Xavier Didelot edited this page Nov 28, 2016 · 5 revisions

Input

There are two input files needed to run ClonalFrameML. The first one is a starting tree, which must be in Newick format. The second one is an alignment of the sequences which can be either in fasta format or extended multi fasta (XMFA) format. There must be as many leaves in the tree as there are sequences in the alignment file, and the names of the leaves must match the names in the headers of the alignment file.

The starting tree can be generated from the alignment for example using RAxML or PhyML.

Running

The basic command for running ClonalFrameML is as follows:

ClonalFrameML newick_file seq_file output_prefix [OPTIONS]

The newick_file and seq_file are the two input files described above. The parameter kappa specifies the transition/transversion bias, and is an output of the phylogenetic reconstruction software. The output_prefix is the prefix used for all output files generated by ClonalFrameML.

Output

Running ClonalFrameML produces several output files, each of which starts with the output_prefix specified in the command line and ending with the following extensions:

ML_sequence.fasta

This file contains the sequence reconstructed by maximum likelihood for all internal nodes of the phylogeny, as well as for all missing data in the input sequences. It is an alignment with a sequence for each leaf and each internal node of the phylogeny. In this alignment there is one position for each unique pattern of the sequences in the input file. The mapping between positions in the input file and in the ML_sequence.fasta output file is given in the position_cross_reference.txt output file (see below).

position_cross_reference.txt

A vector of comma-separated values indicating for each location in the input sequence file the corresponding position in the sequences in the output ML_sequence.fasta file. The values in the position_cross_reference.txt file correspond to positions along the ML_Sequence.fasta file. For example, to find out what was reconstructed at the 10th position in the input file, one needs to first look in the position_cross_reference.txt at the tenth value, and if this is equal to 5 for example, then one needs to look at the fifth position in the ML_sequence.fasta file.

em.txt

This file contains the point estimates for R/theta, nu, delta and the branch lengths.

emsim.txt

This file contains the bootstrapped values for the three parameters R/theta, nu and delta.

importation_status.txt

This file contains the list of reconstructed recombination events. There is one line for each event, the first column indicates the branch on which the event was found, and the second and third columns indicate the first and last genomic positions affected by the recombination event.

labelled_tree.newick

This file contains the output tree with all nodes labelled so that they can be referred to in other files.

Graphical output

To produce a graphical representation of the ClonalFrameML output, use the following command. This requires R to be installed with the ape and phangorn packages. The cfml_results.R script is available in the svn repository.

Rscript cfml_results.R output_prefix

The result is a PDF file named output_prefix.pdf

ClonalFrameML usage

Example: standard model

Start by downloading the example files from here. Unzip on Mac/Linux as follows:

tar -xzvf cfml.tgz

The file contains the S. aureus FASTA file (Saureus.fasta), maximum likelihood tree (Saureus.phyML.newick), lists of core and non-core sites (Saureus.core-sites.txt and Saureus.non-core-sites.txt) and some R code (cfml_results_2.R).

Run the standard ClonalFrameML analysis as follows. Note! This is a real-world example, and requires around 12 hours of run time.

./ClonalFrameML Saureus.phyML.newick Saureus.fasta example.output -kappa 4.967695 -emsim 100 -ignore_user_sites Saureus.non-core-sites.txt > example.log.txt

Note that the transition:transversion ratio of 4.967695 was estimated by PhyML. In this, the standard analysis, recombination parameters are shared by all branches, and the -emsim 100 option requests 100 pseudo-bootstrap replicates. The positions listed in the file specified by the -ignore_user_sites option lists any site that was not callable or present in all the genomes. These sites are treated as missing data, which is important since uncalled sites can cause artefactual clustering of substitutions.

