Sequence and Expression Levels of Circular-RNAs in Progenitor Cell Types During Mouse Corticogenesis

Circular (circ) RNAs have recently emerged as a novel class of non coding transcripts whose identification and function remain elusive. Among many tissues and species, the mammalian brain is the organ in which circRNAs are more abundant and in which the first evidence of functional significance started to emerge. Yet, even within this well studied organ, annotation of circRNAs remains fragmentary, their sequence is unknown and their expression patterns in specific cell types was never investigated. Overcoming these limitations, here we provide the first comprehensive identification of circRNAs and their expression in proliferating neural stem cells, neurogenic progenitors and newborn neurons of the developing mouse cortex. Extending the current knowledge about the diversity of this class of transcripts by the identification of nearly 4,000 new circRNAs, our study is the first to provide the full sequence information and expression patterns of circRNAs in specific cell types and representing the lineage toward neurogenic commitment. We further exploited our data by evaluating the coding potential, evolutionary conservation and biogenesis of circRNAs that we found to arise from a specific sub-class of linear mRNAs. Our study provides the arising field of circRNA biology with a new resource essential to address the complexity and potential biological significance of this new class of transcripts Circular RNA profiles in different cell population (proliferating and differentiating progenitors and newborn neurons) of E14.5 developing mouse cortex. Profiles were obtained by deep-sequencing of RNaseR treated total RNA, in triplicate, using Illumina HiSeq 2500