Nature Podcast

This is a transcript of the 19th March 2015 edition of the weekly Nature Podcast. Audio files for the current show and archive episodes can be accessed from the Nature Podcast index page (http://www.nature.com/nature/podcast), which also contains details on how to subscribe to the Nature Podcast for FREE, and has troubleshooting top-tips. Send us your feedback to mailto:podcast@nature.com.

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Geoff Marsh: This week, a simple solution to the myopia epidemic.

Ian Morgan: Give kids a lot more light exposure and help to bring myopia under control.

Kerri Smith: And science, say cheese.

Greg Hobson: These images are incredibly interesting because of the scientific information that's contained within them but also really exciting because of their beauty and their aesthetic properties.

Geoff Marsh: And finally the genetics of being British, marvellous, plus loads of other cool stuff, another awesome episode of the Nature Podcast. I'm Geoff Marsh.

Geoff Marsh: And I'm Kerri Smith.

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Geoff Marsh: We're all guilty of this, holding our phones too close to our faces or hunching over a lab bench or pouring deeply over books, especially during school but whilst your brain might love being filled with juicy, juicy knowledge, your eyeballs might be less grateful. In young people who are still growing, intense studying seems to throw the developments of their eyes out of kilter, causing them to elongate also known as myopia. That's why you can see objects close to you perfectly clearly but those at a distance fade into blurriness. East Asia is particularly badly hit. In several Chinese cities for example, 80% to 90% of teenagers are now myopic. A few decades ago it was only 10 to 20% but what exactly is it about too much studying that's causing this epidemic. Ian Morgan, a biologist from the Australian National University in Canberra thinks that the culprit is not the act of looking at books or screen per se but rather the associated lack of exposure to bright light. In a recent study in Guangzhou, China, Morgan tested his theory by simply boosting the amount of time children spent outside by 40 minutes a day. Myopia levels in those children dropped by a quarter. And based on a couple of chicken models of the disease he thinks he knows the mechanism behind the eye bending effect of too much study. Nature 519, 276–278 (19 March 2015)

Ian Morgan: I'll tell you what if you were at a dinner party where people was saying what work you did and I said oh well I'm another world expert from neurotransmitters in the chicken retina, people would drop to sleep all around you (laughs). When you say, I'm trying to prevent an epidemic of myopia in China people wake up and become very interested.

Geoff Marsh: And myopia or near-sightedness or short-sightedness is on the rise all over the world.

Ian Morgan: Yes, it's certainly on the rise all over the world. We started to see very clear evidence coming out of a number of countries in Eastern Southeast Asia that the prevalence is really increasing and in a generation or two it's gone from the order of 20% of people leaving schools short sighted to 80 to 90%. So quite a staggering change.

Geoff Marsh: Right and the speed of that drastic increase kind of rules out an underlying genetic cause.

Ian Morgan: It means that it can't be genetic change. Genetic change doesn't happen that fast. There is another way in which you can look at it however, you can ask the question well is it something to do with East Asian genomes, the answer to that is also no.

Geoff Marsh: And although this is on a huge scale, is myopia just an inconvenience that, you know, requires a new pair of glasses or what are the implications of this epidemic?

Ian Morgan: It is much more than just a set of glasses. When you get to high levels of myopia, the eye becomes so enlarged that people become at risk of blindness. You could possibly see an increase of two, three, four fold in the amount of blindness in the elderly and that would be at an enormous social cost.

Geoff Marsh: And so this idea that there is an environmental cause behind myopia it isn't a new one, is it?

Ian Morgan: No it's not a new one, the people started to see an increase in the prevalence of myopia about a 150 years ago, associated it seemed to them, with increased schooling. We suggested that it was bright light because we know that bright light stimulates the release of dopamine from the retina. We know that in animal models of experimental myopia, if we put compounds that mimic the action of dopamine into the eye while the eye is being pushed to grow, it blocks the growth. So this seems to give us a pretty clear case that we understand the mechanism, bright light outside, stimulates dopamine release and that in turn blocks what's called axially elongation of the eye. So, yeah there was a pretty coherent and plausible story.

Geoff Marsh: You also conducted a study in children in China where you also worked, tell me about that?

