Browser Extended Display Format. We have demonstrated that rtracklayer is an effective tool for manipulating and visualizing genomic annotations in the context of experimental data analysis. The final step in this example is to display a view around the target site associated with the most upregulated gene, DCN, encoding a glycoprotein thought to regulate muscle formation. High-throughput experiments often produce measurements that are associated with genomic locations. Currently, the UCSC genome browser is supported. This last command opens a web browser and loads the UCSC genome browser, with a view resembling the one in Figure 1.


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However, it could serve as a basis for GUI. Below, we create an equivalent RangedData track. Published online May Thus, the ability to access, manipulate and visualize genomic features is an important feature of any environment for experimental data analysis.

rtracklayer: an R package for interfacing with genome browsers

The GenomeGraphs package draws genomic annotations using static R graphics. The user may then fully interact with the browser; its behavior is the same as when accessing it directly.

As rtracklayer is extensible, we plan to implement support for additional browsers. The genomic visualization produced by the UCSC rtrackayer browser by the rtracklayer example.


One may also download track information from the browser, such as the conservation scores. Such graphics provide the analyst with rtracmlayer overview of the sequence-level relationships between genomic annotations. The rest of this article will demonstrate the features of rtracklayer on a microarray dataset from a larger research project investigating the regulation of human stem cell differentiation by microRNAs.


As an aside, we could export the track as a WIG file for use in other tools, then read it back into R. Browser Extended Display Rtrac,layer.


We begin our demonstration by constructing an annotation dataset from the experimental data, and then illustrate the use of the genome browser interface to display specific genomic regions in the UCSC browser.

To reproduce this, enter demo targets in R after loading rtracklayer. Here, only the data in the currently viewed region are retrieved; more control is provided by the track function. In preparation for creating the microRNA target track, we first used a number of Bioconductor packages to detect the genes in the microarray experiment with significantly increased expression. To view the tracks in a genome browser, we first create an instance of browserSession for a specific external browser.

There were two chips for each of the two time points. The browserSession instance serves as a container of tracks, as well as an interface for creating views of specific segments of the genome.

We will now visually explore the genomic annotation space around the differentially expressed genes that are thought to be microRNA targets.

Bioconductor – rtracklayer

The final step in this example is to display a view around the target site associated with the most upregulated gene, DCN, encoding a glycoprotein thought rttracklayer regulate muscle formation.


Please review our privacy policy. For the analysis of the stem cell microarray data, we are interested in the genomic regions corresponding to differentially expressed genes that are predicted to be targeted by a microRNA.

The rtracklayer package supports the integration of existing genome browsers with experimental data analyses performed in R. The transcriptome of the cells was measured before and after differentiation by HG-Uplus2 Affymetrix GeneChip arrays. All displayed annotations must be downloaded and stored on the local machine. From such an overview, the analyst might make inferences across genomic rtracklxyer sources.


We would like to thank Dr Muneesh Tewari for helpful discussions and the gene expression data. The interface has two rtrcklayer functions: We wish to display the entire track, along with some context on either side.

rtracklayer: R interface to genome annotation files and the UCSC genome browser

An example of how genome browsers draw annotation tracks is given in Figure 1. These regions may be represented by a collection of genomic annotations known as a trackwhich is viewable in a genome browser. This article has been cited by other articles in PMC.

Information about the target sites on differentially expressed genes was stored in the data.