QTLtools-quan

NAME

QTLtools quan - Quantify gene and exon expression from RNA-seq

SYNOPSIS

QTLtools quan --bam [in.sam|in.bam|in.cram] --gtf gene_annotation.gtf --out-prefix output [OPTIONS]

DESCRIPTION

This mode quantifies the expression of genes and exons in the provided --gtf file using the RNA-seq reads in the --bam file. The method counts the number of reads overlapping the exons in the --gtf file. Firstly all exons of a gene are converted into meta-exons where overlapping exons are merged into a single exon encompassing all the overlapping exons. Any overlap between the read and the exon is considered a match, that is a read is not required to be in between start and end positions of an exon to count towards that exon’s quantification. Split reads aligning to multiple exons contribute to each exon it overlaps with based on the fraction of the read that overlaps with a given exon. Thus split reads contribute less than a single count to each of the overlapping exons. Reads aligning to multiple exons (i.e. overlapping exons of multiple genes) count towards the quantification of all the exons that it overlaps with. If the --bam file contains paired-end reads and if there are cases where the two mate pairs overlap with each other (i.e. have an insert size < 0), then each of these reads contribute less then a single count towards the quantifications unless --no-merge is provided. The following diagram, with two genes with overlapping exons and one paired-end read where both mate pairs are split reads and overlap with each other, illustrates how the quantification works:

x x
/ \ / \
+---------+ +---------+ +---------+
| Exon1|1 | | Exon1|2 | | Exon1|3 | Gene1
+---------+ +---------+ +---------+
x
/ \
+------------+ +-------------+
| Exon2|1 | | Exon2|2 | Gene2
+------------+ +-------------+
x
/ \
+------------+ +----+ RNAseq Read Mate1

|--a-||-b-||c| |-d--||--e-|
x
/ \
+------+ +----------+ RNAseq Read Mate2

Left Mate1 = ((b * 0.5) + a) / (a + b + d)
Right Mate1 = (d * 0.5)/(a + b + d)
Left Mate2 = (b * 0.5)/(b + d + e)
Right Mate2 = ((d * 0.5) + e)/(b + d + e)

Exon1|2 = Left Mate1 + Left Mate2
Exon1|3 = Right Mate1 + Right Mate2
Exon2|1 = Left Mate1 + Left Mate2
Exon2|2 = Right Mate2 + Right Mate2

Gene1 = Exon1|2 + Exon1|3
Gene2 = Exon2|1 + Exon2|2

The quan mode in version 1.2 and above is not compatible with the quantifications generated by the previous versions. This due to bug fixes and slight adjustments to the way we quantify. DO NOT MIX QUANTIFICATIONS GENERATED BY EARLIER VERSIONS OF QTLTOOLS WITH QUANTIFICATIONS FROM VERSION 1.2 AND ABOVE AS THIS WILL CREATE A BIAS IN YOUR DATASET.

OPTIONS

--gtf gene_annotation.gtf

Gene annotations in GTF format. These can be obtained from <https://www.gencodegenes.org/>. REQUIRED.

--bam [in.bam|in.sam|in.cram]

Sequence data in BAM/SAM/CRAM format sorted by chromosome and then position. One sample per BAM file. REQUIRED.

--out-prefix output

Output prefix. REQUIRED.

--sample sample_name

The sample name of the BAM file. If not provided the sample name will be taken as the BAM file path.

--rpkm

Output RPKM values.

--tpm

Output TPM values.

--xxhash

Rather than using the GTF file name to generate unique hash for the options used, use the hash of the GTF file.

--no-hash

Do not include a hash signifying the options used in the quantification in the output file names. NOT RECOMMENDED.

--gene-types gene_type ...

Only quantify these gene types. Requires gene_type attribute in GTF. It will also use transcript_type if present.

--filter-mapping-quality integer

Minimum mapping quality for a read or read pair to be considered. Set this to only include uniquely mapped reads. DEFAULT=10.

--filter-mismatch integer|float

Maximum mismatches allowed in a read. If between 0 and 1 taken as the fraction of read length. Requires NM attribute in the BAM file. DEFAULT=OFF.

--filter-mismatch-total integer|float

Maximum total mismatches allowed in paired-reads. If between 0 and 1 taken as the fraction of combined read length. Requires NM attribute in the BAM file. DEFAULT=OFF.

--filter-min-exon integer

Minimum length of an exon for it to be quantified. Exons smaller than this will not be printed out in the exon quantifications, but will still count towards gene quantifications. DEFAULT=0.

--filter-remove-duplicates

Remove duplicate sequencing reads,as indicated by the aligner, in the process. NOT RECOMMENDED.

--filter-failed-qc

Remove fastq reads that fail sequencing QC as indicated by the sequencer.

--check-proper-pairing

If provided only properly paired reads according to the aligner that are in correct orientation will be considered. Otherwise all pairs in correct orientation will be considered.

--check-consistency

If provided checks the consistency of split reads with annotation, rather than pure overlap of one of the blocks of the split read.

--no-merge

If provided overlapping mate pairs will not be merged. Default behavior is to merge overlapping mate pairs based on the amount of overlap, such that each mate pair counts for less than 1 read.

--legacy-options

Exactly replicate Dermitzakis lab original quantification script. DO NOT USE.

--region chr:start-end

Genomic region to be processed. E.g. chr4:12334456-16334456, or chr5.

OUTPUT FILES

Unless --no-hash is provided, all output files will include a hash value corresponding to combination of the specific options used. This is given so that one does not merge quantifications from samples that were quantified differently, which would create a bias in the dataset.
.gene.count.bed .exon.count.bed .gene.rpkm.bed .exon.rpkm.bed .gene.tpm.bed
.exon.tpm.bed

These are the quantification results files with the following columns:

.stats

Details the statistics of the quantification, with the following rows:

EXAMPLE

	o		Quantifying a sample mapped with GEM, outputting TPM and RPKM values, and taking the hash of the GTF file:
			QTLtools quan --bam HG00381.chr22.bam --gtf gencode.v19.annotation.chr22.gtf.gz --out-prefix HG00381 --sample HG00381 --rpkm --tpm --xxhash --filter-mismatch-total 8 --filter-mapping-quality 150

SEE ALSO

QTLtools(1)

QTLtools website: <https://qtltools.github.io/qtltools>

BUGS

Please submit bugs to <https://github.com/qtltools/qtltools>

CITATION

Delaneau, O., Ongen, H., Brown, A. et al. A complete tool set for molecular QTL discovery and analysis. Nat Commun 8, 15452 (2017). <https://doi.org/10.1038/ncomms15452>

AUTHORS

Halit Ongen (halitongen@gmail.com), Olivier Delaneau (olivier.delaneau@gmail.com)