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[
WormBook,
2006]
Wild C. elegans and other nematodes live in dirt and eat bacteria, relying on mechanoreceptor neurons (MRNs) to detect collisions with soil particles and other animals as well as forces generated by their own movement. MRNs may also help animals detect bacterial food sources. Hermaphrodites and males have 22 putative MRNs; males have an additional 46 MRNs, most, if not all of which are needed for mating. This chapter reviews key aspects of C. elegans mechanosensation, including MRN anatomy, what is known about their contributions to behavior as well as the neural circuits linking MRNs to movement. Emerging models of the mechanisms used to convert mechanical energy into electrical signals are also discussed. Prospects for future research include expanding our understanding of the molecular basis of mechanotransduction and how activation of MRNs guides and modulates behavior.
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[
WormBook,
2007]
Acetylcholine is the major excitatory neurotransmitter at nematode neuromuscular junctions, and more than a third of the cells in the C. elegans nervous system release acetylcholine. Through a combination of forward genetics, drug-resistance selections, and genomic analysis, mutants have been identified for all of the steps specifically required for cholinergic function. These include two enzymes, two transporters, and a bewildering assortment of receptors. Cholinergic transmission is involved, directly or indirectly, in many C. elegans behaviors, including locomotion, egg laying, feeding, and male mating.
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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.
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Genetics,
2019]
Mitotic cell divisions increase cell number while faithfully distributing the replicated genome at each division. The <i>Caenorhabditis elegans</i> embryo is a powerful model for eukaryotic cell division. Nearly all of the genes that regulate cell division in <i>C. elegans</i> are conserved across metazoan species, including humans. The <i>C. elegans</i> pathways tend to be streamlined, facilitating dissection of the more redundant human pathways. Here, we summarize the virtues of <i>C. elegans</i> as a model system and review our current understanding of centriole duplication, the acquisition of pericentriolar material by centrioles to form centrosomes, the assembly of kinetochores and the mitotic spindle, chromosome segregation, and cytokinesis.
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[
WormBook,
2005]
Ion channels are the "transistors" (electronic switches) of the brain that generate and propagate electrical signals in the aqueous environment of the brain and nervous system. Potassium channels are particularly important because, not only do they shape dynamic electrical signaling, they also set the resting potentials of almost all animal cells. Without them, animal life as we know it would not exist, much less higher brain function. Until the completion of the C. elegans genome sequencing project the size and diversity of the potassium channel extended gene family was not fully appreciated. Sequence data eventually revealed a total of approximately 70 genes encoding potassium channels out of the more than 19,000 genes in the genome. This seemed to be an unexpectedly high number of genes encoding potassium channels for an animal with a small nervous system of only 302 neurons. However, it became clear that potassium channels are expressed in all cell types, not only neurons, and that many cells express a complex palette of multiple potassium channels. All types of potassium channels found in C. elegans are conserved in mammals. Clearly, C. elegans is "simple" only in having a limited number of cells dedicated to each organ system; it is certainly not simple with respect to its biochemistry and cell physiology.