cisVar
======
cisVar is a pipeline to estimate pre-ChIP frequencies from pooled post-ChIP
frequencies via a regression on the genotypes of the individuals in the pool. To
use this code you must have a mapped BAM file for each pool (a single pool is
fine) as well as genotype info for all individuals in the pool in VCF format.
Additional information can be provided also, see below for information.
For an overview of this method, or to cite this work, please see the following:
Tehranchi, Ashley K., Marsha Myrthil, Trevor Martin, Brian L. Hie, David Golan,
and Hunter B. Fraser. “`Pooled ChIP-Seq Links Variation in Transcription Factor
Binding to Complex Disease Risk <https://doi.org/10.1016/j.cell.2016.03.041>`_.”
Cell 165, no. 3 (April 21, 2016): 730–41.
This code was written by Ashley Tehranchi with minor modifications by Mike
Dacre. It was produced at Stanford University, but is released here under the
MIT license.
Current version: 2.0.0b3
.. contents:: **Contents**
Overview
--------
``cisVar.py`` is the pipeline written in python3 and uses ``regression_qtls.R``
(``regression_qtls.R`` is called inside of ``cisVar.py`` so you will not run it
directly).
In addition, the code at ``scripts/combine.py`` can be used to create combined
and merged (per-SNP) pandas dataframes from the outputs of ``cisVar.py`` for
multiple samples.
A complete example Snakemake pipeline is provided in ``pipeline``, you should be
able to run it by modifying only the ``cisvar_config.json`` file, see the
Snakemake section below.
Right now the default minor allele frequency filter is ``0.1>MAF<0.99``. To
change these and other regression constants, edit the ``regressions_qtls.R``
script.
Installation
~~~~~~~~~~~~
Install via PyPI:
.. code:: shell
pip install cisVar
Or install from github:
.. code:: shell
pip install https://github.com/TheFraserLab/cisVar/tarball/master
Alternatively, you can just clone the repo and use it directly from
there.
.. code:: shell
git clone https://github.com/TheFraserLab/cisVar.git
It should work with python 2 or 3, but python 3 is highly recommended.
Prereqs
.......
Requires ``samtools v1.9`` and ``bedtools v2.26.0`` as well as the
following python modules (installed automatically by pip):
``pandas``, ``numpy``, ``psutil``, ``snakemake``, ``wget``
Additionally requires that ``R`` with ``Rscript`` are installed, with
the ``ggplot2`` module installed.
Usage
~~~~~
To run this code on your own data you need:
- VCF(s) with genotypes and ref/alt alleles for every SNP you wish to
test
- A mapped BAM file, ideally this will make use of `Hornet
<https://github.com/TheFraserLab/Hornet>`_ to remove reference bias.
In addition, the following data can be helpful:
- A list of individuals to filter genotypes with (one newline separated file of
individuals per pool)
- A file with ref and alt alleles for your SNPs of interest, to modify those in
the genotype VCF files (BED/VCF/txt)
- A file to limit the SNPs to consider to a subset of those in the VCF
(BED/VCF/txt)
Example pipeline:
.. code:: shell
cisVar.py prep -F SampleName -i individuals.txt.gz --chrom-format chr /path/to/geno/*vcf.gz
cisVar.py mpileup -F SampleName -f fastaFile -B sortedBam
cisVar.py post -F SampleName -r readDepth -a allelesFile
cisVar.py geno -F SampleName -r readDepth -i individualsFile -g genotypesFile
cisVar.py qtls -F SampleName -r readDepth -n numberIndividuals
cisVar.py tidy -F SampleName -r readDepth
scripts/combine.py {sample}.readDepth.regression.pd
A readDepth of 20 is generally optimal, the sample name can be whatever you
want, but should be unique per sample. ``{sample}`` is a placeholder to allow
any number of samples to be combined in the last step.
Snakemake
.........
The above pipeline can be automated with
`Snakemake <https://snakemake.readthedocs.io/en/stable/>`_.
To use, install cisVar, navigate to the root of your project, and run
``cisVar.py get_snake`` to copy the Snakefile and config file over . Then edit
the ``cisvar_config.json`` file to match your needs.
You will also need to edit the ``Snakefile`` to set the ``script_prep`` string
to match what is needed by your system.
