Kubota, A.; Kojima, K.; Koketsu, S.; Kannon, T.; Sato, T.; Hosomichi, K.; Shinohara, Y.; Tajima, A.

Brain asymmetry is widely observed in different species. Studies on rodent hippocampi have provided morphological and physiological explanations for left-right asymmetry and have shown that the environment influences hippocampal lateralization in the CA1 region. However, how the left-right asymmetry arises, and its significance are not fully understood. In this study, we aimed to elucidate the transcriptome profiles of the rat hippocampus associated with lateralization and to assess the sensitivity of the bilateral CA1 region to an enriched environment. Transcriptomic analysis using RNA-seq was performed on the left and right CA1 regions of male rats reared in isolated or enriched environments. Although differentially expressed genes (DEGs) were not found between left and right CA1 under either environmental condition, environment-induced DEGs were significantly detected in both left and right CA1. DEGs common to both hemispheres were also found in the environmental comparison, and immediate early genes were suggested as relevant together with gene co-expression network analysis. Gene set enrichment analysis revealed that the profiles of gene expression change due to the enriched environment in the bilateral CA1 were significantly enriched in the suppressed direction in several gene sets, including those related to synaptic signaling and organization, and neuronal connection.