Biology subjects

Langmead, B.

Publications and source records attributed to Langmead, B..

4 recordsLinked to original sources

bioRxiv2018

FORGe: prioritizing variants for graph genomes

There is growing interest in using genetic variants to augment the reference genome into a \"graph genome\" to improve read alignment accuracy and reduce allelic bias. While adding a variant has the positive effect of removing an undesirable alignment-score penalty, it also increases both the ambiguity of the reference genome and the cost of storing and querying the genome index. We introduce methods and a software tool called FORGe for modeling these effects and prioritizing variants accordingly. We show that FORGe enables a range of advantageous and measurable trade-offs between accuracy and computational overhead.

bioinformatics↗

bioRxiv2017

Scaling read aligners to hundreds of threads on general-purpose processors

General-purpose processors can now contain many dozens of processor cores and support hundreds of simultaneous threads of execution. To make best use of these threads, genomics software must contend with new and subtle computer architecture issues. We discuss some of these and propose methods for improving thread scaling in tools that analyze each read independently, such as read aligners. We implement these methods in new versions of Bowtie, Bowtie 2 and HISAT. We greatly improve thread scaling in many scenarios, including on the recent Intel Xeon Phi architecture. We also highlight how bottlenecks are exacerbated by variable-record-length file formats like FASTQ and suggest changes that enable superior scaling.

bioinformatics↗

bioRxiv2017

A tandem simulation framework for predicting mapping quality

Read alignment is the first step in most sequencing data analyses. Because a reads point of origin can be ambiguous, aligners report a mapping quality: the probability the reported alignment is incorrect. Despite its importance, there is no established and general method for calculating mapping quality. We describe a framework for predicting mapping qualities that works by simulating a set of tandem reads, similar to the input reads in important ways, but for which the true point of origin is known. We implement this in an accurate and low-overhead tool called Qtip, which is compatible with popular aligners.

bioinformatics↗

bioRxiv2017

Snaptron: querying and visualizing splicing across tens of thousands of RNA-seq samples

As more and larger genomics studies appear, there is a growing need for comprehensive and queryable cross-study summaries. Snaptron is a search engine for summarized RNA sequencing data with a query planner that leverages R-tree, B-tree and inverted indexing strategies to rapidly execute queries over 146 million exon-exon splice junctions from over 70,000 human RNA-seq samples. Queries can be tailored by constraining which junctions and samples to consider. Snaptron can also rank and score junctions according to tissue specificity or other criteria. Further, Snaptron can rank and score samples according to the relative frequency of different splicing patterns. We outline biological questions that can be explored with Snaptron queries, including a study of novel exons in annotated genes, of exonization of repetitive element loci, and of a recently discovered alternative transcription start site for the ALK gene. Web app and documentation are at http://snaptron.cs.jhu.edu. Source code is at https://github.com/ChristopherWilks/snaptron under the MIT license.

bioinformatics↗