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Microgravity induced changes of gene expression in the developing zebrafish heart.  I. Gillette-Ferguson, D.G. Ferguson and S.J. Moorman.  Department of Anatomy, Case Western Reserve University, Cleveland, OH.

     Microgravity induced changes in gene expression have been documented for cultured cells flown on the Space Shuttle and in cells grown in bioreactors that NASA designed to simulate microgravity for cells in culture on Earth.  However, little is understood about the mechanisms that underlie these effects and it is not known whether similar changes in gene expression might be seen in animals.  Using transgenic zebrafish that express the gfp gene under the influence of a Я-actin promoter, we examined the affect of simulated microgravity on GFP expression in the developing heart.  Using one of the NASA-designed bioreactors, we exposed zebrafish embryos to simulated microgravity for 24 hours beginning at 24 hours after fertilization.  The amount of GFP fluorescence associated with the heart was then determined using fluorescence microscopy of live embryos.  Video images of the heart were acquired using an intensified CCD camera.  Average intensity of fluorescence of the heart was measured from the video images using NIH Image software.  On the average, there was a 3-9% increase in GFP-associated fluorescence in the heart of the experimental animals compared to the controls.  Preliminary data from images of the caudal end of the embryo did not show significant changes in GFP fluorescence.  This suggests that these changes are specific to the heart although other specific organs have not yet been analyzed.  These studies indicate that microgravity can induce changes in gene expression in vivo.  They also demonstrate the usefulness of transgenic zebrafish to determine the effects of microgravity on gene expression, in vivo.

     (Supported by NIH: DC03531 and NASA: NAG2-1356 and NCC2-1204)