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tinyRNA provides an all-in-one solution for precision analysis of sRNA-seq data. At the core of tinyRNA is a highly flexible counting utility, tiny-count, that allows for hierarchical assignment of reads to features based on positional information, extent of feature overlap, 5’ nucleotide, length, and strandedness.

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tinyRNA: precision analysis of small RNA high-throughput sequencing data

Feedback, suggestions, and bug reports are welcome under the issues tab. Thank you!

tinyRNA is a set of tools to simplify the analysis of next-generation sequencing data. The goal of this specific repository is to provide an entire workflow for processing small RNA sequencing data with user-defined hierarchical feature selection rules.

The Current Workflow

tinyRNA basic pipeline

tinyRNA Installation

Stable Releases

  1. Download the latest release from the releases link on the sidebar
  2. Decompress the archive and navigate to the resulting directory in your terminal
  3. Run ./setup.sh to install the project and its dependencies in a conda environment named "tinyrna"

Installation Tips

  • If the installation script runs the Miniconda installer:
    • Press "q" if you find yourself trapped on the license page
    • We recommend answering "yes" to running conda init
  • A custom environment name can be passed as the first argument to setup.sh

Development Releases

This option provides the latest features but stable releases are more rigorously tested.

# Clone the repository into a local directory
 git clone https://github.com/MontgomeryLab/tinyrna.git
 cd tinyrna

# Install the tinyrna environment and dependencies
 ./setup.sh

Updating an Existing Installation

When it's time to update your installation of tinyRNA, simply repeat the procedure you used for installation. Note that the existing Conda environment, including any additional packages you may have installed within it, will be removed by the installation script.

tiny-count Standalone Installation

Alternatively, you can install tinyRNA's precision counting tool by itself. Unlike the full tinyRNA suite, this option can be installed in existing conda environments and requires fewer dependencies.

conda install -c bioconda -c conda-forge tiny-count

If you'd like to jump right in and start using tiny-count, see our
👉 tutorial 👈

Usage

The tinyrna conda environment must be activated before using the tinyRNA workflow.

# Activate the tinyrna environment
 conda activate tinyrna
 
## (your commands here: tiny run, tiny-count, etc.)

# When you are done running tinyRNA, you can deactivate the conda environment
 conda deactivate

If you'd like to jump right in and start using tinyRNA, see our
👉 tutorial 👈

You can execute the workflow in its entirety for a full end-to-end analysis pipeline, or you can execute individual steps on their own. In most cases you will use the command tiny for pipeline operations.

Configuration Files

The pipeline requires that you identify:

  • Your preferences for the pipeline and its steps via the Run Config
  • The location of your config files and other file inputs via the Paths File
  • Your selection preferences for feature counting via the Features Sheet
  • Your samples via the Samples Sheet

[Configuration File Diagram]

For more information, please see the configuration file documentation. The START_HERE directory demonstrates a working configuration using these files. You can also get a copy of them by running the command:

tiny get-templates

Requirements for User-Provided Input Files

Input Type File Extension Requirements
Reference annotations
(example)
GFF3 / GFF2 / GTF Column 9 attributes (defined as "tag=value" or "tag value"):
  • Each feature must have an ID or gene_id or Parent tag (referred to as ID henceforth).
  • Discontinuous features must be defined with the Parent tag whose value is the logical parent's ID, or by sharing the same ID.
  • Attribute values containing commas must represent lists.
  • Parent tags with multiple values are not yet supported.
  • See the example link (left) for col. 9 formatting.
Sequencing data
(example)
FASTQ(.gz) Files must be demultiplexed.
Reference genome
(example)
FASTA Chromosome identifiers (e.g. Chr1):
  • Should match your reference annotation file chromosome identifiers
  • Are case sensitive

Running an End-to-End Analysis

In most cases you will use this toolset as an end-to-end pipeline. This will run a full, standard small RNA sequencing data analysis according to your configuration file. Before starting, you will need the following:

  1. High-throughput sequencing data in fastq format.
  2. The genome sequence of interest in fasta format.
  3. Genome coordinates of small RNA features of interest in GFF format.
  4. A completed Samples Sheet (samples.csv) with paths to the fastq files.
  5. A completed Features Sheet (features.csv) with feature selection rules.
  6. An updated Paths File (paths.yml) with paths to your GFF files, the genome sequence and/or your bowtie index prefix, as well as the paths to samples.csv and features.csv.
  7. A Run Config file (run_config.yml) located in your working directory or the path to the file. The template provided does not need to be updated if you wish to use the default settings.