Ian Morgan: What we did was to give children in grades 1 through to 3 and we followed them for 3 years an additional 40 minutes a day outside and the end result was that these children became less myopic than the children who were not getting that extra time outside. The study that we've carried out is pretty well matched with the study that was carried out in Taiwan. In East Asia it is very common for children to stay in the classrooms at recess times, at lunch times. So, in Taiwan all they did was drop the children out of the classrooms and then locked the door that would give kids, if they took full advantage of it, about 80 minutes a day. So about twice of what we added to the school day and they got twice the effect we did. So it looks as though we even have a dose response curve.

Geoff Marsh: How do we put these findings into action? I mean, it sounds fairly difficult to implement an extra hour outside for all young people around the world.

Ian Morgan: A whole range of initiatives are going to have to be thought about to try and create a bit more space within the school day for children to get outside, and a bit less homework study pressure so that children have the capacity to get outside, outside of school hours. One of the things that we are currently carrying out a feasibility trial on is what we call a glass classroom, up towards the sorts of light intensities you'll get outside. And we hope that if this works as a mechanism that this will give kids a lot more light exposure and help to bring myopia under control. There's a cheap alternative to all of this, just get outside for the right amount of time, but there are strong practical cultural reasons why that might be difficult to achieve.

Geoff Marsh: That was Ian Morgan from the Australian National University in Canberra, Australia. And now longsighted Kerri goes and takes us squintzy look at a new exhibition on early scientific photography.

Kerri Smith: Scientists are often in the business of measuring things they can't really see. Exoplanets crossing in front of a star, making that star blink ever so faintly or the structures of a protein or some DNA using firing x-rays at it, but this is not really a new thing and here in the Science Museum's Media Space, a technology from the 19th century that helped scientists to do this is being showcased. Here with me is Greg Hobson who is the co-curator of the exhibition and where better to start than comparatively near the beginning with William Henry Fox Talbot, one of the pioneers of photography.

Greg Hobson: Well, the inventor of photography in fact in Britain. So Talbot was interested in how photography might be used to record scientific phenomena.

Kerri Smith: So, in this we're standing in a little kind of in a little box actually surrounded by a few lovely prints on the wall um, here at the start of the exhibition and one of them is a very fragile looking, I mean, both the subject matter and the photograph itself look pretty fragile of a butterfly wing under a microscope, right, let's just go a bit near.

Greg Hobson: These are actually the wings of an insect called a lantern fly which had a proboscis which would light up slightly almost like a firefly and what's really fascinating and very beautiful about these is they had a pair of wings and they were entirely different in their patterning which is something that Talbot wanted to show. And what we see here is both the photographic negative which was a waxed paper negative and then the positive image that was made from that negative and these are taken in 1840, so, very soon after the invention of photography. These will have been quite remarkable things for people to look at in the 19th century because what they will have been familiar with is the drawn image made by artists from their observations through a microscope but these are records of the actual microscopic image.

Kerri Smith: What would have been the impact on the scientists of the day having this kind of facility?

Greg Hobson: It wasn't immediately evident what that impact was. I think people were still slightly sceptical about the quality of photographic images but having said that I think quite quickly people were beginning to try and see how far they could push photography to record other kinds of scientific phenomena and in particular observing things that were very far away but also record things like movement and so on.

Kerri Smith: Now on the subject of things that are very far away, there's another beautiful set of photographs, which we should move to next, and unlike the microscope images, I suppose these are things that people could not have seen before photography.

Greg Hobson: They will have been able to see, to see the nebula in Orion which this photograph by Andrew Ainslie Common is of. There's a series of three photographs here and they will have seen something very much like the first photograph in the series, which is a series of little dots in night sky. What Common was interested in doing was seeing how far he could push the photographic process to allow the camera to see more than the human eye. And so in these three photographs, we go from an exposure of one minute, an exposure of twenty minutes through to an exposure of 68 minutes and very same few of the night sky changes quite radically depending on how long the exposure was on for and in the third picture we see something that is really quite beautiful almost like a painting. But in a way that only the film in the camera could capture, the human eye could not see this particular phenomena at all. These images are incredibly interesting because of the scientific information that's contained within them but also really exciting because of their beauty and their aesthetic properties.

Kerri Smith: Did people immediately trust their cameras, I mean, if we can't see this thing we just have to trust that the camera has taken a picture of what's there. Did that bother anyone at the time, does that bother anyone now?

Greg Hobson: Of course, it bothers people now, we have to question every image that we look at and add the question its veracity and in a sense this picture, this final picture, the 68-minute exposure of the great nebula in Orion is a false representation of the thing itself because this is not how it looks to us and in fact not even how it exists. It can only exist in this form as a photograph on photographic paper and taken by a camera. However, when photography was invented and when people were first looking at these pictures they did describe them as being images from life, so they didn't really question what they were looking at but accepted it as something as the form itself.

