The thymus undergoes atrophy during spaceflight. In this study we analyzed gene expression of the thymus of mice on board International space station to elucidate molecular aspects of the thymic atrophy by spaceflight.

Plants are primary producers of food and oxygen on Earth and will likewise be indispensable to the establishment of large-scale sustainable ecosystems and human survival in space. To contribute to the understanding of how plants respond to spaceflight stresses, we examined the relevance of the unfolded protein response (UPR), a conserved signaling cascade that responds to a number of unfavorable environmental stresses, in the model plant species Arabidopsis thaliana. To do so, we compared the transcriptional responses of wild type and UPR-defective seedlings to spaceflight during the SpaceX-CRS12 mission to the International Space Station. We established that orbital culture substantially altered the expression of hundreds of stress related genes compared to ground control conditions. Although many of these genes were differentially regulated in the UPR mutants in the ground control conditions compared to wild type, their expression was largely equalized in all genotypes by flight. Our results have yielded new information on how plants respond to growth in orbit and support the hypothesis that spaceflight induces the activation of signaling pathways that compensate for the loss of UPR regulators in the control of downstream transcriptional regulatory networks.

The Characterizing Arabidopsis Root Attractions (CARA) spaceflight experiment provides comparative transcriptome analyses of plants grown in both light and dark conditions within the same spaceflight. CARA compared three genotypes of Arabidopsis grown in ambient light and in the dark on board the International Space Station (ISS); Col-0, Ws, and phyD, a phytochrome D mutant in the Col-0 background. In all genotypes, leaves responded to spaceflight with a higher number of differentially expressed genes (DEGs) than root tips, and each genotype displayed distinct light / dark transcriptomic patterns that were unique to the spaceflight environment. The Col-0 leaves exhibited a substantial dichotomy, with ten-times as many spaceflight DEGs exhibited in light-grown plants versus dark-grown plants. Although the total number of DEGs in phyD leaves is not very different from Col-0, phyD altered the manner in which light-grown leaves respond to spaceflight, and many genes associated with the physiological adaptation of Col-0 to spaceflight were not represented. This result is in contrast to root tips, where a previous CARA study showed that phyD substantially reduced the number of DEGs. There were few DEGs, but a series of space-altered gene categories, common to genotypes and lighting conditions. This commonality indicates that key spaceflight genes are associated with signal transduction for light, defense, and oxidative stress responses. However, these key signaling pathways enriched from DEGs showed opposite regulatory direction in response to spaceflight under light and dark conditions, suggesting a complex interaction between light as a signal, and light-signaling genes in acclimation to spaceflight.

In prospective human exploration of outer space the need to maintain a species over several generations under changed gravity conditions may arise. This paper reports the analysis of the third generation of fruit fly Drosophila melanogaster obtained during the 44.5-day space flight (Foton-M4 satellite 2014 Russia) followed by the fourth generation on Earth and the fifth generation under conditions of a 12-day space flight (2014 in the Russian Segment of the ISS). The obtained results show that it is possible to obtain the third-fifth generations of a complex multicellular Earth organism under changed gravity conditions (in the cycle weightlessness - Earth - weightlessness) which preserves fertility and normal development. However there were a number of changes in the expression levels and content of cytoskeletal proteins that are the key components of the spindle apparatus and the contractile ring of cells.

The objective of the Rodent Research-10 mission (RR-10) was to investigate how spaceflight affects the cellular and molecular mechanisms of normal bone tissue regeneration in space. To this end, ten (10) 14-15 weeks-old female B6129SF2/J Wild Type (WT), and ten (10) 14-15 weeks-old female B6;129S2-Cdkn1atm1Tyj/J (p21-null) mice received a pre-flight subcutaneous injection of the bone marker (Alizarin Red), and were then delivered to the ISS aboard SpaceX-21. At 7 days before euthanasia, all 20 mice received an intraperitoneal (IP) injection with a bone formation marker (Calcein). At 48 +/- 2 hours before euthanasia, all 20 mice received an IP injection with a second dose of Calcein as well as a cell proliferation marker (BrdU). Then, following 28-29 days in microgravity, the Flight mice were euthanized. Following removal of hindlimbs, carcasses were wrapped in aluminum foil, preserved in the CryoChiller, and stored at -80 C or colder until return to Earth. In addition to the Flight group, three ground control groups were also part of the study: Basal (representing the pre-launch state), Vivarium (standard vivarium housing for the same duration of time as flight), and Ground (flight habitat in the International Space Station Environment Simulator, ISSES). Twenty mice (10 of each strain) were included in each of these control groups (except Vivarium which included 12 of each strain). These were treated, euthanized and processed on the same schedule and in the same manner as the flight samples. This study includes bulk RNA sequencing ribodepleted gene expression data from 10 Basal animals (5 WT and 5 p21-null), 9 Flight animals (4 WT and 5 p21-null), 10 Ground animals (5 WT and 5 p21-null), and 10 Vivarium animals (5 WT and 5 p21-null).

