Clinorotation To Simulate Microgravity: Defining A Model Gravitome In C. Elegans

We introduce the term, gravitome, to include the set of genes that are responsive to changes in the gravitational vector. Understanding how the gravitome functions will be important as humans begin a new era of long term space exploration and exploitation. To this end, we have developed a novel microscope clinostat to visualize microorganisms and cell cultures growing in real-time during simulated microgravity. Microspheres were used to calibrate the clinostat rotation and verify orbital trajectories. We take advantage of the unique ability of the nematode, C. elegans, to live and reproduce in liquid cultures, and use our clinostat to essentially cause these animals to live their lives in free-fall, nullifying the gravitational force. In addition to microscopy data, the clinorotated animals were harvested and their transcriptomes and histone-marked epigenomes were determined using next-generation sequencing. Here, we present the first genetic confirmation that ground-based clinostats can capture elements of the space environment by comparing our results with previous studies of C. elegans on the International Space Station (ISS). In particular, we also find significant changes in genes belonging to the insulin, longevity, metabolic and muscle-related pathways in simulated microgravity, and also have identified large alterations in the dorsal-ventral pathway. Because next-generation sequencing provides more information than the previously used gene arrays onboard the ISS, we also detect the expression of hundreds of novel long non-coding RNAs as a result of simulated microgravity. These new findings will help elucidate the intricate genetic regulatory networks that are responsible for adaptation of higher organisms in microgravity.