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. 2018 Jul 1;34(13):i43-i51.
doi: 10.1093/bioinformatics/bty255.

Novo&Stitch: accurate reconciliation of genome assemblies via optical maps

Weihua Pan  1 , Steve I Wanamaker  2 , Audrey M V Ah-Fong  3 , Howard S Judelson  3 , Stefano Lonardi  1
Affiliations

Novo&Stitch: accurate reconciliation of genome assemblies via optical maps

Weihua Pan et al. Bioinformatics. .

Abstract

Motivation: De novo genome assembly is a challenging computational problem due to the high repetitive content of eukaryotic genomes and the imperfections of sequencing technologies (i.e. sequencing errors, uneven sequencing coverage and chimeric reads). Several assembly tools are currently available, each of which has strengths and weaknesses in dealing with the trade-off between maximizing contiguity and minimizing assembly errors (e.g. mis-joins). To obtain the best possible assembly, it is common practice to generate multiple assemblies from several assemblers and/or parameter settings and try to identify the highest quality assembly. Unfortunately, often there is no assembly that both maximizes contiguity and minimizes assembly errors, so one has to compromise one for the other.

Results: The concept of assembly reconciliation has been proposed as a way to obtain a higher quality assembly by merging or reconciling all the available assemblies. While several reconciliation methods have been introduced in the literature, we have shown in one of our recent papers that none of them can consistently produce assemblies that are better than the assemblies provided in input. Here we introduce Novo&Stitch, a novel method that takes advantage of optical maps to accurately carry out assembly reconciliation (assuming that the assembled contigs are sufficiently long to be reliably aligned to the optical maps, e.g. 50 Kbp or longer). Experimental results demonstrate that Novo&Stitch can double the contiguity (N50) of the input assemblies without introducing mis-joins or reducing genome completeness.

Availability and implementation: Novo&Stitch can be obtained from https://github.com/ucrbioinfo/Novo_Stitch.

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Figures

Fig. 1.
Fig. 1.
(A) Contigs (blue) of eight assemblies mapped to one optical molecule (green); minimum tiling path contigs are highlighted in red; (B) final stitched contig, at the end of the iterative stitching process (observe that the final contig spans a genomic region longer than the two MTP contigs)
Fig. 2.
Fig. 2.
Pipeline of Novo&Stitch; the input to the pipeline is a set of chimera-free contigs and an optical map
See this image and copyright information in PMC

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