BrAD-seq (Breath Adapter Directional sequencing) – a streamlined, ultra-simple and fast library preparation protocol for strand specific mRNA library construction

Next Generation Sequencing (NGS) is driving rapid advancement in biological understanding and RNA-sequencing (RNA-seq) has become an indispensable tool for biology and medicine. There is a growing need for access to these technologies although preparation of NGS libraries remains a bottleneck to wider adoption.

Here researchers from the University of California, Davis report a novel method for the production of strand specific RNA-seq libraries utilizing the terminal breathing of double-stranded cDNA to capture and incorporate a sequencing adapter. Breath Adapter Directional sequencing (BrAD-seq) reduces sample handling and requires far fewer enzymatic steps than most available methods to produce high quality strand-specific RNA-seq libraries. The method they present is optimized for 3-prime Digital Gene Expression (DGE) libraries and can easily extend to full transcript coverage shotgun (SHO) type strand-specific libraries and is modularized to accommodate a diversity of RNA and DNA input materials. BrAD-seq offers a highly streamlined and inexpensive option for RNA-seq libraries.

Schematic diagram of strand-specific library synthesis mechanism. mRNAs are fragmented by heat and magnesium (1) and primed for cDNA synthesis by an adapter-containing oligonucleotide (2,3). Size selection and cleanup removes unincorperated oligonucleotides and small cDNA fragments (4). Transient duplex breathing at the terminus of the RNA-cDNA hybrid (5) facilitates interaction with the single-stranded portion of the 5-prime capturing adapter (6) and E. coli DNA Polymerase I catalyses its incorporation into a complete library molecule (7).