Doh, J. | bioRxiv Science

bioRxiv2019

Comparative Transcriptomic Signature of the Simulated Microgravity Response in Caenorhabditis elegans

BackgroundGiven 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. ResultsHere, 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. ConclusionsOur 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.

genomics↗

bioRxiv2018

F-actin dynamics transform filopodial bridges into intercellular nanotubes capable of distant cell communication

A novel actin-based bridge connecting cells has been recognized as a new pathway for the distant transport of cytoplasmic components, viruses, or pathogenic substances between cells. However, it is not yet known how such a fine structure extends over several hundred micrometres and remains robust for several hours. Using optical fluorescence imaging methods, we found that random contact promotes the formation of filopodial bridges through N-cadherin interactions between filopodia, which are slender actin-rich plasma membrane protrusions. These filopodial bridges eventually evolve into a single actin-based bridge (intercellular nanotube) that connects two cells via an intermediate state that involves a helical structure. Surprisingly, the twisting of two filopodia is likely to result from the rotational motion of actin filaments inside the filopodia by myosin V. The accumulated torsion of the filopodia triggers the release of one of the paired filopodia, whose end is attached to the other cell body by an N-cadherin cluster. The resulting retraction of the filopodium by retrograde F-actin flow leaves a single bridge. The N-cadherin/catenin cluster is likely to form a synapse between the intercellular nanotube and the cell body. This study sheds light on the formation mechanism of the filopodial bridge-based intercellular nanotubes for long-distance communication between cells.

biophysics↗