facetsSuite

See the release notes for information on the new facet-suite version. Backwards compatibility is currently limited, as documented here.

facetsSuite is an R package with functions to run FACETS—an allele-specific copy-number caller for paired tumor-normal DNA-sequencing data from genome-wide and targeted assays. facetSuite both wraps the code to execute the FACETS algorithm itself as well as performs post-hoc analyses on the resulting data. This package was developed by members of the Taylor lab and the Computational Sciences group within the Center for Molecular Oncology at Memorial Sloan Kettering Cancer Center.

Installation

You can install facetsSuite in R from this repository with:

devtools::install_github("mskcc/facets-suite")

Also follow the instructions for installing FACETS.

Note: For the wrapper script snp-pileup-wrapper.R you need to specify the variable snp_pileup_path in the script to point to the installation path of snp-pileup or set the environment variable SNP_PILEUP. Alternatively, the docker image contains the executable.

Usage

R functions

The R functions in this package are documented and their description and usage is available in R by doing:

?facetsSuite::function_name

Central to most functionality in the package is the output from the run_facets, which runs the FACETS algorithm based on provided tumor-normal SNP pileup (i.e. genotyping). The output is a list object with the following named objects:

• snps: SNPs used for copy-number segmentation, where het==1 indicates heterozygous loci.
• segs: Inferred copy-number segmentation. – purity: Inferred sample purity, i.e. fraction of tumor cells of the total cellular population.
• ploidy: Inferred sample ploidy.
• diplogr: Inferred dipLogR, the sample-specific baseline corresponding to the diploid state.
• alballogr: Alternative dipLogR value(s) at which a balanced solution was found.
• flags: Warning flags from the naïve segmentation algorithm.
• em_flags: Warning flags from the expectation-maximization segmentation algorithm.
• loglik: Log-likelihood value of the fitted model.

Note that FACETS performs segmentation with two algorithms, the "naïve" base method and an expectation-maximization algorithm. The latter (columns suffixed .em) is used as a default for most of the functions in this package.

Wrapper scripts

Most use of this package can be done from the command line using three wrapper scripts:

• snp-pileup-wrapper.R:
  This wraps the snp-pileup C++ script that genotypes sites across the genome in both normal and tumor samples. The output from this is the input to FACETS. Most default input arguments are appropriate regardless of usage, but --max-depth may need adjustment depending on the overall depth of the samples used.
  Example command:

  snp-pileup-wrapper.R \
      --snp-pileup-path <path to snp-pileup executable> \
      --vcf-file <path to SNP VCF> \
      --normal-bam normal.bam \
      --tumor-bam tumor.bam \
      --output-prefix <prefix for output file, preferrably tumorSample__normalSample>

  The input VCF file should contain polymorphic SNPs, so that FACETS can infer changes in allelic configuration at genomic loci from changes in allele ratios. dbSNP is a good source for this. By default, snp-pileup also estimates the read depth in the input BAM files every 50th base.

• run-facets-wrapper.R:
  This wrapper takes above SNP "pileup" as input and executes the FACETS algorithm. The ouputs are in the form of Rdata objects, TXT files, and PNGs of the samples overall copy-number profile. The wrapper allows for running FACETS in a two-pass mode, where first a "purity" run estimates the overall segmentation profile, sample purity and ploidy, and subsequently the dipLogR value from this run seeds a "high-sensitivity" run which may detect more focal events. To run in the two-pass mode, specify the input arguments prefixed by purity. The cval (--purity-cval and --cval) parameters tune the segmentation coarseness.
  Example command:

  run-facets-wrapper.R \
      --counts-file tumor_normal.snp_pileup.gz \
      --sample-id tumorID__normalID \
      --purity-cval 1000 --cval 500 \
      --everything

  The above command runs FACETS in the two-pass mode, first at cval 1000, then at cval 500 based on the sample-specific baseline found at the higher cval. The full suite of analysis and QC is run with the --everything flag. If no output directory is specified, a directory named sample-id is created.

• annotate-maf-wrapper.R:
  This script estimates the cancer-cell fractions (CCFs) of somatic mutations using purity and ploidy estimates from FACETS. It requires a input MAF file and a mapping of sample names in the MAF file (column Tumor_Sample_Barcode) to FACETS output RDS files (i.e. file paths). Alternatively, it can be run in a single-sample mode by pointing direct to the RDS and providing a MAF file with only mutation calls for the given sample.
  Example command:

  annotate-maf-wrapper.R \
      --maf-file somatic_mutations.maf
      --facets-output <path to facets_output.rds>

  Or run with a mapping file as input (--sample-mapping), in the following format:

  > cat sample_map.txt
  sample      file
  SampleA     SampleA_facets.rds
  SampleB     SampleB_facets.rds
  ...         ...

All three wrappers use argparse for argument handling and can thus be run with --help to see the all input arguments.

Run wrappers from container

In order to run the containerized versions of the wrapper scripts, first pull the docker image:

## Docker
docker pull philipjonsson/facets-suite:dev

## Singularity
singularity pull --name facets-suite-dev.img docker://philipjonsson/facets-suite:dev

Then run either of the scripts as such:

## Docker
docker run -it -v $PWD:/work philipjonsson/facets-suite:dev run-facets-wrapper.R \
    --counts-file work/SampleA.snp_pileup.gz \
    --sample-id SampleA \
    --directory work

## Singularity
singularity run facets-suite-dev.img run-facets-wrapper.R \
    --counts-file SampleA.snp_pileup.gz \
    --sample-id SampleA

For Docker, note the binding (-v) of the current directory on the host to the directory named work inside the container. This is required for the input file, in the current directory, to be accessible inside the container. This, in its turn requires the output to be written to work inside the container so that it is available on the host once the script has executed. Singularity always mounts the directory from which it is being executed.

The image contains the snp-pileup executable used by snp-pileup-wrapper.R, so it can be run without specifying its path. Example for Singularity:

singularity run -B <path to BAMs> -B <path to VCF> facets-suite-dev.img snp-pileup-wrapper.R \
    --vcf-file <path to VCF>/dbsnp.vcf \
    --normal-bam <path to BAMs>/NormalA.bam \
    --tumor-bam <path to BAMs>/TumorA.bam \
    --output-prefix TumorA__NormalA

Note: The binding of full paths to any files outside of the run directory is necessary.