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WormBook,
2006]
Form follows function, and this maxim is particularly true for the nematode sperm cell. Motility is essential for fertilization, and the process of spermatogenesis culminates in the production of a crawling spermatozoon with an extended pseudopod. However, the morphological similarity to amoeboid cells of other organisms is not conserved at the molecular level. Instead of utilizing the actin cytoskeleton and motor proteins, the pseudopod moves via the regulated assembly and disassembly of filaments composed of the major sperm protein (MSP). The current work reviews the structure and dynamics of MSP filament formation, the critical role of pH in MSP assembly, and the recent identification of components that regulate this process. The combination of cytological, biochemical, and genetic approaches in this relatively simple system make nematode sperm an attractive model for investigating the mechanics of amoeboid cell motility.
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J Cell Sci,
2012]
MicroRNAs (miRNAs) are a class of short non-coding RNAs that bind mRNAs through partial base-pair complementarity with their target genes, resulting in post-transcriptional repression of gene expression. The role of miRNAs in controlling aging processes has been uncovered recently with the discovery of miRNAs that regulate lifespan in the nematode Caenorhabditis elegans through insulin and insulin-like growth factor-1 signaling and DNA damage checkpoint factors. Furthermore, numerous miRNAs are differentially expressed during aging in C. elegans, but the specific functions of many of these miRNAs are still unknown. Recently, various miRNAs have been identified that are up- or down-regulated during mammalian aging by comparing their tissue-specific expression in younger and older mice. In addition, many miRNAs have been implicated in governing senescence in a variety of human cell lines, and the precise functions of some of these miRNAs in regulating cellular senescence have helped to elucidate mechanisms underlying aging. In this Commentary, we review the various regulatory roles of miRNAs during aging processes. We highlight how certain miRNAs can regulate aging on the level of organism lifespan, tissue aging or cellular senescence. Finally, we discuss future approaches that might be used to investigate the mechanisms by which miRNAs govern aging processes.
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Mech Ageing Dev,
2007]
Technological advancements in invertebrate model organisms have recently made it possible to survey many or all of the genes in the genome for phenotypes of interest. In both C. elegans and S. cerevisiae, genome-wide searches for hypomorphic mutations that extend life span have been performed. The results from these screens are starting to provide a more complete view of the range of life span determinants in eukaryotes. In addition, it is becoming possible to test the premise that conserved aging genes and pathways regulate aging in disparate eukaryotic species. Here we compare and contrast the results from genome-wide aging screens and assess the likelihood that there are "public" aging mechanisms.
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Ann N Y Acad Sci,
2009]
Obligate aerobes, by definition, require oxygen in order to sustain life. Therefore, changes in environment or physiology that cause metabolic demand for oxygen to exceed supply (hypoxia) can be highly detrimental. Despite considerable variation in physiology and habitat between species, a majority of metazoa employ homologues of the hypoxia-inducible factor (HIF) transcription factors to adapt to oxygen deprivation. Studies in mammals, Drosophila and C. elegans have shown that regulation of HIF-alpha by prolyl hydroxylase (PHD)-mediated proteasomal degradation is conserved, as are a number of HIF target genes. More recently, analysis of coral and beetle HIFs has revealed that, unlike flies and worms, the C-terminal transactivation domain of HIF-alpha and its regulatory hydroxylase FIH-1 are also preserved. The reasons for variable conservation of this system are unknown. However, discovery of the "intermediary" properties of the beetle HIF pathway may prove a useful tool to better define HIF signaling in both mammals and invertebrates.
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Curr Opin Genet Dev,
1998]
Maternal factors laid down in the oocyte regulate blastomere identities in the early Caenorhabditis elegans embryo by activating zygotic patterning genes and restricting their expression to the appropriate lineages. A number of early-acting zygotic genes that specify various cell fates have been identified recently and their temporal and spatial regulation by maternal factors has begun to be elucidated.
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Semin Cell Dev Biol,
2022]
The nervous system emerges from a series of genetic programs that generate a remarkable array of neuronal cell types. Each cell type must acquire a distinct anatomical position, morphology, and function, enabling the generation of specialized circuits that drive animal behavior. How are these diverse cell types and circuits patterned along the anterior-posterior (A-P) axis of the animal body? Hox genes encode transcription factors that regulate cell fate and patterning events along the A-P axis of the nervous system. While most of our understanding of Hox-mediated control of neuronal development stems from studies in segmented animals like flies, mice, and zebrafish, important new themes are emerging from work in a non-segmented animal: the nematode Caenorhabditis elegans. Studies in C. elegans support the idea that Hox genes are needed continuously and across different life stages in the nervous system; they are not only required in dividing progenitor cells, but also in post-mitotic neurons during development and adult life. In C. elegans embryos and young larvae, Hox genes control progenitor cell specification, cell survival, and neuronal migration, consistent with their neural patterning roles in other animals. In late larvae and adults, C. elegans Hox genes control neuron type-specific identity features critical for neuronal function, thereby extending the Hox functional repertoire beyond early patterning. Here, we provide a comprehensive review of Hox studies in the C. elegans nervous system. To relate to readers outside the C. elegans community, we highlight conserved roles of Hox genes in patterning the nervous system of invertebrate and vertebrate animals. We end by calling attention to new functions in adult post-mitotic neurons for these paradigmatic regulators of cell fate.
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Trends in Ecology & Evolution,
1999]
In a recent TREE news & comment, Gadagkar made some useful comments on LaMunyon and Ward's interesting study on sexual reproduction in nematodes. I think, however, that he - and LaMunyon and Ward - have confused the benefits of sex for species or demes with those for individuals or genes. For females and hermaphrodites (but not for species or demes), the twofold cost of sexual reproduction or producing males' in Maynard Smith's sense implies the cost of producing offspring that have only half of the hermaphrodite parent's genome set - not directly that of producing males. An offspring of a hermaphrodite Caenorhabditis briggsae inherits half, not more, of each parental genome set. The hermaphrodite parent still pays the two fold cost of sexual reproduction in the same way as
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Exp Gerontol,
2011]
Reproduction shortens lifespan in practically all organisms examined so far, but the underlying mechanisms remain largely unknown to date. Here I review what evolutionary and molecular biologists have learned about such "costs of reproduction" in the fruit fly (Drosophila melanogaster) since Maynard Smith's (1958) seminal discovery that sterile mutants in D. subobscura live substantially longer than fertile wildtype flies. Together with observations from the nematode worm (Caenorhabditis elegans) and other organisms, the data from Drosophila suggest that there are at least four general principles that underlie trade-offs between reproduction and lifespan: (1) trade-offs between survival and reproduction are widespread; (2) the relationship between increased lifespan and decreased fecundity can be uncoupled under certain conditions; (3) while survival costs of reproduction might not necessarily be due to competitive resource allocation, we lack robust alternative explanations for their occurrence; and (4) physiological trade-offs between reproduction and longevity do not always translate into evolutionary genetic trade-offs. I conclude that - despite much recent progress - our current understanding of the proximate basis of survival costs of reproduction remains very limited; much future work on the genetics and physiology of such trade-offs will be required to uncover their mechanistic basis.
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International Journal of Developmental Biology,
1998]
Pleiotropy , a situation in which a single gene influences multiple phenotypic tra its, can arise in a variety of ways. This paper discusses possible underlying mechanisms and proposes a classification of the various phenomena involved.
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Curr Biol,
2003]
A novel protein in Caenorhabditis elegans, SAS-4, is a component of centrioles and is required for centriole duplication. Depletion of SAS-4 results in stunted centrioles and a smaller centrosome, suggesting a link to organelle size control.