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White coat hair appears when one or more regulator genes cause hair follicle melanocytes to inject no melanin pigment granules into the hair fiber as it is formed in the follicle structure. One of the most quoted books on dog genetics and coat color is "The Inheritance of Coat Color in Dogs" by Clarence C. Little, first published by Comstock in 1957. Several editions of Little's book have been published in the intervening years and most other books that discuss dog genetics and coat color are based on Little's work. Little's genetic research is based on hypothesized alleles with hypothesized dominance at hypothesized gene loci to fit data obtained by observing and categorizing coat colors and color patterns appearing in various dogs breeds and litters. Little's work continues to serve as the foundation of understanding for the determinants of coat color, but genetic science is starting to show where Little was right and where he was wrong. Modern genetic research now reveals that for some observed traits, or phenotypes, like coat color, the actual genetics are different from those hypothesized by Little and others.

Little (1957) hypothesized that dilution or partial albinism ceca and cch alleles of the so called (C) gene caused the cream and white coat color variants in domestic dogs. Locus (C), commonly referred to as the albino and paling gene, was historically used to explain the cream and white coat color variants of many species. For dogs, Little hypothesized that a possible cch (chinchilla) allele of the (C) gene pales phaeomelanin to cream, that a second possible allele ce dilutes phaeomelanin to white and a third possible allele ca causes pure albinism in homozygotes. Little's 1957 hypothesized explanation for cream and white colored coats has been applied across many domestic dog breeds, including white coat dogs from Pomeranian breed lines.

Most genetic researchers now map the so-called (C) gene to the tyrosinase (TYR) gene because albinism has been found to be the result of various genotype mutations at this locus in mice, humans, rabbits, cattle, and cats. The TYR locus is known to encode for tyrosinase, an enzyme that ultimately leads to the formation of the two natural melanin pigments eumelanin and phaeomelanin within melanocyte cell membranes. The most frequent form of albinism results from genotype mutations at the TYR locus that cause the tyrosinase enzyme to malfunction such that eumelanin and phaeomelanin production is retarded to varying degrees or fully eliminated. Over 100 different mutations within the tyrosinase gene are now known to cause the most frequent form of albinism genetically labeled as oculocutaneous albinism type 1, or OCA1.2 The specific mutations that encode for pink-eyed albinism in the domestic dog have not yet been identified through genetic testing.

A research project at the University of Saskatchewan Genetic Research Laboratory has, at least partially, identified the actual genetic mechanisms behind white and cream colored coats in several breeds of domestic dog. This research laboratory also searched for and has not found tyrosinase malfunction in white coat dogs common to those breeds. Little's 1957-era tyrosinase malfunction dilution or partial albinism explanation of the C locus ceca and cch alleles, as applied to explain domestic dog white and cream coat colors, therefore, can be replaced by the findings of modern genetic research.

A Gene Fundamental to Colored Coats Also Codes for White



The Melanocortin-1 receptor (MC1R) gene, more commonly known as the Extension (E) gene, regulates the production of eumelanin (brown/black) pigment in hair follicle melanocytes. Informed breeders have long understood the importance of the (E) gene in the formation of the breed’s distinctive coloration. This gene was originally identified as the Extension (E) gene because it was thought the dominant E allele of this gene "extends" eumelanin (brown/black) pigmentation over the entire body. An additional allele Em at the MC1R (E) locus was historically thought to modify pigment production over the face area to create the "melanistic" eumelanin black face mask color pattern common in many breeds, including the standard color Pomeranian breed.

An additional recessive e allele was also long thought to exist at the MC1R (E) gene locus, but most experts traditionally focus attention only on the dominant E and Em alleles while giving little notice to the recessive e allele.*  The e/e genotype was not considered important to Pomeranian breed conformation.

In dogs carrying a genotype that includes at least one of the dominant E or Em alleles (i.e. genotypes of E/e or Em/e also see table below) eumelanin production is not inhibited and eumelanin pigment is produced per the dominant allele’s signature trait. In dogs carrying a genotype that includes combinations of the dominant E or Em alleles (i.e. genotypes of E/E, E/Em and Em/Em) eumelanin pigment production varies according to the signature traits of the dominant allele pairings. The "melanistic" face mask will appear when a dog has either the E/Em or Em/Em genotype.

