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# how to select a private SNP with GATK from a multisample VCF file

Member

I ran in to the situation now a couple of times that I need to extract a set of private SNPs from a multisample VCF file. For example in a forward genetics knockout screen of a large set of samples.

It is possible with vcf-contrast from vcf-tools:

 vcf-contrast +sample1 -sample2 -sample3 -n input.vcf > private sample1.vcf

 vcf-contrast -sample1 +sample2 -sample3 -n input.vcf > private sample2.vcf

vcf-contrast -sample1 -sample2 +sample3 -n input.vcf > private sample3.vcf

After this I still would have to filter out the private 0/0 calls and doing this for a large multisample VCF means entering this command for all the combinations which is not really nice.

Surely this must be possible with GATK. Does anyone know how to do this with GATK.

Maybe it is somewhere in the SelectVariants? The --discordance option looked promissing but there is something about that the samples should be the same? Or is it possible to write another variant walker or a JEXL expression?

P.S. By accident I also posted this question in the XHMM, an admin could remove it there.

Tagged:

See the --excludeNonVariants option in SelectVariants (to be used in conjunction with -sn sample1).

• Member
edited January 2013

That would give the variants for each sample. But then I still need to get the private variants per sample. In other words the variants that are only found in 1 sample. All the other samples should be 0/0 for that variant. It would be nice if this could be done in a single command, since there are 70 samples in my multisample VCF

• Member

Yes that should to it I think. How do I add the JEXL expression to SelectVariants? When I try

java -jar GenomeAnalysisTK-2.3-9-ge5ebf34/GenomeAnalysisTK.jar -T SelectVariants -R /referencel/reference_GATK_sorted.fa -V my70Samples.vcf -o selectVariantsPrivate.vcf -select "AC==1" 

I get

Invalid JEXL expression detected for select-0 with message ![0,7]: 'AC == 1;' == error`

This question has been covered in other threads on this forum already.

• Member

Ok so I had to restrict to BIALLELIC SNPs. If anybody else wants to find all the information in one place:

java -jar GenomeAnalysisTK-2.3-9-ge5ebf34/GenomeAnalysisTK.jar -T SelectVariants -R reference.fa -V input.vcf -o biAllelicPrivate.vcf --restrictAllelesTo BIALLELIC -select "AC==1"

• Member

Hi, may I ask you a question? I have used GATK to call snp in a pair of cancer and normal samples, and obtained the final filtered snp.vcf file. Do you know how to use SelectVariants tool to filter out cancer-specific snps? Do you know the command line to do so? Any suggestion will be appreciated.