filtering pileup file with samtools for SomaticSniper
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Entering edit mode
5.5 years ago
TriS ★ 4.3k

hi all

I'm working with matched tumor-normal samples and I want to call somatic variants using Somatic Sniper

So far I got the main function working with

bam-somaticsniper -Q 40 -G -L -f genome/hg19.fa Results/kayrotypicT.bam Results/kayrotypicN.bam SomSniperResults.txt

and now I need to filter the results.

I'm following what the SomaticSniper guide says and running the pipeline following this guide on Synapse.

first question is:

the SomaticSniper guide says explicitly NOT to use mpileup

You will also need to generate a samtools pileup (not mpileup) indel file.

so, an old post explains the difference..while I think samtools replaced pileup with mpileup, so, since mpileup should output pileup still, is mpileup fine then?

since the example uses a -vcf output I'm creating the pileup and doing the filtering in the following way

# create pileup file 
samtools mpileup -A -B -vuf genomes/hg19.fa Results/kayrotypic.bam > SomSniperResults/var.raw.pileup 

a snapshot of my output looks like this:

##FORMAT=<ID=PL,Number=G,Type=Integer,Description="List of Phred-scaled genotype likelihoods">
#CHROM  POS     ID      REF     ALT     QUAL    FILTER  INFO    FORMAT  RS-01926692_JC590_RS-01925823
chr1    10008   .       A       <X>     0       .       DP=1;I16=0,1,0,0,33,1089,0,0,0,0,0,0,0,0,0,0;QS=1,0;MQ0F=1      PL      0,3,4
chr1    10009   .       A       <X>     0       .       DP=1;I16=0,1,0,0,30,900,0,0,0,0,0,0,1,1,0,0;QS=1,0;MQ0F=1       PL      0,3,4
chr1    10010   .       C       <X>     0       .       DP=1;I16=0,1,0,0,33,1089,0,0,0,0,0,0,2,4,0,0;QS=1,0;MQ0F=1      PL      0,3,4

however, when i call

samtools.pl varFilter test.pileup | awk '$6>=20'

I get the following error:

Argument "DP=1;I16=0,1,0,0,33,1089,0,0,0,0,0,0,0,0,0,0;QS=1,0;MQ0F=1" isn't numeric in numeric lt (<) at samtools.pl line 117, <> line .

which comes from the fact that the 7th column should be numeric while what I have is the info from the vcf file...

I also tried not to output a vcf file and tried to use bcftools as:

samtools mpileup -A -B -guf /genomes/hg19.fa chr20_bam.bam > test.pileup
bcftools/bcftools view -Hgc test.pileup

[bcf_sync] incorrect number of fields (0 != 5) at 0:0

I looked at the post here but it didn't solve my problem since i'm not piping and I am testing only one small chr (chr20) from the bam file

 

so I'm not totally sure how to get it to work.

thanks!

-- txt was edited with some updated info --

SomaticSniper SNP samtools pileup • 3.1k views
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Entering edit mode
5.5 years ago
TriS ★ 4.3k

alright, not sure ppl will have the same problem but here's what I think can be the solution:

1) I had IT install the newer samtools 1.2 + bcftools 1.2 on the server

2) using the following command line:

samtools mpileup -A -B -uf genomes/hg19.fa Results_Norm/norm.bam | bcftools call -c | vcfutils.pl varFilter -Q 20 | awk 'NR > 55 {print}'> indel_pileup_Norm.pileup
samtools mpileup -A -B -uf genomes/hg19.fa Results_Tum/Tum.bam | bcftools call -c | vcfutils.pl varFilter -Q 20 | awk 'NR > 55 {print}' > indel_pileup_Tum.pileup

I was able to get (hopefully) the correct files for normal and tumor samples to then use in SomaticSniper

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Entering edit mode

It works well. Thanks.

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Entering edit mode
4.4 years ago
guangxujin • 0

It works well. Thanks.

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