Nanopore native RNA sequencing of a human poly(A) transcriptome: RNA extraction, cDNA conversion and direct RNA and cDNA library preparation for Oxford Nanopore

Abstract High throughput cDNA sequencing technologies have dramatically advanced our understanding of transcriptome complexity and regulation. However, these methods lose information contained in biological RNA because the copied reads are often short and because modifications are not carried forward in cDNA. We address these limitations using a native poly(A) RNA sequencing strategy developed by Oxford Nanopore Technologies (ONT). Our study focused on poly(A) RNA from the human cell line GM12878, generating 9.9 million aligned sequence reads. These native RNA reads had an aligned N50 length of 1294 bases, and a maximum aligned length of over 21,000 bases. A total of 78,199 high-confidence isoforms were identified by combining long nanopore reads with short higher accuracy Illumina reads. We describe methods for extracting intact RNA, poly-A selection, cDNA conversion for a portion of sample, and library preparation for both direct RNA and cDNA libraries.