Frontiers of Sequencing: Putting Long Reads and Graph Assemblies to Work

Mike Schatz, Associate Professor, Cold Spring Harbor Laboratory

Maria Nattestad, Graduate Student, Cold Spring Harbor Laboratory


Listen 0:00 100 to 1000 times improvement with long reads (7:01)

Listen 7:01 Rethinking HER2 (2:56)

Listen 10:02 How do you decide where to apply long read technology? (7:08)

Listen 17:09 The next level of reference genomes (3:16)

Listen 20:25 Graph assemblies and the challenge of visualization (5:29)

Listen 25:56 Headline for 2016? (6:06)

OK, so we get it. Long read sequencing technology is cool. But how cool? Is it another great player on the field, or does it change the game altogether? 

The Mike Schatz lab at Cold Spring Harbor is well know for de novo genome assemblies and their work on structural variation in cancer genomes, so we were curious to hear how long reads have impacted their work. In todays show, lab leader, Mike Schatz, and doctorate student, Maria Nattestad tell of two new projects that include the de novo assembly of a very difficult but important flatworm genome and, secondly, making better variant calls for oncogenes such as HER2.

In the case of the flatworm, Mike says that the move to using PacBio’s long reads improved the assembly by more than a 100 times. That means the difference of looking at a super high resolution picture versus a fuzzy, blurry one, he says. With her work on cancer cell lines, Maria is seeing variants that just weren’t there with short reads. Will her work translate to lower false positive rates for HER2 in clinical diagnostics?

What will be the major headline for sequencing and informatics in 2016?

Mike says we’ll see many more reference genomes done, that the term “reference genome” itself is changing as we go from the one standard reference genome to multiple reference genomes representing the broader population. These new reference genomes are pushing bioinformaticians to come up with new ways to visualize and compare the genomes. Maria details her work into using “graph” assemblies as opposed to the linear approach made popular by the Genome Browser. She says that already a new generation of informaticians are rethinking genome visualization using graph assemblies. (Included below is an image representing her work.)

Neither mentioned it, so we ask at the end, what about Oxford Nanopore’s tech?


(The spectral karyotype of the Her2-amplified breast cancer cell line SK-BR-3. The original chromosomes are different colors, so this genome is a complex mixture of various chromosomes. The total number of chromosomes has also jumped from 46 to 80, and there is approximately twice as much DNA as in a normal human genome. Maria Nattestad and Mike Schatz are studying this genome to see how oncogenes like Her2 became amplified while all these changes took place in the big picture of the genome.)

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