bionic (1) rsem-calculate-expression.1.gz
NAME
rsem-calculate-expression
PURPOSE
Estimate gene and isoform expression from RNA-Seq data.
SYNOPSIS
rsem-calculate-expression [options] upstream_read_file(s) reference_name sample_name
rsem-calculate-expression [options] --paired-end upstream_read_file(s) downstream_read_file(s) reference_name sample_name
rsem-calculate-expression [options] --alignments [--paired-end] input reference_name sample_name
ARGUMENTS
upstream_read_files(s)
Comma-separated list of files containing single-end reads or upstream reads for paired-end data. By
default, these files are assumed to be in FASTQ format. If the --no-qualities option is specified,
then FASTA format is expected.
downstream_read_file(s)
Comma-separated list of files containing downstream reads which are paired with the upstream reads.
By default, these files are assumed to be in FASTQ format. If the --no-qualities option is
specified, then FASTA format is expected.
input
SAM/BAM/CRAM formatted input file. If "-" is specified for the filename, the input is instead
assumed to come from standard input. RSEM requires all alignments of the same read group together.
For paired-end reads, RSEM also requires the two mates of any alignment be adjacent. In addition,
RSEM does not allow the SEQ and QUAL fields to be empty. See Description section for how to make
input file obey RSEM's requirements.
reference_name
The name of the reference used. The user must have run 'rsem-prepare-reference' with this
reference_name before running this program.
sample_name
The name of the sample analyzed. All output files are prefixed by this name (e.g.,
sample_name.genes.results)
BASIC OPTIONS
--paired-end
Input reads are paired-end reads. (Default: off)
--no-qualities
Input reads do not contain quality scores. (Default: off)
--strand-specific
The RNA-Seq protocol used to generate the reads is strand specific, i.e., all (upstream) reads are
derived from the forward strand. This option is equivalent to --forward-prob=1.0. With this option
set, if RSEM runs the Bowtie/Bowtie 2 aligner, the '--norc' Bowtie/Bowtie 2 option will be used,
which disables alignment to the reverse strand of transcripts. (Default: off)
-p/--num-threads <int>
Number of threads to use. Both Bowtie/Bowtie2, expression estimation and 'samtools sort' will use
this many threads. (Default: 1)
--alignments
Input file contains alignments in SAM/BAM/CRAM format. The exact file format will be determined
automatically. (Default: off)
--fai <file>
If the header section of input alignment file does not contain reference sequence information, this
option should be turned on. <file> is a FAI format file containing each reference sequence's name and
length. Please refer to the SAM official website for the details of FAI format. (Default: off)
--bowtie2
Use Bowtie 2 instead of Bowtie to align reads. Since currently RSEM does not handle indel, local and
discordant alignments, the Bowtie2 parameters are set in a way to avoid those alignments. In
particular, we use options '--sensitive --dpad 0 --gbar 99999999 --mp 1,1 --np 1 --score-min
L,0,-0.1' by default. The last parameter of '--score-min', '-0.1', is the negative of maximum
mismatch rate. This rate can be set by option '--bowtie2-mismatch-rate'. If reads are paired-end, we
additionally use options '--no-mixed' and '--no-discordant'. (Default: off)
--star
Use STAR to align reads. Alignment parameters are from ENCODE3's STAR-RSEM pipeline. To save
computational time and memory resources, STAR's Output BAM file is unsorted. It is stored in RSEM's
temporary directory with name as 'sample_name.bam'. Each STAR job will have its own private copy of
the genome in memory. (Default: off)
--append-names
If gene_name/transcript_name is available, append it to the end of gene_id/transcript_id (separated
by '_') in files 'sample_name.isoforms.results' and 'sample_name.genes.results'. (Default: off)
--seed <uint32>
Set the seed for the random number generators used in calculating posterior mean estimates and
credibility intervals. The seed must be a non-negative 32 bit integer. (Default: off)
--single-cell-prior
By default, RSEM uses Dirichlet(1) as the prior to calculate posterior mean estimates and credibility
intervals. However, much less genes are expressed in single cell RNA-Seq data. Thus, if you want to
compute posterior mean estimates and/or credibility intervals and you have single-cell RNA-Seq data,
you are recommended to turn on this option. Then RSEM will use Dirichlet(0.1) as the prior which
encourage the sparsity of the expression levels. (Default: off)
--calc-pme
Run RSEM's collapsed Gibbs sampler to calculate posterior mean estimates. (Default: off)
--calc-ci
Calculate 95% credibility intervals and posterior mean estimates. The credibility level can be
changed by setting '--ci-credibility-level'. (Default: off)
-q/--quiet
Suppress the output of logging information. (Default: off)
-h/--help
Show help information.
