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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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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.
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Trends Immunol,
2001]
A current area of interplay between immunologists, geneticists and developmental biologists concerns how Toll receptors assumed their dual roles in pathogen recognition end insect embryo patterning. The development of mechanisms that recognize and control infectious pathogens has been essential for the survival of metazoan organisms. Here, Padraic Fallen and colleagues consider the insights that might be gained from using nematodes to study immune signalling pathways.
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Science,
1995]
The contrasts between the sexes have inspired countless plays, novels, and other creative works. Sex differences inspire a group of developmental biologists, too-but there's a twist. While artists and most of the rest of us are fascinated by the effects of the male-female divide, these biologists are trying to learn how it arises in the first place. Their goal: to trace out the gene pathways that turn an embryo into a male or female. This quest has recently become one of the hottest areas of developmental biology, as two meetings held this year and devoted solely to the subject attest.
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Nature,
1996]
During the development of many, if not all, complex organisms, specific cells are marked out for elimination in a process known as programmed cell death, or apoptosis, a form of cell suicide. For example, during the development of the hermaphrodite nematode worm Caenorhabditis elegans, 131 of the 1,090 cells produced are genetically destined to die. Drosophila embryos without the necessary genes to execute this death programme do not survive. In vertebrates, failure to delete malformed or potentially autoreactive immune cells during development can eventually lead to autoimmunity or leukaemia. So too much or too little cell death threatens the whole organism.
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Nature,
1987]
The molecular mechanisms responsible for development of metazoan pattern and form are largely unknown. Embryos have been described and experimentally manipulated for more than a century, but only in the past few years have some of the genes and proteins that influence, and perhaps govern, development been isolated and scrutinized. These genes, cloned chiefly from the fruitfly Drosophila melanogaster, constitute the 'nuts-and-bolts' of developmental decision-making. The challenge to developmental biologists today is to understand the functions of these genes and to describe them in biochemical terms. Results reported at a recent meeting indicate that some elucidation of development at a molecular level will emerge from investigations of the nematode worm Caenorhabditis elegans.