Yesterday’s Ion Torrent Proton PII™ and Illumina NextSeq 500™ post certainly got a reaction from several quarters, including detailed pricing information about the 1x75bp format for the high-throughput configuration on the consumables. Instead of making edits to the original here are some clarifying points, as it is clear that Illumina is making a break from … Read more
Every mother-to-be who has what is considered an ‘at-risk’ pregnancy is informed of the risks to the fetus of a genetic abnormality. ‘At-risk’ can involve a long list of medical conditions (diabetes or cancer for example) or poor health choices (illegal drug use or smoking). Yet a common cause of an at-risk pregnancy is age, having a child before the age of 17 or older than 35. In the US, no less than 750,000 are considered at-risk.
Immunology is a fascinating subject. Immense in its complexity, debilitating when the immune system malfunctions, our ability to fend off bacterial and viral infection, cancers of different types, and other foreign invaders is a remarkable biological capability.
The NIH estimates 24M Americans are affected with an autoimmune disorder, but that number rises to 50M when the definition is expanded from a list of 24 disorders to over 100 by the American Autoimmune Related Disease organization. It is the second highest form of chronic illness, arthritis being the most familiar to many.
This week a remarkable paper was published in Nature, called “Accurate whole-genome sequencing and haplotyping from 10 to 20 human cells”. What makes it remarkable is the ability of this method to obtain rare variant phase information by changing the library preparation method. Until now to obtain completely phased individual genomes required a fair amount of laboratory manipulation.
Although the whole genome versus whole exome discussion was held previously, details around the methods of selecting out the whole exome have been not discussed (also called ‘targeted selection’), and the wide array of methods, costs, and effort required can be a rather complicated affair.
The myth of the complete genome is something that is not commonly known to active observers of genomic technologies. (The term ‘active observer’ is from the point of view of one with varying degrees of background in the biological sciences, and is in noway an aspersion.) The ‘first draft’ of the human genome was announced at a Clinton-era press conference on June 26, 2000, and it was an agreement between the two famously competitive individuals (Francis Collins and Craig Venter) representing the public (NIH and DOE) effort and the private one (Celera). This first draft was exactly that – about 90% complete, and the completed version was declared in 2003. This is not to discount the first seminal publications of this draft, as in 2001 when these papers were published (in Science and Nature respectively) the largest previously sequenced genome was 1/25th the size. In other words, the human genome represented a 25-fold leap in size and complexity of anything done to-date.
Oxford Nanopore, based in Oxford U.K., made a remarkable announcement that surprised many in February’s AGBT meeting in Marco Island. A GridION and MiniION single-molecule sequencers were announced, promising 15 minute runtimes, no sample preparation, and a disposable USB-stick sequencer for $900 (in the case of the MiniION), with 50kb long readlengths (and 100kb promised) at only a 4% error rate it appears to be a dream come true for many research challenges that await.
Recently I was asked what Roche would purchase when they said publicly that they “would not revisit Illumina, and will pursue smaller takeovers”, and I answered there were a few small development companies out there but even fewer with something ready to sell. (Roche isn’t known for development of NGS as witnessed with their 454 / Curagen acquisition.) And among the firms that was preparing a launch, including GnuBio and Oxford Nanopore, was a small company called Intelligent Bio-Systems.
In every technological revolution, there is a first seminal breakthrough, a burst of commercial activity from many individual companies, and then the eventual maturing of a market, of standards, and the discovery of new uses for the technology in often surprising ways.
Complete Genomics is a startup business founded upon a particular idea – that the whole genome sequencing of human individuals is going to be industrialized, commonplace, and have such clinical utility so as to become the dominant application for next-generation sequencing. (Disclosure – I have no financial interest in this company, just an interested observer.)
After preparation of the library (and careful quantitation) and preparation of the amplified template comes the main event: the sequencing itself. While there are several methods available, the methods can be divided into three broad divisions.
The three divisions are (firstly) Pyrophosphate Release (named for the original patent by Mostafa Ronaghi and others in 1998 when he was a graduate student at the Royal Institute of Technology in Stockholm); this is the method that uses individual nucleotide flow across all templates, and then detects the signal. (Pyrosequencing – now owned by QIAGEN – detects pyrophosphate, but is not a ‘next-generation’ sequencer as it is not massively parallel; however Roche / 454 FLX used essentially the same method.) Jonathan Rothberg, who parallelized the FLX pyrosequencing method at Curagen, simply changed the detection method with Ion Torrent.
After a library is properly prepared, (remember it can be from many sources – randomly sheared genomic DNA, cDNA from a small RNA sample, an immunoprecipitated sample) the library molecules need to be amplified in some manner, before the sequencing takes place. Thus there is a critical need for accurate quantitation of the library DNA, whose importance can be overlooked.