--version
Show version information.
OUTPUT OPTIONS
--sort-bam-by-read-name
Sort BAM file aligned under transcript coordidate by read name. Setting this option on will produce
deterministic maximum likelihood estimations from independent runs. Note that sorting will take long
time and lots of memory. (Default: off)
--no-bam-output
Do not output any BAM file. (Default: off)
--sampling-for-bam
When RSEM generates a BAM file, instead of outputting all alignments a read has with their posterior
probabilities, one alignment is sampled according to the posterior probabilities. The sampling
procedure includes the alignment to the "noise" transcript, which does not appear in the BAM file.
Only the sampled alignment has a weight of 1. All other alignments have weight 0. If the "noise"
transcript is sampled, all alignments appeared in the BAM file should have weight 0. (Default: off)
--output-genome-bam
Generate a BAM file, 'sample_name.genome.bam', with alignments mapped to genomic coordinates and
annotated with their posterior probabilities. In addition, RSEM will call samtools (included in RSEM
package) to sort and index the bam file. 'sample_name.genome.sorted.bam' and
'sample_name.genome.sorted.bam.bai' will be generated. (Default: off)
--sort-bam-by-coordinate
Sort RSEM generated transcript and genome BAM files by coordinates and build associated indices.
(Default: off)
--sort-bam-memory-per-thread <string>
Set the maximum memory per thread that can be used by 'samtools sort'. <string> represents the memory
and accepts suffices 'K/M/G'. RSEM will pass <string> to the '-m' option of 'samtools sort'. Note
that the default used here is different from the default used by samtools. (Default: 1G)
ALIGNER OPTIONS
--seed-length <int>
Seed length used by the read aligner. Providing the correct value is important for RSEM. If RSEM
runs Bowtie, it uses this value for Bowtie's seed length parameter. Any read with its or at least one
of its mates' (for paired-end reads) length less than this value will be ignored. If the references
are not added poly(A) tails, the minimum allowed value is 5, otherwise, the minimum allowed value is
25. Note that this script will only check if the value >= 5 and give a warning message if the value <
25 but >= 5. (Default: 25)
--phred33-quals
Input quality scores are encoded as Phred+33. (Default: on)
--phred64-quals
Input quality scores are encoded as Phred+64 (default for GA Pipeline ver. >= 1.3). (Default: off)
--solexa-quals
Input quality scores are solexa encoded (from GA Pipeline ver. < 1.3). (Default: off)
--bowtie-path <path>
The path to the Bowtie executables. (Default: the path to the Bowtie executables is assumed to be in
the user's PATH environment variable)
--bowtie-n <int>
(Bowtie parameter) max # of mismatches in the seed. (Range: 0-3, Default: 2)
--bowtie-e <int>
(Bowtie parameter) max sum of mismatch quality scores across the alignment. (Default: 99999999)
--bowtie-m <int>
(Bowtie parameter) suppress all alignments for a read if > <int> valid alignments exist. (Default:
200)
--bowtie-chunkmbs <int>
(Bowtie parameter) memory allocated for best first alignment calculation (Default: 0 - use Bowtie's
default)
--bowtie2-path <path>
(Bowtie 2 parameter) The path to the Bowtie 2 executables. (Default: the path to the Bowtie 2
executables is assumed to be in the user's PATH environment variable)
--bowtie2-mismatch-rate <double>
(Bowtie 2 parameter) The maximum mismatch rate allowed. (Default: 0.1)
--bowtie2-k <int>
(Bowtie 2 parameter) Find up to <int> alignments per read. (Default: 200)
--bowtie2-sensitivity-level <string>
(Bowtie 2 parameter) Set Bowtie 2's preset options in --end-to-end mode. This option controls how
hard Bowtie 2 tries to find alignments. <string> must be one of "very_fast", "fast", "sensitive" and
"very_sensitive". The four candidates correspond to Bowtie 2's "--very-fast", "--fast", "--sensitive"
and "--very-sensitive" options. (Default: "sensitive" - use Bowtie 2's default)
--star-path <path>
The path to STAR's executable. (Default: the path to STAR executable is assumed to be in user's PATH
environment variable)
--star-gzipped-read-file
(STAR parameter) Input read file(s) is compressed by gzip. (Default: off)
--star-bzipped-read-file
(STAR parameter) Input read file(s) is compressed by bzip2. (Default: off)
--star-output-genome-bam
(STAR parameter) Save the BAM file from STAR alignment under genomic coordinate to
'sample_name.STAR.genome.bam'. This file is NOT sorted by genomic coordinate. In this file, according