Recent DNA research has verified function of the recessive e allele at MC1R in several domestic dog breeds, including white coat dogs Pomeranian  breed lines. It is known the e allele at MC1R does not signal hair follicle melanocytes to "switch on" eumelanin production, as do the dominant E and Ealleles. Therefore, in dogs carrying an e/e genotype, there is no eumelanin available for the Agouti (A) gene awat and a alleles to regulate, and no eumelanin (brown/black) pigment to inject into the growing strands of hair. When an e allele at MC1R is inherited from each parent, the e/e genotype offspring can have only phaeomelanin (yellow/red) based coat colors of yellow, tan, light brown, red/rust or cream.

Furthermore, genetic research at the University of Saskatchewan has recently demonstrated that e/e genotype offspring, in some breeds, always inherit a cream to white coat color. Apparently, the phaeomelanin (yellow/red) hair follicle pigmenting processes in these dogs are strongly regulated to form cream colors, or are not "switched on" at all to form white coats. Researchers believe, therefore, that an as yet undiscovered allele or alleles of one or more other gene(s) must regulate phaeomelanin (yellow/red) pigment production in hair follicle melanocytes in a manner similar to the MC1R eumelanin regulating function.* White coat dogs apparently have neither hair follicle phaeomelanin nor eumelanin for the Agouti (A) gene awat and a alleles to regulate, and no eumelanin (brown/black) or phaeomelanin (yellow/red) pigment to inject into the growing strands of hair.

* - Positive identification of the specific allele, or alleles, that regulate phaeomelanin (yellow/red) pigment production in hair follicle melanocytes will complete our full understanding of the genetic mechanisms responsible for the formation of cream to white coat color. We must wait for additional genetic research for this answer.

The MC1R recessive e allele has been found in several dog breeds1, 3: Afghan, Akita*, American Eskimo Dog***, Australian Cattle Dog, Australian Shepherd, Beagle, Border Collie, Brittany Spaniel, Cardigan Welsh Corgi*, Caucasian Mountain Dog*, Chinese Shar-Pei*, Chow Chow, Cocker Spaniel, Dachshund, Dalmatian, Doberman Pinscher, English Cocker Spaniel, English Setter, English Springer Spaniel, Field Spaniel, Flat-Coated Retriever, Foxhound, French Bulldog, German Longhaired Pointer, German Shepherd Dog*, German Shorthaired Pointer, German Wirehaired Pointer, Golden/Yellow Labrador Retriever**, Great Pyrenees*, Irish Setter, Lowchen, Miniature Schnauzer*, Pointer, Pomeranian, Poodle*, Pudelpointer, Puli*, Samoyed***, West Highland White Terrier***.

* - e/e genotype breed that always presented cream to white coat color in DNA research at University of Saskatchewan. ** - e/e genotype breed tested at University of Saskatchewan where some dogs presented cream color coats and other dogs presented yellow color coats. *** - e/e genotype breed tested at University of Saskatchewan where white is the only standard breed color1.

It should be noted that the cream to white coat animals shown to carry the MC1R e/e genotype predominately have dark eyes and black skin on the nose, eyes and paws. It can then be inferred that yet another gene likely regulates pigmentation of these other structures.

White Pomeranian's  Carry Colored Coat DNA

DNA research at the University of Saskatchewan has shown that dogs carrying cream to white colored coats from several breeds, including white coat dogs from Pomeranian breed lines, always have an e/e genotype at MC1R. The Agouti (A) gene awat and a alleles, that e/e genotype white coat Pomeranian's  continue to carry, are hidden, or masked. The alleles are hidden because neither phaeomelanin nor eumelanin is made in the hair follicles giving Agouti (A) gene awat and a alleles nothing to regulate, and no eumelanin (brown/black) and phaeomelanin (yellow/red) pigment to inject into the growing strands of hair.

The successive white to white breeding programs that formally established the White Pomeranian and White Swiss Pomeranian breed(s) have "fixed"+ the e allele (and e/e genotype) at the MC1R gene locus, but the Agouti color coat alleles remain hidden in the DNA. Only a potential for the "melanistic" eumelanin black face mask color pattern has been eliminated from fixed e/e genotype White (Swiss) Pomeranian and White  Pomeranian breed lines. However, a single pairing of a White (Swiss) Pomeranian dam of genotype e/e - aw/aw with, for example, a Em/Em - aw/awgenotype standard color wolf sable Pomeranian Dog will produce a litter of Em/- aw/aw full sable colored Pomeranian puppies with "melanistic" eumelanin black face mask  A simple breed type DNA test on a White (Swiss) Pomeranian dog would return Pomeranian as the probable breed type because the dog carries Agouti (A) gene awat or a alleles.

