LiftoverVcf (Picard)

Lifts over a VCF file from one reference build to another.

Summary

Tool for "lifting over" a VCF from one genome build to another, producing a properly headered, sorted and indexed VCF in one go.

Details

This tool adjusts the coordinates of variants within a VCF file to match a new reference. The output file will be sorted and indexed using the target reference build. To be clear, REFERENCE_SEQUENCE should be the target reference build (that is, the "new" one). The tool is based on the UCSC LiftOver tool (see http://genome.ucsc.edu/cgi-bin/hgLiftOver) and uses a UCSC chain file to guide its operation. For each variant, the tool will look for the target coordinate, reverse-complement and left-align the variant if needed, and, in the case that the reference and alternate alleles of a SNP have been swapped in the new genome build, it will adjust the SNP, and correct AF-like INFO fields and the relevant genotypes.

Example

java -jar picard.jar LiftoverVcf \ I=input.vcf \ O=lifted_over.vcf \ CHAIN=b37tohg38.chain \ REJECT=rejected_variants.vcf \ R=reference_sequence.fasta

Caveats

Rejected Records

Records may be rejected because they cannot be lifted over or because of sequence incompatibilities between the source and target reference genomes. Rejected records will be emitted to the REJECT file using the source genome build coordinates. The reason for the rejection will be stated in the FILTER field, and more detail may be placed in the INFO field.

Memory Use

LiftOverVcf sorts the output using a "SortingCollection" which relies on MAX_RECORDS_IN_RAM to specify how many (vcf) records to hold in memory before "spilling" to disk. The default value is reasonable when sorting SAM files, but not for VCFs as there is no good default due to the dependence on the number of samples and amount of information in the INFO and FORMAT fields. Consider lowering to 100,000 or even less if you have many genotypes.

Category Variant Manipulation

Overview

Summary

Tool for "lifting over" a VCF from one genome build to another, producing a properly headered, sorted and indexed VCF in one go.

Details

This tool adjusts the coordinates of variants within a VCF file to match a new reference. The output file will be sorted and indexed using the target reference build. To be clear, #REFERENCE_SEQUENCE should be the target reference build (that is, the "new" one). The tool is based on the UCSC LiftOver tool and uses a UCSC chain file to guide its operation.
For each variant, the tool will look for the target coordinate, reverse-complement and left-align the variant if needed, and, in the case that the reference and alternate alleles of a SNP have been swapped in the new genome build, it will adjust the SNP, and correct AF-like INFO fields and the relevant genotypes.

Example

 java -jar picard.jar LiftoverVcf \\
     I=input.vcf \\
     O=lifted_over.vcf \\
     CHAIN=b37tohg38.chain \\
     REJECT=rejected_variants.vcf \\
     R=reference_sequence.fasta

Caveats

Rejected Records

Records may be rejected because they cannot be lifted over or because of sequence incompatibilities between the source and target reference genomes. Rejected records will be emitted to the #REJECT file using the source genome build coordinates. The reason for the rejection will be stated in the FILTER field, and more detail may be placed in the INFO field.

Memory Use

LiftOverVcf sorts the output using a htsjdk.samtools.util.SortingCollection which relies on #MAX_RECORDS_IN_RAM to specify how many (vcf) records to hold in memory before "spilling" to disk. The default value is reasonable when sorting SAM files, but not for VCFs as there is no good default due to the dependence on the number of samples and amount of information in the INFO and FORMAT fields. Consider lowering to 100,000 or even less if you have many genotypes.

LiftoverVcf (Picard) specific arguments

This table summarizes the command-line arguments that are specific to this tool. For more details on each argument, see the list further down below the table or click on an argument name to jump directly to that entry in the list.

