Contextual fear conditioning regulates the expression of brain-specific small nucleolar RNAs in hippocampus.

Some small nucleolar RNAs (snoRNAs) are exclusively expressed in the brain but they have no known role in higher brain function. We analysed the expression pattern of four brain-specific snoRNAs: MBI-36, MBII-48, MBII-52 and MBII-85, in mouse brain using in situ hybridization. All of these genes were expressed in the hippocampus and, except for MBII-85, their levels in ventral parts were higher than those in dorsal parts. Using quantitative real-time polymer chain reaction we determined hippocampal expression changes after contextual fear conditioning in mice. Ninety minutes, but not 25 h, after conditioning, we observed significant downregulation of MBII-48 and upregulation of MBII-52. Our finding that the expression of MBII-48 and MBII-52 is regulated during learning suggests that these snoRNAs have an important role in higher brain function.