Jasper Verwilt from Ghent University in Belgium presented at the Nanopore Community Meeting 2022 on “Revealing plasma exRNA’s deepest secrets.” The title of this ten-minute session was intriguing. Verwilt explained that human blood is a very unfriendly environment, yet some exRNA exist! I had never thought about this! There are, Verwilt shared, linear and circular RNA! What is circular RNA!? Back-t0-back exons coming together. With short read Illumina sequencing, one cannot differentiate between two circular RNA molecules. With Oxford Nanopore sequencing the complete order can be obtained using rolling circle sequencing. Verwilt and the research team asked: does full-length intact mRNA exist in plasma? They did a plasma preparation from samples with a range of platelets. They extracted RNA, prepared libraries, and sequenced. Verwilt shared graphs of end-to-end reads mapped to the transcriptome and the matching length was divided by the transcript length. On the x-axis of the graph, comparisons of platelet richness and its effect were depicted. Mitochondrial RNA and platelet transcripts were detected, along with intact hemoglobin transcripts. In extracellular vesicles they had trouble sequencing and found hemoglobin transcripts. They then asked if circular RNA could be detected in plasma. To do this, they extracted RNA from plasma and used primers to detect circular RNAs (circRNAs). Intact circles were detected, and this is a new finding. Verwilt concluded that: they detected intact mRNA and circRNA in human plasma and intact mRNA in extracellular vesicles. Importantly, they developed “an extremely valuable technique for low-input long-read RNA-sequencing.
