Question: Long read alignment
5
gravatar for bdeonovic
4.3 years ago by
bdeonovic130
United States
bdeonovic130 wrote:

Does anyone have any recommendations for

What aligners to use for long reads (e.g. Pac Bio, Oxford nanopore)?
Currently I am using gmap, blast, lastz, and blasr (I'm going to try out blat as well). 

What particular parameters to use for these aligners to map long reads well.

For pac bio long reads I have been using gmap. In several presentations on oxford nanopore I have heard that they have used either blast or lastz to map reads. These programs have tons of parameters to tweak. I'd like to hear what some good choices are .

 

This was crossposted at seqanswers (http://seqanswers.com/forums/showthread.php?p=152941#post152941)

rna-seq alignment • 9.3k views
ADD COMMENTlink modified 4.3 years ago by lh331k • written 4.3 years ago by bdeonovic130
9
gravatar for lh3
4.3 years ago by
lh331k
United States
lh331k wrote:

Nick Loman recommended LAST (not lastz) for mapping oxford nanopore reads. As I have tried, it worked very well at least for small genomes. A few others also seconded. For PacBio, its native mapper blasr is the proven tool, though some complain it is a bit slow. Another option is bwa-mem from github (self advertisement). It is better than the latest release 0.7.10. Bwa-sw is not as good. I reviewed a manuscript where the authors claim that older bwa-mem and bowtie2 don't work well (probably true) and that gem works well, but at my hand gem does not really work at all with their setting. I haven't heard from the authors yet. As to others, blat uses non-overlapping 11bp seeds (by default) and gmap use 20bp (or 24bp) exact seeds. Even if they work, you may need a lot of tuning. According to the email provided by coreruhno, STAR does not work with raw pacbio reads. It only works with CCS reads. Smalt, BBmap and MUMmer are all claimed to work with PacBio reads, but I have not tried myself. Finally, blast, lastz and blastz should also work provided that you use the right settings.

Probably I need to do a brief survey.

Self promotion: PacBio/Oxford Nanopore alignment with bwa-mem:

git clone https://github.com/lh3/bwa.git
cd bwa; make
bwa index ref.fa
bwa mem -x pacbio ref.fa pacbio.fq > aln.sam
bwa mem -x ont2d ref.fa ont-2D.fq > aln.sam

 

ADD COMMENTlink modified 4.3 years ago • written 4.3 years ago by lh331k

Excellent, I see an option for oxford nanopore 2D reads, what if I want to align template and complement reads? 

ADD REPLYlink written 4.3 years ago by bdeonovic130
1

You can still use the 2d option, but the sensitivity will be lower. On the one dataset I have tried, last is slightly (IMO) better than bwa-mem. It is worth trying last as well.

ADD REPLYlink written 4.3 years ago by lh331k

You can still use the 2d option, but the sensitivity will be lower. On the one dataset I have tried, last is slightly (IMO) better than bwa-mem. It is worth trying last as well.

ADD REPLYlink written 4.3 years ago by lh331k

One more thing, when I trried the command you suggested ( bwa mem -x ont2d ref.fa ont-2D.fq > aln.sam) I got something along the lines of index not found.

ADD REPLYlink written 4.3 years ago by bdeonovic130

Hi Heng!  Is the ont2d mode new?  I haven't seen that yet.  I have some BLAST results of the public ONP E. coli dataset; I'll have to give bwa-mem a try and compare.  Thanks for the constant support of and updates to BWA!

ADD REPLYlink written 4.3 years ago by Rob3.1k
0
gravatar for Dgg32
4.3 years ago by
Dgg3260
Bremen
Dgg3260 wrote:

 

Just look this up yesterday, go take a look at bwa's long read Version: bwa-sw 

ADD COMMENTlink modified 4.3 years ago • written 4.3 years ago by Dgg3260
0
gravatar for Stoploss25
4.3 years ago by
Stoploss250
United States
Stoploss250 wrote:

I really like STAR as an aligner, and recommend it if you have a high-memory pc or cluster. It can be configured for use with long reads. See here:

https://groups.google.com/forum/#!searchin/rna-star/starlong/rna-star/-2mBTPWRCJY/PKSPCNcade8J

ADD COMMENTlink written 4.3 years ago by Stoploss250
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