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[
Nature,
1994]
RNA trespasses in what was once thought to be protein's province. The notion that RNAs can be enzymes, binding specifically to ligands, cofactors and substrates, is now commonplace; yet only a few years ago, these were the sacred acts of proteins. History may be about to repeat itself. Regulatory proteins bind to specific sequences in the genes or messenger RNAs they control, and so determine how much a gene is expressed, in what cells, and when. But why should these regulators have to be protein? Why not RNA? We already know, in bacteria, of RNAs that can control gene expression through remarkably sophisticated mechanisms. Now, two reports in Cell not only identify a tiny, repressing RNA in animal cells, but also show that it acts upon a region of mRNA often thought to be barren and insignificant. Although this could be a rare, deviant case, there is the tantalizing possibility that a new family of regulatory RNAs awaits discovery.
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[
Experimental Neurology,
1975]
The precision of neuronal development is programmed genetically. The genes involved must be expressed in an orderly sequence so that their products appear in the right cell at the right time. By studying mutants in which this sequence is altered, it should be possible to dissect the development and recognize the steps controlled by individual genes.
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[
Nat Neurosci,
2001]
A characterization of C. elegans lacking the gene for Rim suggests that this protein may be involved in pruning synaptic vesicles for fusion, not in docking or organizing active zones.
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[
Nat Neurosci,
2000]
A recent Nature paper on mice lacking the Na+ channel BNC1 shows that this channel is essential for neuronal touch receptor function and may be part of a mechanosensory complex.
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[
Nature,
2000]
A tiny RNA molecule ensures that the larvae of a roundworm develop into adults. The discovery of this RNA in many other animal groups implies that this way of keeping developmental time may be universal.
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[
Nature,
2002]
The genomes of animals, plants and fungi seem to be relatively disorganized. Genes appear to be randomly distributed, with only a few exceptions: repeats of similar sequences caused by gene duplications, for example, and a limited number of ancient gene clusters containing functionally related genes (such as the Hox genes that are involved in control of animal development). Apart from these, the average gene is generally assumed to be independent of its neighbours, and genomes are constantly rearranged and shuffled. However, in one group of animals the nematodes (small, unsegmented worms) neighboring genes are occasionally assembled into regulatory units called operons. On page 851 of this issue, Blumenthal et al. now report the first whole-genome characterization of such operons in a mulicellular organism, an raise intriguing questions as to how (and why) they have evolved.
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[
Nat Neurosci,
2003]
In C. elegans, social and solitary feeding behavior can be determined by a single amino acid change in a G protein-coupled receptor. A new study identifies ligands for this receptor and suggests how changes in behavior evolve at the molecular level.
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[
Science,
1990]
An exhaustive study of the tiny roundworm C. elegans has revealed a wealth of information about development and the brain. And now the effort to decipher the worm's genome is fast becoming the benchmark by which the human genome project will be measured.
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[
Nature,
1994]
Many bacterial genes are organized into operons which are transcribed as polycistronic messenger RNAs. By contrast, eukaryotic genes were thought to be regulated individually and transribed as monocistronic mRNAs. Last year, however, a group led by Tom Blumenthal announced the discovery that the nematode Caenorhabditis elegans uses both the prokaryotic and the eukaryotic patterns of gene organization and transcription. Blumenthal and colleagues have now taken this work further (page 270 of this issue). They describe how they have examined the C. elegans genomic database and found that at least a quarter of the genes seem to be organized into operons.
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[
Nature,
1999]
Animal evolution is commonly viewed as producing diverse, environmentally adapted bodies to propagate the germ line. The evolutionary theory of ageing suggests that genetic limits to lifespan may be inadvertent consequences of evolutionary selection for maximizing that propagation. In other words, trade-offs occur that favour reproductive success over post-reproductive longevity; lifespan should be inversely correlated with fecundity when progeny production diverts resources from the maintenance of somatic (non-reproductive) cells. The germ line contains all the genetic information to specify the soma. But it is also possible that there are other, environmentally modulated instructions for life history that the germ line conveys to the soma to maximize reproduction.