DNA 5-methylcytosine detection and methylation phasing using PacBio circular consensus sequencing

Existing methods for detecting DNA methylation (5mC) are less accurate and robust. Here, the authors develop a deep learning tool ccsmeth and a Nextflow pipeline ccsmethphase for genome-wide 5mCpG detection and phasing with high accuracy from CCS reads in human. Long single-molecular sequencing technologies, such as PacBio circular consensus sequencing (CCS) and nanopore sequencing, are advantageous in detecting DNA 5-methylcytosine in CpGs (5mCpGs), especially in repetitive genomic regions. However, existing methods for detecting 5mCpGs using PacBio CCS are less accurate and robust. Here, we present ccsmeth, a deep-learning method to detect DNA 5mCpGs using CCS reads. We sequence polymerase-chain-reaction treated and M.SssI-methyltransferase treated DNA of one human sample using PacBio CCS for training ccsmeth. Using long (& GE;10 Kb) CCS reads, ccsmeth achieves 0.90 accuracy and 0.97 Area Under the Curve on 5mCpG detection at single-molecule resolution. At the genome-wide site level, ccsmeth achieves >0.90 correlations with bisulfite sequencing and nanopore sequencing using only 10x reads. Furthermore, we develop a Nextflow pipeline, ccsmethphase, to detect haplotype-aware methylation using CCS reads, and then sequence a Chinese family trio to validate it. ccsmeth and ccsmethphase can be robust and accurate tools for detecting DNA 5-methylcytosines.

Automated summary

The authors develop a deep learning tool ccsmeth and a Nextflow pipeline ccsmethphase for accurate detection and phasing of DNA 5mCpG using CCS reads in human. Existing methods for detecting 5mCpGs using PacBio CCS are less accurate and robust. By training ccsmeth with PacBio CCS reads, the authors achieve high accuracy in 5mCpG detection at single-molecule resolution and strong correlations with bisulfite sequencing and nanopore sequencing at the genome-wide level.