, which allowed for the construction of its entire cell lineage, and also led to the productive use of fluorescent markers as reporters for gene expression.10 A wiring diagram of every synapse of the hermaphrodite’s 302 neurons is known, and a huge catalog of data has been shared online for decades. The advent of fluorescent markers for specific cells has only increased the importance of this transparency.10

  Two additional tools have greatly added to the utility of this model organism. The entire C. elegans genome was sequenced in 1998.11 When the human genome was eventually sequenced, it was somewhat surprising to discover that 60%–80% of the nematode genes have homologues in humans.11 , 12 This strongly supported the use of C. elegans as a model for mammalian development for a wide range of genetic studies. Second, RNA interference (RNAi), discovered in the nematode, was developed as a successful way to knockdown expression of essentially any gene in the organism.13 , 14 Coupled with the known sequence of the genome, an RNAi library has been constructed and made available to all laboratories working on C. elegans. Mutants, either classically generated or achieved via RNAi, can interrogate the function of almost every gene in the worm’s genome. This technique is quite straightforward in C. elegans

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  BIOS Instant Notes in Developmental Biology

  • Dr Richard Twyman(Author)
  • 2023(Publication Date)
  • Taylor & Francis

    (Publisher)

  fruiting body from which spores are released. Unicellular developmental models are discussed in more detail in Section D.

  Model invertebrates

  The two major invertebrate developmental models are the fruit fly Drosophilamelanogaster and the nematode worm Caenorhabditis elegans. Drosophila was chosen because of its early pivotal role in the study of genetics. Saturation mutagenesis screens are relatively straightforward, allowing mutants for any system of biological interest to be isolated. It has become established as a developmental model over the last 20 years through the identification and cataloging of many hundreds of developmentally important genes. Genetic manipulation in Drosophila is also a simple procedure, involving the injection of recombinant P-elements (Drosophila transposons; see Topic B3) into the egg. Early Drosophila development is described in Topics Fl and F2. The molecular basis of axis specification and patterning in Drosophila is the subject of Section H (also see Topics J5, L2 and L3).

  C. elegans is a remarkably simple organism, containing approximately 1000 somatic cells and a similar number of germ cells. Like Drosophila, C. elegans is amenable to genetic analysis and modification, and the embryos are transparent. Further advantages of C. elegans include the fact that adults can be stored as frozen stocks and recovered later by thawing, and that the species is hermaphrodite, so that one individual can seed an entire population. One remarkable feature of C. elegans is that the somatic cell lineage is invariant, i.e. every cell division and inductive interaction between cells is programmed and predictable. This has allowed the entire somatic cell lineage from egg to adult to be mapped out. There is also a complete wiring diagram of the C. elegans nervous system. C. elegans

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  The Biology of Nematodes

  • Donald L Lee(Author)
  • 2002(Publication Date)
  • CRC Press

    (Publisher)

  17. Ageing David Gems The Galton Laboratory, Department of Biology, University College London, 4 Stephenson Way, London NW1 2HE, England Keywords Ageing, nematode, evolution, Caenorhabditis elegans, genetics, life span Introduction This chapter aims to draw together the diverse elements of the study of ageing in nematodes into a single account, encompassing evolutionary biology, parasitology, nematology, gerontology and genetics. It also aims to provide an account of the biology of ageing in the model species C. elegans for those working on other areas of nematode biology, and information about ageing in other nematode species for C. elegans specialists. The tendency for separation into subdisciplines that exists in the study of nematode ageing also extends to model species studies themselves, where research on C. elegans has focused predominantly on the genetic specification of life span, and work on C. briggsae and T. aceti on other aspects, such as age-related changes in biochemical function and ultrastructure. In the developing field of biological gerontology, rapid advances have recently been made in the genetics of ageing in C. elegans. The aim of this work is to develop an understanding of the general mechanisms determining the ageing process. Within the last 10 years the possibility of actually achieving this somewhat hubristic aim has begun to look startlingly real. The potential consequences for humanity of achieving this goal are great

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