Title
Accurate estimation of short read mapping quality for next-generation genome sequencing.
Abstract
Several software tools specialize in the alignment of short next-generation sequencing reads to a reference sequence. Some of these tools report a mapping quality score for each alignment-in principle, this quality score tells researchers the likelihood that the alignment is correct. However, the reported mapping quality often correlates weakly with actual accuracy and the qualities of many mappings are underestimated, encouraging the researchers to discard correct mappings. Further, these low-quality mappings tend to correlate with variations in the genome (both single nucleotide and structural), and such mappings are important in accurately identifying genomic variants.We develop a machine learning tool, LoQuM (LOgistic regression tool for calibrating the Quality of short read mappings, to assign reliable mapping quality scores to mappings of Illumina reads returned by any alignment tool. LoQuM uses statistics on the read (base quality scores reported by the sequencer) and the alignment (number of matches, mismatches and deletions, mapping quality score returned by the alignment tool, if available, and number of mappings) as features for classification and uses simulated reads to learn a logistic regression model that relates these features to actual mapping quality.We test the predictions of LoQuM on an independent dataset generated by the ART short read simulation software and observe that LoQuM can 'resurrect' many mappings that are assigned zero quality scores by the alignment tools and are therefore likely to be discarded by researchers. We also observe that the recalibration of mapping quality scores greatly enhances the precision of called single nucleotide polymorphisms.LoQuM is available as open source at http://compbio.case.edu/loqum/.matthew.ruffalo@case.edu.
Year
DOI
Venue
2012
10.1093/bioinformatics/bts408
Bioinformatics
Keywords
Field
DocType
reliable mapping quality score,actual mapping quality,short read mapping quality,reported mapping quality,accurate estimation,mapping quality score,quality score,correct mapping,next-generation genome sequencing,low-quality mapping,zero quality score,alignment tool,base quality score
Data mining,Quality Score,Simulation software,Computer science,Genomics,Software,DNA sequencing,Genome human,Bioinformatics,Reference genome
Journal
Volume
Issue
ISSN
28
18
1367-4811
Citations 
PageRank 
References 
5
0.50
6
Authors
4
Name
Order
Citations
PageRank
Matthew Ruffalo1513.60
Mehmet Koyutürk269353.38
Soumya Ray3948.89
Thomas LaFramboise4629.02