New consensus from VCF

[dbrami]

Hello,

I have a reference file in FASTA format and list of indels in VCF format (courtesy of GATK).

How can I generate a NEW consensus that incorporates the modifications from the the VCF file?
I am positive a tool like this must exist, although I've written my own naive version in Perl.

Would it be a part of GATK, VCFTools or other?

Regards,

Daniel

[iansealy]

Dear Daniel,

I haven't tried it yet, but the announcement for the latest version of SAMtools says:

Implemented "vcfutils.pl vcf2fq" to generate a consensus sequence similar to "samtools.pl pileup2fq".

See http://sourceforge.net/mailarchive/f...tools-announce and http://samtools.svn.sourceforge.net/...ls.pl?view=log

Cheers,
Ian

[dbrami]

Thank you Ian,

I will give it a look.

[iansealy]

Sorry, looks like I led you astray:

http://sourceforge.net/mailarchive/forum.php?thread_name=9338F579-CA19-4EB2-9775-3D20D8E4AD57%40sanger.ac.uk&forum_name=samtools-help

[dbrami]

It didnt work for me.
I wrote to the SAM toosl developer and got this response:

Firstly, vcf2fq only filters SNPs around indels, but does not build indels into the consensus. Secondly, it requires nearly *every* base in the reference genome to be present in the input, no matter whether there is a variant. For now, vcf2fq only works with samtools all-site BCF/VCF as other callers do not generate information at all sites.

vcf2fq is mainly useful to people who not only want to get the SNPs, but also intend to know the regions where a call can be made. This is essential for most popgen studies.

Heng

I think I might have to find a perl VCF parser (part of sam tools page) and write my own consensus script.

[wormseq]

Hi dbrami,

If you find a solution (i.e a perl script) could you please post it.

Thank you.

[dagarfield]

Does this link help you out?
It describes moving from mpileup (pileup is now outdated) into a consensus sequence by shooting the results of mpileup through two other utilities.

http://samtools.sourceforge.net/mpileup.shtml

[nupurgupta]

Yeah, except that vcfutils has an error if your VCF entry doesn't have an FQ value. Which is true in current format of VCF. And I don't feel comfortable modifying the vcfutils.pl file. So if anyone knows of another solution, would be great to know.

[James Hane]

I haven't used vcf2fq before, however samtools pileup in the past had problems with incorporating indels into the consensus. I regularly use GATK's FastaAlternateReferenceMaker for this which handles both SNPs and indels very well... GATK also allows you to vastly improve the accuracy of your variant calls by running steps like RealignerTargetCreator/IndelRealigner prior to final consensus generation.

[dagarfield]

I think this problem of indels has been at least partially addressed using mpileup. That said, I've heard good things about the route James is recommending.