Peak memory improvements

Thanks to new data compression methods, our latest release (50963) reduces the peak memory required for large genomes. The exact peak memory required depends on a number of factors, including the nature of the genome and the quality of the data, but is mostly determined by coverage and genome size.

Assembly graph visualization tool released

The assembly graph can be large, complex and unwieldy, so DISCOVAR de novo does not generate a viewable graph directly. Instead we have developed an interactive tool that allows you to explore your assembly by creating smaller viewable graphs of the regions you are interested in. This new tool, called NhoodInfo, is now part of the DISCOVAR package, as of release 50612 . It is also the engine behind our online demoso you can try it out right now without having to create an assembly of your own. Full instructions on using NhoodInfo are included in the DISCOVAR package.

Clarification of DISCOVAR input requirements

DISCOVAR takes as input read pairs from fragments of size 400-500 bp, with some larger and some smaller. The blog and manual contained references to fragments of size 700 bp, which were outdated, and have now been removed. Note that the protocol yields a wide size distribution, including some large fragments.

Understanding DISCOVAR output

A DISCOVAR de novo assembly is a graph. A typical assembly consists almost entirely of linear stretches, typically like this

simple

which we call ‘lines’, and providing a rich data type that captures polymorphism and other important features. Further, with some loss of information, these lines may be ‘flattened’ into standard contigs. We have added a tutorial explaining how these data types are available as part of the DISCOVAR output. We are also interested in hearing your thoughts regarding the utility of these output types and others that might be useful to you.

Large genome de novo assembler released

We are pleased to announce the release of our new de novo assembler suitable for large genomes up to human size. This is an early release and should be considered experimental, but is fully functioning. Download it now.

Our new assembler, called DISCOVAR de novo (experimental), uses the same cheap data that the original DISCOVAR release does: 250 base paired-end PCR-free Illumina reads. No other libraries are required. The runtime for a human genome on a 48 core, 0.5 Tb server is only 36 hours, and produces an assembly with a contig N50 of ~100 kb.

We are actively developing DISCOVAR de novo, so check back often for updates.

Explore a de novo human assembly online now

Want a sneak preview of what we’ve been working on lately? Then check out this online demo that lets you explore a de novo human assembly produced by our new assembler DISCOVAR de novo.

Developed over the past 6 months, the new DISCOVAR de novo algorithm will be released later this summer. Unlike DISCOVAR, it can assemble large genomes de novo. It is also much faster, but still takes the same low-cost single-library input data that DISCOVAR does.

Whilst we prepare DISCOVAR de novo for release, take a look at the online demo we’ve set up. Here you can explore and visualize an assembly of the human cell line NA12878. You can enter any coordinates on the human reference sequence GRCh38, and the demo will show you the part of the assembly that aligns there. Using this tool, large structural variation events can be directly visualized, and simple SNPs appear as short bubbles.

Please check it out and let us know what you think via the forum.

HiSeq 2500 data quality

We have been asked what our DISCOVAR input data looks like, and the best way to answer this question is with some examples. We don’t claim that these data are necessarily representative, but they do illustrate what we are able to generate here at the Broad Institute.