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Hic format is an indexed binary format designed to permit fast random access to contact matrix heatmaps. The format was designed by the Aiden Lab at Baylor College of Medicine. More information on the hic format itself can be found in the documentation on Github.
The format is used for displaying chromatin conformation data in the browser. This format is useful for displaying interactions at a scale and depth that exceeds what can be easily visualized with the interact and bigInteract formats. After running a chromatin conformation experiment such as in situ Hi-C, researchers can pass their results through the Juicer pipeline to produce a hic file. Due to the large size of many of these files, UCSC is not able to support direct upload via our Custom Track interface. Instead, users should place their Hic files in a web-accessible space and enter the URL as a bigDataUrl. If you do not have access to a web-accessible server and need hosting space for your Hic files, please see the Hosting section of the Track Hub Help documentation.
The UCSC tools currently support hic versions 6-8. The hic track configuration help page describes hic display options.
The typical workflow for generating a hic custom track is this:
track type=hic name="My HIC" bigDataUrl=http://myorg.edu/mylab/my.hic
All options are placed in a single line separated by spaces (lines are broken only for readability here):
track type=hic bigDataUrl=http://... name=track_label description=center_label visibility=display_mode db=db
Note if you copy/paste the above example, you must remove the line breaks. Click here for a text version that you can paste without editing.
The track type and bigDataUrl are REQUIRED:
The remaining settings are OPTIONAL:
name track label # default is "User Track" description center label # default is "User Supplied Track" visibility full|dense|hide # default is hide (will also take numeric values 4|1|0) db genome database # e.g. hg19 for Human Feb. 2009 (GRCh37)
Note that hic tracks currently only support the full, dense, and hide visibility modes. The hic track configuration help page describes the hic track configuration page options.
In this example, you will create a custom track for a hic file that is already on a public internet server — data from an in situ Hi-C experiment on the HMEC cell line mapped to the hg19 assembly (Rao et al., 2014).
The line breaks inserted in the track line for readability must be removed before submitting this entry as a Custom Track. Click here for a text version you can paste without editing. The "browser" line above is used set the default view to a region of chromosome 21.
browser position chr21:32,000,000-35,000,000 track type=hic name="hic Example One" description="hic Ex. 1: in situ Hi-C on HMEC" db=hg19 visibility=dense bigDataUrl=http://hgdownload.soe.ucsc.edu/gbdb/hg19/bbi/hic/GSE63525_HMEC_combined.hic
Paste the "browser" line and "track" line into the custom track management page for the human assembly hg19 (Feb. 2009), then click the "submit" button. On the following page, click the "chr21" link in the custom track listing to view the hic track in the Genome Browser.
In this example, you will load a hub that has hic data described in a hub's trackDb.txt file. First, navigate to the Basic Hub Quick Start Guide and review an introduction to hubs.
Visualizing hic files in hubs involves creating three text files: hub.txt, genomes.txt, and trackDb.txt. The browser is passed a URL to the top-level hub.txt file that points to the related genomes.txt and trackDb.txt files. The trackDb.txt file contains stanzas for each track that outlines the details and type of each track to display, such as these lines for a hic file located at the bigDataUrl location:
track hic1 bigDataUrl http://http://hgdownload.soe.ucsc.edu/gbdb/hg19/bbi/hic/GSE63525_GM12878_insitu_primary+replicate_combined.hic shortLabel hic example longLabel This hic file shows in situ Hi-C data from Rao et al. (2014) on the GM12878 cell line type hic visibility dense
Note: there is now a
useOneFile on hub setting that allows the hub
properties to be specified in a single file. More information about this setting can be found on the
Genome Browser User Guide.
Here is a direct link to the trackDb.txt file to see more information about this example hub, and below is a direct link to visualize the hub in the browser, where this example hic file displays in dense mode alongside the other tracks in this hub. You can find more Track Hub hic display options on the Track Database (trackDb) Definition Document page.
If you would like to share your hic data track with a colleague, there are a couple of options. One method is to load your data track into the UCSC Genome Browser and then create a saved session by following the instructions here. If you are looking for a more automated method of sharing data, you may be interested to learn how to create a direct URL that loads custom data files. For a demonstration of this, see Example 6 on the custom tracks page.