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Countering spaceflight effects on C. elegans biology.  F. Selch¹, N.J. Szewczyk^2,3,  and C. A. Conley^{2 1},    Department of Molecular Cell Biology, University of Vienna,  ² NASA Ames Research Center,  ³Department of Biological Sciences, University of Pittsburgh

Despite common study of C. elegans, there is little evidence that worms sense or respond to gravity. We find C. elegans grown on solid or in liquid chemically defined medium display reproducible gene expression changes (Stanford microarray), likely due to the difference in externally-applied surface tension, a force roughly equivalent to 10,000 x unit Gravity. When plotted on the C. elegans gene expression self organizing map, the data indicate that mounts 8 (intestinal), 12 (neuronal), 15, 22 (collagen), and 36 (heat shock) are down regulated and 4 (sperm), 19 (amino acid metabolism), 21 (lipid metabolism), and 24 (fatty acid oxidation) are up regulated in response to increased mechanical load (p<.0001). Conversely, the gravitational unloading of a 10 day spaceflight increased expression of mounts 8 and 36 and decreased expression of mounts 19 and 21 (p<.001). Additionally, spaceflight decreased expression of mounts 1 (muscle) and 17 (collagen) and produced a movement defect. Together these results show that C. elegans sense gravity and suggest that 70% of the genes induced and 40% of the genes repressed by spaceflight can be blocked by increased mechanical load alone. Increased expression of mount 36 can be reversed while decreased expression of muscle or skeletal (collagen) genes cannot be reversed by mechanical load alone in C. elegans.  Strikingly in accordance with these predictions, the movement defect is not rescued by growth on solid medium during spaceflight (i.e. increased mechanical load). These results demonstrate C. elegans can be used to study the effects of altered gravity and suggest that artificial gravity alone is sufficient to only partially counter the biological effects of spaceflight.

(Supported by NASA: NNA04CK22A)