Spaceflight-related suboptimal conditions can accentuate the altered gravity response of Drosophila transcriptome

Abstract

Genome-wide transcriptional profiling shows that reducing gravity levels during Drosophila metamorphosis in the International Space Station (ISS) causes important alterations in gene expression: a large set of differentially expressed genes (DEGs) are observed compared to 1g controls. However, the preparation procedures for spaceflight and the nonideal environmental conditions on board the ISS subject the organisms to additional environmental stresses that demonstrably affect gene expression. Simulated microgravity experiments performed on the ground, under ideal conditions for the flies, using the random position machine (RPM), show much more subtle effects on gene expression. However, when the ground experiments are repeated under conditions designed to reproduce the additional environmental stresses imposed by spaceflight procedures, 79% of the DEGs detected in the ISS are reproduced by the RPM experiment. Gene ontology analysis of them shows they are genes that affect respiratory activity, developmental processes and stress-related changes. Here, we analyse the effects of microgravity on gene expression in relation to the environmental stresses imposed by spaceflight. Analysis using 'gene expression dynamics inspector' (GEDI) self-organizing maps reveals a subtle response of the transcriptome to microgravity. Remarkably, hypergravity simulation induces similar response of the transcriptome, but in the opposite direction, i.e. the genes promoted under microgravity are usually suppressed under hypergravity. These results suggest that the transcriptome is finely tuned to normal gravity and that microgravity, together with environmental constraints associated with space experiments, can have profound effects on gene expression.

The behavioural-driven response of the Drosophila imago transcriptome to different types of modified gravity

“…Interestingly, the internal controls used in the ground-based facility experiments described here also reveal some effects on the gene expression profile, possibly due to magnetic stresses in levitation or subtle mechanical forces in the RPM such as vibrations, other than those which compensate gravity. Nevertheless, these results, in combination with earlier experiments in real or simulated microgravity conditions [7,29], indicate that the transcriptome is finely tuned to Earth´s gravity and that the synergic effects exerted by microgravity and environmental suboptimal conditions may be explained by this "out of tune" state of the transcriptome in microgravity.…”

“…All samples were processed using Affymetrix Drosophila (Drosophila Genome2) chips covering near the whole fly coding genome. A validation of this approach, including qRT-PCR has been already published by our team [7].…”

“…Although previous investigations [1][2][3][4][5] have not yet led to a consensus on how the environment in spacecraft affects the genetic behaviour of living organisms, studies of the overall transcriptome response to microgravity of some species [6], including Drosophila [7], have revealed interesting effects.…”

Microgravity simulation by diamagnetic levitation: effects of a strong gradient magnetic field on the transcriptional profile of Drosophila melanogaster

“…The main conclusions from the gene expression analysis are that the exposure of the samples to the strong magnetic field, with or without a field-gradient, caused significant changes in the expression of immune, stress, and temperature response genes (several heat shock proteins, for instance, appear affected). It is notable that experiments of different durations activated or repressed different genes, although in similar GO groups (Figure 3), and also that these GO groups are similar to the ones found in real microgravity conditions in space [21,23]. Our results indicate that the vertical diamagnetic force (that levitated the flies in the 0 g * tube and enhanced the net effective weight of the flies in the 2 g * tube) had less of an influence on the transcription profile than other effects of the strong magnetic field, which was present in all three tubes (11.5 T in 0 g * and 2 g *, and 16.5 T in 1 g *).…”

The Development Of Drosophila Melanogaster under Different Duration Space Flight and Subsequent Adaptation to Earth Gravity

“…The genome-wide transcriptional profile showed that the presence of the reduced gravity level during Drosophila metamorphosis in the experiment at the ISS resulted in changes in the gene expression profile, primarily in stress reactions [22], which was confirmed in the experiments conducted using the random position machine [23]. The products of these differentially expressed genes are involved in respiration, development, morphogenesis processes, and the formation of the stress response [24].…”