[annie123 (OP)]

Does anyone know how one can find out how much one's brain is methylated? Apparently brains of depressed people or those who have committed suicide are more methylated than others so it would be interesting to know how much one's own brain had been epigenetically affected because of life events.

[evan_au]

DNA methylation occurs in all cells in the body, and is an essential step in the development and specialisation of cells, as well as in in disease processes like cancer.

The effect of DNA methylation is to reduce the transcription of certain genes, which then impacts production of certain proteins, and regulation of other sections of DNA. It is possible that the reduction of one regulatory section of DNA could actually increase the production of a different protein.

It is likely that many disease states (including mental disorders) could reflect insufficient or excess production of certain proteins. But all cells in the body use methylation, so it would be more useful to discuss which genes are more methylated in a particular disease, rather than the overall degree of methylation. Discovering the link between transcription of certain genes and associated diseases seems a worthwhile area of research.

Some modern DNA sequencing methods are able to detect epigenetic markers like methylation - but this needs to be done on relevant tissues; the methylation of genes in a skin, muscle or gut cell is less likely to impact disorders like depression than DNA methylation of certain areas of the brain.
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[schneebfloob]

Bisulphite sequencing is used to look at DNA methylation. Bisulphite will convert cytosine bases into uracils which will become thymines in the next round of replication, but it cannot do this for methylated cytosines. DNA methylation occurs on cytosines, so if you sequence the DNA following bisulphite treatment you're only going to see those sites that are methylated. To do this for the brain specifically then you'd need to take the DNA you use from brain tissue, which perhaps you could compare with methylation in different tissues.