What is the DNA sequencing platform, MGI-seq or DNB-seq?

MGI-seq or DNB-seq is a next-generation sequencing (NGS) platform developed by MGI Tech Co., Ltd. It could perform whole-genome sequencing (WGS), sequencing of cell-free DNA fragments (cfDNA), ATAC-Seq, etc. It is also a form of sequencing by synthesis (SBS) technology. But different from Illumina sequencing which utilizes bridge amplification, DNB-Seq requires the rolling circle amplification of circular DNA to form DNA nanoball (DNB) for library preparation.

Let’s introduce the library preparation steps, that could be done manually or with automation platforms, for example, MGISP-100, MGISP-960. For WGS, the genomic DNA is fragmented. The fragments are end-repaired into 5’phosphorylated blunt-ended DNA, size-selected with magnetic beads, then ligated to adaptor pairs. After cleanup (repurification), the two ends of the DNA fragmented are ligated to form circular single-stranded DNA (ssDNA). The products (either the product DNA fragments or the DNB library below) from multiple samples could be pooled together for sequencing, while each sample having different barcodes (index).

DNA nanoballs (DNB) are produced by rolling circle amplification of the circular ssDNA, forming a clump of long ssDNA. The DNBs are then loaded and hybridized into the positively charged spots on a patterned array on the flowcell (chip). Sequencing process could proceed with the sequencing machine, such as DNBSEQ-T7, DNBSEQ-G400, DNBSEQ-G99, etc. The sequencing mode is also divided into single-end or paired-end sequencing (e.g., SE50, PE150). And in sequencing-by-synthesis, labeled antibodies that bind specific nucleotide with reversible terminator can be used to identify the sequence rather than using fluorescent-labeled dNTPs. This is called CoolMPS technology. See more details in later posts.To access the accuracy of the sequencing data, the quality score Q30 (%) is often used, with 100% being the best score. Q40 is the upcoming quality score.

The team has been trying to develop the best DNA polymerase mutants, MDA (multiple displacement amplification) enzymes, better dNTP designs, etc., to improve this fantastic technology.