The wonderful world of RNA

Kat - Another story that you highlighted to me was some research from Eric Axelsson and his team in Scandinavia and the US, and this is in Nature. And this is about dogs because I love dogs. We always have some kind of animal genetics thing. What's this about dogs?

Nell - So, I think this is really interesting because essentially, what it's doing is using genetics to go back and try and find evidence to help answer the question about how dogs might have evolved. Obviously, this is a really tricky question because we don't have a lot of evidence. There's no written records, we haven't got any scientists from 14,000 years ago who've published paper on what happened. But instead, we can go back, we can look at the DNA of dogs and we can figure out how that's changed compared to wolves on the assumption that dogs evolved from wolves. So, these scientists have looked at the genetic code of wolves and dogs. They've compared it in loads and loads of detail to see exactly what those differences might be.

Kat - What can it tell us about the relationship of dogs to us and how they evolved?

Nell - So essentially, what they found is there were two main areas where there were obvious differences between the dog DNA and the wolf DNA. One of those was in various brain pathways, so that could be to do with the way that dogs' behaviour is clearly quite different from wolves. The other one that I really was interested in was looking at starch metabolism. So essentially, they found that dogs tend to have many more genes that allow them to metabolise starch in their cells. And this links in quite nicely with the theory that dogs may have evolved by taking advantage of all the waste produced by human societies. So, you can imagine a group of hunter gatherers perhaps. They leave these waste dumps wherever they go, so they have bits of food they don't want anymore, bits of crops maybe if they're farming, and dogs could be able to take advantage of that. So there might have been wolves who'll go, "Okay, here's some food I could eat." The ones who are better able to digest the starch, to digest all these kind of waste food would've been more successful and perhaps could've gone on to evolve into these other species.

Kat - And presumably, with the evolution in the brain as well and giving them characteristics that might make them more amenable to hanging around with humans. It's not a done-deal. It's quite controversial because from what I know, there's another theory that dogs evolved because humans were sort of harnessing wolves for hunting or using wolves for hunting.

Nell - Exactly. I mean, I just like the idea that you could maybe come up with an idea for which of those theories was more accurate using genetics and exactly, you can look perhaps as well at the behaviour because we know that if you breed dogs, you can quite quickly select the ones that are more tamed and are more docile. And there's a theory that that's exactly what happened with wolves. So, if people were using them for hunting, it would be much easier to have wolves that were less aggressive, had better behaviour. And if you ended up selecting those, that could change their behaviour every time.

Kat - I saw an article about this describing dogs is basically more like puppies. They're just grown up puppies and we see these in many species. For example, the human face is basically a baby monkey face and the idea that in behaviour as well, you can preserve those juvenile characteristics into adults.

Nell - Yeah, exactly and that so some of these genes that they were looking at, there's some evidence that that could be maybe what they're doing. But clearly, it's really difficult because we've got all those evidence from a long, long time ago, from thousands of years ago, but there's not a lot to go on in terms of what we know about what happened when. And there's also this theory that dog domestication could have happened multiple times in different ways, in different places. So, it's not necessarily true that there's one answer to that question.

Kat - Well, that's one "ruff" idea. Anyway, thanks very much. That's Nell Barrie science writer. 

As we approach Valentine's day, much is made of the difference between the behaviour of men's and women's hearts in the romantic sense. But in purely biological terms there's little difference between these organs, except for small differences in the electrical signals they produce. Now researchers at Washington University in St Louis have managed to track down some important molecular differences in human hearts from both sexes that could lead to more personalised treatment for cardiac problems in the future.

Publishing their results in the journal PLoS One, the researchers looked at samples taken from 34 human hearts from people that were either receiving a heart transplant following heart failure, or whose healthy hearts had been rejected for transplantation, and looked at nearly 90 important genes involved in heart rhythms and other functions. They found major differences in the activity levels of many key genes in the atria - the chambers at the top of the heart - rather than the lower chambers, or ventricles. Overall men had higher levels of activity of nearly all the genes, while women with failing hearts had unusually low levels of gene activity - in some cases less than half of that seen in men.

The scientists hope their findings will shed light on how best to treat men and women with heart failure.

