Novel imprinted transcripts from theDlk1-Gtl2intergenic region,Mico1andMico1os, show circadian oscillations

Most of the known imprinted genes are assembled into clusters that share common imprinting control regions (ICRs). Non-coding transcripts are often associated with ICRs and implicated in imprinting regulation. We undertook a systematic search for transcripts originating from the Dlk1-Gtl2 intergenic region that contains the ICR for the chromosome 12 imprinted cluster and identified two overlapping transcripts expressed from opposite strands exclusively from the maternal chromosome. These novel imprinted transcripts most likely represent non-coding RNAs and are located telomeric to the IG DMR, extending the proximal boundary of the region of maternal-specific transcription. Their expression is tissue-specific and shows diurnal and circadian oscillations.Therefore, we named these novel transcripts maternal intergenic circadian oscillating 1 (Mico1) and Mico1, opposite strand (Mico1os).