Effects of different modalities of simulated microgravity on embryonic development of zebrafish, Danio Rerio

The zebrafish is a widely used model vertebrate for research in molecular and developmental biology. Recently this species has been used for studies of the effects of microgravity on fundamental biological processes. Zebrafish, being small in size, develop rapidly to sexual maturity and produce relatively large numbers of transparent embryos, so are ideal for space research. Understanding the development of such model organisms under conditions of reduced gravity is important not only in order to fathom for fundamental biological studies processes but also to further the development and use of bioregenerative life support systems. Given the limited opportunities for space flights, ground based experiments represent an important means for providing initial data regarding the effects of microgravity to guide future work in space. Currently there are four commonly used methods to simulate microgravity for periods sufficient to investigate developmental processes: the rotating wall vessel (RWV), 2- and 3-D clinostats and the random positioning machine (RPM). To date most research simulating microgravity has utilized the rotating wall vessel and focused on cell cultures, the results suggesting that simulated microgravity causes changes in the rates of cellular proliferation and differentiation. In this study we aimed to test whether these effects were present in whole organisms. In a previous study (Stoyek et ai, 2010) it was found that embryos reared in the RWV reached key developmental staging points more rapidly from early somitogenesis (3-4 somite stage) through late somitogenesis (21 somite stage) than fish raised at 1 G. Our laboratory is currently developing protocols for the use of zebrafish embryos in the 3-D clinostat, as well as in the 2-D clinostat and RPM to test whether this trend is observed in other modalities of simulated microgravity (SMG). Preliminary studies (Stoyek et al., 2011) have shown embryos raised under conditions of SMG using the 3-D clinostat showed similar trends of accelerated embryonic development from early somitogenesis through 24 hours post fertilization (hpf). Investigations of the effects of RPM and 2-D clinostat simulations of microgravity conditions are currently ongoing. Our results will allow for the first time a comparison of the effects of different methods of simulating microgravity on whole-embryo development.These findings provide insights into how zebrafish may develop when eventually flown in space, thus permitting better formulation of experiments to test the mechanisms by which microgravity affects ontogeny in this model organism.