'Ageing atlas' reveals how time reshapes our genes

Scientists are building the clearest picture yet of how we age - right down to our cells and DNA

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The visible signs of ageing – wrinkles, greying hair, aching joints - are only the surface expression of something far more intricate happening inside our cells.

Beneath the surface, every organ in our bodies undergoes a subtle molecular transformation as we grow older.

Now, scientists have built the most comprehensive map yet of how that process unfolds.

Drawing on data from more than 15,000 samples, the findings - detailed in a preprint study awaiting peer review offer an unprecedented view of how ageing rewrites our genome's operating manual from head to toe.

Researchers from around the world teamed up to create a sweeping 'ageing atlas' that charts DNA methylation (chemical tags that regulate gene activity) across 17 types of human tissue, tracking changes as we grow older.

"DNA methylation, very simply, is a chemical modification on your DNA," Dr Jesse Poganik, an instructor in medicine at Harvard Medical School and one of the authors of the new study, told BBC Science Focus. “At the very basic level, the main function is to control which genes get expressed and which don't.”

Each of your cells has, essentially, the same genetic information in the form of your genome. Yet somehow, the cells in your lungs behave differently from those in your stomach, skin and brain. How do they know what to become and what to do? This is the role methylation performs.

“Depending on the methylation or unmethylation status of particular points on the genome, the expression of particular genes is turned on or off,” Poganik said.

"Scientists know methylation changes as people age, but they don't know whether those changes cause ageing or whether ageing causes those changes"