Kerri Smith: From these observations of the astronomical world, to something a bit more for us at least very common place today and that is electricity but of course in the late 1800 nobody had really seen this before.

Greg Hobson: These really quite strange looking pictures, almost organic forms, made by someone who was an electrical engineer called Campbell-Swinton and he was making experiments to try and depict electricity as a photographic image and he did that by firing electric charges at the photographic negative and the electricity would essentially try and escape across the negative and in doing so create this kind of slightly crazed the patterns with these feathery little entrails of energy.

Kerri Smith: They're amazing. They're sort of sepia toned and this looks like an elaborate alien fern plant

Greg Hobson: It does, it does. It's the most unusual depiction of electricity.

Kerri Smith: That was curator Greg Hobson. The exhibition is called Revelations and covers not only early scientific photography but the influence of those techniques on later art. It opens at London Science Museum on the 20th of March and runs until September and if you're not local, the science museum web site has some lovely examples of the collection, http://sciencemuseum.org.uk/revelations. Checkout our twitter feed for pictures as well, that's at @NaturePodcast.

Geoff Marsh: Time now for the research highlights read by Noah Baker.

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Noah Baker: Some flowers are able to choose who they mate with. A pretty impressive skill for a plant. The tropical Heliconia tortuosa a beautiful red and yellow number is visited by lots of different humming birds species, who come bearing pollen but the plant only turns on reproduction after visits from long-billed humming birds. They drink more nectar and that triggers the plants to become receptive to the incoming pollen. They also travel further than other humming birds perhaps helping the plant to share a healthy mix of genes. That paper appears in PNAS. Nature 519, 264 (19 March 2015)Time now for an update on prehistoric fashion. Eight eagle talons found in a cave in Croatia are now reanalyzed, could have been used as Neanderthal bling. They have clear cut marks on them probably made when the claws were cut from the bird's legs. Some of them look polished. If the talons are Neanderthal trinkets, they're another piece of evidence that Neanderthals may have had human-like capacities for symbolic behaviour, making artefacts of no obvious practical use. More in the Journal, PLoS One. Nature

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Geoff Marsh: Who do you think you are, I mean, who were your ancestors, where did you come from, what shape is your family tree? Genealogies become well trendy and loads of us are interested in these questions that include scientists. A team based in Oxford has just published a detailed genetic ancestry map of Britain, kind of like a country-family tree. To be included in this study, you had to live in a rural area in the UK and all four of your grandparents had to come from that area too within an 80 kilometre radius. The genomes therefore provided a record of the British gene pool of the grandparents' time around the late 1800s before lots of people moved to cities and before big migrations in and out of the country. It's a snapshot of British-genetic history. Peter Donnelly is the team leader and he came to the studio to tell gene-geek Ewen Callaway about the study. Nature 519, 309–314 (19 March 2015)

Peter Donnelly: So, our study focused on people in the UK of European ancestry to a first approximation, people of European ancestry in the UK look extremely similar genetically. What we were able to do though was to delve under the surface and look at quite subtle but real differences and then so we did all of that analysis of the genetic data and then we looked at the clusters that came out of the genetic analysis and we put out those on a map of Britain to see what they revealed.

Ewen Callaway: And it's a pretty astounding map, tell us a little bit more about I mean, the kind of differentiation you saw.

Peter Donnelly: It was extraordinary when we first looked at the maps. We had no idea what to expect. It'd be known from other studies some that we've been involved in many others that they were broad genetic trends in the UK, but what we are able to do through our study was to really zoom in on, as I said, quite subtle but real differences and the patterns we saw were extraordinary. Two counties right next to each other, Devon and Cornwall in the South West of Britain each corresponded to different genetic groups and indeed the set of individuals who were in the cluster only based on genetics in Devon geographically matched remarkably well with the modern county boundary.

Ewen Callaway: So, what created these differences that you just talked about between people from Devon and people from Cornwall, etcetera?

Peter Donnelly: There are two different forces that would result in the patterns of differences that we see. One of them is that there will be different inputs of DNA through migrations from Europe. The other effect particularly in smaller groups like the Islands in Orkney is that when populations evolve over time in a way which is relatively isolated from each other, then just by chance genetic differences will accrue between.

