🔬 A multi-method comparative bioinformatics pipeline to detect and study circRNAs from RNA-seq data
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Title Subtitle Project Author Affiliation Web Date output
a multi-method comparative bioinformatics pipeline to detect and study circRNAs from RNA-seq data
Enrico Gaffo
Compgen - University of Padova
December 21, 2016
keep_md number_sections toc


CirComPara is a computational pipeline to detect, quantify, and correlate expression of linear and circular RNAs from RNA-seq data.

Quick install

Execute the following commands to download and install (locally) in your system the scripts and tools required to run CirComPara. If something goes wrong with the installation process try to manually install the software as described below.

Download and extract the latest release of CirComPara, or clone the GIT repository, enter CirComPara directory and run the automatic installer script:

git clone http://github.com/egaffo/CirComPara
cd CirComPara

Test your installation

NB: in the sed string change the /full/circompara/dir/path path with your installation directory

cd test_circompara/analysis

If you plan to use single-end reads, test with:

cd test_circompara/analysis_se

If you receive some error messages try to follow instructions in Installation troubleshooting section.

Add CirComPara to your environment

Once completed the installation, if you do not want to type the whole path to the CirComPara executable each time, you can update your PATH environment variable. From the terminal type the following command (replace the /path/to/circompara/install/dir string with CirComPara's actual path)

export PATH=/path/to/circompara/install/dir:$PATH

Another way is to link CirComPara's main script in your local bin directory

cd /home/user/bin
ln -s /path/to/circompara/install/dir/circompara

CirComPara Docker image

A Docker image of CirComPara is available from DockerHub.

To pull the image:

docker pull egaffo/circompara-docker

You'll find the instructions on how to use the docker image at https://hub.docker.com/r/egaffo/circompara-docker.

How to use

Set your analysis project

This section shows how to set your project directory and run the analysis. To run an analysis usually you want to specify your data (the sequenced reads in FASTQ format) and a reference genome in FASTA format.

Compose META file

You have to specify read files, sample names and sample experimental condition in a metadata table file. The file format is a comma separated text file with the following header:


Then, each row corresponds to a read file. If you have paired-end sequenced samples write one line per file with the same sample name and condition.

An example of the metadata table:

file sample condition
/home/user/reads_S1_1.fq S1 WT
/home/user/reads_S1_2.fq S1 WT
/home/user/reads_S2_1.fq S2 MU
/home/user/reads_S2_1.fq S2 MU

and metadata file content:


In the meta file you can also specify the adapter sequences to preprocess the reads, just add an adapter column with the adpter file.

file sample condition adapter
/home/user/reads_S1_1.fq S1 WT /home/user/circompara/adapter.fa
/home/user/reads_S1_2.fq S1 WT /home/user/circompara/adapter.fa

Specify the reference genome file

A required parameter is the reference genome. You can either pass the reference genome from the command line

./circompara "GENOME_FASTA='/home/user/genomes/Homo_sapiens.GRCh38.dna.primary_assembly.fa'"

or by setting the GENOME_FASTA parameter in the vars.py file; e.g.:

GENOME_FASTA = '/home/user/genomes/Homo_sapiens.GRCh38.dna.primary_assembly.fa'

Specify options in vars.py

Although parameters can be set from command line (sorrounded by quotes), you can set them in the vars.py file, which must be placed into the directory where CirComPara is called.
Below there is the full list of the parameters:

META: The metadata table file where you specify the project samples, etc.
    default: meta.csv

ANNOTATION: Gene annotation file (like Ensembl GTF/GFF)

GENOME_FASTA: The FASTA file with the reference genome

CIRCRNA_METHODS: Comma separated list of circRNA detection methods to use. Repeated values will be collapsed into unique values. Currently supported: ciri, find_circ, circexplorer2_star, circexplorer2_bwa, circexplorer2_tophat, circexplorer2_segemehl, testrealign (unfiltered segemehl; use of circexplorer2_segemehl is recommended for a better filtering of segemehl predictions). Set an empty string to use all methods available (including deprecated methods). 
    default: ciri,find_circ,circexplorer2_star,circexplorer2_bwa,circexplorer2_segemehl

CPUS: Set number of CPUs
    default: 4

GENEPRED: The genome annotation in GenePred format

GENOME_INDEX: The index of the reference genome for HISAT2

SEGEMEHL_INDEX: The .idx index for segemehl

BWA_INDEX: The index of the reference genome for BWA

BOWTIE2_INDEX: The index of the reference genome for BOWTIE2

STAR_INDEX: The directory path where to find Star genome index

BOWTIE_INDEX: The index of the reference genome for BOWTIE when using CIRCexplorer2_tophat

HISAT2_EXTRA_PARAMS: Extra parameters to add to the HISAT2 aligner fixed parameters '--dta --dta-cufflinks --rg-id <SAMPLE> --no-discordant --no-mixed --no-overlap'. For instance, '--rna-strandness FR' if stranded reads are used.

