A unique coat color pattern, termed Panda, occurs in a single bloodline of
German Shepherd Dogs. With the help of the founding breeder, Ms. Cindy
McCann of Ohio, we have analyzed the DNA of Panda dogs and their non-Panda littermates using modern genetic tools. We have found the following:
· The coat color pattern stems from a spontaneous mutation; it was not introduced from another breed or population.
· The novel mutation occurred in the Sire's germ line, and was then passed
down to his daughter, who was the only offspring of that sire to show the distinguishing markings.
· In subsequent generations, the Panda pattern has exhibited an autosomal dominant mode of inheritance, consistent with the action of a single gene acting with full penetranpe.
· No discernible health affects have been observed in these dogs, though a
double Panda dog has not yet been produced.
As the principal investigator of this study, I would be delighted to answer
questions by breeders and owners who are interested in the genetics and biology of this coat color pattern. I can be contacted at:
Mark Neff, Ph.D.
VGL Canine Genetics
Center for Veterinary Genetics
School of Veterinary Medicine
University of California
Davis, CA 95616-8744
Piebalding in a German Shepherd?
How many of you have seen a purebred German Shepherd that is 35% white, the remainder of color is black and tan, and has no white German Shepherds in its ancestry?
Breeders of purebred animals are responsible for the quality of future generations of their respective breed. German Shepherd breeders, both in the US and abroad, have refined their breeding programs to reduce or eliminate certain genetic characteristics with the intention of maintaining the genetic integrity of their animals. Many German Shepherd breeders have avoided the introduction of white genes into their breeding program. The gene that codes for the white coloration may be a gene that dilutes normal coloration. These animals most often have normal skin coloration and dark eyes, however many breeders associate the white coloration with skin, eye, or ear problems.
Since the exact genetic mechanism, which causes white coat coloration in German Shepherds, is not understood, most breeders only breed solid black or black/brown/tan (agouti) colored animals. One particular German Shepherd breeder did just that. She bred her animals from a long pedigree of solid black or black/tan agouti animals. The litters were predictably of the same coloration. However, she was distraught to find that a litter between a black dam and black/tan sire produced three black/tan pups and one black/tan/white pup. The black/tan/white pup also sported two striking blue eyes.
Since her animals’ genetic lineage was now under scrutiny, the breeder brought her pup to The Ohio State University Veterinary Hospital to determine the exact cause of the anomaly. Genetic testing by the AKC diagnostic laboratory confirmed the parentage of the pup. The sire and dam were bred successfully three additional times and all pups from these litters were predictably black or black/tan agouti.
To explain the characteristics of the anomalous pup, known as Frankie, exhaustive research into canine genetics and coat color inheritance of German Shepherds was conducted. Frankie matured and was bred to a male of consistent dark (black or black/tan agouti) lineage. The breeding produced four pups. Three pups were black/tan/white and one pup was black/tan agouti. Three pups had inherited the white coloration of their mother, however, none of the pups had blue eyes. It appeared that the white coat coloration was a genetic mutation and not the result of a recessive trait hiding within the lineage of the owners breeding stock. Although this was encouraging information for the breeder, the task was now to determine the characteristics of a possible mutation and how a coat color and eye color mutation could occur simultaneously.
The inheritance of coat colors in the German Shepherd has been studied based on records of the American Kennel Club over a twenty-five year period. Dogs considered being agouti consisted of either a dominant black coloration; or recessive tan-sable, gray-sable, and black and tan with the dominance in the order listed. Agouti is a protein produced within the hair follicle that acts to inhibit pigment production. The back coloration of the black and tan ranges from a small patch on the back to nearly complete body coverage. Many genes cause the variation in amount of black coverage of the back.
White color in the German Shepherd has been controversial since the origin of the breed and the white German Shepherds are not permitted to be registered in Germany. In Germany, the color transmission has been considered to be a recessive albino trait. Albinism is rare in the canine. An albino animal would have no pigment to the skin and pink eyes - blue-eyed animals are not albino. Others have proposed that the white coat color is due to a different gene that causes spotting. A completely white animal would be an example of the entire body being spotted white.
The white color pattern for dogs possibly having white as part of their normal coat color has been described in detail. There are eleven grades of color, which represent the extremes the white can occupy on the dog. Zero represents an all-solid nonwhite animal and a ten is an all white animal. The genetic reasons for the amount of white can be due to: many genes acting together, specific spotting genes, and accidents during development of the embryo. Skin under the white areas caused by the spotting gene is not pigmented.
White German Shepherds produced from nonwhite breedings had an almost complete white hair coat with a dark pigmented skin beneath. The nose, eyes, and exposed skin of these animals were reported to be heavily pigmented. This information would discredit the spotting gene theory since the pigment under the hair should be light colored if this were the method of transmission. The recessive albino theory also would not account for the color inheritance since the skin and eyes from two dark parents are always pigmented in the offspring. The breeding of white German Shepherds to dark German Shepherds produce dark colored, white, and light colored offspring.
The eye color is determined by the color of the iris and is dependent upon many genes. A possible gene for blue eyes has described, which was independent of coat color and recessive to brown iris coloration. The color of a dog’s hair is due to the presence of a protein called melanin made by cells called melanocytes. There are only two melanin types in hair, eumelanin (brown-black) and phaeomelanin (yellow-red). If the hair has neither pigment the color is white. One way to remove the pigment is by the presence of a mutant gene.
Some non-spotted breeds that are generally dark-colored produce occasional white dogs. These include the German Shepherd. In this breed there is a recessive gene that encodes for white hair with normal skin pigment and normally colored eyes. However, the most likely probability as to the origin of the white in this particular German Shepherd is a mutation affecting the spotting gene, since white on the chest, nose, toes or tail tips is due to this gene and is found in this breed. If the recessive gene caused the white coloration of Frankie, the offspring of the female should not be spotted white unless the sire of the three white and one black and tan offspring also carried the gene and then only half of the litter would be spotted white. The white color in this animal is not due to the white gene since the eyes are blue and only approximately 30% of the animal is white, the remainder is black and tan.
Frankie is a very structurally sound individual from a long lineage of excellent quality animals. The fact that she has had a mutation occur in her color pattern does not make her any less of a quality animal. One should realize when this type of “unusual event” occurs, do not necessarily reach the conclusion that the parents are “not” the parents. Mutations have occurred in all breeds of dogs; some good and some that are not. Furthermore, some affect the animal and some the people. This is a case of genetic mutation, which has not affected the quality of Frankie but may have an affect on the owners of German Shepherds. None of our dogs or us would be where we are today without genetic mutations!