Compute differentially expressed genes (Affymetrix probes) (workflow)

Workflow title

Compute differentially expressed genes (Affymetrix probes)

Provider

geneXplain GmbH

Workflow overview

Description

This workflow is designed to identify up-regulated, down-regulated and non-changed genes for experimental data with three and more data points for each experiment and control.  

As input, normalized data with Affymetrix probeset IDs can be submitted. Such normalized files are the output of the “Normalize data” procedure.

In the next step, p-values for up- and down-regulated probes are calculated for all probes using the “Up and Down Identification” analysis. This analysis applies Student’s T-test for p-value calculation, thus the number of data points should be at least three for each experiment and control. 

Simultaneously, the log fold change is calculated for each probeset ID, and as the result of this step, a table is produced in which both log fold change and p-value are assigned to each probeset ID. A histogram with log fold change distribution is calculated and generated as one of the output files.

In addition this table is filtered by several conditions in parallel applying the “Filter table” method, to identify up-regulated, down-regulated, and non-changed Affymetrix probeset IDs. The filtering criteria are set as follows:

For up-regulated probes: LogFoldChange>0.5 and -log_P_value_>3.

For down- regulated probes: LogFoldChange<-0.5 and -log_P_value_<-3.

For non-changed genes : LogFoldChange<0.002 and LogFoldChange>-0.002

The resulting tables of up-regulated, down-regulated, and non-changed Affymetrix probeset IDs are converted into a gene set via the “Convert table” method and annotated with additional information, gene descriptions, gene symbols, and species via “Annotate table”. Two tables are produced, one with Ensembl Gene IDs and one with Entrez IDs.

A new folder is generated as output containing Ensemble and Entrez gene tables for up-regulated, down-regulated, up- and down-regulated combined, and non-changed genes. After completion of the workflow, a script generates a report which gives a summary of the workflow output files.

Parameters

Experiment normalized

Control normalized

Species

Probe type

Results folder