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Trends Genet,
2002]
Almost ten years ago, the Ambros laboratory made the extraordinary discovery that a gene essential for development in Caenorhabditis elegans encoded a 22-nucleotide, untranslated RNA. Further genetic studies in this nematode revealed the existence of a second tiny RNA gene that turned out to be conserved in animals as diverse as flies and humans. Now, the Ambros, Bartel and Tuschl laboratories have proven that those odd RNAs were just the first examples of a large family of RNAs, termed microRNAs (miRNAs). Although untranslated RNA genes, such as transfer RNAs and ribosomal RNAs, perform essential housekeeping roles in all living organisms, growing numbers of other RNAs, some widely conserved across phyla and others limited to certain species, are being uncovered and shown to fulfill specific duties. The discovery of miRNAs establishes a new class of regulatory RNAs and highlights the existence of unexpected RNA genes that, although ancient, are not extinct.
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Genes Dev,
2016]
In this issue of Genes & Development, Drexel and colleagues (pp. 2042-2047) present a beautiful example of how microRNAs (miRNAs) can regulate tissue-specific gene expression in a biologically relevant setting. They found that miR-791 is expressed in only three types of carbon dioxide (CO2)-sensing neurons in Caenorhabditis elegans, and its primary function there seems to be repression of two target genes that interfere with the behavioral response to CO2 Interestingly, these two targets are broadly expressed across other tissues. Thus, restricted miRNA expression can lead to target repression in select tissues to promote distinct cellular physiologies.
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Genes Dev,
2018]
Adenosine deaminases that act on RNA (ADARs) convert adenosines (A) to inosines (I) in stretches of dsRNA. The biological purpose of these editing events for the vast majority of ADAR substrates is largely unknown. In this issue of<i>Genes & Development,</i>Reich and colleagues (pp. 271-282) demonstrate that in<i>Caenorhabditis elegans</i>, A-to-I editing in double-stranded regions of protein-coding transcripts protects these RNAs from targeting by the RNAi pathway. Disruption of this safeguard through loss of ADAR activity coupled with enhanced RNAi results in developmental abnormalities and profound changes in gene expression that suggest aberrant induction of an antiviral response. Thus, editing of cellular dsRNA by ADAR helps prevent host RNA silencing and inadvertent antiviral activity.
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Curr Biol,
2019]
The complete description of the expression of gap junction proteins in the nervous system of the worm reveals a great complexity of their distribution amongst different neuronal classes, opening an unprecedented opportunity to expose the functional diversity of electrical synapses.
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Nat Rev Genet,
2001]
The molecular mechanisms that time development are now being deciphered in various organisms, particularly in Caenorhabditis elegans. Key recent findings indicate that certain C. elegans timekeeping genes are conserved across phyla, and their developmental expression patterns indicate that a timing function might also be conserved. Small regulatory RNAs have crucial roles in the timing mechanism, and the cellular machinery required for production of these RNAs intersects with that used to process double-stranded RNAs during RNA interference.
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Nat Rev Microbiol,
2019]
The health and fitness of animals, including humans, are influenced by the presence and composition of resident microbial communities. The development of rational microbial therapies to alleviate chronic immunological, metabolic and neurobiological diseases requires an understanding of the processes underlying microbial community assembly and the mechanisms by which microorganisms influence host traits. For fundamental discovery, simple animal models (that is, lower vertebrate and invertebrate species with low diversity microbiomes) are more cost-effective and time-efficient than mammal models, especially for complex experimental designs and sophisticated genetic screens. Recent research on these simple models demonstrates how microbiome composition is shaped by the interplay between host controls, mediated largely via immune effectors, inter-microorganism competition, and neutral processes of passive dispersal and ecological drift. Parallel research on microbiome-dependent host traits has identified howspecific metabolites and proteins released from microorganisms can shape host immune responsiveness, ameliorate metabolic dysfunction and influence behavioural traits. In this Review, the opportunity for microbiome research on the traditional biomedical models zebrafish, Drosophila melanogaster and Caenorhabditis elegans, which command superb research resources and tools, is discussed. Other systems, for example, hydra, squid and the honeybee, are valuable alternative models to address specific questions.