How to find MNI coordinates for gene expression zscore data

Technical
1

I am trying to pull data from the human gene microarray data and have successfully downloaded the the zscore data. The “Contents.txt” file that is downloaded with the data explains that the headers, “sample_mri_0, sample_mri_1, sample_mri_2 should be understood to be MRI coordinates of the sample in x,y,z order”. However the coordinates don’t seem to correspond to the MNI coordinate system. For example, a point identified in the structure “anterior orbital gyrus”, has coordinates 135, 102, 92, which is outside the MNI brain, assuming the 0,0,0 point is at the anterior commissure. Am I misunderstanding the coordinate system, or do I need to make some correction? When I visualize the data in BrainExplorer2, the coordinates look correct, so I feel like I am missig something.

2

Hi @axlander,

When you download the files from here here…
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…you should have a zip file that includes multiple files. In the file called “SampleAnnot.csv” there are TWO sets of coordinates for each sample: the MRI coordinates that you mention, alongside the MNI coordinates. I’m not sure what the MRI coordinates represent, but this should allow immediate translation between both sets of coordinates. If you need more, please reply and I can ask around.

Best,
Jeremy

3

Hi Jeremy.

Thanks for your response. When I download the zip file, it has 4 files enclosed: Columns.csv, Contents.csv, Expression.csv and Probes.csv, but no SampleAnnot.csv. The Columns file has 17 columns including the MRI coordinates (sample_mri_0, sample_mri_1, sample_mri_2) as well as some columns of donor info, and others of brain regions. But no other coordinates.

Any ideas?

Thanks,

Alex

4

Hi Alex,

The files you need to download are the six files circled below. I’m not sure why the file you downloaded is missing the MNI coordinates, but these files have it. Unless you care about the microarray data itself (which you will also be downloading), the only thing you’ll need in the zip files is “SampleAnnot.csv”.

Best,
Jeremy

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5

Hi Jeremy.

Thanks for the instructions for Dummies – I clearly need to work on my reading skills.

Alex