to STAR's manual, 'paired ends of an alignment are always adjacent, and multiple alignments of a read
are adjacent as well'. (Default: off)
ADVANCED OPTIONS
--tag <string>
The name of the optional field used in the SAM input for identifying a read with too many valid
alignments. The field should have the format <tagName>:i:<value>, where a <value> bigger than 0
indicates a read with too many alignments. (Default: "")
--forward-prob <double>
Probability of generating a read from the forward strand of a transcript. Set to 1 for a strand-
specific protocol where all (upstream) reads are derived from the forward strand, 0 for a strand-
specific protocol where all (upstream) read are derived from the reverse strand, or 0.5 for a non-
strand-specific protocol. (Default: 0.5)
--fragment-length-min <int>
Minimum read/insert length allowed. This is also the value for the Bowtie/Bowtie2 -I option.
(Default: 1)
--fragment-length-max <int>
Maximum read/insert length allowed. This is also the value for the Bowtie/Bowtie 2 -X option.
(Default: 1000)
--fragment-length-mean <double>
(single-end data only) The mean of the fragment length distribution, which is assumed to be a
Gaussian. (Default: -1, which disables use of the fragment length distribution)
--fragment-length-sd <double>
(single-end data only) The standard deviation of the fragment length distribution, which is assumed
to be a Gaussian. (Default: 0, which assumes that all fragments are of the same length, given by the
rounded value of --fragment-length-mean)
--estimate-rspd
Set this option if you want to estimate the read start position distribution (RSPD) from data.
Otherwise, RSEM will use a uniform RSPD. (Default: off)
--num-rspd-bins <int>
Number of bins in the RSPD. Only relevant when '--estimate-rspd' is specified. Use of the default
setting is recommended. (Default: 20)
--gibbs-burnin <int>
The number of burn-in rounds for RSEM's Gibbs sampler. Each round passes over the entire data set
once. If RSEM can use multiple threads, multiple Gibbs samplers will start at the same time and all
samplers share the same burn-in number. (Default: 200)
--gibbs-number-of-samples <int>
The total number of count vectors RSEM will collect from its Gibbs samplers. (Default: 1000)
--gibbs-sampling-gap <int>
The number of rounds between two succinct count vectors RSEM collects. If the count vector after
round N is collected, the count vector after round N + <int> will also be collected. (Default: 1)
--ci-credibility-level <double>
The credibility level for credibility intervals. (Default: 0.95)
--ci-memory <int>
Maximum size (in memory, MB) of the auxiliary buffer used for computing credibility intervals (CI).
(Default: 1024)
--ci-number-of-samples-per-count-vector <int>
The number of read generating probability vectors sampled per sampled count vector. The crebility
intervals are calculated by first sampling P(C | D) and then sampling P(Theta | C) for each sampled
count vector. This option controls how many Theta vectors are sampled per sampled count vector.
(Default: 50)
--keep-intermediate-files
Keep temporary files generated by RSEM. RSEM creates a temporary directory, 'sample_name.temp', into
which it puts all intermediate output files. If this directory already exists, RSEM overwrites all
files generated by previous RSEM runs inside of it. By default, after RSEM finishes, the temporary
directory is deleted. Set this option to prevent the deletion of this directory and the intermediate
files inside of it. (Default: off)
--temporary-folder <string>
Set where to put the temporary files generated by RSEM. If the folder specified does not exist, RSEM
will try to create it. (Default: sample_name.temp)
--time
Output time consumed by each step of RSEM to 'sample_name.time'. (Default: off)
DESCRIPTION
In its default mode, this program aligns input reads against a reference transcriptome with Bowtie and
calculates expression values using the alignments. RSEM assumes the data are single-end reads with
quality scores, unless the '--paired-end' or '--no-qualities' options are specified. Alternatively, users
can use STAR to align reads using the '--star' option. RSEM has provided options in
'rsem-prepare-reference' to prepare STAR's genome indices. Users may use an alternative aligner by
specifying '--alignments', and providing an alignment file in SAM/BAM/CRAM format. However, users should
make sure that they align against the indices generated by 'rsem-prepare-reference' and the alignment
file satisfies the requirements mentioned in ARGUMENTS section.