This analysis utilizes the default gamma priors, which are implemented as pseudocounts in the likelihood, and which can be modified using -prior_mean and -prior_sd. They specify the parameters in the following order: R/theta (relative rate of recombination to mutation), 1/delta (inverse mean DNA import length), nu (mean divergence of imported DNA) and mean branch length. The default values specify distributions with means of R/theta = 0.1, 1/delta = 0.001, nu = 0.1 and mean branch length of 0.0001. It may be advisable to change the latter to reflect the mean branch length in the PhyML tree. The default prior standard deviations equal the prior means. This produces priors that support values over roughly three orders of magnitude. Modest increases or decreases in prior_sd relative to prior_mean will be reflected by increases or decreases in the numbers of orders of magnitude over which the prior assigns reasonable support. It is not advisable to make prior_sd appreciably larger than prior_mean.

Once the analysis has finished, a figure can be produced with an R script. The R script optionally takes a list of the core sites (the complement of the non-core sites fed into ClonalFrameML):

Rscript cfml_results.R example.output core-sites.txt

This will generate a pdf similar to the figures in the paper.

Example: per-branch model

Run the ClonalFrameML analysis in which recombination parameters are estimated per branch as follows. Note! This is a real-world example, and requires around 12 hours of run time.

./ClonalFrameML Saureus.phyML.newick Saureus.fasta example2.output -kappa 4.967695 -embranch true -embranch_dispersion 0.1 -ignore_user_sites Saureus.non-core-sites.txt -initial_values "0.141679 0.002856294 0.0147762" > example2.log.txt

This time -embranch is specified instead of -em. The -embranch_dispersion option specifies the constraint on the variability of recombination parameters among branches of the tree. It is on a scale of 0-1, with 0 being the most constrained (least dispersed). The -initial_values of R/theta, 1/delta and nu can be set. It is advisable to run the simpler model first, and use the results to initialize the per-branch model. Again the R code can be used to generate a figure.

Full list of options

The options of ClonalFrameML are listed in full below:

Syntax: ClonalFrameML newick_file fasta_file output_file [OPTIONS]

Options specifying the analysis type:
-em                            true (default) or false   Estimate parameters by a Baum-Welch expectation maximization algorithm.
-embranch                      true or false (default)   Estimate parameters for each branch using the EM algorithm.
-rescale_no_recombination      true or false (default)   Rescale branch lengths for given sites with no recombination model.
-imputation_only               true or false (default)   Perform only ancestral state reconstruction and imputation.
Options affecting all analyses:
-kappa                         value > 0 (default 2.0)   Relative rate of transitions vs transversions in substitution model
-fasta_file_list               true or false (default)   Take fasta_file to be a white-space separated file list.
-xmfa_file                     true or false (default)   Take fasta_file to be a XMFA file.
-ignore_user_sites             sites_file                Ignore sites listed in whitespace-separated sites_file.
-ignore_incomplete_sites       true or false (default)   Ignore sites with any ambiguous bases.
-use_incompatible_sites        true (default) or false   Use homoplasious and multiallelic sites to correct branch lengths.
-show_progress                 true or false (default)   Output the progress of the maximum likelihood routines.
-min_branch_length             value > 0 (default 1e-7)  Minimum branch length.
-reconstruct_invariant_sites   true or false (default)   Reconstruct the ancestral states at invariant sites.
Options affecting -em and -embranch:
-prior_mean                    df "0.1 0.001 0.1 0.0001" Prior mean for R/theta, 1/delta, nu and M.
-prior_sd                      df "0.1 0.001 0.1 0.0001" Prior standard deviation for R/theta, 1/delta, nu and M.
-initial_values                default "0.1 0.001 0.05"  Initial values for R/theta, 1/delta and nu.
-guess_initial_m               true (default) or false   Initialize M and nu jointly in the EM algorithms.
-emsim                         value >= 0  (default 0)   Number of simulations to estimate uncertainty in the EM results.
-embranch_dispersion           value > 0 (default .01)   Dispersion in parameters among branches in the -embranch model.
Options affecting -rescale_no_recombination:
-brent_tolerance               tolerance (default .001)  Set the tolerance of the Brent routine for -rescale_no_recombination.
-powell_tolerance              tolerance (default .001)  Set the tolerance of the Powell routine for -rescale_no_recombination.

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