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[
Trends in Genetics,
2005]
Eleven of the twelve recognized wingless (Wnt) subfamilies are represented in the sea anemone Nematostelia vectensis, indicating that this developmentally important gene family was already fully diversified in the common ancestor of ''''higher'''' animals. In deuterostomes, although duplications have occurred, no novel subfamilies of Wnts have evolved. By contrast, the protostomes Drosophila and Caenorhabditis have lost half of the ancestral Writs. This pattern - loss of genes from an ancestrally complex state - might be more important in animal evolution than previously recognized.
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Curr Biol,
2005]
During gastrulation of the nematode worm Caenorhabditis elegans, individual cells ingress into a solid ball of cells. Gastrulation in a basal nematode, in contrast, has now been found to occur by invagination into a blastocoel, revealing an unanticipated embryological affinity between nematodes and all other triploblastic metazoans.
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Curr Opin Genet Dev,
2006]
Morphogenesis is the process by which multicellular organisms transform themselves from a ball of cells into an organized animal. Certain virtues of Caenorhabditis elegans make it an excellent model system for the study of this process: it is genetically tractable, develops as a transparent embryo with small cell-numbers, and yet still contains all the major tissues typical of animals. Furthermore, certain morphogenetic events are also amenable to study by direct manipulation of the cells involved. Given these advantages, it has been possible to use C. elegans to investigate the different ways in which the actin cytoskeleton drives the cellular rearrangements underlying morphogenesis, through regulated polymerization or actomyosin contraction. Recent insights from this system have determined the involvement in morphogenesis of key proteins, including the actin-regulating WASP and Ena proteins, potential guidance molecules such as the Eph and Robo receptors, and the cell-cell signaling proteins of the Wnt pathway.
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[
Bioessays,
2001]
The change in shape of the C. elegans embryo from an ovoid ball of cells into a worm-shaped larva is driven by three events within the cells of the hypodermis (epidermis): (1) intercalation of two rows of dorsal cells, (2) enclosure of the ventral surface by hypodermis, and (3) elongation of the embryo. While the behavior of the hypodermal cells involved in each of these processes differs dramatically, it is clear that F-actin and microtubules have essential functions in each of these processes, whereas contraction of actomyosin structures appears to be involved specifically in elongation. Molecular analysis of these processes is revealing components specific to C. elegans as well as components found in other systems. Since C. elegans hypodermal cells demonstrate dramatically different behaviors during intercalation, enclosure and elongation, the study of cytoskeletal dynamics in these processes may reveal both unique and conserved activities during distinct epithelial morphogenetic movements. BioEssays 23:12-23, 2001.
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Wissenschaftlechen Filmen, Sekt. Biol.,
1984]
Summary of the Film: Embryonic Development of the Nematode Caenorhabditis elegans. A major part of the body cavity of the free-living nematode Caenorhabditis elegans is occupied by oocytes and fertilized eggs. Within about 12 hours the fertilized egg develops into a worm. The transparent eggshell and the ability to develop normal outside the mother allow detailed microscopic observation of cellular development. After fertilization both pronuclei are positioned at opposite poles of the uncleaved egg. They migrate towards each other, fuse and form the zygote. A series of asymmetric divisions results in the formation of 5 "somatic founder cells" and one "primordial germ cell". In addition to the typical synchronous cell divisions within individual cell lines characteristic cell and nuclear migrations during embyrogenesis are shown. Taking the primordial gut cells as an example, formation of an organ is described. Colored computer reconstructions aid a better understanding of cellular topography and document early formation of symmetry within individual cell lines. After the first half of embryonic development nearly all cells are present. During the second half the ball of cells stretch, first muscle contractions occur, gradually a worm is formed. When it hatches, it is about 4x as long as the long axis of the egg shell.