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[
Curr Biol,
2004]
Vulval patterning in Caenorhabditis elegans is controlled by both Ras-mediated 'inductive' signaling and LIN-12/Notch-mediated 'lateral' signaling. Recent studies have identified the lateral signal as well as various genes that are targets of the lateral signaling pathway, and begun to define the multiple molecular links connecting Ras and Notch.
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[
Nematologica,
1971]
Caenorhabditis briggsae was used as a model to study aging of a metazoan under gnotobiotic conditions. At higher temperatures nematodes were shorter-lived and had a shorter generation time. Nematodes moved more slowly as they aged. Physiologic aging was marked by a decreased ability to withstand osmotic stress, a possible increase in the body's internal solute concentration, and increased sensitivity to formaldehyde. These results suggest that the ability to osmoregulate and the permeability of the body wall are altered during senescence. The interchordal hypodermis, as well as the chordal hypodermis, contained fairly abundant structures having biosynthetic activity. During aging mitochondria of the hypodermis degenerated, some areas of the thin hypodermal band thickened and lysosome-like bodies formed in the interchordal hypodermis. Changes in osmoregulatory and excretory mechanisms are probably associated with deterioration of hypodermis organelles.
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Dev Biol,
2017]
Breaking symmetry in populations of uniform cells, to induce adoption of an alternative cell fate, is an essential developmental mechanism. Similarly, domain and boundary establishment are crucial steps to forming organs during development. Notch signaling is a pathway ideally suited to mediating precise patterning cues, as both receptors and ligands are membrane-bound and can thus act as a precise switch to toggle cell fates on or off. Fine-tuning of signaling by positive or negative feedback mechanisms dictate whether signaling results in lateral induction or lateral inhibition, respectively, allowing Notch to either induce entire regions of cell specification, or dictate binary fate choices. Furthermore, pathway activity is modulated by Fringe modification of receptors or ligands, co-expression of receptors with ligands, mode of ligand presentation, and cell surface area in contact. In this review, we describe how Notch signaling is fine-tuned to mediate lateral induction or lateral inhibition cues, and discuss examples from C.elegans, D. melanogaster and M. musculus. Identifying the cellular machinery dictating the choice between lateral induction and lateral inhibition highlights the versatility of the Notch signaling pathway in development.
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Semin Cell Dev Biol,
2023]
Apical-Basal polarity is a fundamental property of all epithelial cells that underlies both their form and function. The gut is made up of a single layer of intestinal epithelial cells, with distinct apical, lateral and basal domains. Occluding junctions at the apical side of the lateral domains create a barrier between the gut lumen and the body, which is crucial for tissue homeostasis, protection against gastrointestinal pathogens and for the maintenance of the immune response. Apical-basal polarity in most epithelia is established by conserved polarity factors, but recent evidence suggests that the gut epithelium in at least some organisms polarises by novel mechanisms. In this review, we discuss the recent advances in understanding polarity factors by focussing on work in C. elegans, Drosophila, Zebrafish and Mouse.
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[
Cell,
1992]
Equivalent cells have the same set of potential fates and must choose one of the available options. In many cases, the choice is influenced by intercellular signaling events. If the signal originates outside the population of equivalent cells (equivalence group), the signaling process is termed induction. If the signal arises within the equivalence group, the signaling process is termed lateral specification (or lateral inhibition). Cells that do not receive and respond to the signal express a default fate, while cells that receive and respond to the signal express an alternative fate. In this review, we describe in detail one example of each process in Caenorhabditis elegans and Drosophila. In both organisms, powerful methods of genetic analysis and single cell resolution have facilitated the identification of molecules involved in induction and lateral specification, and are beginning to lead to an understanding of the biochemical circuitry that mediates cellular decisions. Common features emerge from a comparison of the worm and fly examples that are immediately applicable to higher organisms. Key components of identified signaling systems have proven to be members of highly conserved gene families, implying that similar molecular mechanisms underlie cell-cell interactions that specify cell fate decisions in all animals.