To run an end-to-end analysis, be sure that you're working within the conda tinyrna environment (instructions above) in your terminal and optionally navigate to the location of your Run Config file. Then, simply run the following in your terminal:

tiny run --config run_config.yml

Resuming an End-to-End Analysis

The tiny-count and tiny-plot steps offer a wide variety of options for refining your analysis. You might find that repeat analyses are required while tuning these options to your goals. To save time and skip redundant compute-heavy preprocessing steps, you can resume a prior analysis using its outputs from the early pipeline steps.

# Resume a prior analysis at the tiny-count step
tiny recount --config processed_run_config.yml

# Resume a prior analysis at the tiny-plot step
tiny replot --config processed_run_config.yml

For more information and prerequesites, see the pipeline resume documentation.

CWL-Wrapped Third Party Tools.

fastp, bowtie-build, and bowtie can be run from the terminal (within the tinyRNA conda environment) just as you would if they were installed in the host environment. Normally, tinyRNA will handle the execution of these tools for you, but if you would like to run them as individual steps you may find that their commandline arguments can be lengthy. With a little setup you can make things easier for yourself by using our CWL wrappers and a configuration file for each tool. This allows you to more easily set commandline parameters from a text editor and reuse configuration files. See the pipeline documentation for details.

Workflow Steps

See the current workflow diagram for a bird's eye view of the workflow.

tiny-config

At the beginning of pipeline execution, tinyRNA digests your configuration files and produces a processed Run Config which determine's how the CWL runner, cwltool, directs the workflow. If you would like to produce a processed Run Config without running the rest of the pipeline, you can do so with the command tiny-config --input-file your_run_config.yml. This is useful if you wish to use an alternative CWL runner. In most circumstances you will not need to use this command.

fastp

fastp is used to trim adapters and remove poor quality reads from FASTQ input files. Summary and quality statistics reports are generated for each library.

tiny-collapse

After quality filtering, unique sequences are counted in each library and a FASTA file is produced which contains only these unique sequences and their counts. This "collapsing" process significantly reduces the resource demands of genomic alignment and feature counting. tiny-collapse can also trim the degenerate bases often included in the adapter sequences used in library preparation.

bowtie

Genomic alignment of collapsed reads is performed by bowtie.

tiny-count

At the core of tinyRNA is tiny-count, a highly flexible counting utility that allows for hierarchical assignment of small RNA reads to features based on positional information, extent of feature overlap, 5’ nucleotide, length, and strandedness. The parameters of selection are defined in the Features Sheet.

Full documentation for tiny-count can be found here.

Feature Selection Diagram

tiny-deseq.r

A wrapper R script for DESeq2 facilitates DGE analysis of counted sample files.

tiny-plot

The results of feature counting and DGE analysis are visualized with high resolution plot PDFs. User-defined plot styles are also supported via a Matplotlib style sheet.

Full documentation for tiny-plot can be found here.

Outputs

The files produced by each pipeline step are included in the final output directory where they are organized into subdirectories by step.

Data Pre-Processing

fastp is used to trim adapters and remove poor quality reads from FASTQ input files. Summary and quality statistics reports are generated for each library. These reports are used to calculate the pipeline summary statistics for total reads and retained reads.

Collapsed FASTA files

A "collapsed" FASTA contains unique reads found in fastp's quality filtered FASTQ files. Each header indicates the number of times that sequence occurred in the input. This allows for faster bowtie alignments while preserving counts for downstream analysis.

Counts and Pipeline Statistics

The tiny-count step produces a variety of outputs

Feature Counts

Custom Python scripts and HTSeq are used to generate a single table of feature counts which includes each counted library. Each matched feature is represented with the following metadata columns:

  • Feature ID is determined, in order of preference, by one of the following GFF column 9 attributes: ID, gene_id, Parent.
  • Classifier is determined by the rules in your Features Sheet. It is the Classify as... value of each matching rule. Since multiple rules can match a feature, some Feature IDs will be listed multiple times with different classifiers.
  • Feature Name displays aliases of your choice, as specified in the alias key under each GFF listed in your Paths File. If alias is set to ID, the Feature Name column is left empty.

