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Front Behav Neurosci,
2022]
Learning to identify and predict threats is a basic skill that allows animals to avoid harm. Studies in invertebrates like Aplysia californica, Drosophila melanogaster, and Caenorhabditis elegans have revealed that the basic mechanisms of learning and memory are conserved. We will summarize these studies and highlight the common pathways and mechanisms in invertebrate fear-associated behavioral changes. Fear conditioning studies utilizing electric shock in Aplysia and Drosophila have demonstrated that serotonin or dopamine are typically involved in relaying aversive stimuli, leading to changes in intracellular calcium levels and increased presynaptic neurotransmitter release and short-term changes in behavior. Long-term changes in behavior typically require multiple, spaced trials, and involve changes in gene expression. C. elegans studies have demonstrated these basic aversive learning principles as well; however, fear conditioning has yet to be explicitly demonstrated in this model due to stimulus choice. Because predator-prey relationships can be used to study learned fear in a naturalistic context, this review also summarizes what is known about predator-induced behaviors in these three organisms, and their potential applications for future investigations into fear conditioning.
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Mech Ageing Dev,
2005]
The ageing process precipitates dramatic alterations in the physiology of all organisms, including reduced cellular function, compromised resistance to stress and pathological agents, and increased likelihood of developing age-related diseases. Among the, most characteristic pathologies associated with old age are numerous late-onset neurodegenerative disorders such as Alzheimer's. Parkinson's and Huntington's diseases. In addition to stroke, which also inflicts loss of neuronal cells, these conditions account for ever-increasing debilitation among the elderly. Recent studies in model organisms such as the nematode Caenorhabditis elegans and the fruit fly Drosophila melanogaster. which offer the prowess of sophisticated genetic approaches. have uncovered significant, novel aspects of the molecular mechanisms that underlie both neurodegeneration and the ageing process. These advances hold promise that the intimate link between the, aged state and the manifestation of several neurodegenerative diseases will be deciphered. Here. we discuss the mechanisms by which ageing interfaces with. and influences, the progression of neurodegeneration.
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J Genet Genomics,
2021]
A mechanistic understanding of biology requires appreciating spatiotemporal aspects of gene expression and its functional implications. Conditional expression allows for (ir)reversible switching of genes on or off, with the potential of spatial and/or temporal control. This provides a valuable complement to the more often used constitutive gene (in)activation through mutagenesis, providing tools to answer a wider array of research questions across biological disciplines. Spatial and/or temporal control are granted primarily by (combinations of) specific promoters, temperature regimens, compound addition, or illumination. The use of such genetic tool kits is particularly widespread in invertebrate animal modelsbecause they can be applied to study biological processes in short time frames and on large scales, using organisms amenable to easy genetic manipulation. Recent years witnessed an exciting expansion and optimization of such tools, of which we provide a comprehensive overview and discussion regarding their use in invertebrates. The mechanism, applicability, benefits, and drawbacks of each of the systems, as well as further developments to be expected in the foreseeable future, are highlighted.
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Genesis,
2016]
Forward and reverse genetic approaches have been well developed in the nematode Caenorhabditis elegans; however, efficient genetic tools to generate conditional gene mutations are still in high demand. Recently, the Clustered Regularly Interspaced Short Palindromic Repeats/CRISPR-associated protein 9 (CRISPR-Cas9) system for genome modification has provided an additional tool for C. elegans researchers to achieve simple and efficient conditional targeted mutagenesis. Here, we review recent advances in the somatic expression of Cas9 endonuclease for conditional gene editing. We present some practical considerations for improving the efficiency and reducing the off-target effects of somatic CRISPR-Cas9 and highlight a strategy to analyze somatic mutation at single-cell resolution. Finally, we outline future applications and consider challenges for this emerging genome editing platform that will need to be addressed in the future. This article is protected by copyright. All rights reserved.
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Biochem Soc Trans,
2000]
Comparison of peptidase gene families in the newly released Drosophila melanogaster and Caenorhabditis elegans genomes highlights important differences in peptidase distributions with relevance to the evolution of both form and function in these two organisms and can help to identify the most appropriate model when using comparative studies relevant to the human condition.
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Adv Exp Med Biol,
2013]
The intersection between developmental programs and environmental conditions that alter physiology is a growing area of research interest. The C. elegans germ line is emerging as a particularly sensitive and powerful model for these studies. The germ line is subject to environmentally regulated diapause points that allow worms to withstand harsh conditions both prior to and after reproduction commences. It also responds to more subtle changes in physiological conditions. Recent studies demonstrate that different aspects of germ line development are sensitive to environmental and physiological changes and that conserved signaling pathways such as the AMPK, Insulin/IGF, TGF, and TOR-S6K, and nuclear hormone receptor pathways mediate this sensitivity. Some of these pathways genetically interact with but appear distinct from previously characterized mechanisms of germline cell fate control such as Notch signaling. Here, we review several aspects of hermaphrodite germline development in the context of "feasting," "food-limited," and "fasting" conditions. We also consider connections between lifespan, metabolism and the germ line, and we comment on special considerations for examining germline development under altered environmental and physiological conditions. Finally, we summarize the major outstanding questions in the field.
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Quarterly Review of Biology,
1969]
Possible selective advantages, including some new ones, for hermaphroditism are reviewed. It is proposed that hermaphroditism should evolve under the following conditions: (a) where it is hard to find a mate; (b) where one sex benefits from being larger or smaller than the other; or (c) where there are small, genetically isolated populations. Some conceptual problems and a comparative means of study are discussed. The literature is reviewed to show the conditions under which hermaphroditism may have evolved. It is concluded that all three explanations have some validity.
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Curr Biol,
2005]
Neural components of the circuits that transform sensory cues into changes in motor activities are largely unknown. Several recent studies have now functionally mapped the sensorimotor circuits responsible for locomotion behaviors under defined environmental conditions in the nematode Caenorhabditis elegans.
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Cell,
2007]
Organisms from bacteria to humans have the capacity to gauge the quality of their respective environments. Recent advances in understanding how various types of environmental conditions are sensed and interpreted by cells and by organisms have established a critical role for these systems in the modulation of physiology, health, and aging.
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WormBook,
2012]
The pharynx is a neuromuscular pump at the anterior end of the alimentary tract. It is made up of 20 muscle cells, 20 neurons, and 20 other cells. Pharyngeal activity correlates with food intake. The proper feeding rate, as well as the precise timing of pharyngeal movements, is required for efficient feeding and likely for survival in nature. For most purposes, pharyngeal behavioral analysis requires no more than a routine stereomicroscope and a pair of eyes, but accuracy can be increased by video recording followed by off-line analysis in slow motion. Like other C. elegans behaviors, pharyngeal behavior is sensitive to both the immediate environmental conditions as well as to the history of such conditions.