An international team led by researchers from the National Human Genome Research Institute (NHGRI), part of the National Institutes of Health (NIH), has identified a genetic variant that is a major contributor to small size in dogs.
The findings appear in the April 6, 2007 issue of the journal Science.
?The identification and characterization of a key genetic variant that accounts for differences in dog size is particularly exciting because the underlying gene is present in all dogs and other diverse species, including humans,? said Eric Green, M.D., Ph.D., scientific director of the NHGRI Division of Intramural Research. ?Discoveries like this illustrate the exciting promise of genomics research for understanding the inheritance of a wide range of traits, including those that have an impact on health and disease.?
The branch of the canine family tree that includes domestic dogs diverged from that of the gray wolf more than 15,000 years ago. Due to selective breeding by humans throughout history, dogs today exhibit an extremely wide range of body types and behaviors. In fact, dogs exhibit the greatest diversity in body size of any mammalian species.
In their study, researchers explored the genetic basis for size variation among dogs by comparing the DNA of various small dog breeds, including Chihuahuas, Toy Fox Terriers and Pomeranians, to an array of larger dog breeds, including Irish Wolfhounds, Saint Bernards and Great Danes. Their investigation found that variation in one gene ? IGF-1, which codes for a protein hormone called insulin-like growth factor 1, is very strongly associated with small stature across all dog breeds studied.
?We have been intrigued by the population structure of dogs, which over the years have been selectively bred, allowing us to more readily analyze the genetic causes of particular traits than is possible in humans,? said the study?s senior author Elaine A. Ostrander, Ph.D., chief of NHGRI?s Cancer Genetics Branch. ?Nearly all of what we learn from studying body structure, behavior and disease susceptibility in dogs helps us understand some aspect of human health and biology.?
In addition to Ostrander and her colleagues at NHGRI, the team included researchers from Cornell University in Ithaca, N.Y.; the University of Utah in Salt Lake City; the University of California, Los Angeles; the University of Southern California in Los Angeles; the University of Missouri in Columbia; the Waltham Centre for Pet Nutrition in Leicestershire, England; and the Nestle Research Center in St. Louis. Postdoctoral Fellow Nathan B. Sutter, Ph.D. from NHGRI?s Cancer Genetics Branch, served as lead author.