Overview
Create a metadata “samplesheet.csv” for small RNAseq datasets.
Learn to use a “nextflow.config” file in the working directory to override Nextflow parameters (e.g., specify where to find the pipeline assets).
Learn how to prepare a PBS script to run the expression profiling of small RNAs against the reference miRBase database annotated microRNAs.
Preparing the pipeline inputs
The pipeline requires preparing at least 2 files:
Metadata file (samplesheet.csv) thatspecifies the name of the samples, location of FASTQ files ('Read 1' and ‘Read 2’), and strandedness (forward, reverse, or auto. Note: auto is used when the strandedness of the data is unknown)
PBS Pro script (launch_nf-core_RNAseq_QC.pbs) with instructions to run the pipeline
Nextflow.config - revision 2.3.1 of the nf-core/smrnaseq pipeline may not be able to identify the location of reference adapter sequences, thus, we will use a local nextflow.config file to tell Nextflow where to find the reference adapters necessary to trim the raw small_RNA-Seq data
A. Create the metadata file (samplesheet.csv):
Change to the data folder directory:
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cp /work/training/2024/smallRNAseq/scripts/create_nf-core_smallRNAseq_samplesheet.sh $HOME/workshop/2024-2/session6_smallRNAseq/data/human_disease |
Note: you could replace ‘$HOME/workshop/data’ with “.” A dot indicates ‘current directory’ and will copy the file to the directory where you are currently located
View the content of the script:
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cat create_nf-core_smallRNAseq_samplesheet.sh |
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NOTE: modify ‘read1_extension’ as appropriate for your data. For example: _1.fastq.gz or _R1_001.fastq.gz or _R1.fq.gz , etc
Let’s generate the metadata file by running the following command:
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Copy the PBS Pro script for running the full small RNAseq pipeline (launch_nf-core_smallRNAseq_miRBase.pbs)
Copy and paste the code below to the terminal:
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cp $HOME/workshop/2024-2/session6_smallRNAseq/data/human_disease/samplesheet.csv $HOME/workshop/2024-2/session6_smallRNAseq/runs/run1_human_miRBase cp /work/training/2024/smallRNAseq/scripts/launch_nf-core_smallRNAseq_miRBase.pbs $HOME/workshop/2024-2/session6_smallRNAseq/runs/run1_human_miRBase cp /work/training/2024/smallRNAseq/scripts/nextflow.config $HOME/workshop/2024-2/session6_smallRNAseq/runs/run1_human_miRBase cd $HOME/workshop/2024-2/session6_smallRNAseq/runs/run1_human_miRBase |
Line 1: Copy the samplesheet.csv file to the working directory
Line 2: Copy the launch_nf-core_smallRNAseq_human.pbs submission script to the working directory
Line 3: Copy the nextflow.config file from shared folder to my working directory.
Line 4: move to the working directory
View the content of the launch_nf-core_RNAseq_QC.pbs script:
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TIP: when running the nf-core/smrnaseq pipeline (release 2.3.1) the pipeline is not able to find the location of the reference adapter sequences for trimming of the raw small RNAseq pipeline, so we need to specify where to find the folder where the adapter sequences file is located. To do this, we prepare a “nextflow.config” file (see below). This file should be already in your working directory. Print the content as follows:
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Note: if a config file is placed in the working folder it can override parameters define by the global ~/.nextflow/config file or the config file define as part of the pipeline.
Submit the job to the HPC cluster:
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Note: the “mature_counts.csv” needs to be transposed prior running the statistical analysis. This can be done either user the R script or using a script called “transpose_csv.py”.
Let’s copy the transpose_csv.py script to the working folder:
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