Cellular reprogramming

Changing a cell's identity or apparent age by switching on genes that reset which parts of its genome are active.

• Every cell carries the same DNA; its identity is set by epigenetic marks, chemical tags that keep some genes on and others off.
• Master regulator proteins can rewrite those marks, turning skin cells directly into neurons, or all the way back into stem cells.
• Resetting also rolls back molecular signs of ageing, such as epigenetic clock readings, suggesting age is partly a reversible state.
• In mice, repeated brief reprogramming improved some ageing measures; the risk is tumours from cells losing identity, and human benefit is unproven.