RNASeq Pipeline

The Databricks RNASeq pipeline handles short read alignment and quantification using STAR v2.6.1a and ADAM. v.0.25.0

Beta

The Azure Databricks RNASeq pipeline requires Databricks Runtime HLS, which is in Beta. Interfaces and pricing are subject to change before general availability.

Setup

The pipeline is run as an Azure Databricks job. Most likely, an Azure Databricks solutions architect will set up the initial job for you. The necessary details are:

  • The task should be the RNASeq notebook provided at the bottom of this page.
  • For best performance, use the compute optimized VMs with at least 60GB of memory. We recommend Standard_F32s_v2 VMs.

Parameters

The pipeline accepts a number of parameters that control its behavior. The most important and commonly changed parameters are documented here; the rest can be found in the RNASeq notebook. All parameters can be set for all runs or per-run.

Parameter Default Description
manifest n/a The path of the manifest file describing the input.
output n/a The path where pipeline output should be written.
replayMode skip

One of:

  • skip: stages are skipped if output already exists.
  • overwrite: existing output is deleted.

In addition, you must configure the reference genome using environment variables. To use Grch37, set the environment variable:

refGenomeId=grch37_star

To use Grch38 instead, set an environment variable like this:

refGenomeId=grch38_star

Walkthrough

The pipeline consists of two steps:

  1. Alignment: Map each short read to the reference genome using the STAR aligner.
  2. Quantification: Count how many reads correspond to each reference transcript.

Additional usage info and troubleshooting

The operational aspects of the RNASeq pipeline are very similar to the DNASeq pipeline. For more information about manifest format, output structure, programmatic usage, and common issues, see DNASeq Pipeline.