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[
Discover,
1991]
Undulating under the microscope, its muscle and nerve cells visible within its transparent body, the tiny roundworm Caenorhabditis elegans is normally a creature of surprising grace. But one mutant strain is not elegans at all. It thrashes about in such an uncoordinated fashion that researchers have dubbed the mutant worm "unc"...
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[
Nature,
1996]
Classical results in experimental embryology established long ago that cells of the developing animal have a regional identity. They can be characterized not only as 'skin', 'nerve' and 'bone', but also as 'arm' and 'leg'. But how cells know what body region they belong to, and what to do there, is not known. Results reported in this issue and in Development describe unexpected properties of a key player, one of the Hox genes-the dynamic, lineage-based regulation of a Hox gene in the nematode Caenorhabditis elegans is at odds with a traditional view of Hox genes as relatively fixed markers of regional identity.
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[
Science,
1996]
The one-cell animal embryo, or zygote, faces a daunting engineering task: implementing the architectural plans inscribed in its DNS for building a complex, multicelled body. So, like any sensible construction supervisor, the zygote swiftly divides the project into manageable chunks, assigning some of its progeny to build only gut, for example, and other to make only muscle or skin. Just how each early embryonic cell gets its orders is understood only for the fruit fly Drosophila melanogaster-an achievement that helped win 1995's Nobel Prize in medicine for three developmental biologists. Now, however, the communication lines governing embryonic development are emerging in another animal beloved of developmental researchers: the tiny worm known as Caenorhabditis elegans.
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[
Nature,
2001]
In all animals, the process of programmed cell suicide (apoptosis) is coordinated by enzymes known as caspases, which cut up key substrates in the cell. The dying cell is then neatly packaged, engulfed by neighbouring "phagocytic" cells, and cleared from the body without fanfare, leaving no evidence of the catastrophic events that preceded. It has always been assumed that there is a "point of no return" in this death cascade - at or shortly before the time at which caspases are activated - beyond which the process of cell execution proceeds inexorably. This view is challenged by Reddien et al. and Hoeppner et al. on pages 198 and 202 of this issue. It seems that cells in which caspases have been activated can in fact progress through a state of being "mostly dead", a stage that physically resembles the early phase of apoptosis but from
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[
Science,
1996]
In creatures from worms to people, it takes two sexes to reproduce, but it's often the female who gets stuck with the real work of childbearing. This division of labor is even mirrored in sperm and eggs. The unfertilized eggs of fruit flies, for example, already contain the molecular signals needed to direct one of the first events in embryonic growth, the creation of distinct body segments. The paternal contribution to early development, in contrast, seems paltry. Sperm carries nuclear material and organelles called centrosomes - organizing sites for cell division - that come into play later on, but no biochemical factors that guide early embryogenesis have been traced back to the father. In the January issue of the journal Development, however, molecular biologist Heidi Browning of the University of Colorado and developmental geneticist Susan Strome of Indiana University report that SPE-11, a protein produced only in the sperm of the nematode Caenorhabditis elegans, may play a crucial role during the first few minutes after the embryo is fertilized.