Comparative Transcriptomic Signature of the Simulated Microgravity Response in Caenorhabditis elegans

Background: Given the growing interest in human exploration of space, it is crucial to identify the effect of space conditions on biological processes. The International Space Station (ISS) greatly helps researchers determine these effects. However, the impact of the ISS-introduced potential confounders (e.g., the combination of radiation and microgravity exposures) on the biological processes are often neglected, and separate investigations are needed to uncover the impact of individual conditions. Results: Here, we analyze the transcriptomic response of Caenorhabditis elegans to simulated microgravity and observe the maintained transcriptomic response after return to ground conditions for four, eight, and twelve days. Through the integration of our data with those in NASA GeneLab, we identify the gravitome, which we define as microgravity-responsive transcriptomic signatures. We show that 75% of the simulated microgravity-induced changes on gene expression persist after return to ground conditions for four days while most of these changes are reverted after twelve days return to ground conditions. Our results from integrative RNA-seq and mass spectrometry analyses suggest that simulated microgravity affects longevity regulating insulin/IGF-1 and sphingolipid signaling pathways. Conclusions: Our results address the sole impact of simulated microgravity on transcriptome by controlling for the other space-introduced conditions and utilizing RNA-seq. Using an integrative approach, we identify a conserved transcriptomic signature to microgravity and its sustained impact after return to the ground. Moreover, we present the effect of simulated microgravity on distinct ceramide profiles. Overall, this work can provide insights into the sole effect of microgravity on biological systems.