Ewen Callaway: Is one example of that say the differences between people from Cornwall and Devon where you got this giant extensive moor kind of separating the two counties.

Peter Donnelly: Yes in the south there's a river, the Tamar River and in the north there's Bodmin Moor, makes perfect sense and would be expected that geographical boundaries to migration and movement of people will tend to foster relative isolation and that can lead to genetic differences. Also cultural differences or a particular sense of identity in Southwest Wales for example in Pembrokeshire, we saw two genetic groups and it's been known that over a 1000 years that the very tip of southwest Wales, the language spoken was English, whereas as you moved in to Wales, people spoke Welsh and the two genetic groups we see, the boundary between them, matches something that's called the Landsker line which has been in place for almost a 1000 years to mark the differences in language between the two groups. So, language can be another factor which discourages marriage and mating between people in different regions.

Ewen Callaway: These differences that you found across Britain between people with genetic differences also tells us a lot about Britain's history, what kinds of events did you uncover in the genomes of Brits?

Peter Donnelly: We saw evidence of a number of the known migration events. We see evidence in England of the Anglo-Saxon invasions, we are also able to quantify that. So in the case of the Anglo-Saxons, a typical person of European ancestry in modern day England has a, maybe a quarter and certainly somewhere under a half of the DNA is a result of that Saxon migration. So there's been a longstanding controversy amongst historians about what happened when the Anglo-Saxons arrived in the UK. When they arrived the place names all changed, the language changed, the cereal crops changed and the pottery styles changed. So, some had argued that that was because the Anglo-Saxons replaced the existing population, whereas our data shows that we see clear evidence of the Anglo-Saxon DNA but because it's in the minority, it must have been the case that they intermarried with the existing population, so we are able to resolve that historical question.

Ewen Callaway: Does knowing the structure of Britain's population, does it help with anything other than reconstructing Britain's history?

Peter Donnelly: It's potentially helpful background for doing studies of the genetic basis of disease in Britain and that was one of our primary motivations at the outset of the study. So, when we look for genetic factors which may influence people's risk of disease, we tend to compare sick people and healthy people and look for genetic differences. If there are differences geographically and you sample more sick people for one region and healthy people from another then that can confound and complicate those studies. So, having a good sense of the background can well be important in knowing what sorts of things we can rule out in terms of confounding factors.

Ewen Callaway: Of course you've got people whose ancestry traces from all over the world, who are much more British than me who has, you know, a great great great great parent from Scotland.

Peter Donnelly: Yes many of the people in the UK particularly due to migrations in the last century don't have European ancestry and they bring with them their own rich genetic diversity, some of which is and will be extremely helpful in studying the genetics of diseases and in using genetics to better understand human biology and changes the way we do healthcare.

Geoff Marsh: That was Ewen Callaway talking to Peter Donnelly.

Kerri Smith: Finally this week, the news chat. One of our newest editors, Richard van Noorden joins us. You might recognize that name, he's on an editing stint and a vacation from being a reporter for a while. Richards thanks for joining us in your new capacity. First this week, to gene editing. Now we've talked about this on the podcast before. There are several quite new techniques to precisely edit bits of the genome, people are using them in all sorts of different cells, but what's the latest on this technique, it's quite a juicy story. Nature 519, 410–411 (26 March 2015)

Richard van Noorden: There's been a kind of public outcry over the idea of editing the DNA of human embryos or eggs or sperm in other words any reproductive cells. Last week, Edward Lanphier, Chairman of the Alliance for Regenerative Medicine in DC. He's also CEO of a company called Sangamo BioSciences and he wrote a comment piece in Nature saying there should be a moratorium, a halt on the use of this technology in reproductive cells, not just on creating an embryo, creating a baby which is many, many years into the future, may never happen, but just on even researching the idea of editing genes in cells that theoretically might then pass on those changes to future generations if they were developed into a human being.

Kerri Smith: We'll get to that moratorium in just a second but the background is that there have been some rumours this past week that these kinds of experiments have in fact already been done on human embryos.

Richard van Noorden: Exactly. So, MIT Tech Review, the news outlet published a story that they've been told that papers had been written, where researchers had edited embryos and we've also been told that by people, no one wants to say their names publicly. So those are the rumours flying around that reporters are getting. There are also many other researchers who will publicly freely admit that yes we would like to try editing the DNA of an embryo or of an unfertilized egg. They want to research it to find out whether these gene editing techniques are as precise and as easy to use as they seem to be.

