Rapid coupling between gravitational forces and the transcriptome in human myelomonocytic U937 cells

Abstract

The gravitational force has been constant throughout Earth’s evolutionary history. Since the cell nucleus is subjected to permanent forces induced by Earth’s gravity, we addressed the question, if gene expression homeostasis is constantly shaped by the gravitational force on Earth. We therefore investigated the transcriptome in force-free conditions of microgravity, determined the time frame of initial gravitational force-transduction to the transcriptome and assessed the role of cation channels. We combined a parabolic flight experiment campaign with a suborbital ballistic rocket experiment employing the human myelomonocytic cell line U937 and analyzed the whole gene transcription by microarray, using rigorous controls for exclusion of effects not related to gravitational force and cross-validation through two fully independent research campaigns. Experiments with the wide range ion channel inhibitor SKF-96365 in combination with whole transcriptome analysis were conducted to study the functional role of ion channels in the transduction of gravitational forces at an integrative level. We detected profound alterations in the transcriptome already after 20 s of microgravity or hypergravity. In microgravity, 99.43% of all initially altered transcripts adapted after 5 min. In hypergravity, 98.93% of all initially altered transcripts adapted after 75 s. Only 2.4% of all microgravity-regulated transcripts were sensitive to the cation channel inhibitor SKF-96365. Inter-platform comparison of differentially regulated transcripts revealed 57 annotated gravity-sensitive transcripts. We assume that gravitational forces are rapidly and constantly transduced into the nucleus as omnipresent condition for nuclear and chromatin structure as well as homeostasis of gene expression.

Rapid Cellular Perception of Gravitational Forces in Human Jurkat T Cells and Transduction into Gene Expression Regulation

“…If 99% of such pivotal events cannot be simulated by analogous clinostat experiments, the general assumption that 2D clinostats provide a valid simulation of microgravity and can be recommended for most biological organisms [20] should be revised. If in addition the primary trigger of gravity-induced gene expression response [10,46] is less than one second, the fundamental question of suitability of the clinostat system for the investigation of mammalian cells arises. We therefore recommend that sufficient validation experiments should be carried out before starting experiments with vag as simulation for real microgravity.…”

“…Changes of the gravitational environment induce strong alterations of human physiological systems, which respond and adapt within hours and weeks [44]. At the cellular level, changes of the gravitational force affect morphology, proliferation, differentiation, signal transduction, and gene expression [45] and have been detected within seconds in isolated cells of the immune system [10,12,13,46,47]. We recently investigated the dynamics of gene expression response to different gravitational environments in human Jurkat T lymphocytes in combination of parabolic flights with a suborbital ballistic rocket experiment and with control experiments for excluding all possible other factors of influence [13,14].…”

Transcriptional Homeostasis of Oxidative Stress-Related Pathways in Altered Gravity

“…As already described by Thiel [ 35 , 36 ], human U937 myelomonocytic cells and human Jurkat T cells were subjected to 20 s of hypergravity (1.8 g) and subsequently to 20 s of microgravity during the first parabola of parabolic flight campaigns (19th and 23rd German Aerospace Center (DLR) PFC), and samples were obtained at the end of each flight phase. Control samples were obtained in-flight five min before the first parabola and on ground in the identical hardware and under identical conditions except for the gravitational force ( Table 1 , Supplementary Figure S1 ).…”

Schnelle zelluläre Reaktion und Anpassung an Schwerelosigkeit

“…In unseren Studien untersuchten wir Signaltransduktionskaskaden [3,[6][7][8], Adhäsionsmoleküle [9][10][11], Stoffwechsel [11], funktionelle Parameter [12,13], Genexpressionsreaktionen [6,[14][15][16][17][18][19]…”

“…In der Realität der zellulären Signaltransduktion kommt es aber zur hochkomplexen Transformation und Integration mehrerer simultaner Inputs in die zeitliche und strukturelle Komplexität der lebenden Zelle [24]. Führt die omnilateral wirkende Gravitationskraft dennoch zu einem anscheinend zelltypspezifischen Muster einer veränderten Transkriptomantwort [15,16,18], so stellt sich die unmittelbare Frage nach dem Grund der Transduktion einer unspezifischen Kraft in eine spezifische Antwort, die somit nur in der Spezifität der zellulären Eigenschaft begründet liegen kann.…”