Title
Strand-seq enables reliable separation of long reads by chromosome via expectation maximization.
Abstract
Motivation: Current sequencing technologies are able to produce reads orders of magnitude longer than ever possible before. Such long reads have sparked a new interest in de novo genome assembly, which removes reference biases inherent to re-sequencing approaches and allows for a direct characterization of complex genomic variants. However, even with latest algorithmic advances, assembling a mammalian genome from long error-prone reads incurs a significant computational burden and does not preclude occasional misassemblies. Both problems could potentially be mitigated if assembly could commence for each chromosome separately. Results: To address this, we show how single-cell template strand sequencing (Strand-seq) data can be leveraged for this purpose. We introduce a novel latent variable model and a corresponding Expectation Maximization algorithm, termed SaaRclust, and demonstrates its ability to reliably cluster long reads by chromosome. For each long read, this approach produces a posterior probability distribution over all chromosomes of origin and read directionalities. In this way, it allows to assess the amount of uncertainty inherent to sparse Strand-seq data on the level of individual reads. Among the reads that our algorithm confidently assigns to a chromosome, we observed more than 99% correct assignments on a subset of Pacific Bioscience reads with 30.1 x coverage. To our knowledge, SaaRclust is the first approach for the in silico separation of long reads by chromosome prior to assembly.
Year
DOI
Venue
2018
10.1093/bioinformatics/bty290
BIOINFORMATICS
Field
DocType
Volume
Genome,Data mining,Chromosome,Coding strand,Computer science,Expectation–maximization algorithm,Latent variable model,Posterior probability,Computational biology,Sequence assembly
Journal
34
Issue
ISSN
Citations 
13
1367-4803
0
PageRank 
References 
Authors
0.34
3
7
Name
Order
Citations
PageRank
Maryam Ghareghani100.34
David Porubsky200.34
Ashley D. Sanders301.35
Sascha Meiers400.34
Evan E. Eichler515616.89
Jan O. Korbel611110.36
Tobias Marschall712113.65