Argument name(s)	Default value	Summary
Required Arguments
--CHAIN -C	null	The liftover chain file. See https://genome.ucsc.edu/goldenPath/help/chain.html for a description of chain files. See http://hgdownload.soe.ucsc.edu/downloads.html#terms for where to download chain files.
--INPUT -I	null	The input VCF/BCF file to be lifted over.
--OUTPUT -O	null	The output location for the lifted over VCF/BCF.
--REFERENCE_SEQUENCE -R	null	The reference sequence (fasta) for the TARGET genome build (i.e., the new one. The fasta file must have an accompanying sequence dictionary (.dict file).
--REJECT	null	File to which to write rejected records.
Optional Tool Arguments
--ALLOW_MISSING_FIELDS_IN_HEADER	false	Allow INFO and FORMAT in the records that are not found in the header
--arguments_file	[]	read one or more arguments files and add them to the command line
--help -h	false	display the help message
--LIFTOVER_MIN_MATCH	1.0	The minimum percent match required for a variant to be lifted.
--LOG_FAILED_INTERVALS -LFI	true	If true, intervals failing due to match below LIFTOVER_MIN_MATCH will be logged as a warning to the console.
--RECOVER_SWAPPED_REF_ALT	false	If the REF allele of the lifted site does not match the target genome, that variant is normally rejected. For bi-allelic SNPs, if this is set to true and the ALT allele equals the new REF allele, the REF and ALT alleles will be swapped. This can rescue some variants; however, do this carefully as some annotations may become invalid, such as any that are alelle-specifc. See also TAGS_TO_REVERSE and TAGS_TO_DROP.
--TAGS_TO_DROP	[MAX_AF]	INFO field annotations that should be deleted when swapping reference with variant alleles.
--TAGS_TO_REVERSE	[AF]	INFO field annotations that behave like an Allele Frequency and should be transformed with x->1-x when swapping reference with variant alleles.
--version	false	display the version number for this tool
--WARN_ON_MISSING_CONTIG -WMC	false	Warn on missing contig.
--WRITE_ORIGINAL_ALLELES	false	Write the original alleles for lifted variants to the INFO field. If the alleles are identical, this attribute will be omitted.
--WRITE_ORIGINAL_POSITION	false	Write the original contig/position for lifted variants to the INFO field.
Optional Common Arguments
--COMPRESSION_LEVEL	5	Compression level for all compressed files created (e.g. BAM and VCF).
--CREATE_INDEX	false	Whether to create a BAM index when writing a coordinate-sorted BAM file.
--CREATE_MD5_FILE	false	Whether to create an MD5 digest for any BAM or FASTQ files created.
--GA4GH_CLIENT_SECRETS	client_secrets.json	Google Genomics API client_secrets.json file path.
--MAX_RECORDS_IN_RAM	500000	When writing files that need to be sorted, this will specify the number of records stored in RAM before spilling to disk. Increasing this number reduces the number of file handles needed to sort the file, and increases the amount of RAM needed.
--QUIET	false	Whether to suppress job-summary info on System.err.
--TMP_DIR	[]	One or more directories with space available to be used by this program for temporary storage of working files
--USE_JDK_DEFLATER -use_jdk_deflater	false	Use the JDK Deflater instead of the Intel Deflater for writing compressed output
--USE_JDK_INFLATER -use_jdk_inflater	false	Use the JDK Inflater instead of the Intel Inflater for reading compressed input
--VALIDATION_STRINGENCY	STRICT	Validation stringency for all SAM files read by this program. Setting stringency to SILENT can improve performance when processing a BAM file in which variable-length data (read, qualities, tags) do not otherwise need to be decoded.
--VERBOSITY	INFO	Control verbosity of logging.
Advanced Arguments
--showHidden	false	display hidden arguments

Validation stringency for all SAM files read by this program. Setting stringency to SILENT can improve performance when processing a BAM file in which variable-length data (read, qualities, tags) do not otherwise need to be decoded.

The --VALIDATION_STRINGENCY argument is an enumerated type (ValidationStringency), which can have one of the following values: