This is a bit silly, eh. Every cell in your body does this kind of epigenetic modification, there are a whole host of factors whose only job is to methylate DNA. Furthermore, this is not really "altering DNA", the sequence doesn't change, this is just a way to mask gene expression - if you methylate cytosines near the promoter region of a gene, RNA polymerase has a harder time sitting down and transcribing the gene, reducing its expression.

Neurons do this, germ cells do this, immune cells do this, every cell in the body does this.

What's interesting here is the specific factor (Tet3), not the occurrence of epigenetic modification. The perils of science journalism, as usual.