BWA_PARAMS: Extra parameters for BWA


TOPHAT_PARAMS: Extra parameters to pass to TopHat

STAR_PARAMS: Extra parameters to pass to STAR

CUFFLINKS_PARAMS: Cufflinks extra parameters. F.i. '--library-type fr-firststrand' if dUTPs stranded library were used for the sequencing

CUFFQUANT_EXTRA_PARAMS: Cuffquant parameter options to specify. E.g. --frag-bias-correct $GENOME_FASTA  --multi-read-correct --max-bundle-frags 9999999

CUFFDIFF_EXTRA_PARAMS: Cuffdiff parameter options to specify. E.g. --frag-bias-correct $GENOME_FASTA  --multi-read-correct

CUFFNORM_EXTRA_PARAMS: Extra parameters to use if using Cuffnorm
    default: --output-format cuffdiff  

STRINGTIE_PARAMS: Stringtie extra parameters. F.i. '--rf' assumes a stranded library fr-firststrand, to be used if dUTPs stranded library were sequenced  

CIRI_EXTRA_PARAMS: CIRI additional parameters

PREPROCESSOR: The preprocessing method
    default: trimmomatic

PREPROCESSOR_PARAMS: Read preprocessor extra parameters. F.i. if Trimmomatic, an empty string defaults to MAXINFO:40:0.5 LEADING:20 TRAILING:20 SLIDINGWINDOW:4:30 MINLEN:50 AVGQUAL:30 

LINEAR_EXPRESSION_METHODS: The method to be used for the linear expression estimates/transcriptome reconstruction. To run more methods use a comma separated list. However, only the first method in the list will be used in downstream processing. Currently supported methods: stringtie,cufflinks,htseq.  
    default: stringtie  

TOGGLE_TRANSCRIPTOME_RECONSTRUCTION: Set True to enable transcriptome reconstruction. Default only quantifies genes and transcripts from the given annotation GTF file
    default: False

DIFF_EXP: Set the method to and enable differential expression computation for linear genes/transcripts. Current methods supported: cufflinks, ballgown, DESeq2. Only available if more than one sample and more than one condition are given. N.B: differential expression tests for circRNAs is not yet implemented

READSTAT_METHODS: Comma separated list of methods to use for read statistics. Currently supported: fastqc,fastx
    default: fastqc

MIN_METHODS: Number of methods that commmonly detect a circRNA to define the circRNA as reliable. If this value exceeds the number of methods specified, it will be set to the number of methods.
    default: 2

MIN_READS: Number of reads to consider a circRNA as expressed
    default: 2

BYPASS_LINEAR: Skip analysis of linear transcripts. This will also skip the analysis of linear-to-circular expression correlation
    default: False

CIRC_PE_MAPPING: By default, linearly unmapped reads are collapsed into single-end reads to search for circRNA backsplices. Set this option to "True" to force circRNA method aligners to maintain paired-end read alignment
   default: False  

Run the analysis

To trigger the analyses you simply have to call the ./circompara script in the analysis directory. Remember that if you used the vars.py option file, this has to be in the analysis directory.

cd /home/user/circrna_analysis

Additional options from the Scons engine:

  • Basic execution: run the analysis as a linear pipeline, i.e. no parallel task execution, and stop on errors
  • Show parameters: to show the parameters set before actually run the analysis, use -h:
/path/to/circompara/dir/circompara -h
  • Dryrun: to see which commands will be executed without actually execute them, use the -n option. NB: many commands will be listed, so you should redirect to a file or pipe to a reader like less
/path/to/circompara/dir/circompara -n | less -SR
  • Multitasks: the -j option specifies how many tasks can be run in parallel. N.B: "j x CPUS <= available cores", i.e: the j option value times the CPUS parameter value should not be greater than the number of CPU cores available, unless you want to overload your machine.
/path/to/circompara/dir/circompara_CirComPara -j4
  • Ignore errors: keep executing the tasks even when some of them fails. Caveat: this can break downstream analyses
/path/to/circompara/dir/circompara -i
  • Combine options: to set multiple options you must sorround them with quotes
/path/to/circompara/dir/circompara_CirComPara "-j4 -i"

Output files

  • Statistics on the read quality, read filtering steps and alignments can be found into read_statistics directory. A report is saved in read_statistics.html file.
  • Results regarding circRNAs (expression matrices, etc.) will be saved into the circular_expression/circrna_analyze directory, as well as a summary report in circRNAs_analysis.html file.
  • Gene expression values for each gene and sample will be saved in the linear_expression/linear_quantexp/geneexp/ directory: gene_expression_FPKM_table.csv file reports FPKMs and gene_expression_analysis.html file reports summary analysis.
  • Linear transcript sequences are saved as a multi-FASTA file into the linear_expression/transcript_sequences directory.

