Many thanks for your help! With the extractRepeats script, I am getting 
something closer to the alignment generated by UCSC, but there are still 
discrepancies.

These are the steps that I am taking to create the pairwise alignments, using 
the alignment of rheMac2 chr7 to rn4 chr6 as an example:

First I download chromFa.tar.gz and chromOut.tar.gz from 
goldenPath/rheMac2/bigZips/ and goldenPath/rn4/bigZips/

For rheMac2, I run

DateRepeats chr7.fa.out -query human -comp mouse -comp dog

extractRepeats 1 chr7.fa.out_mus-musculus_canis-lupus-familiaris > chr7.out.spec

select_rpts chr7.out.spec 1 169801366 chr7.rpts

strip_rpts chr7.fa chr7.rpts > chr7.strip.fa


For rn4, I run

DateRepeats chr6.fa.out -query rat -comp human -comp mouse

extractRepeats 1 chr6.fa.out_homo-sapiens_mus-musculus > chr6.out.spec

select_rpts chr6.out.spec 1 147636619 chr6.rpts

strip_rpts chr6.fa chr6.rpts > chr6.strip.fa


Then I run 

lastz chr7.strip.fa chr6.strip.fa --gap=400,30 --hspthresh=3000 
--gappedthresh=2200 --inner=2000 B=0 > rheMac2.chr7.rn4.chr6.strip.plus.lav

(using blastz instead of lastz gives the same result).

Then I call restore_rpts, lavToPsl, and axtChain to generate 
rheMac2.chr7.rn4.chr6.chain.

This is the first chain in the rheMac2 chr7 to rn4 chr6 alignment that I 
created:

chain 526821446 chr7 169801366 + 87564296 168894851 chr6 147636619 + 64051113 
138192842 1
17      2       0
57      0       1
19      0       1
7       7       0
139     6       0
15      1       0
12      7       0
4       3       0
11      0       1
57      1       0
52      0       1
23      6       0
61      0       1
51      2       0
71      1       0
14      1       0
15      4632    674
37      14      184  <=== first discrepancy occurs here
...

and this is the corresponding chain generated by UCSC:

chain 547645084 chr7 169801366 + 87564296 169142947 chr6 147636619 + 64051113 
138454126 1
17      2       0
57      0       1
19      0       1
7       7       0
139     6       0
15      1       0
12      7       0
4       3       0
11      0       1
57      1       0
52      0       1
23      6       0
61      0       1
51      2       0
71      1       0
14      1       0
15      4632    674
39      0       154  <=== first discrepancy occurs here

This discrepancy can be identified already in 
rheMac2.chr7.rn4.chr6.strip.plus.lav before calling restore_rpts, lavToPsl, and 
axtChain, so it must be caused by some mistake in my call to lastz or some 
earlier step.

The only difference I can see with the UCSC pipeline is that I skip the call to 
fasta-subseq, because I couldn't find this program and anyway I am running 
lastz on the full chromosomes.

Is there any other difference between the UCSC pipeline and what I am doing? If 
not, would it be possible to make intermediate files of the UCSC pipeline 
available for comparison? For example, it would be really informative if the 
*.lav file with its header were available for one pairwise alignment for 
comparison.

Thanks again, and best wishes,
--Michiel de Hoon, RIKEN Omics Science Center.


--- On Fri, 6/24/11, Hiram Clawson <[email protected]> wrote:

> From: Hiram Clawson <[email protected]>
> Subject: Re: [Genome] Repeat regions in whole-genome alignments
> To: "Michiel de Hoon" <[email protected]>
> Cc: [email protected]
> Date: Friday, June 24, 2011, 12:46 PM
> Good Morning Michiel:
> 
> Please try this perl script:
> 
> http://genomewiki.ucsc.edu/index.php/File:ExtractRepeats.txt
> 
> --Hiram
> 
> Michiel de Hoon wrote:
> > Dear Pauline,
> > 
> > Many thanks for your reply. I think you are right and
> that I am inadvertently removing repeats that should not be
> removed.
> > 
> > To select the appropriate repeats from the DateRepeats
> output, UCSC uses the extractRepeats and extractLinSpecReps
> scripts. Can these scripts be made available somewhere? I
> couldn't find them in Jim Kent's software collection or
> elsewhere.
> > 
> > Thank you again again,
> > --Michiel
> 
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