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Scientists Searching for Clues to The First Dog

JB: What’s going on in your lab now?

AB: We’re collecting DNA samples and the genetic information we need so we can start piecing together what’s going on in these interesting but largely neglected free-ranging dog populations. We are seeking insights into dog population history to discover patterns of selection around certain genes that can then become the basis of further study. Our work is very hypothesis-driven. We have certain hypotheses about how dogs evolved, and we try to collect the right samples to test these hypotheses.

As geneticists learn more about how genetic variation controls complex traits in purebred dogs, we find it’s quite different than what we see in humans. Why? There are at least two competing hypotheses, and by gathering data from free-ranging dogs, we can start testing them to figure it out. Some of this gets into technical discussion about genetic architecture, recombination, epistasis and pleiotropy and such, so I’ve avoided getting too academic. But I also don’t want to be dismissive of it since those technical, hypothesis-driven aspects of the project are the bread and butter of my lab in terms of student training.

JB: In longitudinal studies such as the Morris Animal Foundation’s Golden Retriever Lifetime Study, researchers gather information from participants’ DNA and then match what they find to traits the test dogs may display over a lifetime. Will you have an opportunity to see how, for example, an immunesystem mutation affects a village dog’s health as it ages?

AB: Our project is a huge undertaking, and there’s a ton of data we’d love to gather on each dog but just simply aren’t able to since, at this point, we’re focused on sampling as many dogs from as many populations as possible to maximize the amount of diversity we can analyze. I really don’t want to overstate what we’re able to do in one visit to check out a dog and draw blood, which is limited to looking for genetic signatures in the genome of these dogs showing signs of selection and/or local adaptation.

But, since we have a fairly good idea of what genes do in modern dogs, at least in a rough sense, if we see a genetic signature in village dogs for positive selection around a gene we know is involved in immune function (for example), that’s a big discovery.

JB: At the risk of oversimplifying, say you’re looking at a region that you know to be linked to a negative trait and you see that the switch is turned off in the village dog DNA and turned on in modern dog DNA—would you feel that you’d found a “smoking gun”?

AB: It’s possible. Then, of course, as you allude, we would want to go back, look at dogs carrying that mutation versus other dogs, and see if there are different health outcomes. Perhaps [dogs with the mutation] are more resistant to intestinal parasites or perhaps they are more prone to autoimmune disease or something. Until we find the mutations, it’s a bit speculative to make predications about what exactly the findings will mean to owners. This is certainly “basic research” in the purest sense.

JB: In people, size is determined by hundreds of genes, each with a small effect. In purebred dogs, body size can be regulated by a single gene. Is this unique to dogs?

AB: It depends. There are other traits in other species controlled by a couple of loci [location of a gene on a chromosome]. I would argue that yes, it’s pretty unique. Whether or not dogs are special in that there is something about their genome that predisposes them to this type of diversity, or perhaps because humans worked so hard at creating them, we don’t know. This debate is still raging in the literature. It is definitely the case that genes have many, many effects. Rather than being a blueprint in which each gene is responsible for just one part of building the whole organism, the genome is more complicated, with each gene taking on different roles at different times or in different tissues.

JB: Do multiple-trait relationships also show up in village dogs?


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