We have identified and validated a spaceflight-associated microRNA (miRNA) signature that is shared by rodents and humans in response to simulated, short-duration and long-duration spaceflight. Previous studies have identified miRNAs that regulate rodent responses to spaceflight in low-Earth orbit, and we have confirmed the expression of these proposed spaceflight-associated miRNAs in rodents reacting to simulated spaceflight conditions. Moreover, astronaut samples from the NASA Twins Study confirmed these expression signatures in miRNA sequencing, single-cell RNA sequencing (scRNA-seq), and single-cell assay for transposase accessible chromatin (scATAC-seq) data. Additionally, a subset of these miRNAs (miR-125, miR-16, and let-7a) was found to regulate vascular damage caused by simulated deep space radiation. To demonstrate the physiological relevance of key spaceflight-associated miRNAs, we utilized antagomirs to inhibit their expression and successfully rescue simulated deep-space-radiation-mediated damage in human 3D vascular constructs.

MicroRNAs (miRNAs) are small non-coding RNAs involved in post-transcriptional gene regulation that have a major impact on many diseases and provide an exciting avenue toward antiviral therapeutics. From patient transcriptomic data, we determined that a circulating miRNA, miR-2392, is directly involved with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) machinery during host infection. Specifically, we show that miR-2392 is key in driving downstream suppression of mitochondrial gene expression, increasing inflammation, glycolysis, and hypoxia, as well as promoting many symptoms associated with coronavirus disease 2019 (COVID-19) infection. We demonstrate that miR-2392 is present in the blood and urine of patients positive for COVID-19 but is not present in patients negative for COVID-19. These findings indicate the potential for developing a minimally invasive COVID-19 detection method. Lastly, using in vitro human and in vivo hamster models, we design a miRNA-based antiviral therapeutic that targets miR-2392, significantly reduces SARS-CoV-2 viability in hamsters, and may potentially inhibit a COVID-19 disease state in humans.

Telomere length dynamics and DNA damage responses were assessed before, during, and after one-year or shorter duration missions aboard the International Space Station (ISS) in a comparatively large cohort of astronauts (n = 11). Although generally healthy individuals, astronauts tended to have significantly shorter telomeres and lower telomerase activity than age- and sex-matched ground controls before and after spaceflight. Although telomeres were longer during spaceflight irrespective of mission duration, telomere length shortened rapidly upon return to Earth, and overall astronauts had shorter telomeres after spaceflight than they did before; inter-individual differences were identified. During spaceflight, all crewmembers experienced oxidative stress, which positively correlated with telomere length dynamics. Significantly increased frequencies of chromosomal inversions were observed during and after spaceflight; changes in cell populations were also detected. We propose a telomeric adaptive response to chronic oxidative damage in extreme environments, whereby the telomerase-independent Alternative Lengthening of Telomeres (ALT) pathway is transiently activated in normal somatic cells.

The BCL6 transcriptional repressor is required for the development of germinal center (GC) B cells and diffuse large B cell lymphomas (DLBCLs). Although BCL6 can recruit multiple corepressors, its transcriptional repression mechanism of action in normal and malignant B cells is unknown. We find that in B cells, BCL6 mostly functions through two independent mechanisms that are collectively essential to GC formation and DLBCL, both mediated through its N-terminal BTB domain. These are (1) the formation of a unique ternary BCOR-SMRT complex at promoters, with each corepressor binding to symmetrical sites on BCL6 homodimers linked to specific epigenetic chromatin features, and (2) the "toggling" of active enhancers to a poised but not erased conformation through SMRT-dependent H3K27 deacetylation, which is mediated by HDAC3 and opposed by p300 histone acetyltransferase. Dynamic toggling of enhancers provides a basis for B cells to undergo rapid transcriptional and phenotypic changes in response to signaling or environmental cues.

Understanding the impact of space exploration remains biologically elusive. Cell Press is dedicating this month to spaceflight (Afshinnekoo et al., 2020), with the open science NASA GeneLab database enabling the study revealing mitochondria as a key biological feature from spaceflight (da Silveira et al., 2020).

