In a tiny country of just 320,000 people, scientists have begun to discover precisely how our DNA makes us who we are — and how it might turn on us.
This week, researchers used the complete genomes of 2,636 Icelanders, coupled with a trove of historical data and medical records, to create the most complete genetic map of a nation we’ve ever seen. (A genome is the complete set of a person’s genetic material.)
They also spotted several life-changing tweaks in those genes that apply to us all, including one that doubles the risk of developing Alzheimer’s and another that causes a disease that leads to heart palpitations.
Iceland is the perfect living laboratory for this kind of research.
Since Scandinavians first settled here more than 1,000 years ago, locals have kept detailed records on family relationships. Most people living in the country today can trace back their family history to one of those original northern settlers. Plus, so few people have immigrated to the country since then that the population has stayed pretty homogeneous — at least as far as genetic diversity goes.
Because the country has so little genetic variation, it means it’s much easier to zero in on what’s notable and pick out the specific gene variants that cause disease.
Icelandic neurologist Kari Stefansson had this in mind when he founded a company called deCODE in the mid-90s with the idea of mapping the the genetic information of everyone in the country.
Since then, more than a third of all Icelanders have given the company a cheek swab with a sample of their DNA — just enough to run a basic genetic test but not complex enough to see all the changes that can contribute to disease.
This new research, also done by researchers at his company, helps fill in some of the gaps left by these basic tests.
Starting with the 2,636 complete genomes (from people who chose to participate in the most recent study), they combined that information with the DNA samples from more than a third of the country’s residents. Finally, they added that to the country’s trove of 1,000-year-old genealogical records.
Then they picked out the stretches of genes people most commonly shared with close relatives and used those to make educated guesses about how the rest of the population’s genes would look.
Et voila! They came up with rough sketches of the genetic makeup of 101,584 more Icelanders — including people whose DNA had been sampled previously but who didn’t take part in the study.
In addition to their Icelandic gene map, the scientists pinpointed a couple of very important gene tweaks, or mutations, that can influence how likely we are to develop certain diseases.
For example, the researchers found a specific genetic mutation in a gene called ABCA7 (rolls right off the tongue, doesn’t it?) that doubles a person’s chances of developing Alzheimer’s.
While past studies have suggested this gene could raise the risk of getting the disease, this study was the first to confirm it by picking out the precise mutation that occurs. We still can’t tell exactly how the particular genetic tweak goes on to cause Alzheimer’s, but just spotting it is pretty groundbreaking, Stefansson said on a call with reporters.
The researchers also identified a specific gene mutation that causes atrial fibrillation, a kind of irregular heartbeat. (Of the 8 study participants who had the genetic tweak, all of them also had the condition.) In addition, the scientists either spotted or confirmed several changes that raise the risk of diabetes, heart disease, and gallstones.
All of the changes above affect how genes function. A tiny mutation here might prevent the production of a particular protein; another tweak there might cause that same protein to come out oddly-shaped.
But what about changes that stop genes from functioning altogether?
Scientists call these mutations knockouts — and for good reason. Genes that have been knocked out can’t do their jobs at all, sometimes dramatically raising our risk of certain illnesses or diseases, like cystic fibrosis. Of the Icelanders they studied, nearly 8% had a knockout.
For decades, researchers have studied how genes work in mice by inactivating, or knocking out, specific chunks of their DNA and then seeing what happens to them in the lab. We can’t ethically create knockouts in people (obviously), but we can find the ones that already exist. Then, we can pinpoint the roots of more genetic diseases and potentially create new treatments.
All of this represents a vastly different way of studying genes and disease than what scientists have been using for the past few decades.
Instead of taking a group of patients who have a certain disease, such as cystic fibrosis, and then looking through their genes for commonalities that may (or may not) affect the disease, the researchers first found the individuals with genetic tweaks, and then looked to see what diseases or illnesses they had.
“This approach completely turns the tables,” said Stefansson, and could be the shape of things to come.
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