18 February 2013

episode

Health Report 28 min 2 speakers 8 chapters transcribed 14 hours ago

▲ 0

Transcript

jump: chapters · speakers · find in transcript

Transcript

Transcript generated automatically by AI and may contain errors.

What is a genome‑wide association study and why is it used in health research?

Norman Swann 0:00

Hello and welcome to the Health Report with me, Norman Swann. Today a mystery a sense of smell with a mind of its own.

Unknown 0:09

There it is again. What's that? Can you

Gretchen Miller 0:15

It's

Unknown 0:16

Gretchen Miller 0:16

it's gone. Never mind. It woke me the first time in the middle of the night when I Oh, I thought, in the darkness, that's weird. Some kind of bakery's started up nearby. Don't think much of it.

Norman Swann 0:34

Plus sleeping in your genes, the implications of having an Orcadian surname, and many of you do, and a salutary factor or two before you run off to get your genome mapped. The hunt for genes associated with our health and well being has been on for many years now, and in particular since the human genome was mapped, the genome being the DNA on our chromosomes. But it's still too expensive and slow to go fishing for genes by sequencing or decoding the DNA of every single one of them, which is why a technique called genome wide association studies have become popular. They're a much faster way to find neighborhoods or genes on our chromosomes which might be important in the search for causes of common problems and possibly new treatments for them.

Norman Swann 1:18

For example, research at the University of Oxford in the UK has found a new and surprising gene linked to the risk of stroke. They've also uncovered some frustrating news about an important vaccine. Professor Peter Donnelly is director of the Welcome Trust Center for Human Genetics at the University of Oxford, which is a world leader in genome wide association studies.

Peter Donnelly 1:39

There are large genetic studies where typically we would take if we're focusing on a particular disease, which might be heart disease or diabetes or schizophrenia, we take a lot of people who are sick with the disease, maybe two or three or four thousand of them, and measure their genomes, so their DNA, at a set of maybe half a million or a million positions. So our DNA is about three billion positions long. We'd measure a selected subset of that. We do the same in three or four or five or six thousand. And healthy people, and we look for differences in the variants between the sick people and the healthy people. If it works well, and many of these studies have been undertaken now and they have been quite successful, what they identify are genetic variants which change people's risk of a disease.

Peter Donnelly 2:19

Parts of the genome which matter for that disease, and then the next stage is to actually work out what's going on biologically, and through doing that, to get new insights into the biology of the diseases.

Norman Swann 2:29

Before we start that, we're going to talk about your study of a vaccine for pneumococcus, a common cause of pneumonia and meningitis.

Peter Donnelly 2:36

That's right. It's responsible, particularly in young children, for many millions of deaths around the world each year. In developed countries, vaccines have been developed which try and protect young children and have been very successful. The bacteria have a kind of capsule that protects them to coat. It's their coat, in effect, yes. So the vaccines which have been developed target those coats. And it's not possible to target all the possible coats. The vaccine makers have been selective. The initial vaccines And then we're going to be able to

Norman Swann 3:07

There have been a couple of issues about this. One is that have you knocked off those seven different types and then other dangerous forms of pneumococcus come in and filled the space in the ecosystem, if you like?

Peter Donnelly 3:17

Yes, and indeed broadly speaking that did occur. The vaccine created a space in the a niche in the ecology of these bugs so that other types were able to expand and fill that niche. And partly because of that there's been a subsequent vaccine introduced which targets an extra six of the types of bacteria.

Norman Swann 3:33

And you've been looking at how the bug itself responded to the vaccine.

Peter Donnelly 3:37

That's right. They do rather clever things. It wasn't a genome wide association study.

How did researchers discover a new gene linked to stroke risk?

Peter Donnelly 3:41

We read most of the genome of the bug. And it turns out that the bugs do clever things. So if you think of the analogy of the vaccine as being like a policeman that's able to spot baddies who are wearing particular kinds of coats, what some of the bugs did was to swap their coats with another version of the bug, which wasn't targeted by the vaccine and hence became invisible to the vaccine.