Clonal hematopoiesis (CH) occurs when blood cells harboring an advantageous mutation propagate faster than others. These mutations confer a risk for hematological cancers and cardiovascular disease. Here, we analyze CH in blood samples from a pair of twin astronauts over 4 years in bulk and fractionated cell populations using a targeted CH panel, linked-read whole-genome sequencing, and deep RNA sequencing. We show CH with distinct mutational profiles and increasing allelic fraction that includes a high-risk, TET2 clone in one subject and two DNMT3A mutations on distinct alleles in the other twin. These astronauts exhibit CH almost two decades prior to the mean age at which it is typically detected and show larger shifts in clone size than age-matched controls or radiotherapy patients, based on a longitudinal cohort of 157 cancer patients. As such, longitudinal monitoring of CH may serve as an important metric for overall cancer and cardiovascular risk in astronauts.

Telomeres, repetitive terminal features of chromosomes essential for maintaining genome integrity, shorten with cell division, lifestyle factors and stresses, and environmental exposures, and so they provide a robust biomarker of health, aging, and age-related diseases. We assessed telomere length dynamics (changes over time) in three unrelated astronauts before, during, and after 1-year or 6-month missions aboard the International Space Station (ISS). Similar to our results for National Aeronautics and Space Administration's (NASA's) One-Year Mission twin astronaut (Garrett-Bakelman et al., 2019), significantly longer telomeres were observed during spaceflight for two 6-month mission astronauts. Furthermore, telomere length shortened rapidly after return to Earth for all three crewmembers and, overall, telomere length tended to be shorter after spaceflight than before spaceflight. Consistent with chronic exposure to the space radiation environment, signatures of persistent DNA damage responses were also detected, including mitochondrial and oxidative stress, inflammation, and telomeric and chromosomal aberrations, which together provide potential mechanistic insight into spaceflight-specific telomere elongation.

Type I interferons (IFNs) induce hundreds of IFN-stimulated genes (ISGs) in response to viral infection. Induction of these ISGs must be regulated for an efficient and controlled antiviral response, but post-transcriptional controls of these genes have not been well defined. Here, we identify a role for the RNA base modification N6-methyladenosine (m6A) in the regulation of ISGs. Using ribosome profiling and quantitative mass spectrometry, coupled with m6A-immunoprecipitation and sequencing, we identify a subset of ISGs, including IFITM1, whose translation is enhanced by m6A and the m6A methyltransferase proteins METTL3 and METTL14. We further determine that the m6A reader YTHDF1 increases the expression of IFITM1 in an m6A-binding-dependent manner. Importantly, we find that the m6A methyltransferase complex promotes the antiviral activity of type I IFN. Thus, these studies identify m6A as having a role in post-transcriptional control of ISG translation during the type I IFN response for antiviral restriction.

The National Aeronautics and Space Administration (NASA) Twins Study created an integrative molecular profile of an astronaut during NASA's first 1-year mission on the International Space Station (ISS) and included comparisons to an identical Earth-bound twin. The unique biochemical profiles observed when landing on Earth after such a long mission (e.g., spikes in interleukin-1 [IL-1]/6/10, c-reactive protein [CRP], C-C motif chemokine ligand 2 [CCL2], IL-1 receptor antagonist [IL-1ra], and tumor necrosis factor alpha [TNF-α]) opened new questions about the human body's response to gravity and how to plan for future astronauts, particularly around initiation or resolution of inflammation. Here, single-cell, multi-omic (100-plex epitope profile and gene expression) profiling of peripheral blood mononuclear cells (PBMCs) showed changes to blood cell composition and gene expression post-flight, specifically for monocytes and dendritic cell precursors. These were consistent with flight-induced cytokine and immune system stress, followed by skeletal muscle regeneration in response to gravity. Finally, we examined these profiles relative to 6-month missions in 28 other astronauts and detail potential pharmacological interventions for returning to gravity in future missions.