Advanced features

Make genome indexes for multiple instances of CirComPara: the make_indexes utility

Building the genome indexes for each mapper can take lot of computing time. However, the same indexes can be used in different CirComPara runs, saving time and disk space. In CirComPara's package the ./make_indexes script can be used to automatically build the genome index (and gene annotation formats) for each of the supported read aligner, and save them into a directory. In addition, it gives the parameter values to be set to use the index files to be shared.
Example commands using the test data follows:

cd test_circompara
mkdir genome_indexes
cd genome_indexes
../../make_indexes "-j2 GENOME=../annotation/CFLAR_HIPK3.fa ANNOTATION=../annotation/CFLAR_HIPK3.gtf" 

The above commands will eventually generate a annotation_vars.py file that can be appended to the vars.py file of your project so that CirComPara will skip the building of genome indexes. Note that make_indexes can use the same options provided by Scons showed above: -j 2 option will allow the script to build two indexes in parallel.

cd test_circompara
## clear CirComPara files in the test directory
cd analysis
../../circompara -c
cd ..
## overwrite the vars.py file omitting the genome and annotation parameters
grep -v "GENOME\|ANNOTATION" vars.py > analysis/vars.py
## append the parameters for the genome, the annotation and the genome indexes
## generated by the make_indexes utility
cat genome_indexes/annotation_vars.py >> analysis/vars.py
## run the test analysis
cd analysis

Stranded libraries

Some tools in CirComPara require special parameters to handle properly stranded reads. CirComPara allows to specify such parameters Example: include the following parameters if you used the Illumina TruSeq Stranded Total RNA Library Prep Kit with Ribo-Zero Human/Mouse/Rat

HISAT2_EXTRA_PARAMS = "--rna-strandness FR "
CUFFLINKS_PARAMS = "--library-type fr-firststrand "


Installation troubleshooting

System packages dependencies

In a freshly installed Ubuntu Server 16.04 LTS (x64) you need to install the dependency packages listed below (you need root system rights, or ask your system administrator):

sudo apt-get install python2.7 python-pip python-numpy zlib1g-dev unzip pkg-config libncurses5-dev default-jre r-base-core libcurl4-openssl-dev libxml2-dev libssl-dev libcairo2-dev pandoc

(pandoc >= 1.12.3 is required, try install latest packages from http://github.com/jgm/pandoc/releases/)
You also need to upgrade pip version (pip v8.1.1 has an issue with the --install-option parameter; tested working with pip v9.0.1):

pip install --upgrade pip

Manual installation of dependency tools

To run CirComPara you need several software to be available in your system. If the automatic installation does not work for some reason, try to install the required tools in your system. Here there is the list of the tools used in CirComPara with the version that we used during development. We do not list each tool dependencies and if you need support for a specific tool, please refer to the relative software support.

Software Website Version
Ubuntu Linux http://www.ubuntu.com Precise (14.04 LTS) Server
R http://cran.r-project.org/ 3.2.5 (2016-04-14)
Python http://www.python.org/ 2.7.3
Scons http://www.scons.org 2.5.1
Trimmomatic http://www.usadellab.org/cms/?page=trimmomatic 0.36
FASTQC http://www.bioinformatics.babraham.ac.uk/projects/fastqc/ 0.11.5
HISAT2 http://ccb.jhu.edu/software/hisat2/index.shtml 2.0.4
STAR http://github.com/alexdobin/STAR 2.5.2a
BWA http://bio-bwa.sourceforge.net/ 0.7.15-r1140
Bowtie2 http://bowtie-bio.sourceforge.net/bowtie2/index.shtml 2.2.9
Bowtie http://bowtie-bio.sourceforge.net/index.shtml 1.1.2
TopHat http://ccb.jhu.edu/software/tophat/index.shtml 2.1.0
Segemehl http://www.bioinf.uni-leipzig.de/Software/segemehl/ 0.2.0-418
CIRI http://ciri.sourceforge.io/ 2.0.2
CIRCexplorer2 http://github.com/YangLab/CIRCexplorer 2.2.7
find_circ http://github.com/marvin-jens/find_circ 1.2
testrealign http://www.bioinf.uni-leipzig.de/Software/segemehl/ 0.1
Cufflinks http://cole-trapnell-lab.github.io/cufflinks/ 2.2.1
BEDtools http://bedtools.readthedocs.io 2.26.0
Samtools http://www.htslib.org/ 1.3.1
ggplot2 http://ggplot2.org/ 2.2.0
data.table https://cran.r-project.org/web/packages/data.table/index.html 1.10.0
knitr http://yihui.name/knitr/ 1.14.0

Errors with R packages

If you get error messages from R packages of your already installed CirComPara, maybe some update occurred in your R system. Try to re-install all CirComPara R package dependencies by using the reinstall_R_pkgs command.

How to cite

If you used CirComPara for your analysis, please add the following citation to your references:

Gaffo, E., Bonizzato, A., Kronnie, G. te & Bortoluzzi, S. CirComPara: A Multi‐Method Comparative Bioinformatics Pipeline to Detect and Study circRNAs from RNA‐seq Data. Non-Coding RNA 3, 8 (2017). http://www.mdpi.com/2311-553X/3/1/8