Kerri Smith: Back to the moratorium then, this is Nature's comment piece from just a few days ago now. This group of scientists calling for researchers to agree not to do this work, but this gene editing technique is just an extension of others. I mean, gene therapy has involved gene editing and that's in clinical trials around the world. So what's different here?

Richard van Noorden: What's different say the Sangamo scientists is the idea that just the ethical problem that you are editing a reproductive cell that kind of change a person created using those cells would have had their makeup changed without consent and would pass on that change to future generations permanently. Public alarm at that kind of research could be so great, say the Sangamo scientists. That a public outcry could hinder the promising areas of gene editing that you're talking about for example, gene-editing someone's blood cells to cure them of some kind of blood disease and in that case you're not necessarily affecting the next generation at all. Well, you could argue it's a little self-serving for Sangamo which is doing some of this gene editing. That's a worry about a public outcry of editing is reproductive cells because they fear that it could somehow taint their research, but that is their position.

Kerri Smith: Or to try and squash a competing technique I suppose.

Richard van Noorden: Well exactly, maybe that is, you know, that's some scientists said hmm.., this is coming from Sangamo, interesting position that they have. Now the real danger here is that these kinds of gene editing techniques are so simple that a private clinic could do this, even though it is illegal in many countries.

Kerri Smith: You've given an idea of some of the reaction to this. This hasn't been very long since this comment piece was published; another is coming out in Science later this week. What have the rest of community been saying?

Richard van Noorden: Well George Church who is one of the authors of the Science commentary that's coming out says well it's a bit like in vitro fertilization, IVF babies. You know, everyone said there was a fundamental line there, but then after research was done and IVF babies were born, now they don't think there is, so not necessarily a slippery slope towards designer babies as the Sangamo scientists are suggesting.

Kerri Smith: It's certainly a story that's going to run and run what with the rumours being confirmed or denied. The Science coverage coming out on our own in Nature continuing. Okay so onto story number two then which is about the US government's central marijuana repository. Nature 519, 269–270 (19 March 2015)

Richard van Noorden: If you're a researcher in the United States, you can buy marijuana from the National Institute of Drug Abuse and that is your sole dealer. If you want to research marijuana for something like conditions like epilepsy or chronic pain you have to buy from this agency, it's got to contract with the University in Mississippi, but now that legal marijuana is increasingly available for the US public, the institute, NIDA is quietly changing its course, it's massively scaling up the amount of marijuana it's growing and the marijuana's potency and these new drugs could be available for researchers that do science quite soon that's what we're reporting about this week.

Kerri Smith: Yes in fact as of last year, making a lot more, making it more powerful, and this is because researchers were complaining at sometimes that it's, you know, it wasn't potent enough to do the job they wanted it to do in their research studies.

Richard van Noorden: Right, essentially the marijuana was too weak and didn't represent at all what it was sold on the street. In rather more detail, it didn't have enough levels of the non-psychedelic chemicals that show therapeutic promise. Now NIDA has two new strains of marijuana, although some people are still not very impressed with these plants. For example, at least 90% of the marijuana that the DEA, the Drug Enforcement Administration seizes off the street contains high levels of tetrahydrocannabinol which is the primary active ingredient. Often more than 20% by weight whereas NIDA's pot only has 12% THC. It may be that what is going to happen is that NIDA will end up not being the sole provider of weed for researchers.

Kerri Smith: Well, my idea was going to be that they use the stuff they've seized off the streets and just repurpose it for science, but the article gives us a different idea and that is that state universities perhaps could just grow their own.

Richard van Noorden: Right, may be NIDA will face competition. Last December Colorado State Government asked the federal government, can you please let the state universities grow marijuana for research because we're having awful trouble getting the products from NIDA and from private growers overseas. Another idea is that growers in the UK and Israel and Canada might produce research-grade marijuana that scientists are able to buy. So, with pot increasingly available to scientists outside the United States and perhaps the researchers would buy from other sources, it looks like the NIDA's monopoly of weak weed is doomed.

Kerri Smith: (Laughs) Richard, thank you very much for regaling us with those facts and also just like to say quick thanks to David Cyranoski and Sarah Reardon, the reporters on those stories. More at http://nature.com/news. That's it, we're out of time and I need to go and spend some time in bright sunlight. See you next week. I'm Kerri Smith.

Geoff Marsh: And I'm Geoff Marsh.