VCF Trimmer for UK Biobank RAP

Developed by Andrew Wood. University of Exeter

This applet performs parallel processing of VCFs through bcftools. This applet has been designed to reduce file sizes down when required for merging of data by:

• Splitting multiallelic sites (note left-alignment and normalisation not presently set)
• Removing fields within INFO and/or FORMAT
• Applies inclusion quality control thresholding based on field in INFO

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Obtaining and installing the applet

Clone this github repo to a local directory:

git clone https://github.com/drarwood/vcf_trimmer

Navigate to a relevant directory within the project directory on the DNAnexus platform

dx cd /path/to/install/apps

Now you are ready to build and upload the applet to the DNAnexus platform directory

dx build -f vcf_trimmer

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Inputs

This applet takes one file in as input that simply lists the VCFs to process, one per line. VCFs will be processed in the order as the appear in the file. For example:

/Bulk/Whole genome sequences/Population level WGS variants, pVCF format - interim 200k release/ukb24304_c1_b0_v1.vcf.gz
/Bulk/Whole genome sequences/Population level WGS variants, pVCF format - interim 200k release/ukb24304_c1_b1_v1.vcf.gz
/Bulk/Whole genome sequences/Population level WGS variants, pVCF format - interim 200k release/ukb24304_c1_b2_v1.vcf.gz
/Bulk/Whole genome sequences/Population level WGS variants, pVCF format - interim 200k release/ukb24304_c1_b3_v1.vcf.gz
/Bulk/Whole genome sequences/Population level WGS variants, pVCF format - interim 200k release/ukb24304_c1_b4_v1.vcf.gz
/Bulk/Whole genome sequences/Population level WGS variants, pVCF format - interim 200k release/ukb24304_c1_b5_v1.vcf.gz
/Bulk/Whole genome sequences/Population level WGS variants, pVCF format - interim 200k release/ukb24304_c1_b6_v1.vcf.gz
/Bulk/Whole genome sequences/Population level WGS variants, pVCF format - interim 200k release/ukb24304_c1_b7_v1.vcf.gz
/Bulk/Whole genome sequences/Population level WGS variants, pVCF format - interim 200k release/ukb24304_c1_b8_v1.vcf.gz
/Bulk/Whole genome sequences/Population level WGS variants, pVCF format - interim 200k release/ukb24304_c1_b9_v1.vcf.gz

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Command line usage

Strings that define inclusion criteria and fields to exclude should be consistent with input expected by bcftools and placed within quotes. See the bcftools manual for more information.

Example 1:

Removing all fields within FORMAT except for GT and applying inclusion critera of an AAscore > 0.5:

dx run vcf_trimmer \
  -ivcf_file_list=/path/to/vcf_file_list.txt \
  -ifile_label=trimmed1 \
  -ioutput_dir=/path/to/output/dir \
  -iqc_thresholds="INFO/AAScore>0.5" \
  -ifields_to_remove="FORMAT/FT,FORMAT/AD,FORMAT/MD,FORMAT/DP,FORMAT/RA,FORMAT/PP,FORMAT/GQ,FORMAT/PL" \
  -y

Example 2:

Removing all fields within FORMAT except for GT and INFO except for AAscore which must remain as as inclusion critera of an AAscore > 0.5:

dx run vcf_trimmer \
  -ivcf_file_list=/path/to/vcf_file_list.txt \
  -ifile_label=trimmed2 \
  -ioutput_dir=/path/to/output/dir \
  -iqc_thresholds="INFO/AAScore>0.5" \
  -ifields_to_remove="FORMAT/FT,FORMAT/AD,FORMAT/MD,FORMAT/DP,FORMAT/RA,FORMAT/PP,FORMAT/GQ,FORMAT/PL,INFO/ABHet,INFO/ABHom,INFO/ABHetMulti,INFO/ABHomMulti,INFO/AC,INFO/AF,INFO/AN,INFO/CR,INFO/CRal,INFO/CRalt,INFO/END,INFO/FEATURE,INFO/GT_ANTI_HAPLOTYPE,INFO/GT_HAPLOTYPE,INFO/GT_ID,INFO/HOMSEQ,INFO/INV3,INFO/INV5,INFO/LEFT_SVINSSEQ,INFO/LOGF,INFO/MaxAAS,INFO/MaxAASR,INFO/MaxAltPP,INFO/MMal,INFO/MMalt,INFO/MQ,INFO/MQalt,INFO/MQSal,INFO/MQsquared,INFO/NCLUSTERS,INFO/NGT,INFO/NHet,INFO/NHomRef,INFO/NHomAlt,INFO/NUM_MERGED_SVS,INFO/OLD_VARIANT_ID,INFO/ORSTART,INFO/OREND,INFO/QD,INFO/QDalt,INFO/PASS_AC,INFO/PASS_AN,INFO/PASS_ratio,INFO/RefLen,INFO/RELATED_SV_ID,INFO/RIGHT_SVINSSEQ,INFO/SB,INFO/SBAlt,INFO/SBF,INFO/SBF1,INFO/SBF2,INFO/SBR,INFO/SBR1,INFO/SBR2,INFO/SDal,INFO/SDalt,INFO/SEQ,INFO/SeqDepth,INFO/SV_ID,INFO/SVINSSEQ,INFO/SVLEN,INFO/SVMODEL,INFO/SVSIZE,INFO/SVTYPE,INFO/VarType" \
  -y

Example 3:

Removing all fields within FORMAT except for GT without applying inclusion critiera:

dx run vcf_trimmer \
  -ivcf_file_list=/path/to/vcf_file_list.txt \
  -ifile_label=trimmed3 \
  -ioutput_dir=/path/to/output/dir \
  -iqc_thresholds="NA" \
  -ifields_to_remove="FORMAT/FT,FORMAT/AD,FORMAT/MD,FORMAT/DP,FORMAT/RA,FORMAT/PP,FORMAT/GQ,FORMAT/PL" \
  -y

Example 4:

Applying inclusion critiera of AAscore > 0.5 but do not remove any fields from VCF:

dx run vcf_trimmer \
  -ivcf_file_list=/path/to/vcf_file_list.txt \
  -ifile_label=trimmed4 \
  -ioutput_dir=/path/to/output/dir \
  -iqc_thresholds="INFO/AAScore>0.5" \
  -ifields_to_remove="NA" \
  -y

Additional parameters

To assist in the throughput of this applet, multiple VCFs will be processed at the same time on a given workstation. The default instance type is mem1_ssd1_v2_x36. Benchmarking has been based on this server type for the 200K WGS data on chromosome 17 and the maximum number of concurrent VCFs processed at a time to 20 to avoid resource issues. For other datasets, you may need to lower this limit if jobs fail due to errors raised because of server response timeouts (e.g. 12).

-iconcurrent_processes (default: 20) : maximum number of VCFs to process at a given time.
-ithreads (default: 4) : number of threads bcftools should use when writing compressed output