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[
1975]
Studies in behaviour genetics have covered a wide field: motivation, development, sensory capacities, intelligence, learning, evolution, neuromorphology and neurochemistry have all been approached using genetic techniques, and there are probably others. Whilst it is at present impossible to construct any unities one must accept that many such studies have as their common aim one of the most fundamental problems in biology: how is behavioral potential encoded in genetic terms and expressed in the course of development? The relative enormity of this problem is often matched by its inaccessibilty. It cannot be claimed that there is any agreed view of the way forward and much of the work has frankly to be opportunistic-seizing on some favourable material or a useful new analytical technique to gain a limited objective. Consequently, behaviour genetics often presents a confusing picture of numerous disjointed studies, with
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[
WormBook,
2005]
The knowledge about C. elegans provides a paradigm for comparative studies. Nematodes are very attractive in evolutionary developmental biology given the species richness of the phylum and the easiness with which several of these species can be cultured under laboratory conditions. Embryonic, gonad, vulva and male tail development were studied and compared in nematodes of five different families, providing a detailed picture of evolutionary changes in development. In particular, vulva development has been studied in great detail and substantial differences in the cellular, genetic and molecular mechanisms have been observed between C. elegans and other nematodes. For example, vulva induction relies on the single anchor cell in C. elegans, whereas a variety of different cellular mechanisms are used in related species. In recent years, a few species have been developed as satellite systems for detailed genetic and molecular studies, such as Oscheius tipulae and Pristionchus pacificus.
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[
Adv Exp Med Biol,
2010]
Nematode neuropeptide systems comprise an exceptionally complex array of approximately 250 peptidic signaling molecules that operate within a structurally simple nervous system of approximately 300 neurons. A relatively complete picture of the neuropeptide complement is available for Caenorhabditis elegans, with 30 flp, 38 ins and 43 nlp genes having been documented; accumulating evidence indicates similar complexity in parasitic nematodes from clades I, III, IV and V. In contrast, the picture for parasitic platyhelminths is less clear, with the limited peptide sequence data available providing concrete evidence for only FMRFamide-like peptide (FLP) and neuropeptide F (NPF) signaling systems, each of which only comprises one or two peptides. With the completion of the Schmidtea meditteranea and Schistosoma mansoni genome projects and expressed sequence tag datasets for other flatworm parasites becoming available, the time is ripe for a detailed reanalysis ofneuropeptide signalingin flatworms. Although the actual neuropeptides provide limited obvious value as targets for chemotherapeutic-based control strategies, they do highlight the signaling systems present in these helminths and provide tools for the discovery of more amenable targets such as neuropeptide receptors or neuropeptide processing enzymes. Also, they offer opportunities to evaluate the potential of their associated signaling pathways as targets through RNA interference (RNAi)-based, target validation strategies. Currently, within both helminth phyla, theflp signaling systems appear to merit further investigation as they are intrinsically linked with motor function, a proven target for successful anti-parasitics; it is clear that some nematode NLPs also play a role in motor function and could have similar appeal. At this time, it is unclear if flatworm NPF and nematode INS peptides operate in pathways that have utility for parasite control. Clearly, RNAi-based validation could be a starting point for scoring potential target pathways within neuropeptide signaling for parasiticide discovery programs. Also, recent successes in the application of in planta-based RNAi control strategies for plant parasitic nematodes reveal a strategy whereby neuropeptide encoding genes could become targets for parasite control. The possibility of developing these approaches for the control of animal and human parasites is intriguing, but will require significant advances in the delivery of RNAi-triggers.
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[
Curr Top Membr,
1999]
The DNA sequence data produced by the Caenorhabditis elegans genome sequencing project has revealed a large extended family of potassium channels, the outlines of which are conserved with vertebrates. This initial peek into the nearly complete library of potassium channels from a single 'simple' organism has revealed a number and complexity of potassium channel types that surpassed expectations. The vast majority of potassium channel types revealed by expressed sequence tags (EST) sequencing projects from many vertebrate and invertebrate animals fit within the outlines of families present in C. elegans. Thus, the broad picture of potassium channel families in C. elegans may represent family relationships conserved among most vertebrate and invertebrate animals. This conservation implies that the electrical lives of cell from most metazoans have similar requirements and are similarly diverse. Furthermore, the fact that the structures and possible biophysical properties of many distinct potassium channel types are conserved implies that specific functional roles of potassium channels may be conserved, as well. Studies now underway to reveal the tissue channels in C. elegans could reveal such conserved roles. These studies may be a guide to similar studies in higher
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[
WormBook,
2005]
Sex determination was a founding topic of C. elegans research. After three decades of research, a complex signal transduction pathway with multiple layers of regulation has been elucidated. This pathway links karyotype to phenotype by coordinating the development of sexually dimorphic tissues. In this article, this pathway is placed in two broader contexts. The first is that of nematodes and animals in general. The important role of C. elegans studies in revealing the first universally conserved component of metazoan sex determination is discussed, as is the role of cooption of genes into the sex determination and dosage compensation pathways. The second context is that of a subset of more closely related species, with emphasis on other members of the genus Caenorhabditis. Studies reviewed here have determined the gene-level conservation of the known pathway and the relative rates of molecular evolution in conserved components, and made substantial progress in the manipulation of gene activity in non- elegans species. Special attention is paid to the origins of hermaphroditism, which evolved from gonochorism through germline-specific changes in sex determination. Recent studies suggest that the most rapidly evolving aspects of sex determination are germline functions related to evolutionary shifts in mating systems, while somatic sex determination is relatively conservative. From all of these studies, a picture emerges in which C. elegans utilizes an intriguing mixture of general and species-specific genes and regulatory mechanisms.