+ - An allele for which all members of the population are homozygous, so that no other alleles for this locus exist in the population.
 

This table shows the combination of displayed and hidden white/cream and AKC breed standard colors that are possible in the various genotypes of the  Pomeranian Dog.

 MC1R (E) 
Genotype 
 Agouti (A) 
Genotype 
Coat Color and Pattern Displayed Hidden Color and Pattern Breeding Potential
Em/e ax/ax sable or black-and-tan w/mask white, lack of mask
Em/e ax/a sable or black-and-tan w/mask white & solid black, lack of mask
Em/e a/a solid black (mask not seen) white, lack of mask
E/e ax/ax sable or black-and-tan white
E/e ax/a sable or black-and-tan white & solid black
E/e a/a solid black white
e/e ax/ax white sable & black-and-tan
e/e ax/a white sable, black-and-tan & solid black
e/e a/a white solid black
note:
ax - denotes the Agouti (A) gene alleles afor sable and at for black-and-tan
a - denotes the Agouti (A) gene allele for solid black
E - denotes MC1R (E) gene dominant allele for eumelanin extension
Em - denotes the MC1R (E) gene allele for eumelanin extension and face mask pattern
e - denotes the recessive allele for eumelanin off.

Alleles of the Agouti (A) gene were genetically identified through a collaborative research project between the laboratories of Dr. Greg Barsh at Stanford University and the Dr. Sheila Schmutz at the University of Saskatchewan. Unfortunately, commercial DNA test commonly available as of Fall 2007 can not differentiate between the Agouti aw and at (and other possible Agouti) alleles, so DNA tests for German Shepherd Dog color may return only an ax indicator to signify only that one of the Agouti (A) gene color pattern alleles is present. Researchers have, however, identified a nucleotide mapped to the recessive a allele at the Agouti (A) gene that signals for a uniform solid black coat.5, 6

DNA Tests To Detect "White Factored" Colored German Shepherds

One of the conclusions drawn in the University of Saskatchewan MC1R e/e genotype research paper may be of particular interest to breeders of standard color only German Shepherd Dogs and White German Shepherd Dogs. This conclusion reads, "Because cream [white] dogs always have an e/e genotype at MC1R, DNA testing for an e allele should be predictive that the dog is heterozygous for cream [white] coat color in breeds such as Akita, Caucasian Mountain Dogs, German Shepherd Dogs, Miniature Schnauzers, and Puli."

Standard color only German Shepherd Dog breeders may wish to test their breeding pairs for the e allele to better refine their respective breeding programs. White German Shepherd Dog breeders who prefer to occasionally include "white factored" colored German Shepherds in their breeding program, may wish to determine if the colored dog breeding candidates are, in fact, heterozygous for white coat color before using them in their breeding program. (HealthGene Molecular Diagnostic and Research Center offers German Shepherd Dog e allele DNA testing that is based in part on the University of Saskatchewan research.)

MC1R e/e Genotype Research

Findings of the white coat MC1R e/e genotype research project at the University of Saskatchewan Genetics Laboratory was published in the July/August 2007 (Volume 98, Number 5) issue of the Journal of Heredity under the title of "The Genetics of Cream Coat Color in Dogs" This research paper also discusses test findings that Little's hypothesized ceca and cch (chinchilla) alleles of the albino TYR (C) locus are likely not relevant determinants of cream to white coats known to commonly occur in domestic dog breed.

Other recent genetic research has shown that other species, including the white “Kermode” black bear found in the rain forests along the north coast of British Columbia, also carry the recessive e/e allele at MC1R. These white coat bears have cream to white coats dark eyes and black skin on the nose, eyes and paws. The recessive e/egenotype at MC1R research paper on the white-phased “Kermodblack bear4 was published in the September 18, 2001 (Volume 11, Issue 18) issue of Current Biology.

