This article was originally published Aug. 15.
NEW YORK (GenomeWeb) – BGI has made slight modifications to Complete Genomics' next-generation sequencing technology in order to enable human exome sequencing, BGI officials told In Sequence. The firm last month began offering exome sequencing services on Complete's technology through its subsidiary BGI Tech.
The service is available globally, Joyce Peng, marketing director of BGI Tech, told IS, and BGI Tech also plans to launch transcriptome sequencing and genotyping by sequencing services on Complete's platform in the near future, she said.
BGI acquired Complete Genomics last year, and previously said that it would focus on incorporating Complete's sequencing technology into its internal research projects rather than its services business.
Complete's technology was originally developed solely for whole-genome sequencing, and the company previously said that this focus enabled extremely high accuracy, one error in 100,000 bases. Peng told IS that the exome sequencing service delivers the same quality as Complete's whole-genome sequencing.
BGI Tech offers exome capture using its own kit, and also offers capture kits from Agilent and other commercial providers, Peng said. The exome service will cost $599 per sample through the end of the year, after which prices will go up, and BGI Tech guarantees 100x average sequencing depth.
In addition, researchers at BGI modified the library construction process to a two-adaptor construction from a four-adaptor construction, she said. The adaptors are synthetic 10-base pieces of known DNA sequence. During library construction, genomic DNA is first lysed into fragments that are between 200 bp and 400 bp in size. Half-adaptors are ligated onto each end of the fragment. Then each end of the half-adaptor is ligated together to form a circular piece of DNA.
The circularized DNA is digested, and the process is repeated with a second adaptor.
In Complete's original design, the process of ligating half-adpators to the ends of a DNA fragment and then ligating the ends of the half-adaptors to circularize the DNA fragment was repeated to incorporate a total of four adapators.
The two-adaptor construction process takes less time, but results in shorter read lengths. Complete uses a sequencing-by-ligation technique in which each end of the adaptor acts as a starting point for sequencing, and up to 10 bases from each end of the adaptor is sequenced. While the four-adaptor approach resulted in 70-base reads, or 35 bases per mate pair, the two-adaptor approach yields mate pairs of 26 bases for a 52-base read.
The rest of the sequencing process is essentially the same as Complete's original technology, which involves forming DNA nanoballs from the circular pieces of DNA and depositing them onto patterned arrays.
Aside from exome sequencing, Peng said BGI Tech would also launch RNA-seq and genotyping-by-sequencing services on Complete's platform in the near future. In addition, she said researchers are working on further modifications to the technology to enable plant and animal sequencing.
BGI has also developed a clinical sequencing platform based on Complete's technology, dubbed BGISEQ-1000. The system was recently approved by the China Food and Drug Administration in conjunction with BGI's noninvasive prenatal diagnostic test, NIFTY, which screens for fetal aneuploidies in chromosomes 21, 18, and 13.