Temporal transcriptomics suggest that twin-peaking genes reset the clock

The mammalian suprachiasmatic nucleus (SCN) drives daily rhythmic behavior and physiology, yet a detailed understanding of its coordinated transcriptional programmes is lacking. To reveal the true nature of circadian variation in the mammalian SCN transcriptome we combined laser-capture microdissection (LCM) and RNA-Seq over a 24-hour light / dark cycle. We show that 7-times more genes exhibited a classic sinusoidal expression signature than previously observed in the SCN. Another group of 766 genes unexpectedly peaked twice, near both the start and end of the dark phase; this twin-peaking group is significantly enriched for synaptic transmission genes that are crucial for light-induced phase-shifting of the circadian clock. 342 intergenic non-coding RNAs, together with novel exons of annotated protein-coding genes, including Cry1, also show specific circadian expression variation. Overall, our data provide an important chronobiological resource (www.wgpembroke.com/shiny/SCNseq/) and allow us to propose that transcriptional timing in the SCN is gating clock resetting mechanisms. Overall design: Pooled dissected tissue of the suprachiasmatic nucleus from five adult male mice provided one of three replicates for each of six timepoints over a 12:12 light/dark (LD) cycle (ZT2, 6, 10, 14, 18 and 22). Each biological replicate was sequenced over 3 seperate lanes using Illumina HiSeq.