For example, if your Paths File has a GFF entry which specifies alias: [sequence_name], and the corresponding GFF file has a feature with the following attributes column:

... ID=406904;sequence_name=mir-1,hsa-miR-1; ...

And this feature matched a rule in your Features Sheet defining Classify as... miRNA, then the entry for this feature in the final counts table would read:

Feature ID Classifier Feature Name Group1_rep_1 Group1_rep_2 ...
406904 miRNA hsa-miR-1, mir-1 1234 999 ...

Normalized Counts

If your Samples Sheet has settings for Normalization, an additional copy of the Feature Counts table is produced with the specified per-library normalizations applied. Note that these normalizations are unrelated to normalization by genomic/feature hits.

Counts by Rule

This table shows the counts assigned by each rule on a per-library basis. It is indexed by the rule's corresponding row number in the Features Sheet, where the first non-header row is considered row 0. For convenience a Rule String column is added which contains a human friendly concatenation of each rule. Finally, a Mapped Reads row is added which represents each library's total read counts which were available for assignment prior to counting/selection.

Alignment Statistics

A single table of alignment statistics includes columns for each library and the following stats:

Stat Description
Total Assigned Reads Counts from sequences that aligned to at least one feature in your Features Sheet
Total Unassigned Reads Total counts for sequences that didn't align to any features in your Features Sheet
Total Assigned Sequences Unique sequences that aligned to at least one feature in your Features Sheet
Total Unassigned Sequences Total unique sequences that didn't align to any features in your Features Sheet
Assigned Single-Mapping Reads Counts from sequences mapping to a single genomic locus and aligning to at least one feature in your Features Sheet
Assigned Multi-Mapping Reads Counts from sequences mapping to multiple genomic loci that aligned to at leats one feature in your Features Sheet
Reads Assigned to Single Feature Counts from sequences that aligned to a single feature in your Features Sheet
Sequences Assigned to Single Feature Unique sequences that aligned to a single feature in your Features Sheet
Reads Assigned to Multiple Features Counts from sequences that aligned to multiple features in your Features Sheet
Sequences Assigned to Multiple Features Unique sequences that aligned to multiple features in your Features Sheet

Summary Statistics

A single table of summary statistics includes columns for each library and the following stats:

Stat Description
Total Reads Total reads represented in FASTQ input files
Retained Reads Total reads passing quality filtering
Unique Sequences Total unique sequences passing quality filtering
Mapped Sequences Total genome-mapping sequences passing quality filtering
Mapped Reads Total genome-mapping reads passing quality filtering prior to counting/selection
Assigned Reads Total genome-mapping reads passing quality filtering that were assigned to at least one feature due to a rule match in your Features Sheet

When normalization by feature and/or genomic hits is disabled, the following stats are reported instead of Mapped Reads:

Stat Description
Normalized Mapped Reads The true mapped read count
Non-normalized Mapped Reads The sum of assigned and unassigned reads according to the normalization settings

5'nt vs. Length Matrix

During counting, size and 5' nt distribution tables are created for each library. The distribution of lengths and 5' nt can be used to assess the overall quality of your libraries. This can also be used for analyzing small RNA distributions in non-model organisms without annotations.

Two tables are produced:

  • ... mapped_nt_len_dist.csv: full counts from all mapped sequences regardless of feature assignment
  • ... assigned_nt_len_dist.csv: only the assigned counts for sequences receiving feature assignment

Diagnostics

Diagnostic information can optionally be produced. If enabled, tiny-count will provide a table for each library which contains feature assignment info on a per-alignment basis, along with a single table that summarizes unassigned counts.

