要旨
Individual variation in behaviour, such as the personality of non-human animals, is essential for ecology and evolution. A recent study uncovered a significant association between anxiety and the copy numbers of two clusters of non-coding regulatory snoRNAs which known as SNORD115 and SNORD116 in populations of two species of wild mice, laboratory mice (C57BL/6), guinea pigs and humans. These snoRNAs regulate post-transcriptional modification of their target genes and consequently significantly regulate animal personality. In mice, new copy number variants are generated at every generation. This fast evolution of the SNORD115/116 copy number provides possibilities to explain the high phenotypic variability of personality traits within populations. In addition to variation in genetic background, environmen-tal enriched (EE) housing has been proven to result in differently expressed genes as well as a reduction in anxiety-related behaviour and improvement in spatial learning and memory in aged mice compared with it in standard housing (SH). So, it is widely accepted that both, genes and the environment contribute to shaping personality traits such as anxiety; however, the underly-ing mechanism of how genetic and environmental cues interact to generate such high variability remain mostly unknown. The present thesis aimed to investigate the possible interaction be-tween environment and SNORDs mechanism.
Using an inbred strain of laboratory mice (C57BL/6), we bred mice under standard housing con-ditions. After conducting the first round of behavioural testing in an open field and elevated plus maze test and also genotyping of each individual for SNORD115/116 copy number, offspring with a similar range of SNORDs copy number and personality were allocated to either EE or SH housing throughout the study. Animal behaviour tests, including open field and elevated plus maze, were examined again in adolescence and adulthood. An additional Maze test was con-ducted at the end of the adolescent phase to assess the spatial learning and memory of each individual. Genotyping of SNORDs copy numbers was also performed once again in adulthood.
I found that the environmental treatment resulted in significant variation in personality traits mostly in locomotor activity but less so in anxiety. Mice housed in EE condition also displayed significantly faster learning compared to that in SH condition. The significant association be-tween SNORD115/116 copy numbers and anxiety-related behaviour in open field also were found regardless of environmental treatment or age. Interestingly, the associations between SNORD115/116 copy numbers and locomotor activity in OF were influenced by environmental treatment and age, suggesting other genetic component(s) might involve in the downstream of snoRNAs to regulated the locomotor activity according to the environmental conditions.
