Drop-seq pipeline

This workflow follows the steps outlined in the Drop-seq alignment cookbook from the McCarroll lab , except the default STAR aligner flags are –limitOutSJcollapsed 1000000 –twopassMode Basic. Additionally the pipeline provides the option to generate count matrices using dropEst.

  1. Copy your sequencing output to your workspace bucket using gsutil in your unix terminal.

    You can obtain your bucket URL in the dashboard tab of your Terra workspace under the information panel.


    Note: Broad users need to be on an UGER node (not a login node) in order to use the -m flag

    Request an UGER node:

    reuse UGER
    qrsh -q interactive -l h_vmem=4g -pe smp 8 -binding linear:8 -P regevlab

    The above command requests an interactive node with 4G memory per thread and 8 threads. Feel free to change the memory, thread, and project parameters.

    Once you’re connected to an UGER node, you can make gsutil available by running:

    reuse Google-Cloud-SDK

    Use gsutil cp [OPTION]... src_url dst_url to copy data to your workspace bucket. For example, the following command copies the directory at /foo/bar/nextseq/Data/VK18WBC6Z4 to a Google bucket:

    gsutil -m cp -r /foo/bar/nextseq/Data/VK18WBC6Z4 gs://fc-e0000000-0000-0000-0000-000000000000/VK18WBC6Z4

    -m means copy in parallel, -r means copy the directory recursively.

  2. Non Broad Institute users that wish to run bcl2fastq must create a custom docker image.

    See bcl2fastq instructions.

  3. Create a sample sheet.

    Please note that the columns in the CSV must be in the order shown below and does not contain a header line. The sample sheet provides either the FASTQ files for each sample if you’ve already run bcl2fastq or a list of BCL directories if you’re starting from BCL directories. Please note that BCL directories must contain a valid bcl2fastq sample sheet (SampleSheet.csv):

    Column Description
    Name Sample name.
    Read1 Location of the FASTQ file for read1 in the cloud (gsurl).
    Read2 Location of the FASTQ file for read2 in the cloud (gsurl).

    Example using FASTQ input files:


    Note that in this example, sample-1 was sequenced across two flowcells.

    Example using BCL input directories:


    Note that the flow cell directory must contain a bcl2fastq sample sheet named SampleSheet.csv.

  4. Upload your sample sheet to the workspace bucket.


    gsutil cp /foo/bar/projects/sample_sheet.csv gs://fc-e0000000-0000-0000-0000-000000000000/
  5. Import dropseq_workflow workflow to your workspace.

    See the Terra documentation for adding a workflow. The dropseq_workflow is under Broad Methods Repository with name “cumulus/dropseq_workflow”.

    Moreover, in the workflow page, click the Export to Workspace... button, and select the workspace you want to export dropseq_workflow workflow in the drop-down menu.

  6. In your workspace, open dropseq_workflow in WORKFLOWS tab. Select Process single workflow from files as below


    and click the SAVE button.


Please see the description of important inputs below.

Name Description
input_csv_file CSV file containing sample name, read1, and read2 or a list of BCL directories.
output_directory Pipeline output directory (gs URL e.g. “gs://fc-e0000000-0000-0000-0000-000000000000/dropseq_output”)
reference hg19, GRCh38, mm10, hg19_mm10, mmul_8.0.1 or a path to a custom reference JSON file
run_bcl2fastq Whether your sample sheet contains one BCL directory per line or one sample per line (default false)
run_dropseq_tools Whether to generate count matrixes using Drop-Seq tools from the McCarroll lab (default true)
run_dropest Whether to generate count matrixes using dropEst (default false)
cellular_barcode_whitelist Optional whitelist of known cellular barcodes
drop_seq_tools_force_cells If supplied, bypass the cell detection algorithm (the elbow method) and use this number of cells.
dropest_cells_max Maximal number of output cells
dropest_genes_min Minimal number of genes for cells after the merge procedure (default 100)
dropest_min_merge_fraction Threshold for the merge procedure (default 0.2)
dropest_max_cb_merge_edit_distance Max edit distance between barcodes (default 2)
dropest_max_umi_merge_edit_distance Max edit distance between UMIs (default 1)
dropest_min_genes_before_merge Minimal number of genes for cells before the merge procedure. Used mostly for optimization. (default 10)
dropest_merge_barcodes_precise Use precise merge strategy (can be slow), recommended to use when the list of real barcodes is not available (default true)
dropest_velocyto Save separate count matrices for exons, introns and exon/intron spanning reads (default true)
trim_sequence The sequence to look for at the start of reads for trimming (default “AAGCAGTGGTATCAACGCAGAGTGAATGGG”)
trim_num_bases How many bases at the beginning of the sequence must match before trimming occur (default 5)
umi_base_range The base location of the molecular barcode (default 13-20)
cellular_barcode_base_range The base location of the cell barcode (default 1-12)
star_flags Additional options to pass to STAR aligner

Please note that run_bcl2fastq must be set to true if you’re starting from BCL files instead of FASTQs.

