Abstract
Cellular responses to micro- and hypergravity are rapid and complex and appear within the first few seconds of exposure. Transcriptomic analyses are a valuable tool to analyze these genome-wide cellular alterations. For a better understanding of the cellular dynamics upon altered gravity exposure, it is important to compare different time points. However, since most of the experiments are designed as endpoint measurements, the combination of cross-experiment meta-studies is inevitable. Microarray and RNA-Seq analyses are two of the main methods to study transcriptomics. In the field of altered gravity research, both methods are frequently used. However, the generation of these data sets is difficult and time-consuming and therefore the number of available data sets in this research field is limited. In this study, we investigated the comparability of microarray and RNA-Seq data and applied the results to a comparison of the transcriptomics dynamics between the hypergravity conditions during two real flight platforms and a centrifuge experiment to identify temporal adaptation processes. We performed a comparative study on an Affymetrix HTA2.0 microarray and a paired-end RNA-Seq data set originating from the same Jurkat T cell RNA samples from a short-term hypergravity experiment. The overall agreeability was high, with better sensitivity of the RNA-Seq analysis. The microarray data set showed weaknesses on the level of single upregulated genes, likely due to its normalization approach. On an aggregated level of biotypes, chromosomal distribution, and gene sets, both technologies performed equally well. The microarray showed better performance on the detection of altered gravity-related splicing events. We found that all initially altered transcripts fully adapted after 15 min to hypergravity and concluded that the altered gene expression response to hypergravity is transient and fully reversible. Based on the combined multiple-platform meta-analysis, we could demonstrate rapid transcriptional adaptation to hypergravity, the differential expression of the ATPase subunits ATP6V1A and ATP6V1D, and the cluster of differentiation (CD) molecules CD1E, CD2AP, CD46, CD47, CD53, CD69, CD96, CD164, and CD226 in hypergravity. We could experimentally demonstrate that it is possible to develop methodological evidence for the meta-analysis of individual data.
Highlights
Gravity has been a constant presence for billions of years, throughout the Earth’s history [1,2]
To further cross-validate these findings, we included two external reference sets from the NASA GeneLab [27] that we identified in our database search (Figure 1): GLDS-13 from T cells that were exposed to 3 days of microgravity and either activated for
Motivated by the observation of the altered immune responses of astronauts during mid- and long-term space missions, cellular reactions to microgravity have been studied on different levels for many decades [54]
Summary
Gravity has been a constant presence for billions of years, throughout the Earth’s history [1,2]. It was observed that cellular reactions to altered gravity appear after seconds to minutes of exposure and include a plethora of effects, including reduced oxidative burst in microgravity and increased burst in hypergravity in macrophages [12,13], chromatin regulatory effects in microgravity [14], cell cycle regulation in microgravity [15], micro-RNA expression in simulated microgravity [16], altered immune cascade-associated messenger protein levels in hypergravity, and microgravity in T cells including surface concentrations of IL-2R and LAT [17], by significantly altering the expression of thousands of transcripts within 20 s of microgravity and hypergravity, and by almost fully adapting the transcriptome pool after
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call