Reusable in-situ sequencing analysis workflow orchestrated by Nextflow

Nextflow workflow for the automated creation of a transcript map from ISS image data.

Installation instructions for Your Repository

Follow these steps to set up and install the necessary environment and dependencies for your project.

Prerequisites

Ensure you have the following installed on your system:

• Git (for cloning the repository)

Clone the Repository

Clone the project repository from GitHub to your machine.

git clone https://github.com/embl-cba/iss-nf.git

How to run the code

1. Prepare Your Dataset

To run the workflow you need the following data:

• Image data with naming scheme: r<Round>_<Channel>.tiff, with
  • <Round>: one-based integer
  • <Channel>: free text without spaces
  • Example: r1_DAPI.tiff
• Codebook: codebook.json, as defined by StarFISH
• Experimental metadata: experimental_metadata.json

Example data

• Mouse brain dataset
  • Image data, codebook and metadata (~11 GB) are available for download on Zenodo.
    • Codebook and metadata are also available in this repo.
    • The original data can be found on the BioImage Archive.

2. Modify the configuration files

• Update the Input Directory: In the nextflow.config file, locate the INPUTDIR variable and set it to the path of your dataset.

  INPUTDIR = "/path/to/your/dataset"

• Prepare the codebook: The workflow uses a codebook.json file that should be readable by the STARFISH library. Use our default format as a guide when preparing your own codebook.

  Important note: For automated threshold finding, the algorithm expects 10-20% of your gene panel to consist of empty barcodes. These empty barcodes should be added at the bottom of your codebook.json.

• Modify the metadata: You’ll also need to update the experiment_metadata.json file. This file contains metadata about your dataset. Modify it to reflect the specifics of your data (e.g., number of rounds, channels, etc.).

3. Load nextflow

To run the workflow, you need to install Nextflow. After installation, your Nextflow environment needs to be activated, e.g., using conda:

conda activate nextflow

On a computer cluster, it may be possible to access nextflow via easy-build modules:

module load Nextflow

4. Run the workflow

Once you’ve updated your configuration files and loaded Nextflow, you can execute the workflow using the following command in your terminal:

nextflow run nf_workflow.nf -profile apptainer 

Troubleshooting

You are welcome to ask us by writing an issue.