Custom Genome JSON

If you’re reference is not one of the predefined choices, you can create a custom JSON file. Example:

        "refflat":        "gs://fc-e0000000-0000-0000-0000-000000000000/human_mouse/hg19_mm10_transgenes.refFlat",
        "genome_fasta":    "gs://fc-e0000000-0000-0000-0000-000000000000/human_mouse/hg19_mm10_transgenes.fasta",
        "star_genome":    "gs://fc-e0000000-0000-0000-0000-000000000000/human_mouse/STAR2_5_index_hg19_mm10.tar.gz",
        "gene_intervals":        "gs://fc-e0000000-0000-0000-0000-000000000000/human_mouse/hg19_mm10_transgenes.genes.intervals",
        "genome_dict":    "gs://fc-e0000000-0000-0000-0000-000000000000/human_mouse/hg19_mm10_transgenes.dict",
        "star_cpus": 32,
        "star_memory": "120G"

The fields star_cpus and star_memory are optional and are used as the default cpus and memory for running STAR with your genome.


The pipeline outputs a list of google bucket urls containing one gene-count matrix per sample. Each gene-count matrix file produced by Drop-seq tools has the suffix ‘dge.txt.gz’, matrices produced by dropEst have the extension .rds.

Building a Custom Genome

The tool dropseq_bundle can be used to build a custom genome. Please see the description of important inputs below.

Name Description
fasta_file Array of fasta files. If more than one species, fasta and gtf files must be in the same order.
gtf_file Array of gtf files. If more than one species, fasta and gtf files must be in the same order.
genomeSAindexNbases Length (bases) of the SA pre-indexing string. Typically between 10 and 15. Longer strings will use much more memory, but allow faster searches. For small genomes, must be scaled down to min(14, log2(GenomeLength)/2 - 1)

dropseq_workflow Terra Release Notes

Version 6

  • Added star_extra_disk_space and star_disk_space_multiplier workflow inputs to adjust disk space allocated for STAR alignment task.

Version 5

  • Split preprocessing steps into separate tasks (FastqToSam, TagBam, FilterBam, and TrimBam).

Version 4

  • Handle uncompressed fastq files as workflow input.
  • Added optional prepare_fastq_disk_space_multiplier input.

Version 3

  • Set default value for docker_registry input.

Version 2

  • Added docker_registry input.

Version 1

  • Renamed sccloud to cumulus
  • Added use_bases_mask option when running bcl2fastq

Version 18

  • Created a separate docker image for running bcl2fastq

Version 17

  • Fixed bug that ignored WDL input star_flags (thanks to Carly Ziegler for reporting)
  • Changed default value of star_flags to the empty string (Prior versions of the WDL incorrectly indicated that basic 2-pass mapping was done)

Version 16

  • Use cumulus dockerhub organization
  • Changed default dropEst version to 0.8.6

Version 15

  • Added drop_deq_tools_prep_bam_memory and drop_deq_tools_dge_memory options

Version 14

  • Fix for downloading files from user pays buckets

Version 13

  • Set GCLOUD_PROJECT_ID for user pays buckets

Version 12

  • Changed default dropEst memory from 52G to 104G

Version 11

  • Updated formula for computing disk size for dropseq_count

Version 10

  • Added option to specify merge_bam_alignment_memory and sort_bam_max_records_in_ram

Version 9

  • Updated default drop_seq_tools_version from 2.2.0 to 2.3.0

Version 8

  • Made additional options available for running dropEst

Version 7

  • Changed default dropEst memory from 104G to 52G

Version 6

  • Added option to run dropEst

Version 5

  • Specify full version for bcl2fastq ( instead of

Version 4

  • Fixed issue that prevented bcl2fastq from running

Version 3

  • Set default run_bcl2fastq to false
  • Create shortcuts for commonly used genomes

Version 2

  • Updated QC report

Version 1

  • Initial release

dropseq_bundle Terra Release Notes

Version 3

  • Added extra disk space inputs
  • Fixed bug that prevented creating multi-genome bundles

Version 2

  • Added docker_registry input

Version 1

  • Renamed sccloud to cumulus

Version 1

  • Changed docker organization

Version 1

  • Initial release