Single-nucleus total RNA sequencing of formalin-fixed paraffin-embedded samples using snRandom-seq.

Formalin-fixed paraffin-embedded (FFPE) samples represent a vast and valuable resource of patient material, often linked to extensive clinical history and follow-up data. However, achieving single-cell or single-nucleus RNA (sc/snRNA) profiling in these archived tissues remains challenging. To address this, we have developed snRandom-seq, a droplet- and random primer-based single-nucleus total RNA sequencing technology specifically designed for FFPE tissues. This method captures total RNAs by using random primers and demonstrates a low doublet rate (0.3%), increased RNA coverage and enhanced detection of non-coding and nascent RNAs compared to state-of-the-art high-throughput sc/snRNA-seq technologies. This protocol provides a comprehensive guide to isolating single nuclei from FFPE samples; performing in situ DNA blocking, reverse transcription and dA tailing reactions; barcoding single-nucleus droplets; and preparing sequencing libraries. The entire snRandom-seq process can be completed in 4 d. This platform serves as a powerful tool for snRNA-seq of clinical specimens, with broad applications in studying complex biological systems.