One simple way to make the alignment file satisfying RSEM's requirements is to use the
'convert-sam-for-rsem' script. This script accepts SAM/BAM/CRAM files as input and outputs a BAM file.
For example, type the following command to convert a SAM file, 'input.sam', to a ready-for-use BAM file,
'input_for_rsem.bam':
convert-sam-for-rsem input.sam input_for_rsem
For details, please refer to 'convert-sam-for-rsem's documentation page.
NOTES
1. Users must run 'rsem-prepare-reference' with the appropriate reference before using this program.
2. For single-end data, it is strongly recommended that the user provide the fragment length distribution
parameters (--fragment-length-mean and --fragment-length-sd). For paired-end data, RSEM will
automatically learn a fragment length distribution from the data.
3. Some aligner parameters have default values different from their original settings.
4. With the '--calc-pme' option, posterior mean estimates will be calculated in addition to maximum
likelihood estimates.
5. With the '--calc-ci' option, 95% credibility intervals and posterior mean estimates will be calculated
in addition to maximum likelihood estimates.
6. The temporary directory and all intermediate files will be removed when RSEM finishes unless
'--keep-intermediate-files' is specified.
OUTPUT
sample_name.isoforms.results
File containing isoform level expression estimates. The first line contains column names separated by
the tab character. The format of each line in the rest of this file is:
transcript_id gene_id length effective_length expected_count TPM FPKM IsoPct [posterior_mean_count
posterior_standard_deviation_of_count pme_TPM pme_FPKM IsoPct_from_pme_TPM TPM_ci_lower_bound
TPM_ci_upper_bound TPM_coefficient_of_quartile_variation FPKM_ci_lower_bound FPKM_ci_upper_bound
FPKM_coefficient_of_quartile_variation]
Fields are separated by the tab character. Fields within "[]" are optional. They will not be
presented if neither '--calc-pme' nor '--calc-ci' is set.
'transcript_id' is the transcript name of this transcript. 'gene_id' is the gene name of the gene
which this transcript belongs to (denote this gene as its parent gene). If no gene information is
provided, 'gene_id' and 'transcript_id' are the same.
'length' is this transcript's sequence length (poly(A) tail is not counted). 'effective_length'
counts only the positions that can generate a valid fragment. If no poly(A) tail is added,
'effective_length' is equal to transcript length - mean fragment length + 1. If one transcript's
effective length is less than 1, this transcript's both effective length and abundance estimates are
set to 0.
'expected_count' is the sum of the posterior probability of each read comes from this transcript over
all reads. Because 1) each read aligning to this transcript has a probability of being generated from
background noise; 2) RSEM may filter some alignable low quality reads, the sum of expected counts for
all transcript are generally less than the total number of reads aligned.
'TPM' stands for Transcripts Per Million. It is a relative measure of transcript abundance. The sum
of all transcripts' TPM is 1 million. 'FPKM' stands for Fragments Per Kilobase of transcript per
Million mapped reads. It is another relative measure of transcript abundance. If we define l_bar be
the mean transcript length in a sample, which can be calculated as
l_bar = \sum_i TPM_i / 10^6 * effective_length_i (i goes through every transcript),
the following equation is hold:
FPKM_i = 10^3 / l_bar * TPM_i.
We can see that the sum of FPKM is not a constant across samples.
'IsoPct' stands for isoform percentage. It is the percentage of this transcript's abandunce over its
parent gene's abandunce. If its parent gene has only one isoform or the gene information is not
provided, this field will be set to 100.
'posterior_mean_count', 'pme_TPM', 'pme_FPKM' are posterior mean estimates calculated by RSEM's Gibbs
sampler. 'posterior_standard_deviation_of_count' is the posterior standard deviation of counts.
'IsoPct_from_pme_TPM' is the isoform percentage calculated from 'pme_TPM' values.
'TPM_ci_lower_bound', 'TPM_ci_upper_bound', 'FPKM_ci_lower_bound' and 'FPKM_ci_upper_bound' are
lower(l) and upper(u) bounds of 95% credibility intervals for TPM and FPKM values. The bounds are
inclusive (i.e. [l, u]).
