A new study has investigated the relative effects of genetics, aging, and the environment on how 20,000 human genes are expressed. The researchers, led by the University of California, Berkeley, found that aging and the environment are far more important than genetic variation in affecting the expression profiles of many of our genes as we get older, leading to diseases such as diabetes or cancer.
“How do your genetics — what you got from your sperm donor and your egg donor and your evolutionary history — influence who you are, your phenotype, such as your height, your weight, whether or not you have heart disease?” asked study senior author Peter Sudmant, an assistant professor of Integral Biology at UC Berkeley.
“There’s been a huge amount of work done in human genetics to understand how genes are turned on and off by human genetic variation. Our project came about by asking, ‘How is that influenced by an individual’s age?’ And the first result we found was that your genetics actually matter less the older you get.”
Thus, while our individual genetic makeup can help predict gene expression when we are younger, it is less useful in predicting which genes are ramped up or down as we age. “Almost all human common diseases are diseases of aging: Alzheimer’s, cancers, heart disease, diabetes. All of these diseases increase their prevalence with age,” Professor Sudmant explained. “Massive amounts of public resources have gone into identifying genetic variants that predispose you to these diseases. What our study is showing is that, well, actually, as you get older, genes kind of matter less for your gene expression. And so, perhaps, we need to be mindful of that when we’re trying to identify the causes of these diseases of aging.”
These findings are in line with Medawar’s hypothesis, which argues that genes that are activated when we are young are more constrained by evolution since they are critical to making sure we will survive long enough to reproduce, while genes that are expressed after we reach reproductive age are under less evolutionary pressure.
“We’re all aging in different ways. While young individuals are closer together in terms of gene expression patterns, older individuals are further apart. It’s like a drift through time as gene expression patterns become more and more erratic,” Professor Sudmant concluded.
The study is published in the journal Nature Communications.
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