Snord116-dependent diurnal rhythm of DNA methylation in mouse cortex

Rhythmic oscillations of physiological processes depend on integrating the circadian clock and diurnal environment. DNA methylation is epigenetically responsive to daily rhythms, as a subset of CpG dinucleotides in brain exhibit diurnal rhythmic methylation. A major genetic effect on rhythmic methylation was identified in a mouse Snord116 deletion model of the imprinted disorder Prader-Willi syndrome (PWS).  > 23,000 diurnally rhythmic CpGs were identified in wild-type cortex, with nearly all lost or phase-shifted in PWS. Circadian dysregulation of a second imprinted Snord cluster at the Temple/Kagami-Ogata syndrome locus was observed at the level of methylation, transcription, and chromatin, providing mechanistic evidence of cross-talk.  Genes identified by diurnal epigenetic changes in PWS mice overlapped rhythmic and PWS-specific genes in human brain and were enriched for PWS-relevant phenotypes and pathways. These results support the proposed evolutionary relationship between imprinting and sleep, and suggest possible chronotherapy in the treatment of PWS and related disorders. Overall design: Examination of whole genome DNA methylation in mouse cerebral cortex throughout the diurnal cycle. Genotypes: WT, Snord116+/- Timepoints: ZT0, ZT3, ZT6, ZT9, ZT12, ZT16 n = 3 per condition