Kat - Here's Susan Gottesman from the Centre for Cancer Research in Bethesda, Maryland, who's an expert on bacterial RNAs. I asked her to explain more about how small RNAs can control the activity of genes in bacteria.

Susan - So, in parallel both in bacteria and humans, some of them have the ability to decide which of the messengers actually get translated into the protein machinery. So they pair with the messages, and then can change their fate, so they can make them disappear from the cell when they otherwise would be there. They can make them more active than they would otherwise be. And so, the cell has a capacity for sending in new signals to these small RNAs which are then regulating these much bigger messages and that's important for development, it's important for cancer, important for disease, it's clearly important for bacteria to respond in a proper way to their host, and cause disease.

Kat - So, how are these small RNAs made?

Susan - So, that's a little bit different between bacteria and animals because animal cells have a very complicated process. In the bacteria, they look just like some of the other genes. They have promoters, they're made of small pieces, and then they fold up and they can work. In the higher animal cells they're made in the nucleus, they have to be folded up, they have to be cut, they have to be sent out of the nucleus, and then processed down. In each of those steps, in some place at which the cell can say, "Okay, I don't really want this or I do want it now."

Kat - And in bacteria that you study, what are these small RNAs up to? What sort of processes are they controlling?

Susan - Well, the more we study them, the more we find out about what they're doing. So, if I tell you what I know now, there'll be something new. We know they regulate whether the bacteria can swim from here to there. They regulate whether the bacteria have enough iron inside them to grow properly and how it gets that iron. They regulate whether the bacteria know to continue growing or stop growing so, almost everything. Every decision the bacteria has to make, and bacteria have to make a lot of decisions, the RNAs are in there, sticking in their two cents.

Kat - And what do we know about how this system has evolved because RNA and DNA kind of growing up in parallel?

Susan - That's really a very interesting question and I don't have an answer to it, so it's one of the things that I really like to play with, trying to figure out where these RNAs [came from] - are they ancient or are they newly evolving? They are evolving quickly. So, I think now that we know that they're there, we know where to look for them, we can start to understand what they do in the more complex behaviours. Let's just stay in the world of bacteria, how the bacteria interacts with its host, how it causes the disease, did that bacteria ever send RNAs to talk to the animal cells or vice versa. A lot of those things that we think would be really interesting that we don't know about yet. So, lots yet to look at.

 Kat - That was Dr Susan Gottesman from the Centre for Cancer Research. 

Louise:: This month's question is from Agum in Canada who asks, "Why are there different skin colours? How did that happen?" And to answer this question, I spoke to Dr. Aylwyn Scally from the Department of Genetics at the University of Cambridge.

Aylwyn:: Skin colour is like lots of human characteristics, one of these things which is predominantly determined by your genetic content. Another way of saying it is that it's determined by your ancestry, so we know the people whose ancestry comes from Africa or regions close to the equator tend to have darker skin colour and people further away in higher latitudes will have lighter skin colour. And that is something which we've recently been able to actually identify in terms of which parts of the genome and how much of our DNA is actually involved in determining skin colour.

We can say quite a lot now about when that might have happened, when these changes might have occurred, and then speculate about the reasons why they might have occurred. But there are still questions that we don't understand; we don't have the answers to. One of which is really the basic thing is, exactly why have these genetic changes taken place, what has been the benefit for people living in northern latitudes for them to have lighter skin colour? We have ideas about that and they're related to protection of the skin from UV light. That's what people have speculated about for a long time, but we don't really have a very clear cut example or reason for why that might be the case.

Alternatively, there's also the idea that when your skin is heavily pigmented, it means it protects you against UV light, but actually, you need certain amount of UV light to synthesise vitamin D in your body. So, when the amount of UV light you're getting is lower, say, when you're living in a northern climate, then that means that it's beneficial to actually increase the amount of UV light and therefore, that could be a reason why people have evolved lighter skin. We were able to look around across the whole genome and look at different regions and see where these changes have taken place, and we can see that in Europeans, it seems to have happened quite recently - recently in terms of human evolution that is. So, within the last 20,000 years or so, that's sometime around since the last Ice Age. And you can also see lighter skin colours elsewhere around the world, in Asia, but the genes involved are not necessarily the same ones. We can identify different genetic changes that you find in east Asians who also have lighter skin than Africans, our ancestors.