ASGSB 2003 Annual Meeting Abstracts


Simulated-microgravity causes changes in heat shock protein expression in zebrafish embryos.  S.J. Moorman.  Dept of Neuroscience and Cell Biology, RWJMS-UMDNJ, Piscataway, New Jersey.

   We have previously demonstrated that the effects of microgravity on gene expression can be monitored in live transgenic zebrafish embryos that express the gene for green fluorescent protein (gfp) under the influence of the promoter/enhancer for the b-actin gene.  The effects that we had documented in the developing heart, notochord, and embryo as a whole could have been due to stress associated with aspects of the bioreactor that we use to simulate microgravity.  Heat shock proteins (hsp) play a central role in cell protection and repair upon stress as well as under certain non-stressful conditions.  Since hsp-70 levels did not change in cells in culture that were exposed to microgravity on the Space Shuttle or cells cultured in the same bioreactor we use for zebrafish embryos, we wanted to know if hsp-70 expression changes in zebrafish embryos in the bioreactor.  We acquired a transgenic strain of zebrafish that expresses gfp under the influence of the promoter/enhancer of the zebrafish hsp-70 gene.  Under normal conditions, embryos from this transgenic strain (hsp70:gfp) only express gfp in the lens.  When exposed to stress, (37oC for 1 hour) there is ubiquitous expression of gfp in these embryos.  When hsp70:gfp embryos were placed in the bioreactor for 24 hours, there was no gfp expression in either the heart or notochord.  However, there was spotty expression in the retina and low-level expression in the skin and hypochord.  Hsp-70 is thought to play a role in protection against apoptosis.  Therefore, the low level expression in the skin might be a protective response to local changes in concentrations of metabolites near the skin that are the result of a decrease in gravity driven diffusion of metabolites away from the skin.  Since there is no skin covering the developing eye, the changes in the retina could also be a protective response to a local environmental stress.  The hypochord is a midline row of cells that lies just ventral to the notochord and has been implicated in influencing the development of a single dorsal aorta.  Because of proximity to the notochord, the hypochord might be responding to other microgravity-induced changes in the notochord.

(Supported by NASA: NAG2-1591)


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