'TPM_coefficient_of_quartile_variation' and 'FPKM_coefficient_of_quartile_variation' are coefficients
of quartile variation (CQV) for TPM and FPKM values. CQV is a robust way of measuring the ratio
between the standard deviation and the mean. It is defined as
CQV := (Q3 - Q1) / (Q3 + Q1),
where Q1 and Q3 are the first and third quartiles.
sample_name.genes.results
File containing gene level expression estimates. The first line contains column names separated by
the tab character. The format of each line in the rest of this file is:
gene_id transcript_id(s) length effective_length expected_count TPM FPKM [posterior_mean_count
posterior_standard_deviation_of_count pme_TPM pme_FPKM TPM_ci_lower_bound TPM_ci_upper_bound
TPM_coefficient_of_quartile_variation FPKM_ci_lower_bound FPKM_ci_upper_bound
FPKM_coefficient_of_quartile_variation]
Fields are separated by the tab character. Fields within "[]" are optional. They will not be
presented if neither '--calc-pme' nor '--calc-ci' is set.
'transcript_id(s)' is a comma-separated list of transcript_ids belonging to this gene. If no gene
information is provided, 'gene_id' and 'transcript_id(s)' are identical (the 'transcript_id').
A gene's 'length' and 'effective_length' are defined as the weighted average of its transcripts'
lengths and effective lengths (weighted by 'IsoPct'). A gene's abundance estimates are just the sum
of its transcripts' abundance estimates.
sample_name.alleles.results
Only generated when the RSEM references are built with allele-specific transcripts.
This file contains allele level expression estimates for allele-specific expression calculation. The
first line contains column names separated by the tab character. The format of each line in the rest
of this file is:
allele_id transcript_id gene_id length effective_length expected_count TPM FPKM AlleleIsoPct
AlleleGenePct [posterior_mean_count posterior_standard_deviation_of_count pme_TPM pme_FPKM
AlleleIsoPct_from_pme_TPM AlleleGenePct_from_pme_TPM TPM_ci_lower_bound TPM_ci_upper_bound
TPM_coefficient_of_quartile_variation FPKM_ci_lower_bound FPKM_ci_upper_bound
FPKM_coefficient_of_quartile_variation]
Fields are separated by the tab character. Fields within "[]" are optional. They will not be
presented if neither '--calc-pme' nor '--calc-ci' is set.
'allele_id' is the allele-specific name of this allele-specific transcript.
'AlleleIsoPct' stands for allele-specific percentage on isoform level. It is the percentage of this
allele-specific transcript's abundance over its parent transcript's abundance. If its parent
transcript has only one allele variant form, this field will be set to 100.
'AlleleGenePct' stands for allele-specific percentage on gene level. It is the percentage of this
allele-specific transcript's abundance over its parent gene's abundance.
'AlleleIsoPct_from_pme_TPM' and 'AlleleGenePct_from_pme_TPM' have similar meanings. They are
calculated based on posterior mean estimates.
Please note that if this file is present, the fields 'length' and 'effective_length' in
'sample_name.isoforms.results' should be interpreted similarly as the corresponding definitions in
'sample_name.genes.results'.
sample_name.transcript.bam
Only generated when --no-bam-output is not specified.
'sample_name.transcript.bam' is a BAM-formatted file of read alignments in transcript coordinates.
The MAPQ field of each alignment is set to min(100, floor(-10 * log10(1.0 - w) + 0.5)), where w is
the posterior probability of that alignment being the true mapping of a read. In addition, RSEM pads
a new tag ZW:f:value, where value is a single precision floating number representing the posterior
probability. Because this file contains all alignment lines produced by bowtie or user-specified
aligners, it can also be used as a replacement of the aligner generated BAM/SAM file.
sample_name.transcript.sorted.bam and sample_name.transcript.sorted.bam.bai
Only generated when --no-bam-output is not specified and --sort-bam-by-coordinate is specified.
'sample_name.transcript.sorted.bam' and 'sample_name.transcript.sorted.bam.bai' are the sorted BAM
file and indices generated by samtools (included in RSEM package).
sample_name.genome.bam
Only generated when --no-bam-output is not specified and --output-genome-bam is specified.
'sample_name.genome.bam' is a BAM-formatted file of read alignments in genomic coordinates.
