Titus Brown's Thoughts on the Assemblathon 2 paper

Titus Brown's Thoughts on the Assemblathon 2 paper

Titus Brown finished reviewing Assemblathon 2 paper and wrote an excellent commentary that the readers should take a look at. Why do we need to pay attention to Titus Brown’s opinions? It is mainly because he is a rare bioinformatician, whose group assembled few genome scale (or bigger) sequence libraries, and yet he does not have his name on the Assemblathon paper. He is not in, mainly because his group is not associated with any large genome center. So, he can be more candid about genome assembly factories than almost everyone else around the world.

…as a field, we have pretended that genome assembly is a reliable exercise and that the results can be trusted; the Assemblathon 2 paper shows that that’s wrong.

So, my first beef is that we have not done a good job of communicating this uncertainty.

My second beef is that we have not done a good job of managing this uncertainty. If there’s one group that should be eyeing the Assemblathon 2 paper with concern, it’s the sequencing and informatics centers, who are increasingly trying to be a one-stop shop for genome analysis. The Assemblathon 2 paper basically points out that you can’t trust what they produce to be what you want, and (from personal experience) I can tell you that very rarely do sequencing centers put significant thought into your specific genome: it tends to be a production pipeline using (shock! surprise!) what they already know how to use, with a minimum of parameter sweeps. When you connect this to the Assemblathon 2 paper, what you get is a near-certain statement that your genome assembly is worse – perhaps considerably worse – than it could be. But nobody recognizes this explicitly, and our sequencing centers are paid to produce sequence, not assemblies, much less good assemblies, so the incentive isn’t there to change.

Instead of trying to repost everything he said, let us briefly go over why biologists seemed to have neglected or underfunded computational people. This is how the field evolved. During 2000-2006, biologists believed that if someone gave them high-quality genomes and few web-based tools to pick primers, etc., they could carry on in their merry old ways. So, the field of bioinformatics partitioned into two groups - (i) those associated with genome centers, who worked on sequencing projects, and (ii) everyone else in various labs. The first group was generally well funded for their computational work and continued to prosper. Second group included few young kids, who learned little bit of python or R on the side, and could download and run simple scripts, if they were asked to. The perception of bioinformatics being easy was further fed by microarray companies, who all provided simple graphical tools to find up/down regulated genes.

Advent of next-gen sequencing through a monkey wrench into that nice arrangement, because it allowed everyone to sequence billions of Gigabases without any ability to process. Even if the researchers were not interested in assembling genomes, assembling transcriptome data (RNAseq) required many of the same skills, and no large assembly factory was interested in assembling everyone’s RNAseq data. Only when a biologist experiences assembly and annotation, he realizes how screwed up things are, and how much make up the pretty genome had to wear to look pretty. We have been working with a group of researchers on a fish genome, and we remember how difficult it was to explain why we did not have ‘THE genome’ and ‘THE genes’, but progressively improving sets of genes and genome. Also, it took us quite some time to explain that instead of targeting some published benchmarks for a perfect ‘THE genome’, we should check what biological problem we are solving and make sure the assembly is giving us correct results.

We agree with Titus on the following point as well, and applied similar thinking, when we picked Minia as the top assembly contributor of 2012 -

We should be making sure that these assemblers can be run quickly, and efficiently, on any given set of data. This would let us actually run them and do parameter sweeps, as opposed to now, where you need to have serious computational infrastructure to run a lot of these assemblers.

Finally, Titus also touched on Fred’s rant, which seemed to have gotten very negative public comments everywhere. We received a nice email from Fred few weeks back, and would like to share one part that may surprise you.

I’m still digging out of the email this generated. Weirdly, the email I received has been universally positive, except for the one that had nothing but “Send from my iPad”, but I’ll be an optimist and assume that was meant positively as well. Compare that to the comments on the public fora.

It is quite possible that many others hold similar lowly opinion about bioinformatics practices as Fred, but unlike Titus, are afraid to write publicly.

Written by M. //