Social genes

Regular Naked Genetics listeners should know by now that our genes help to determine our characteristics, and influence our health and even happiness - although of course they’re not the whole story and the environment plays a role too. But did you know that your partner or housemate’s genes might be having an impact as well? In January, Amelie Baud and her colleagues at the European Bioinformatics Institute published a study in the journal PLoS Genetics, showing that this is in fact the case - or at least it is for mice, as she told Kat Arney.

Amelie - We all know that people influence each other. There's nothing new here, but we’d like to know how this works. What we have found recently is that the genes of our partners influence us indirectly.

Kat - So, my partner’s genes, my boyfriend’s genes having an impact on me. What's going on here? How does this work? What did you do and what did you find?

Amelie - So, I’ll give you an example with my partner. Say for example that his genes tend to make him a very nice person who also cooks well and for example, smells good. This is going to help me for example on bad days or maybe generally going to make me happy. So indirectly, the genes of my partner affect my welfare and health. This example is a bit simplistic of course, but it really shows that it’s not only the behaviour of our partners that matters. There's many other ways in which our partners can influence us. Skills, for example, or physicochemical traits like smell or good looks.

Kat - Being big and cuddly?

Amelie - Exactly. There's really so many ways in which our partners can influence us. What's really amazing is that we can capture this, we can measure this, and hopefully, understand how this works just by measuring the genes of our partners.

Kat - So, this kind of boils down to the assumption that it’s our genes that affect who we are and how we come out, and what we’re like, and how we behave. But from what I understand, it’s not quite as simple as like, one gene, you come out like this.

Amelie - Of course not. It’s not that simple. So first of all, our genes only explain some part of how we behave, how we are, and so on. Our environment, and life experiences, and life habits really also play a major role here. So the contribution of our genetics is limited to begin with. And also, it’s not only one gene for the traits that we are looking at here. It’s more likely many genes – tens, maybe hundreds of genes, so it is complicated.

Kat - So how do you go about starting to unpick this? What are you looking at and how do you start measuring the influence of someone’s genes on their partner?

Amelie - So, I have to say that we haven't looked at people yet. So far, our research has been in laboratory mice. So in laboratory mice, you can group mice in a cage. So you define who you choose which mouse interacts with which other mouse.

Kat - So like a kind of mouse flat share - a mouse share?

Amelie - Exactly. So first of all, you define their social partners which are cage mates in our case and then you measure a number of traits of interest. So we were interested for example in a number of behaviours including anxiety, mood, but also metabolic, immune traits, and also wound healing for example. So you measure those traits in the mice and then you also measure the genotypes or the genes of the mice. And then you simply look for an association between trait of one mouse and genes of the cage mates.

Kat - Are you looking at specific genes or are you just saying, “Okay, this mouse has a genetic variation here and the mice that it’s caged with are more anxious.” Is it at that kind of level?

Amelie - We have quantified the overall effect of the genetic makeup of cage mates. We have not so far identified specific genes. Overall the genes of cage mates affect significantly and substantially a number of traits. And what we want to do next, as you hinted, is to identify specific genes. Because with specific genes, we can get clues on how things work, how partners influence each other.

Kat - Does this work with mice that are related to each other, sort of brothers, sisters, siblings? Or does it work with mice that are completely unrelated say, like flat sharers?

Amelie - We have evidence it works with both. In our published study, we had both unrelated and related mice. In both cases, we found that the genes of one mouse influenced the trait of another mouse.

Kat - Where does this go next? So you say you’ve done this in mice, do you want to look in humans? That’s going to be tricky.

Amelie - Obviously, you want to look at humans. It’s really important to know whether this phenomenon extends to humans. We think it will because first of all, it’s been observed in other species. Not only in mice. This is the first time [in mice] but also in cattle by animal breeders who have been working on this for a while. So, there's evidence that in different species these effects exists, so we think they might exist as well in humans. But obviously, we want to find out with experimental evidence. So, we are going to look at humans. Of course, we do not choose who is interacting with who so we first of all, need to find who interacts with who. One simple way to do that for example is to look at people who live together. And then we can do very similar analysis – the statistical models we use can be used for human populations as well and we definitely want to do that. Interpretation of the results is going to be more tricky in humans than it was in mice.

Kat - So we’re not going to have a genetic dating agency or a genetic flat share agency anytime soon?

Amelie - Not anytime soon, no. It’s really difficult to identify what people expect from their partners, what they really want from their partners and this is complex, unconscious, it changes over time. So it would be really dangerous I think to try to use genetics to tell people to hang out together. It’s really not so much about the genetics, the issue. It’s really about knowing exactly what we want, what we expect from our partners.

Kat - Amelie Baud, from the European Bioinformatics Institute.