Alignments of reads that have identical genomic coordinates (i.e., alignments to different isoforms
that share the same genomic region) are collapsed into one alignment. The MAPQ field of each
alignment is set to min(100, floor(-10 * log10(1.0 - w) + 0.5)), where w is the posterior probability
of that alignment being the true mapping of a read. In addition, RSEM pads a new tag ZW:f:value,
where value is a single precision floating number representing the posterior probability. If an
alignment is spliced, a XS:A:value tag is also added, where value is either '+' or '-' indicating the
strand of the transcript it aligns to.
sample_name.genome.sorted.bam and sample_name.genome.sorted.bam.bai
Only generated when --no-bam-output is not specified, and --sort-bam-by-coordinate and
--output-genome-bam are specified.
'sample_name.genome.sorted.bam' and 'sample_name.genome.sorted.bam.bai' are the sorted BAM file and
indices generated by samtools (included in RSEM package).
sample_name.time
Only generated when --time is specified.
It contains time (in seconds) consumed by aligning reads, estimating expression levels and
calculating credibility intervals.
sample_name.stat
This is a folder instead of a file. All model related statistics are stored in this folder. Use
'rsem-plot-model' can generate plots using this folder.
'sample_name.stat/sample_name.cnt' contains alignment statistics. The format and meanings of each
field are described in 'cnt_file_description.txt' under RSEM directory.
'sample_name.stat/sample_name.model' stores RNA-Seq model parameters learned from the data. The
format and meanings of each filed of this file are described in 'model_file_description.txt' under
RSEM directory.
EXAMPLES
Assume the path to the bowtie executables is in the user's PATH environment variable. Reference files are
under '/ref' with name 'mouse_125'.
1) '/data/mmliver.fq', single-end reads with quality scores. Quality scores are encoded as for 'GA
pipeline version >= 1.3'. We want to use 8 threads and generate a genome BAM file. In addition, we want
to append gene/transcript names to the result files:
rsem-calculate-expression --phred64-quals \
-p 8 \
--append-names \
--output-genome-bam \
/data/mmliver.fq \
/ref/mouse_125 \
mmliver_single_quals
2) '/data/mmliver_1.fq' and '/data/mmliver_2.fq', paired-end reads with quality scores. Quality scores
are in SANGER format. We want to use 8 threads and do not generate a genome BAM file:
rsem-calculate-expression -p 8 \
--paired-end \
/data/mmliver_1.fq \
/data/mmliver_2.fq \
/ref/mouse_125 \
mmliver_paired_end_quals
3) '/data/mmliver.fa', single-end reads without quality scores. We want to use 8 threads:
rsem-calculate-expression -p 8 \
--no-qualities \
/data/mmliver.fa \
/ref/mouse_125 \
mmliver_single_without_quals
4) Data are the same as 1). This time we assume the bowtie executables are under '/sw/bowtie'. We want to
take a fragment length distribution into consideration. We set the fragment length mean to 150 and the
standard deviation to 35. In addition to a BAM file, we also want to generate credibility intervals. We
allow RSEM to use 1GB of memory for CI calculation:
rsem-calculate-expression --bowtie-path /sw/bowtie \
--phred64-quals \
--fragment-length-mean 150.0 \
--fragment-length-sd 35.0 \
-p 8 \
--output-genome-bam \
--calc-ci \
--ci-memory 1024 \
/data/mmliver.fq \
/ref/mouse_125 \
mmliver_single_quals
5) '/data/mmliver_paired_end_quals.bam', BAM-formatted alignments for paired-end reads with quality
scores. We want to use 8 threads:
rsem-calculate-expression --paired-end \
--alignments \
-p 8 \
/data/mmliver_paired_end_quals.bam \
/ref/mouse_125 \
mmliver_paired_end_quals
6) '/data/mmliver_1.fq.gz' and '/data/mmliver_2.fq.gz', paired-end reads with quality scores and read
files are compressed by gzip. We want to use STAR to aligned reads and assume STAR executable is
'/sw/STAR'. Suppose we want to use 8 threads and do not generate a genome BAM file:
rsem-calculate-expression --paired-end \
--star \
--star-path /sw/STAR \
--gzipped-read-file \
-p 8 \
/data/mmliver_1.fq.gz \
/data/mmliver_2.fq.gz \
/ref/mouse_125 \
mmliver_paired_end_quals