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Pathway analysis

The possibility that a single miRNA could potentially control several genes, opens a new perspective of analyzing post-transcriptional gene regulation. Pathway analysis is a powerful technique that allow to determine globally controlled processes by a single or by a combination of miRNAs. In this tutorial we will learn how to use pathway analysis to predict the possible flow control of miR-21. For the analysis, we will use the miRpath server.


TUTORIAL

1.- In the main screen of the miRpath server, select the organism, the target prediction appplication and the microRNA for the pathway analysis. This home screen allow to select a single miRNA for the pathway analysis, however, you will be also able to analyze the combined effect of several miRNAs using the link at the bottom of the page (Multiple miRNA pathway analysis). For the tutorial we will select "human" for the organism, "Targetscan" for the application for predicting miRNA targets and the miR-21 for the final analysis. The output of the server will look like this :





The list include the name of the pathway, genes potentially targetted by miR-21 and a ranking score. The score is calculated on the basis of the number of potentially targetted genes and also the position of these genes within the pathway. Top scores mean a higher possibility of control by the selected miRNA. The pathway names are dynamic links that will redirect us to a graphical display of the pathway flow and the genes with putative targets for miR21 (see diagram below for the results on the TGF-beta signalling pathway).






Look at the putative targets within the context of the pathway represented (TGF-signalling pathway) and comment :

  • Possible role of miR-21 in the pathway.
  • Position of the putative genes controlled by miR-21 in the global pathway flow.
  • Connections with other pathways possibly involved in cancer.