Copy number variation in small nucleolar RNAs regulates personality behavior

Animals show behavioral traits that can be collectively called personality and which can be measured by standardized tests. We have studied the Prader-Willi Syndrom (PWS) gene region which includes two clusters of tandem repeats coding for small nucleolar RNAs, SNORD115 and SNORD116. SNORD115 is known to regulate splicing of the serotonin receptor Ht2cr and SNORD116 is predicted to interact with the transcript of the chromatin regulator Ankrd11. We show here that both snoRNA clusters display major copy number variation within and between populations and that this affects the expression of their specific target genes. Using a set of behavioral scores related to personality in populations of two species of wild mice, guinea pigs and humans, we find a strong correlation between the snoRNA copy number and these scores. Our results suggest that the SNORD clusters in the PWS region are major regulators of personality and correlated traits.