Extract Sub-Set Of Regions From Vcf File
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8.9 years ago
Rubal7 ▴ 790

Hello all,

Sorry if this has been answered before (though I have not found an appropriate answer already) What is an effective way to extract mutliple chromosomal regions from a vcf.gz file? I see that it can be done for single regions using tabix, but I have a file with several regions in a text file in the format:

chromosome:startposition-endposition eg: 19:47366525-47380539

Perhaps there is a way to refer to a file of regions using tabix, or vcf-tools? If anyone could provide an example command line that would be really helpful.

Thanks in advance!

vcf tabix genome filter • 51k views
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$ echo -e "chrN\t123\t456" | bedops -e 1 <(vcf2bed variants.bed) - > answer.bed
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8.9 years ago

I find tabix to be much easier / much sorter command line arguments.

You don't need a fasta for this method. Tabix is screaming fast.

bgzip your.vcf
tabix -p vcf your.vcf
tabix your.vcf.gz chr1:10,000,000-20,000,000
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Thanks, I agree it works fast. Shame it doesn't take a file with a whole list of regions. But I can put it into a loop.

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Two ways: 1) if there are many regions: tabix -fB my.vcf.gz reg.bed 2) if you only have a handful of regions: awk '{print $1":"($2+1)"-"$3}' reg.bed | xargs tabix my.vcf.gz.

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For anyone arriving years later, the command appears to have changed. The command you probably want is: tabix -R reg.bed my.vcf.gz.

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None of these work anymore.

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tabix -R region.txt my.vcf.gz

worked for me

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7.5 years ago
gourneau ▴ 180

For others if you like to use BED files, one way to do this would be like so:

vcftools --vcf input.vcf --bed bed_file_describing_the_range.bed --out output_prefix --recode --keep-INFO-all

Where bed_file_describing_the_range.bed has the positions of interest.

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I am trying to extract specific regions from a VCF file that has SNP information for 16 individuals. My bed file has three columns (scaffold name, start of region, end of region).

When I run vcftools on these files, it runs through the entire vcf file and determines that there are no regions from the bed file contained in the vcf file. A recode vcf file is output, but it only contains the header information from the vcf file.

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Check to ensure your scaffold names match in the BED and VCF files. For example, if your BED file has "chr1" but your VCF file just has "1" for chromosome 1 it will return an empty file.

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i met the same problem with u , so I am wondering how did you solved this problem?

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Answering to help others you are going to need to use sed on the bed file ie sed 's/chr//g' {in_path} > {out_path}

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8.9 years ago
Johan ▴ 870

You could use the GATK SelectVariants Walker, specifying the -L option to set the intervals your are interested in.

Here is an example of how to do that, taken from the link above:

#Select a sample and restrict the output vcf to a set of intervals:     
java -Xmx2g -jar GenomeAnalysisTK.jar \
       -R ref.fasta \
       -T SelectVariants \
       --variant input.vcf \
       -o output.vcf \
       -L /path/to/my.interval_list \
       -sn SAMPLE_1_ACTG

Note that you have to have a fasta reference file with the same names and coordinates as you use in our region file and vcf, and that you can remove the -sn option if you want to extract the variations for all samples.

Hope this helps.

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thanks, I can potentially use this, but having some issues with the reference fasta, so a method that does not require a fasta reference would be preferred.

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I'm not sure if it requires uncompressing the vcf files. I'm not that familiar with vcftools, so I couldn't say if there is an easier way to do it using that suite.

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7.5 years ago

I did something like what you describe, but to create multiple VCF files. Uses bedtools:

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3.6 years ago
geocarvalho ▴ 170

bedtools intersect worked better to me

intersectBed -a input.vcf -b /path/to/my.interval.bed -header > output.vcf
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For some reason by intersected out VCF have more line compare to input vcf. :( :( No idea what could be the possible reason for this !! Any guess ?

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