MSIsensor

MSIsensor is a C++ program to detect replication slippage variants at microsatellite regions, and differentiate them as somatic or germline. Given paired tumor and normal sequence data, it builds a distribution for expected (normal) and observed (tumor) lengths of repeated sequence per microsatellite, and compares them using Pearson's Chi-Squared Test. Comprehensive testing indicates MSIsensor is an efficient and effective tool for deriving MSI status from standard tumor-normal paired sequence data. Since there are many users complained that they don't have paired normal sequence data or related normal sequence data can be used to build a paired normal control, we released MSIsensor V0.3. Given tumor only sequence data, it uses comentropy theory and figures out a comentropy value for a distribution per microsatellite. Our test results show that it's performance is comparable with paired tumor and normal sequence data input. We suggest msi score cutoff 30% for tumor only data. (msi high: msi score >= 30%).

If you used this tool for your work, please cite PMID 24371154

Usage

    Version 0.3
    Usage:  msisensor <command> [options]

Key commands:

    scan            scan homopolymers and miscrosatelites
    msi             msi scoring

msisensor scan [options]:

   -d   <string>   reference genome sequences file, *.fasta format
   -o   <string>   output homopolymer and microsatelittes file

   -l   <int>      minimal homopolymer size, default=5
   -c   <int>      context length, default=5
   -m   <int>      maximal homopolymer size, default=50
   -s   <int>      maximal length of microsate, default=5
   -r   <int>      minimal repeat times of microsate, default=3
   -p   <int>      output homopolymer only, 0: no; 1: yes, default=0

   -h   help

msisensor msi [options]:

   -d   <string>   homopolymer and microsates file
   -n   <string>   normal bam file
   -t   <string>   tumor  bam file
   -o   <string>   output distribution file

   -e   <string>   bed file, optional
   -f   <double>   FDR threshold for somatic sites detection, default=0.05
   -i   <double>   minimal comentropy threshold for somatic sites detection (just for tumor only data), default=0.5
   -c   <int>      coverage threshold for msi analysis, WXS: 20; WGS: 15, default=20
   -r   <string>   choose one region, format: 1:10000000-20000000
   -l   <int>      minimal homopolymer size, default=5
   -p   <int>      minimal homopolymer size for distribution analysis, default=10
   -m   <int>      maximal homopolymer size for distribution analysis, default=50
   -q   <int>      minimal microsates size, default=3
   -s   <int>      minimal microsates size for distribution analysis, default=5
   -w   <int>      maximal microstaes size for distribution analysis, default=40
   -u   <int>      span size around window for extracting reads, default=500
   -b   <int>      threads number for parallel computing, default=1
   -x   <int>      output homopolymer only, 0: no; 1: yes, default=0
   -y   <int>      output microsatellite only, 0: no; 1: yes, default=0

   -h   help

Install

You may already have these prerequisite packages. If not, and you're on Debian or Ubuntu:

sudo apt-get install git libbam-dev zlib1g-dev

If you are using Fedora, CentOS or RHEL, you'll need these packages instead:

sudo yum install git samtools-devel zlib-devel

The Makefile assumes you have samtools-0.1.19 source code in environment variable $SAMTOOLS_ROOT. If not, then download samtools-0.1.19 from SourceForge:

tar jxf samtools-0.1.19.tar.bz2
cd samtools-0.1.19
make
export SAMTOOLS_ROOT=$PWD

Clone the msisensor master branch, and build the msisensor binary:

git clone https://github.com/ding-lab/msisensor.git
cd msisensor
make

Now you can put the resulting binary where your $PATH can find it. If you have su permissions, then we recommend dumping it in the system directory for locally compiled packages:

sudo mv msisensor /usr/local/bin/

Pre-built binaries for Linux x86_64 and Mac OS X are in this directory: ./binary

msisensor_Linux_x86_64: for Linux x86_64
msisensor_Mac_OS_X    : for Mac OS X

Example

1. Scan microsatellites from reference genome:

    msisensor scan -d reference.fa -o microsatellites.list
   

2. MSI scoring:

   for paired tumor and normal sequence data:

    msisensor msi -d microsatellites.list -n normal.bam -t tumor.bam -e bed.file -o output.prefix
   

   for tumor only sequence data:

    msisensor msi -d microsatellites.list -t tumor.bam -e bed.file -o output.tumor.prefix
   