The alignment tables (... alignment_table.csv) include the following information per-alignment:

Column Description
Sequence The read sequence, reverse complemented if antisense
Raw Count The sequence's original read count
Normalized Count The reads available for assignment to features (the sequence's original read count optionally normalized by genomic hits)
Genomic Hits The number of alignments produced for the sequence
Chrom The alignment's RNAME field
Strand The alignment's strand
Start The alignment's 1-based start coordinate
End The alignment's 1-based end coordinate (closed interval)
Mismatches The alignment's reported mismatches between the query sequence and the reference
Candidates The number of features overlapping the alignment by at last one nucleotide
Feature Hits The feature ID and assigning rule's classifier for all features assigned to the alignment, formatted as (feature_id, classifier); (...). If the match was made by an unclassified rule then classifier is left empty. If no features were assigned the cell is left blank.
Feature Aliases The user-defined aliases for all features assigned to the alignment, formatted as (alias1, alias2, ...); (...) where the index of each alias grouping matches the index of the corresponding feature in the Feature Hits column. If a feature has no aliases then () is reported.

The unassigned counts table (assignment_diags.csv) includes the following, with a column per library:

Stat Description
Uncounted alignments The number of alignments that did not receive any feature assignments. This stat has two entries, one for each strand.
No feature counts The total unassigned counts due to alignments that failed to overlap any features
Eliminated counts The total unassigned counts due to alignments whose candidate features were ALL eliminated because they failed to match any selection rules

Differential Expression Analysis

DGE is performed using the DESeq2 R package. Our wrapper script reports differential expression tables for your experiment design, and a table of normalized feature counts. If your control condition is indicated in your Samples Sheet then pairwise comparisons will be made against the control. If a control condition is not indicated then all possible bidirectional pairwise comparisons are made.

Plots

Simple static plots are generated from the outputs of tiny-count and tiny-deseq.r. These plots are useful for assessing the quality of your experiment design and the quality of your libraries. The available plots are:

  • len_dist: A stacked barchart showing size & 5' nucleotide distribution; one output for mapped reads and one for assigned reads.
  • rule_charts: A barchart showing percentages of counts per rule.
  • class_charts: A barchart showing percentages of counts per class.
  • replicate_scatter: A scatter plot comparing replicates for all count files given.
  • sample_avg_scatter_by_dge: A scatter plot comparing all sample groups, with differentially expressed small RNAs highlighted based on P value cutoff.
  • sample_avg_scatter_by_dge_class: A scatter plot comparing all sample groups, with classes highlighted for differentially expressed small RNAs based on P value cutoff.
len_dist 16-32

len_dist
PCA plot by DESeq2
dge_pca_plot
rule_chart with 10 rules

rule_charts
class_chart with 8 classes

class_charts
sample_avg_scatter_by_dge_class

sample_avg_scatter_by_dge_class
sample_avg_scatter_by_dge

sample_avg_scatter_by_dge

tiny-deseq.r will produce a standard PCA plot from variance stabilizing transformed feature counts. This output is controlled by the dge_pca_plot key in the Run Config and by your experiment design. DGE outputs, including the PCA plot, will not be produced for experiments with less than 1 degree of freedom.

Reducing Storage Usage

The files produced by certain steps can be very large and after several runs this may present significant storage usage. You can remove the following subdirectories from a Run Directory to free up space, but you will no longer be able to perform recount analyses within it (i.e. tiny recount):

  • fastp (though we recommend keeping the reports)
  • collapser
  • bowtie

Cleanup commands will be added to tinyRNA in a future release, but for now the following command will remove commonly large files while preserving report files:

# Execute within the Run Directory you want to clean
rm {fastp/*.fastq,{tiny-collapse,bowtie}/*.fa,bowtie/*.sam}

Citation

Tate, A. J., Brown, K. C., & Montgomery, T. A. (2023). tiny-count: A counting tool for hierarchical classification and quantification of small RNA-seq reads with single-nucleotide precision. Bioinformatics Advances. https://doi.org/10.1093/bioadv/vbad065

Contributing

See the CONTRIBUTING.md for guidelines. To see what is actively being worked or planned go to the projects tab or the issues tab.

Authors

  • Alex Tate - 01/2021-present - Colorado State University - AlexTate
  • Kristen Brown - 2018-2019 - Colorado State University - biokcb

See also the list of contributors who participated in this project.

License

This project is licensed under the GPLv3 license (along with HTSeq, bowtie). License - see the LICENSE.md file for details

About

tinyRNA provides an all-in-one solution for precision analysis of sRNA-seq data. At the core of tinyRNA is a highly flexible counting utility, tiny-count, that allows for hierarchical assignment of reads to features based on positional information, extent of feature overlap, 5’ nucleotide, length, and strandedness.

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