Free circular introns with an unusual branchpoint in neuronal projections

In eukaryotic cells, most introns are degraded soon after splicing in the nucleus but some persist either due to lack of splicing (detained/retained introns) or because they contain important functional elements, for example, sno/scaRNAs. Few introns are detectable outside the nucleus. To hunt for interesting new phenomena in cytoplasmic introns and splicing, we conducted a multimodal study of total RNA within projections (axons, dendrites, glial projections) of rat hippocampal neurons and discovered a class of free circular introns enriched in distal projections. Overall design: A variety of sequencing datasets from rat primary hippocampal neurons are provided: From physically separated cellular projections and whole-cell lysates, (a) rRNA-depleted total RNA-seq (5 biological replicates, each) and (b) polyA site sequencing or PAS-seq (3 biological replicates, each); from fractionated cytoplasmic lysate (c) ribosome profiling (3 biological replicates) and (d) polyA+ RNA-seq (3 biological replicates).