Project description:We investigated differentially regulated genes in human myelomonocytic U937 cells in 20s and 5min microgravity and in hypergravity and compared expression profiles to identify potential gravity-regulated genes and adaptation processes.
Project description:We investigated differentially regulated genes in human myelomonocytic U937 cells in 20s and 5min microgravity and in hypergravity and compared expression profiles to identify potential gravity-regulated genes and adaptation processes.
Project description:Euglena gracilis is a unicellular freshwater flagellate, which uses the gravitational vector for orientation in the water column in the dark. This allows the cell to reach areas in the water column for reproduction and growth. How exactly the gravitational vector is perceived, and which intracellular pathways are involved in the signaling is not very well understood so far. In the past, parabolic flight campaigns were used to study the swimming behavior of Euglena gracilis under altered gravitational accelerations. It was shown that cells adapt their swimming direction very fast: in the dark under 1xg cell show negative gravitaxis, i.e. they move upwards in the water column of the experiment hardware and against the gravitational vector. With onset of the first hypergravity period of 1.8xg the precision of upward swimming increases slightly. This first hyper gravity lasts for only 20 seconds and is followed by 22 sec of microgravity. During this period no gravitational vector is perceived by the cells, therefore they lack a cue for orientation and move randomly in all direction. In the subsequent hyper gravity period of 1.8xg, which also lasts for 20 sec, cells direct their movement again and swim upwards. Over different parabolic flight campaigns and other experiments it was shown that this gravitactic behavior is linked to changes in membrane potential, calcium and cAMP concentration. However, due to the lack of genomic and transcriptomic data, it was so far not possible to link the differential movement to the abundance of distinct mRNA transcripts. In contrast, other model organisms, such as Arabidopsis thaliana, have been analyzed by means of gene expression with respect to the effects of altered gravitational accelerations. Also various human cell lines have shown to adapt their gene expression in dependence of the prevailing acceleration. With the recently published Euglena gracilis transcriptome, we now aimed at analyzing effects of altered acceleration on the gene expression in the flagellate. Therefore, Euglena gracilis samples were taken in the course of the 29th DLR parabolic flight campaign during parabola 1 and 31 (time difference of 2 hours and 30 additional parabolas). During both parabolas samples were fixed with TRIzol at 1xg just before onset of the first hyper gravity period, 20 sec into hyper gravity (1.8xg), 20 sec into microgravity (µg) and 20 sec into the last hypergravity period.
