Drosophila melanogaster gene expression changes after spaceflight.

Gene expression levels were determined in 3rd instar and adult Drosophila melanogaster reared during spaceflight, to elucidate the genetic and molecular mechanisms underpinning the effects of microgravity on the immune system. The goal was to validate the Drosophila model for understanding alterations of innate immune responses in humans due to spaceflight. Five containers of flies, with ten female and five male fruit flies in each container, were housed and bred on the space shuttle (average orbit altitude of 330.35 km) for 12 days and 18.5 hours, with a new generation reared in microgravity. RNA was extracted on the day of shuttle landing from whole body animals (3rd instar larvae and adults), hybridized to Drosophila 2.0 Affymetrix genome arrays, and the expression level of all genes was normalized against the gene expression level from the corresponding developmental stage animals raised on ground. Spaceflight altered the expression of larval genes involved in the maturation of plasmatocytes (macrophages) and their phagocytic response, as well as the level of constitutive expression of pattern recognition receptors and opsonins that specifically recognize bacteria, and of lysozymes, antimicrobial peptide pathway and immune stress genes, hallmarks of humoral immunity.

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