Our study aims to comprehensively understand effects induced by the space environment on mammals. To achieve this aim we analyze the male mice housed under environments as the artificial gravity and the microgravity (space environment) in Japanese Experiment Module JEM) of the International Space Station (ISS) on orbit for 35 days. After recovered these mice on the ground transcriptome analysis by next-generation sequencing technology is performed about spleen to examine alteration of gene expression in the space.