   Note: normal and tumor bam index files are needed in the same directory as bam files

Output

The list of microsatellites is output in "scan" step. The MSI scoring step produces 4 files:

    output.prefix
    output.prefix_dis_tab
    output.prefix_germline
    output.prefix_somatic

for tumor only input, the MSI scoreing step produces 3 files:

    output.tumor.prefix
    output.tumor.prefix_dis_tab
    output.tumor.prefix_somatic

1. microsatellites.list: microsatellite list output ( columns with *_binary means: binary conversion of DNA bases based on A=00, C=01, G=10, and T=11 )

    chromosome      location        repeat_unit_length     repeat_unit_binary    repeat_times    left_flank_binary     right_flank_binary      repeat_unit_bases      left_flank_bases       right_flank_bases
    1       10485   4       149     3       150     685     GCCC    AGCCG   GGGTC
    1       10629   2       9       3       258     409     GC      CAAAG   CGCGC
    1       10652   2       2       3       665     614     AG      GGCGC   GCGCG
    1       10658   2       9       3       546     409     GC      GAGAG   CGCGC
    1       10681   2       2       3       665     614     AG      GGCGC   GCGCG
   

2. output.prefix: msi score output

    Total_Number_of_Sites   Number_of_Somatic_Sites %
    640     75      11.72
   

3. output.prefix_dis_tab: read count distribution (N: normal; T: tumor)

    1       16248728        ACCTC   11      T       AAAGG   N       0       0       0       0       1       38      0       0       0       0       0       0       0
    1       16248728        ACCTC   11      T       AAAGG   T       0       0       0       0       17      22      1       0       0       0       0       0       0
   

4. output.prefix_somatic: somatic sites detected ( FDR: false discovery rate )

    chromosome   location        left_flank     repeat_times    repeat_unit_bases    right_flank      difference      P_value    FDR     rank
    1       16200729        TAAGA   10      T       CTTGT   0.55652 2.8973e-15      1.8542e-12      1
    1       75614380        TTTAC   14      T       AAGGT   0.82764 5.1515e-15      1.6485e-12      2
    1       70654981        CCAGG   21      A       GATGA   0.80556 1e-14   2.1333e-12      3
    1       65138787        GTTTG   13      A       CAGCT   0.8653  1e-14   1.6e-12 4
    1       35885046        TTCTC   11      T       CCCCT   0.84682 1e-14   1.28e-12        5
    1       75172756        GTGGT   14      A       GAAAA   0.57471 1e-14   1.0667e-12      6
    1       76257074        TGGAA   14      T       GAGTC   0.66023 1e-14   9.1429e-13      7
    1       33087567        TAGAG   16      A       GGAAA   0.53141 1e-14   8e-13   8
    1       41456808        CTAAC   14      T       CTTTT   0.76286 1e-14   7.1111e-13      9
   

5. output.prefix_germline: germline sites detected

    chromosome   location        left_flank     repeat_times    repeat_unit_bases    right_flank      genotype
    1       1192105 AATAC   11      A       TTAGC   5|5
    1       1330899 CTGCC   5       AG      CACAG   5|5
    1       1598690 AATAC   12      A       TTAGC   5|5
    1       1605407 AAAAG   14      A       GAAAA   1|1
    1       2118724 TTTTC   11      T       CTTTT   1|1
   

Test sample

We provided one small dataset (tumor and matched normal bam files) to test the msi scoring step:

    cd ./test
    bash run.sh

Contact

If you have any questions, please contact one or more of the following folks: Beifang Niu [email protected] Kai Ye [email protected] Li Ding [email protected] Cyriac Kandoth [email protected]