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[
Seminars in Cell & Developmental Biology,
1996]
The six multipotent precursors of the C. elegans vulva generate an invariant pattern of three fates (3 degrees 3 degrees 2 degrees 1 degrees 2 degrees 3 degrees) which determine their future growth and organization. Multiple, partly redundant mechanisms appear necessary to specify this invariant pattern. A key signal here is the EGF-like growth factor LIN-3 which is made by the anchor cell of the gonad and which induces vulval fate according to dose: a high dose promotes a 1 degrees fate; a lower dose promotes a 2 degrees fate. In addition, a lateral signalling pathway promotes 2 degrees fates and prevents adjacent 1 degrees fates. We propose that a gradient of growth factor directly induces a spatially graded pattern of vulval fates, and lateral signalling reinforces this waded induction.
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[
Curr Top Dev Biol,
2001]
Studies of C. elegans vulval development provide insights into the process of pattern formation during animal development. The invariant pattern of vulval precursor cell fates is specified by the integration of at least two signaling systems. Recent findings suggest that multiple, partially redundant mechanisms are involved in patterning the vulval precursor cells. The inductive signal activates the LET-60/RAS signaling pathway and induces the 1 degree fate, whereas the lateral signal mediated by LIN-12/Notch is required for specification of the 2 degrees fate. Several regulatory pathways antagonize the RAS signaling pathway and specify the non-vulval 3 degrees fate in the absence of induction. The temporal and spatial regulation of VPC competence and production of the inductive and the lateral signal are precisely coordinated to ensure the wild-type vulval pattern.
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[
Bioessays,
2001]
The change in shape of the C. elegans embryo from an ovoid ball of cells into a worm-shaped larva is driven by three events within the cells of the hypodermis (epidermis): (1) intercalation of two rows of dorsal cells, (2) enclosure of the ventral surface by hypodermis, and (3) elongation of the embryo. While the behavior of the hypodermal cells involved in each of these processes differs dramatically, it is clear that F-actin and microtubules have essential functions in each of these processes, whereas contraction of actomyosin structures appears to be involved specifically in elongation. Molecular analysis of these processes is revealing components specific to C. elegans as well as components found in other systems. Since C. elegans hypodermal cells demonstrate dramatically different behaviors during intercalation, enclosure and elongation, the study of cytoskeletal dynamics in these processes may reveal both unique and conserved activities during distinct epithelial morphogenetic movements. BioEssays 23:12-23, 2001.
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Cell Biol Int Rep,
1987]
Multiple synaptonemal complexes (polycomplexes) (PC) are similar in structure to synaptonemal complexes (SC) and are also highly conserved through evolution. They have been described in over 70 organisms throughout all life forms. The appearance of PCs are restricted to meiotic and germ-line derived tissues and are most commonly present after SC formation. However, in a number of animals and plants, both extra- and intranuclear PCs are present during premeiotic and pre-pachytene stages. The structure and biochemical composition of PCs is similar to SCs that the basic unit is tripartite, consisting of two lateral elements and a central region (in which transverse elements are located), and the dimensions of such structures are equivalent. Stacking of SC subunits, while still maintaining equivalent SC dimensions, creates a problem since the lateral elements (LE) would then be twice as thick in the PC as compared to the SC. Recently, it has been shown that the LE of the SC is actually multistranded, thus the LE of each subunit of the PC is half as thick as its counterpart in the SC.
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[
Dev Dyn,
2010]
During sexual reproduction in many species, sperm and oocyte secrete diffusible signaling molecules to help orchestrate the biological symphony of fertilization. In the Caenorhabditis elegans gonad, bidirectional signaling between sperm and oocyte is important for guiding sperm to the fertilization site and inducing oocyte maturation. The molecular mechanisms that regulate sperm guidance and oocyte maturation are being delineated. Unexpectedly, these mechanisms are providing insight into human diseases, such as amyotrophic lateral sclerosis, spinal muscular atrophy, and cancer. Here we review sperm and oocyte communication in C. elegans and discuss relationships to human disorders.