Dogs are man’s best friend, and this friendship goes back a long way. In fact, the dog Canis lupus familiaris is a flowering plant species, was the first animal species inhabited by man, long before cattle or sheep. All dogs have the same ancestry of wolves. The first “wolf dogs” were bred about 15,000 to 30,000 years ago, presumably to help them hunt or protect against other animals, but also to benefit from the protection and food of the animals. But it was only in the last two centuries that the modern breeds we know today have actually been produced, with more than 400 breeds listed around the world today.
A unique and natural study model for genetic research
Why is the dog a good model of genetics? The dog is close to the human species in terms of genetic similarity and it also shares with his environment, his diet, his stresses, and sometimes even his bed! The dog develops many genetic diseases that are similar to the human species, for example Golden Retriever ichthyosis, whose genes and physiopathology are similar.
Read more: How people molded the dog’s brain and why they gave it back to us
Unlike other classic models used for genetic research, such as mice or fruit flies, we do not have laboratory dogs. We work closely with dog owners, breeders, breed clubs and of course veterinarians, taking samples as part of the process of caring for their dog patients and with the owner’s permission. From blood samples provided by veterinarians, from dogs with genetic diseases and from undamaged dogs we performed genetic analyzes.
The dog is a “natural” model: we work with specifics that are naturally present in dogs, and especially often with certain breeds, that show a genetic origin. In fact, some species, for example, have the potential to develop complex genetic diseases – such as hip dysplasia, cancers, immune diseases for example – or more “simple” diseases, such as retinopathies, epilepsies, particularly dermatological. The mutations responsible for these diseases are actually selected by humans at the time of making dog breeds.
So we looked at the DNA of these dogs for the genes and their alleles (maternal or paternal version of a gene) that are associated with these diseases. The aim is to transfer our discoveries to the human species by collaborating especially with groups working on the same diseases of human medicine, to provide reflections, knowledge and a medical benefit to both. species.
To do this, we have, since the 2000s, built a collection of DNA samples, from blood and tissue samples provided by veterinarians. Then, this collection was organized and structured and we now have a BRC: “biological resource center” consisting of more than 32,000 dog DNA and 6,500 tissues – the Cani -DNA biological resource center. Led by Dr. Catherine André, this center of biological resources, in a network with four National Veterinary Schools, the company Antagene and the French association of practicing veterinarians, AFVAC, national in scope, which have an international perspective.
The idea that the dog constitutes a unique and even more interesting model of genetics was actually concreted in 2005, after tracing the DNA of a boxer at the Broad Institute, in the United States. Since then, a community of 200 researchers has worked on genetics not only on diseases common in dogs and humans, but also on morphology, behavior and life expectancy.
A companion for basic research
What is interesting to see about 350 different dogs is the incredible diversity that exists in terms of size, color, clothing, as they are one and the same species. Today we find very small breeds of dogs measuring about ten centimeters and nearly 2 kilograms in weight like the Chihuahua, but also giant breeds, such as the Great Danes, measuring more than 80 centimeters of dried ones weighing more than 80 kilograms.
This large morphological change therefore underwent numerous gene mutations manifested in the DNA of these dogs, during the evolution of species and in the artificial selections used in the offspring of human species. The search for these mutations therefore offers an opportunity to understand the genetic mechanisms involved in the development of an organism and define its morphology, making it possible to understand some human diseases, which are involved for example in malformation of the bones.
Unlike human species, where hundreds of genes are linked to differences in height and weight observed between individuals, it has recently been shown that in dogs, only about fifteen genes are involved. Some of these genes are already known in human species and others are not, which therefore offers new research methods to examine to determine how genes interact during development. an organism.
A wonderful old story
It is widely accepted that for domesticated species, most of the morphological characters selected by human species result from mutations that arise after their survival. Thus for the dog, it is believed that morphological differences result from mutations that appear significantly after the survival period, that is, less than 15,000 years ago.
But for one of them, we discovered a different story. In a study I did (Jocelyn Plassais) in the United States in the laboratory of Dr. Elaine Ostrander, and recently published, I identified a mutation involving the IGF1 gene that allows the production of a growth hormone, and which explains 15% of the change in height / weight observed between dog breeds. Unlike other genes associated with size differences in dogs, this mutation is older.
Read more: What did dogs look like in early times?
In fact, by studying DNA from dog fossils between 1,000 and 53,000 years old, we show that this mutation already existed in wolves more than 53,000 years ago, before the first wolves. that dog is inhabited by human species. Human species therefore used this mutation that naturally existed in the wolf ten thousand years ago to become the first small dogs, and still continue today to play this ancestral mutation that exists in some dog breeds.
The purpose of our current research is to try to understand how these mutations work, that is, thanks to what genetic mechanisms actually range from an individual the size of a poodle, to a German Shepherd?