It's a curious disorder. Caused by the deletion of about 27 genes on the long arm of one of the two copies of chromosome 7, it causes some physical symptoms (widely-spaced teeth, a flattened nasal bridge, heart abnormalities) and a number of neurological ones (including the ubiquitous lowering of IQ found in deletion disorders).
What is most curious about patients with WBS, though, is the social results. People with WBS are hypersocial, affable, friendly, empathetic, and far more verbal than you'd expect with someone experiencing the other developmental delays that come along with the disorder. Even more curiously, they show no trace of the racial bias found in developmentally-normal toddlers (a time when most children exhibit a strong preference for children who look like themselves). During social interactions, they cue in on faces much more than unaffected individuals, and in fact are said to "hyperfocus" on the eyes of the person they're speaking with. They tend to trust implicitly and are driven by the desire to make friends. They're highly sensitive to rejection.
On the other hand, kids with WBS can be impulsive, hyperactive, and disobedient (especially when such behavior garners attention).
Interesting that a rare genetic disorder gives us a window into human behavior (and sheds at least a little light on the persistent nature-nurture question). But even more fascinating is the discovery, which was the subject of a paper in Science Advances, that the genes in dogs homologous to the affected sequence in WBS (which happen to be on dogs' chromosome 6) have been under positive selection by humans for thousands of years -- and may be the basis of a lot of characteristically doggy behavior.
In "Structural Variants in Genes Associated With Human Williams-Beuren Syndrome Underlie Stereotypical Hypersociability in Domestic Dogs," the research team, headed by Bridgett M. vonHoldt of Princeton University, write:
Although considerable progress has been made in understanding the genetic basis of morphologic traits (for example, body size and coat color) in dogs and wolves, the genetic basis of their behavioral divergence is poorly understood. An integrative approach using both behavioral and genetic data is required to understand the molecular underpinnings of the various behavioral characteristics associated with domestication. We analyze a 5-Mb genomic region on chromosome 6 previously found to be under positive selection in domestic dog breeds. Deletion of this region in humans is linked to Williams-Beuren syndrome (WBS), a multisystem congenital disorder characterized by hypersocial behavior. We associate quantitative data on behavioral phenotypes symptomatic of WBS in humans with structural changes in the WBS locus in dogs. We find that hypersociability, a central feature of WBS, is also a core element of domestication that distinguishes dogs from wolves. We provide evidence that structural variants in GTF2I and GTF2IRD1, genes previously implicated in the behavioral phenotype of patients with WBS and contained within the WBS locus, contribute to extreme sociability in dogs. This finding suggests that there are commonalities in the genetic architecture of WBS and canine tameness and that directional selection may have targeted a unique set of linked behavioral genes of large phenotypic effect, allowing for rapid behavioral divergence of dogs and wolves, facilitating coexistence with humans.Which is pretty fascinating. When I go back and read the description of the behavioral characteristics of a kid with WBS, I have to admit that it sounds like the results of a personality assessment for my dog Guinness:
He's so stuck on my wife and I that we have nicknamed him Limpet Dog. He wants to be next to us pretty much all the time, if not actually in our laps, even though we have discussed with him more than once that a seventy-pound pit bull mix is not really a lap dog. While you're petting him, he'll stare lovingly into your eyes, as if he's never met anyone he admires more. He not only shares the endearing characteristics with WBS kids, but their more trying behavior -- he can be absolutely insistent about being played with, gets very grumpy when reprimanded, and if he's bored or feels neglected he'll find something naughty to do because it gets him attention.
Like a couple of nights ago. My wife was away, so I was watching television while sitting on the sofa eating dinner. Guinness finally got ticked off that (1) I was eating a t-bone steak and he wasn't getting any, and (2) I was clearly paying more attention to the television than I was to him, so he sauntered up to the coffee table, picked up the TV remote in his mouth, and walked off with it.
Knowing that he's got jaws like a bear trap, I quickly set aside my dinner and jumped up to pry it out of his mouth before he crushed it into tiny useless shards of plastic. I got it back before he damaged it, but in the process spent five minutes interacting with him, which is exactly what he wanted.
Guinness 1, Gordon 0.
The hyperactivity also rings a bell. If we don't tire Guinness out by throwing the tennis ball for him 8,583,192 times, or taking him for a ten-mile run, he gets a bad case of The Zoomies.
Cf. my previous comment about his weighing seventy pounds. Having seventy pounds of dog hurtling around the living room at Mach 2 usually results in damage to the furniture. So needless to say, we play a lot of fetch in this household.
Interesting that the overlap in genes between humans and dogs -- estimated at about 84% of our total genome -- suggests a great deal more homology between not only physical features, but behavioral ones. It seems fitting to end with a quote from the Austrian behavioral scientist Konrad Lorenz: "The fidelity of a dog is a precious gift demanding no less binding moral responsibilities than the friendship of a human being."
The subject of Monday's blog post gave me the idea that this week's Skeptophilia book recommendation should be a classic: Konrad Lorenz's Man Meets Dog. This book, written back in 1949, is an analysis of the history and biology of the human/canine relationship, and is a must-read for anyone who owns, or has ever owned, a doggy companion.
Given that it's seventy years old, some of the factual information in Man Meets Dog has been superseded by new research -- especially about the genetic relationships between various dog breeds, and between domestic dogs and other canid species in the wild. But his behavioral analysis is impeccable, and is written in his typical lucid, humorous style, with plenty of anecdotes that other dog lovers will no doubt relate to. It's a delightful read!
[Note: if you purchase this book using the image/link below, part of the proceeds goes to support Skeptophilia!]
I've been voraciously studying attachment theory (limbic system) fo the past 10 years. WB syndrome is the only non-nurturing (e.g. WB is genetic) condition in which the limbic system seems to be compromised (no fear, e.g. amygdala subdued in its reaction).ReplyDelete