Methylation / DNA Methylation

**What it means:** DNA methylation is an **epigenetic** process — it doesn't change the DNA sequence itself, but adds chemical "tags" (methyl groups) to the DNA that tell genes to be more or less active. Think of it like highlighter marks on a textbook — the words don't change, but the highlighted passages get read more often. **In MHS context:** The episignature paper identified a unique methylation pattern specific to MEF2C deficiency. This methylation pattern acts as a **biomarker** — a signature you can detect in a blood test to confirm or support an MEF2C diagnosis. This is potentially transformative for cases where genetic testing is ambiguous.