The objective of the Rodent Research-7 mission (RR-7) was to study the impact of the space environment on the gut microbiota of two strains of mice and how any changes in-turn affect the immune system metabolic system and circadian or daily rhythms. To this end ten 11-week-old female C57BL/6J and ten 11-week-old female C3H/HeJ mice were flown to the International Space Station on June 29 2018 on SpaceX-15 and housed in two Rodent Habitats. Samples of food swabs from living surfaces and fecal pellets were collected from each animal before launch and regularly during the mission. The mission also involved extended video collection (48 hr video segments per Habitat) to monitor circadian rhythms and on-orbit mass measurement. After 25 days on-orbit half of the mice of each strain were euthanized on the ISS with Ketamine/Xylazine/Acepromazine and cardiac puncture after which carcasses were segmented in three sections and preserved in RNA later. After 75-76 days the remaining 5 animals from each group were euthanized and processed in the same manner. The 25-day dissected carcasses returned on SpX-15 and the 75-day dissected carcasses returned on SpX-16. In addition to the Flight group three ground control groups were also part of the study: Basal (representing the pre-launch state) Vivarium (standard vivarium housing for the same duration of time as flight) and Ground (same habitat in the International Space Station Environment Simulator ISSES). Twenty mice (10 of each strain) were included in each of these control groups which were euthanized and processed on the same schedule and in the same manner as the flight samples. Dissections for tissues from all experimental groups were completed by the PI groups along with NASA s Biospecimen Sharing Program in February 2019. GeneLab received dorsal skin samples from forty C57BL/6J mice: 10 Basal 5 Ground (25 days) 5 Ground (75 days) 5 Flight (25 days) 5 Flight (75 days) 5 Vivarium (25 days) 5 Vivarium (75 days). GeneLab received dorsal skin samples from forty C3H/HeJ mice: 10 Basal 5 Ground (25 days) 5 Ground (75 days) 5 Flight (25 days) 5 Flight (75 days) 5 Vivarium (25 days) 5 Vivarium (75 days). From these skin samples RNA was extracted libraries generated (stranded ribodepleted) and sequenced (target 60 M clusters at PE 98 bp).

These investigations studied the fundamentals of how plants perceive gravity and develop in microgravity. It informs how gene regulation is altered by spaceflight conditions.

On Earth plants are constantly exposed to a gravitational field of 1G. Gravity affects a plant in every step of its development. Germinating seedlings orient their radicle and hypocotyl and growing plants position organs at a specific Gravitropic Set-point Angle dictated by the asymmetric distribution of auxin depending on the gravity vector. Hence gravitropism is one of the fundamental growth responses in plants. For any experiment studying the effects of gravity on plants the ultimate control is the microgravity in space. In this study Arabidopsis seeds were flown to the International Space Station and allowed to germinate and grow for 3 days in microgravity. Arabidopsis Wild Type Col-0 seeds were plated onto twenty-two 60mm Petri plates loaded into PDFUs and inserted 4 Biological Research in Canisters (BRICs). Approximately 800 seeds were sterilized plated on each 60mm Petri plates and cold stratified for 16 hours followed by 2 hours of white light treatment. The BRICs were maintained at 4C until spaceflight to ensure seed germination in microgravity. After 3 days of germination and growth the seedlings were fixed by injecting RNAlater into the chamber. They were kept at ambient temperature for 12 hours followed by freezing at -80C. An additional 22 plates were used as ground controls. After the spaceflight tissue from five plates was pooled to make each of three replicates. Both membrane and soluble proteins were extracted from the pooled seedlings. Proteins were trypsin digested labelled with iTRAQ and identified using tandem mass spectrometry.

The objective of the Rodent Research-9 (RR-9) mission was to use mice to understand the molecular basis of phenomena that affect astronauts during long-duration spaceflight particularly visual impairment and joint tissue degradation. To this end a flight group (FLT) of 10 week-old male C57BL/6J mice were launched from Kennedy Space Center (KSC) on 8/14/2017 and housed in Rodent Habitats on the ISS for 33 days before being returned alive to Earth. After splashdown in the Pacific Ocean the animals were transported to Loma Linda University (LLU) for testing euthanasia and dissection on 9/18/2018. A Basal Control (BSL) was housed in standard cages at Kennedy Space Center (KSC) and euthanized one day after launch of the FLT animals (8/15/2017). Ground Control (GC) and Vivarium Control (VIV) studies were planned to commence at KSC approximately one-week after the conclusion of the flight experiments. However all the GC and VIV mouse studies at KSC had to be cancelled due to Hurricane Irma and potential adverse effects on the animal housing facility. The GC and VIV studies were therefore rescheduled and begun in May 2018. The GC was euthanized and dissected 6/18/2018 - 6/20/2018 while the VIV was euthanized and dissected 6/22/2018 - 6/23/2018. Because this resulted in a different cohort of mice being used for the GC and VIV controls as compared to the flight (FLT) and basal (BSL) groups two cohort controls were included in the study. The first Cohort Control 1 (CC_C1) was from the same cohort as the FLT and BSL animals and was sacrificed and dissected 4 days after the FLT group (9/22/2017). The second Cohort Control 2 (CC_C2) was from the same cohort as the GC and VIV animals and was sacrificed and dissected 2-8 days after the GC and VIV groups (6/24/2018 - 6/26/2018). The CC_C1 and CC_C2 groups were housed in standard cages and fed standard chow in contrast to all other groups which received Rodent Foodbars. To clarify the connections between treatment groups and animal cohorts the following group abbreviations are used in the sample metadata: Flight (FLT_C1); Basal (BSL_C1); Ground Control (GC_C2); Vivarium Control (VIV_C2) Cohort Control 1 (CC_C1); Cohort Control 2 (CC_C2). Upon dissection livers were preserved in liquid nitrogen and stored at -80 C before RNA was extracted libraries generated (stranded ribodepleted) and sequenced (target 60 M clusters at PE 150 bp).

Spaceflight results in a number of adaptations to skeletal muscle including atrophy and shifts towards faster muscle fiber types. To identify changes in gene expression that may underlie these adaptations microarray expression analysis was performed on gastrocnemius from mice flown on the STS-108 shuttle flight (11 days 19 hours) versus mice maintained on earth for the same period. Additionally to identify changes that were due to unloading and reloading microarray analyses were conducted on calf muscle from ground-based mice subjected to hindlimb suspension (12 days) and mice subjected to hindlimb suspension plus a brief period of reloading (3.5 hours) to simulate the time between landing and sacrifice of the spaceflight mice.