Intact messenger RNA exists in human blood plasma and urine, and their purified macromolecular compartments
It is generally assumed that extracellular long RNA molecules in biofluids are fragmented. Few studies have indirectly hinted at the existence of possibly functional, intact long RNA transcripts. In search for such RNA molecules, we developed a long-read full transcript sequencing workflow for low-input and low-quality samples. We applied our method to human blood plasma, urine, and their isolated macromolecular compartments, in parallel with total RNA sequencing. This approach enabled us to find intact messenger RNA molecules in human biofluids and macromolecular compartments. We showed that the full-length transcriptome of human urine and blood plasma differs, but we also reveal intact messenger RNA molecules shared between biofluids. In addition, we show that these intact molecules are differentially distributed over fractionated macromolecular compartments. This study provides a foundation for future extracellular RNA studies to elucidate the human biofluid full-length transcriptome.