Monday, January 21, 2008

Canine Behavioral Genetics Article in AJHG

Back in October I posted this piece about the importance of the Dog Genome Project. The latest issue of The American Journal of Human Genetics has a fascinating article entitled "Canine Behavioral Genetics: Pointing Out the Phenotypes and Herding up the Genes" by Tyrone Spady and Elaine Ostrander that also illustrates the importance of dogs for genetic research. Here is the abstract:

An astonishing amount of behavioral variation is captured within the more than 350 breeds of dog recognized worldwide. Inherent in observations of dog behavior is the notion that much of what is observed is breed specific and will persist, even in the absence of training or motivation. Thus, herding, pointing, tracking, hunting, and so forth are likely to be controlled, at least in part, at the genetic level. Recent studies in canine genetics suggest that small numbers of genes control major morphologic phenotypes. By extension, we hypothesize that at least some canine behaviors will also be controlled by small numbers of genes that can be readily mapped. In this review, we describe our current understanding of a representative subset of canine behaviors, as well as approaches for phenotyping, genome-wide scans, and data analysis. Finally, we discuss the applicability of studies of canine behavior to human genetics.

And a sample:

The domestic dog displays greater levels of morphological and behavioral diversity than have been recorded for any land mammal and holds the unique distinction of being the first species to be domesticated.1 The phenotypic radiation of the dog has been the product of restricted gene flow and generations of intense artificial selection. These factors have generated the astounding level of diversity noted among the more than 350 breeds of dog recognized worldwide, many of which were developed for highly specialized tasks such as herding, hunting, and retrieving. Indeed, breeds are often defined by a combination of their specialized morphological and behavioral traits.

....A long-stated goal of behaviorists is to identify genes that control behavioral traits. Traits that define specific breeds, such as those associated with hunting and herding, are of interest, as are those observed in particular dogs or lineages of dog, such as obsessive-compulsive behaviors in the bull terrier. Because of its inherent complexity, developing reliable behavioral metrics for dogs has been difficult. Currently, four general approaches have been employed to study canine behavior: test battery, owner-directed survey, expert rating of breeds, and observational study,38 with test battery being the most frequently used. In this method, dogs are exposed to novel stimuli, and their responses are recorded.

....For years the dog has been suggested as an ideal system for studies of behavioral genetics. With the genome now mapped and sequenced and tools for building haplotypes and studying expression at hand, it is time to tackle the hard experiments. Why is the basset hound less effective at herding sheep or an Anatolian shepherd less effective as a hunting dog? More importantly, why do Australian shepherd dogs herd and greyhounds chase, both in the absence of instruction? Why did the domestication of dogs lead to a level of loyalty and devotion unrivaled among modern mammals?

For many geneticists, the most interesting behaviors in dogs are those that are highly breed associated, such as herding and pointing. For others, the challenge is to understand the genetic variation that contributes to the individual variation between dogs (personality). Still others see in man's best friend a mirror of our best (loyalty, steadfastness, trainability, strong work ethic) and worst (stubbornness, aggression, and anxiety) qualities. An understanding of the genetics of all of these traits is likely to produce a better understand of not only the canine species, but the human species as well.