Question: ChromHMM Output Descriptions
1
gravatar for Sinji
15 months ago by
Sinji2.5k
UT Southwestern Medical Center
Sinji2.5k wrote:

I've been doing some work that involves characterizing potential chromatin states in a HCT116 cell model. I've successfully been able to run ChromHMM to identify chromatin states using a variety of histone markers and then overlap them with other datasets in order to double-check their annotation.

However, I am having a problem understanding some of the output files that ChromHMM automatically generates. Specifically _emissions.txt and _*.bed. I know there's a couple of people here that are really familiar with the software and could probably help me out.

I have already searched google, and read the ChromHMM manuscript, but neither provided answers.

chromhmm • 835 views
ADD COMMENTlink modified 15 months ago by Ryan Dale4.6k • written 15 months ago by Sinji2.5k
2
gravatar for Ryan Dale
15 months ago by
Ryan Dale4.6k
Bethesda, MD
Ryan Dale4.6k wrote:

The _emissions.txt are the values that go into the _emissions.png figures. Each row is a state, each column is an input data file ("mark" or histone mark in the terminology of ChromHMM). Darker blue indicates a higher likelihood of finding that mark in that state. These, combined with running OverlapEnrichment with biologically meaningful datasets, are critical for figuring out how to interpret the states.

The segments.bed file partitions the genome into contiguous segments, and the names of each feature in that file (E1, E2, etc) correspond to the states (1, 2, etc) in the _emissions.png.

A typical workflow is to figure out what to label each state. Then choose some colors and post-process the BED file with labels and names to get something more useful for downstream analysis.

ADD COMMENTlink written 15 months ago by Ryan Dale4.6k

Appreciate the information!

Do the emission values go directly on the png, or do they first have to be modified in some way? I have some values of 0.02 as an example, but a 6 in others. Would the 0.02 be treated as a 0?

ADD REPLYlink modified 15 months ago • written 15 months ago by Sinji2.5k

Not sure if they're normalized in some way. To figure that out, you need to read the source code or try to reproduce the png given the txt file (and see what, if any, normalization needs to happen). Given the lack of a colormap though, my guess would be that each emissions.txt file is divided by the max of that file.

ADD REPLYlink written 15 months ago by Ryan Dale4.6k

How to figure out the label of each state? I got the output of chromHMM,but can't find the annotation information of each state?Tanks

ADD REPLYlink written 11 weeks ago by weixiaoyu0

The label of each state is subjective. Coming up with good labels requires looking carefully at the enrichments (from running OverlapEnrichment) and emissions heatmaps to decide what you want to name them.

ADD REPLYlink written 10 weeks ago by Ryan Dale4.6k
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