The following are the config options for that file:
+-------------+-------------------------------------------------------+
| Option | Description |
+=============+=======================================================+
| name | A general name for this run, file prefix will be |
| | ``<name>.<sample>.<read_depth>`` |
+-------------+-------------------------------------------------------+
| sample_name | The name of the sample, default is population. Used |
| | only in the combination of multiple samples. |
+-------------+-------------------------------------------------------+
| samples | A list of samples, can just be a list, or a |
| | dictionary of {sample:group}, the 'group' in this |
| | case allows the use of the same genotype files for |
| | multiple samples, can also be a path to a separate |
| | json file |
+-------------+-------------------------------------------------------+
| read_depth | An integer depth to require for each SNP to be |
| | considered |
+-------------+-------------------------------------------------------+
| max_cores | Used only when parsing VCFs, if you have multiple VCF |
| | files ( e.g. per chromosome), they will be parsed in |
| | parallel up to this many cores (or max avaialable on |
| | machine) |
+-------------+-------------------------------------------------------+
| sort_vcfs | Either 1 or 0, if 1 assumes that VCF files contain a |
| | ``chr#`` string in the file name, and sorts the order |
| | of files to be chr1->22,X,Y,MT. Don't use if your |
| | VCFs don't have ``chr#`` in the name |
+-------------+-------------------------------------------------------+
| chrom_form | 'chr', 'num', 'ignore': Force format of chromosome |
| at | name to be ``chr#`` or ``#``. This ensures that all |
| | input files have the same format. Use ignore to do |
| | nothing. |
+-------------+-------------------------------------------------------+
| bams | A path to the mapped BAM files, must contain the |
| | ``{sample}`` string (unless you only have one bam), |
| | e.g. ``/path/to/{sample}.sorted.bam``, ``{sample}`` |
| | must be in samples |
+-------------+-------------------------------------------------------+
| cisVar | Path to the cisVar repository |
+-------------+-------------------------------------------------------+
| vcfs | Can be a single path (for one vcf), a list of vcfs, |
| | or a glob string (e.g. |
| | ``/path/to/vcfs/*.vcf.comm.gz``) |
+-------------+-------------------------------------------------------+
| genome_fa | Path to a FastA file of the genome you mapped to, |
| | single file only. |
+-------------+-------------------------------------------------------+
| inds | Optional: used to filter VCFs so that the genotype |
| | files contain only the individuals in the sample, |
| | e.g. ``/path/to/inds/{sample}.ind.txt.gz``. Newline |
| | separated file of individuals. |
+-------------+-------------------------------------------------------+
| locs | Optional: a BED/VCF/text file of SNP locations to |
| | consider, used to limit the total to be a subset of |
| | the genotype file. |
+-------------+-------------------------------------------------------+
| alleles | Optional: a BED/VCF/text file of alternate ref/alt |
| | alleles. Must be a subset of the genotype VCFs. If |
| | there is an entry in this file, it's ref/alt alleles |
| | will be used instead of those in the genotype file |
+-------------+-------------------------------------------------------+
Note the last three files are optional, also if ``samples`` is a dict, then the
value will be used in place of the sample. For example, if you have two samples
for the same population that are ``yri1`` and ``yri2``, but they both use the
same genotype file ``yri.geno.vcf``, you can make samples ``{'yri1': 'yri',
'yri2': 'yri'}`` and then ``yri`` will be used to pick the ind, loc, and allele
files
Cluster
'''''''
To run on a cluster, run ``cisVar.py get_snake`` with ``-x`` and edit the
``cluster.json`` file to match your cluster environment, then run e.g.:
.. code:: shell
snakemake -j 100 --cluster-config cluster.json \
--cluster "sbatch -n {threads} -t {params.time} --mem={resources.mem_mb} -p {cluster.queue} -o {cluster.out} -e {cluster.err}" \
all
or
.. code:: shell
snakemake -j 100 --cluster-config cluster.json \
--cluster "qsub -l nodes=1:ppn={threads} -l walltime={params.time} -l mem={resources.mem_mb}MB -o {cluster.out} -e {cluster.err}" \
all
To set the maximum allowed memory per job, add the argument ``--resources
mem_mb=32000``. Note, this is for the whole pipeline, not per job, because
snakemake is stupid.
To also combine files, replace ``all`` with ``combine`` at the end of the
command.
