TCGA data rsem

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arash nabbi

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May 19, 2015, 1:49:15 PM5/19/15
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Dear All,

I am very new into this. I am analyzing TCGA data to see the differential expression of a specific gene across samples. I downloaded both rsem.genes.results and rsem.normalized.results. There are many different opinions on this. Which one can I use to do the analysis? There is raw_count and scaled_estimate. From what I read, raw_count can be used as input in edgeR. But scaled_estimate is like transcripts per million and therefore can be used directly with no transformation. And also, I can not use normalized_count to compare across samples, but again I see many papers do a log2 transformation on normalized_count and use that....

I am pretty confused.
Please help
Thanks
Arash

Ning Leng

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May 19, 2015, 1:54:18 PM5/19/15
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Hi Arash,
I believe you'll need to input the raw count into edgeR. The log2 transformed normalized expression are more widely used for visualization purposes.
Hope this is helpful.
Best,
Ning

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RSEM website: http://deweylab.biostat.wisc.edu/rsem/
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Ning Leng, Ph.D
Computational Biologist / Biostatistician
Regenerative Biology Laboratory
Morgridge Institute for Research

Arash Nabbi

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May 19, 2015, 2:02:10 PM5/19/15
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Thanks Ning,

The problem is when I do log2 there is very little difference across samples (7.8 vs 8.1). Is this something I should expect after transformation? When I do z-score (with reference population being normal tissue), the difference is pretty significant, but it is hard to graph it. So I do not know what I should report

Arash

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