Spectacle: Spectral learning for Annotating Chromatin Labels and Epigenomes

Copyright (C) 2013-2015 Jimin Song

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see <http://www.gnu.org/licenses/>.

Spectacle

This software implements a spectral learning algorithm for hidden Markov models for epigenomic data. Please see our paper for further details.

Song, J and Chen, K. C. Spectacle: fast chromatin state annotation using spectral learning. Genome Biology, 16:33, 2015. http://genomebiology.com/2015/16/1/33

Spectacle is written in Java and based on the ChromHMM code. It has been tested on Linux and Windows. It extends LearnModel and MakeSegmentation among the top level commands of ChromHMM (http://compbio.mit.edu/ChromHMM) by adding a spectral learning algorithm for Hidden Markov Model parameter estimation. Other than `LearnModel and MakeSegmentation, all other commands are run as described in the ChromHMM manual (http://compbio.mit.edu/ChromHMM/ChromHMM_manual.pdf).

Installation

• Install Java 1.5 or later if not already installed.

• Download Spectacle:

  Download https://github.com/jiminsong/Spectacle/archive/master.zip
  # If you're on Ubuntu or Mac
  git clone https://github.com/jiminsong/Spectacle.git
  

EXAMPLE

Here is an example of how to run Spectacle.jar with ChIP-seq data from ENCODE.

Prepare the dataset

• Download ChIP-seq data from ENCODE website and put it in the folder SAMPLEDATA_HG19. hg19_cellmarkfiletable.txt contains the names of the files that were downloaded.

• Binarize Bed files:

  java -jar Spectacle.jar BinarizeBed CHROMSIZES/hg19.txt SAMPLEDATA_HG19 hg19_cellmarkfiletable.txt SAMPLEDATA_HG19
  

  hg19_inputfilelist.txt contains the filenames of the binarized data.

Spectral Learning

Spectacle.jar estimates Hidden Markov Model parameters using a spectral learning algorithm as described in our paper.

We also reimplemented the spectral learning algorithm using Python sparse matrix libraries to allow users to analyze a large number of chromatin marks. The Python module makes use of the sparsity of the observed pairs matrix for the SVD computation. The module is implemented in Python using the SciPy library (Python version 2.7.6 and SciPy version 0.13.3) for the SVD computation. The Python module is wrapped with the Spectacle Java code for other tasks- e.g. reading datasets, computing the likelihood, and assigning chromatin states to genomic segments by posterior decoding algorithm etc.

We recommend using the Python module if the number of chromatin marks you would like to use is large.

Spectral Learning without the Python module

• run on whole genome:

  java -mx1200M -jar Spectacle.jar LearnModel -nobrowser -noenrich -f "hg19_inputfilelist.txt" -i spectral -lambda 1 -comb -p 4 SAMPLEDATA_HG19 OUTPUTSAMPLE_HG19 20 hg19
  

• run on one chromosome:

  java -mx1200M -jar Spectacle.jar LearnModel -nobrowser -noenrich -f "hg19_inputfilelist1.txt" -i spectral_chr18 -lambda 1 -comb -p 4 SAMPLEDATA_HG19 OUTPUTSAMPLE_HG19 20 hg19
  

Spectral Learning with the Python module

• run on whole genome:

  java -mx1200M -jar Spectacle.jar LearnModel -nobed -nobrowser -noenrich -f "hg19_inputfilelist.txt" -i spectral -lambda 1 -p 4 -computesamplemomentonly SAMPLEDATA_HG19 OUTPUTSAMPLE_HG19 20 hg19
  python Spectacle_python.py OUTPUTSAMPLE_HG19 spectral 20 8
  java -jar Spectacle.jar MakeSegmentation -f "hg19_inputfilelist.txt" -i spectral -comb "OUTPUTSAMPLE_HG19/model_comb_20_spectral.txt" SAMPLEDATA_HG19 OUTPUTSAMPLE_HG19
  

• run on one chromosome:

  java -mx1200M -jar Spectacle.jar LearnModel -nobed -nobrowser -noenrich -f "hg19_inputfilelist1.txt" -i spectral_chr18 -lambda 1 -p 4 -computesamplemomentonly SAMPLEDATA_HG19 OUTPUTSAMPLE_HG19 20 hg19
  python Spectacle_python.py OUTPUTSAMPLE_HG19 spectral_chr18 20 8
  java -jar Spectacle.jar MakeSegmentation -f "hg19_inputfilelist1.txt" -i spectral_chr18_comb -comb "OUTPUTSAMPLE_HG19/model_comb_20_spectral_chr18.txt" SAMPLEDATA_HG19 OUTPUTSAMPLE_HG19
  

Options for LearnModel

We provide several options in addition to the options of ChromHMM for the LearnModel command.

• -chromhmm : If this flag is set, Spectacle is run exactly the same as ChromHMM as described in the ChromHMM manual. Otherwise, it is run using the spectral learning algorithm.
• -lambda lambdavalue : The Lambda parameter in the data smoothing step is set as lambdavalue. *lambdavalue*=0.95 is the default.
• -spectralrandom : The emission matrix is estimated as described in Appendix C in Hsu et al 2012. Without this option, the emission matrix is estimated using major observations as described in our paper.
• -comb (noindep in the previous versions) : Do not use assumption that all histone marks are conditionally independent given the chromatin state, and consider observations as combinations of marks. There are no EM iterations by default. If EM iterations are run, observations are not considered as combinations of marks anymore.
• -p maxprocessors : A model is trained using multiple processors in parallel.
• -r nmaxiterations : Number of EM iterations. *nmaxiterations*=0 (i.e. no iteration) is the default, in which parameters are not changed but the likelihood is just computed.
• -init load_comb : This loads the parameters specified in modelinitialfile which is in format of output file of the python module Spectacle_python.py. By loading the output file of Spectacle_python.py, -comb is automatically set.
• computesamplemomentonly : This reads histone mark datasets and computes sample moments for spectral learning. Sample moments are written in a file, which is an input file for the python module Spectacle_python.py.

Options for Spectral_python.py

Spectacle_python.py runs as follows:

python Spectral_python.py file_directory fileID num_states num_marks (min_occurrence_observation)

where min_occurrence_observation specifies the minimum number of occurrences of the observation in the genome and the default number is 1.

References

• Ernst J, Kellis M. ChromHMM: automating chromatin state discovery and characterization. Nature Methods, 9:215-216, 2012.
• Hsu D, Kakade SM, Zhang T. A spectral algorithm for learning hidden Markov models. Journal of Computer and System Sciences, 78:1460-1480, 2012.
• Song, J and Chen, K. C. Spectacle: fast chromatin state annotation using spectral learning. Genome Biology, 16:33, 2015.