Script help
-----------
Below are help options available on the command line for cisVar, all these steps
are run by the above snakemake pipeline.
cisVar.py
~~~~~~~~~
.. code::
usage: cisVar.py [-h] {prep,mpileup,post,geno,qtls,tidy,get_snake} ...
cisVar: Find cis QTLs based on an experimental selection method
Ashley Tehranchi <tehranchi576@gmail.com>
Stanford University
Version: 2.0.0b1
Created: 2015-12-12
Updated: 2018-05-16
Example usage:
cisVar prep -F test_new -i individuals.txt.gz --chrom-format chr
cisVar mpileup -F <SampleName> -f <fastaFile> -B <sortedBam>
cisVar post -F <SampleName> -r <readDepth>
cisVar geno -F <SampleName> -r <readDepth> -i <individualsFile>
cisVar qtls -F <SampleName> -r <readDepth> -n <numberIndividuals>
cisVar tidy -F <SampleName> -r <readDepth> -p out.dataframe.pandas -t out.dataframe.txt
Note:
The qtls regression step will use approximately 32GB of memory on an averaged-
sized dataset.
The geno step will use approximately 20GB of memory on the same dataset.
positional arguments:
{mpileup,post,geno,qtls}
prep Prepare genotype files
mpileup (m) Run mpileup
post (p) Run POST frequency calculation
geno (g) Munge genotypes to prepare for regression
qtls (q, regression, r)
Run the regression
tidy (t) Tidy up regression, call open/clsoed
optional arguments:
-h, --help show this help message and exit
prep
....
This step converts VCFs into genotype and individual files that can be used by
the pipeline.
.. code::
usage: cisVar.py prep [-h] [-F PREFIX_NAME] [-r TRIAL_DEPTHS] [-i ALL_INDS]
[-l LIMIT_FILE] [-a ALLELE_FILE]
[--chrom-format {chr,num,ignore}] [--include-indels]
[-c CORES]
vcf_files [vcf_files ...]
Prepare genotype files
optional arguments:
-h, --help show this help message and exit
Run Options:
-F PREFIX_NAME, --SampleName PREFIX_NAME
sample/population name (default: cis_var)
-r TRIAL_DEPTHS, --readDepth TRIAL_DEPTHS
minimum read depth per variant (default: 20)
Prep Options:
-i ALL_INDS, --all-inds ALL_INDS
File of individuals in all groups, one per line
-l LIMIT_FILE, --limit-file LIMIT_FILE
BED/VCF/txt file of SNPs to consider
-a ALLELE_FILE, --allele-file ALLELE_FILE
BED/VCF/txt file of alleles to override VCF allels
(subset of vcf)
--chrom-format {chr,num,ignore}
chr: make format "chr#", num: make format "#", ignore:
do nothing (default: ignore)
--include-indels Do not skip indels
-c CORES, --cores CORES
Number of cores to use (default: all)
vcf_files VCF files with genotypes
mpileup
.......
This is just a simple wrapper for samtools mpileup
.. code::
usage: cisVar.py mpileup [-h] [-F PREFIX_NAME] [-r TRIAL_DEPTHS] -f
ALLCHRFASTA -B SORTEDBAM [-p MPILEUPBEDFILE]
Run mpileup
optional arguments:
-h, --help show this help message and exit
Run Options:
-F PREFIX_NAME, --SampleName PREFIX_NAME
sample/population name (default: cis_var)
-r TRIAL_DEPTHS, --readDepth TRIAL_DEPTHS
minimum read depth per variant (default: 20)
mpileup Options:
-f ALLCHRFASTA, --fasta ALLCHRFASTA
fasta file with all chromosomes (Required)
-B SORTEDBAM, --BAMfile SORTEDBAM
sorted BAM file (Required)
-p MPILEUPBEDFILE, --mpileupBEDfile MPILEUPBEDFILE
BED to use instead of the BED generated in the prep
phase (Do not use if possible, use prep with limit
instead)
post
....
This step actually calculates the POST-frequencies for the data.
.. code::
usage: cisVar.py post [-h] [-F PREFIX_NAME] [-r TRIAL_DEPTHS] [-a GENOSFILE]
Run POST frequency calculation
optional arguments:
-h, --help show this help message and exit
Run Options:
-F PREFIX_NAME, --SampleName PREFIX_NAME
sample/population name (default: cis_var)
-r TRIAL_DEPTHS, --readDepth TRIAL_DEPTHS
minimum read depth per variant (default: 20)
POST Options (Deprecated):
-a GENOSFILE, --allelesFile GENOSFILE
The genotypes file, (Optional, default is file created
in prep)
geno
....
This step converts the genotype file made in the prep step into a matrix that
can be used in the regression. It is important that this genotype file is
perfectly sorted to match the outputs of the POST step.
.. code::
usage: cisVar.py geno [-h] [-F PREFIX_NAME] [-r TRIAL_DEPTHS] [-g GENOSFILE]
[-i INDIVIDUALSLIST]
Munge genotypes to prepare for regression
optional arguments:
-h, --help show this help message and exit
Run Options:
-F PREFIX_NAME, --SampleName PREFIX_NAME
sample/population name (default: cis_var)
-r TRIAL_DEPTHS, --readDepth TRIAL_DEPTHS
minimum read depth per variant (default: 20)
Genotype Options:
-g GENOSFILE, --genoFile GENOSFILE
The genotypes file, (Optional, default is file created
in prep)
-i INDIVIDUALSLIST, --individualsFile INDIVIDUALSLIST
list of individuals matching genotype matrix; one indv
per line
qtls
....
This is the actual regression step, it makes sure all the files are in the right
place and then calls ``regression_qtls.R`` to do the actual regression.
.. code::
usage: cisVar.py qtls [-h] [-F PREFIX_NAME] [-r TRIAL_DEPTHS] [-n NUMINDV]
Run the regression
optional arguments:
-h, --help show this help message and exit
Run Options:
-F PREFIX_NAME, --SampleName PREFIX_NAME
sample/population name (default: cis_var)
-r TRIAL_DEPTHS, --readDepth TRIAL_DEPTHS
minimum read depth per variant (default: 20)
Regression Options:
-n NUMINDV, --numberIndividuals NUMINDV
The number of individuals in the pool (if omitted,
calculated from genotype file length)
The regression produces z-scores and p-values, and additionally writes
coefficients and some simple summary plots in separate files.
tidy
....
This step calls the open/closed alleles and produces a final integrated file
with all available data as both a tad-delimited file and as a pandas dataframe.
.. code::
usage: cisVar.py tidy [-h] [-F PREFIX_NAME] [-r TRIAL_DEPTHS] [-b BEDFILE]
[-t TEXTFILE] [-p PANDASFILE]
Tidy up regression, call open/closed
optional arguments:
-h, --help show this help message and exit
Run Options:
-F PREFIX_NAME, --SampleName PREFIX_NAME
sample/population name (default: cis_var)
-r TRIAL_DEPTHS, --readDepth TRIAL_DEPTHS
minimum read depth per variant (default: 20)
inputs:
-b BEDFILE, --bedfile BEDFILE
BED file to extract rsIDs from (optional)
outputs:
-t TEXTFILE, --textfile TEXTFILE
Parsed output
-p PANDASFILE, --pandasfile PANDASFILE
Parsed dataframe
get_snake
.........
This option just downloads the Snakefile and config files from this repo, for
easy access when code is installed via pip.
.. code::
usage: cisVar.py get_snake [-h] [-x]
Download Snakefile and config to current dir
optional arguments:
-h, --help show this help message and exit
-x, --extra Get additional sample and cluster configs
combine.py
~~~~~~~~~~
This script is separate and is in the ``scripts`` folder. It takes a search string
as an input and produces both combined and merged DataFrames. The combined
dataframe is just all dataframes combined in order with sample data added as a
column and to the index. The merged dataframe is a collapsed dataframe that has
one entry per SNP with p-values combined using Fisher's method and supporting
population data. It also includes information on the level of support for the
open and closed calls.
The search string should match your prefix and depth from the main pipeline. For
example, if you used a name of 'cis_var' plus a sample name (the variable part)
of e.g. CEU and YRI, and a read depth of 20, your search string would be:
``cis_var.{sample}.20.regression.pd``.
The script will write ``cis_var.combined.20.regression.pd`` and
``cis_var.merged.20.regression.pd``.
.. code::
usage: combine.py [-h] [-c COLUMN_NAME] [--no-merge] search_str
Combine a bunch of cisVar pandas files by sample (e.g. population).
Requires a search string such as prefix.{sample}.regression.pd.
Writes
------
prefix.combined.regression.pd
A simple merger of all DataFrames
prefix.merged.regression.pd
A per-snp merger based on p-value
positional arguments:
search_str e.g. name.{sample}.regression.pd, used to find files
optional arguments:
-h, --help show this help message and exit
-c COLUMN_NAME, --column-name COLUMN_NAME
Name for combine column, e.g. population
--no-merge Produce only a combined dataframe, not a merged
dataframe. merging can add half an hour over
combination, which takes seconds
plot_fun.R
~~~~~~~~~~
There is an additional script in ``scripts`` called ``plot_fun.R`` that takes a
single argument—the output of the regression step (e.g.
``cis_var.YRI.20.totals.txt``) and creates a simple density pre-freq vs post freq
plot.