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Conclusion


The recessive gene for white coat hair was cast in the breed gene pool by the late 19th and early 20th century breeding program that developed and expanded the German Shepherd Dog breed in Germany.  It is a historical fact that a white herding dog named Greif von Sparwasser (whelped in Friedrich Sparwasser's Frankfort kennel in 1879) was the Grandfather of Horand von Grafrath, (whelped in Friedrich Sparwasser's Frankfort kennel in January 1895 as Hektor von Sparwasser) the dog acknowledged as the foundation of all contemporary German Shepherd Dog bloodlines.*  “Der Deutsche Schaferhund In Wort Und Bild" ("The German Shepherd Dog in Words and Picture") written by the recognized father of the breed, Rittmeister (Cavalry Captain) Max von Stephanitz, in 1921 included a photo of Berno von der Seewiese, a White German Shepherd directly descended from Horand.  (Photo left of Berno von der Seewiese b.1913 in the kennel of G. Uebe von Seehausen)


Information provided in early books on the German Shepherd Dog, such as "The Alsatian WoIf Dog" written by George Horowitz in 1923, as well as "The German Shepherd, Its History, Development and Genetics" written by M. B. Willis in 1977, make mention of Greif and other white German herding dogs, with upright ears and a general body description that resembles modern German Shepherd Dogs, having been shown in Europe as early as 1882.  (Photo right is a young bitch from a 1906 German newsletter publication, author unknown - photo provided by Ruut Tilstra of the International White Shepherd Federation10.)

The early 20th century German Shepherd breeding program extensively line bred and inbred color coat dogs that carried Greiff's recessive gene for white coats, to refine and expand the population of early German Shepherd Dogs.  Horand’s litter brother Luchs was also widely bred in the same way in the expansion of the modern German Shepherd breed.  In the first 15 years of pedigreed German Shepherd Dog breeding more than half the registered dogs had litters with white puppies.  Many of Horand's and Luchs’ progeny produced white pups, including Berno von der Seewiese (b.1913) who can be found in the SV breed book.


Our more complete understanding of MC1R gene function, perhaps, gives new insight into how the white coat so easily became established in the early population of German Shepherds and why Greif’s genes were essential to the development of the German Shepherd breed.  As do White Shepherds of today, Greif very probably carried Agouti gene alleles, in addition to other gene alleles for conformation features such as upright ears.  We know from written descriptions and pictures that Horand and Luchs had wolf/sable colored coats indicating they carried at least one Aw allele in their genotype and likely carried a full Aw/Awgenotype.  The picture is faded and not of high quality, but the dog appears to have a dark mussel indicating he may carry an Em allele in his genotype. We also know their grandsire was white and that many of their progeny had white coats too.  From this information we can deduce that one or both dogs carried a recessivee allele in their MC1R genotype.  Therefore, either one or both Horand and Luchs must have had a MC1R genotype of at least of E/e, and, if Horand picture does indeed show he has a dark mussel, one or both dogs had a genotype of Em/e.  If so, grandsire Greif then, likely carried an e/e - aw/aw genotype and Horand and Luchs inherited the E and/or Em alleles from their sable/wolf colored parents.  Horand and Luchs then would have had either a Em/- aw/aw or E/- aw/aw "hidden white" genotype.  From the first direct ancestors of the German Shepherd Dog forward to modern German Shepherds, the MC1R recessive allele for white colored coats has been carried in the DNA of some portion of the breed.  (Horand photo left provided by Ruut Tilstra of the International White Shepherd Federation10.)

White coats were listed as disqualifications in the German Shepherd Club of Germany breed standard in 1933, the American Kennel Club (AKC) German Shepherd standard in 1968, the Canadian Kennel Club German Shepherd standard in 1998, and the Australian National Kennel Council German Shepherd list (standard) in 1994, at least partially, on the argument that white coats are the result of an albinism condition that carries risks of breed color paling and genetic health defects.

Genetic research now reveals that one of the alleles that code for white coats in the German Shepherd breed is at the MC1R eumelanin regulation gene locus.  The MC1R gene is fundamental to overall German Shepherd Dog breed color conformation and it is certainly unrelated to albinism.  A reasonable argument can be made that the recessive MC1R e allele is somewhat analogous in magnitude of function to the recessive solid black coat Agouti a allele; Solid black coats are not specified as a German Shepherd Dog breed standard disqualification.

We must wait for further genetic research to give us positive identification of the allele, or alleles, which regulate phaeomelanin pigment production in hair follicle melanocytes to complete our understanding of cream to white coat color in the Shepherd breed.  Even so, factual evidence is growing against the argument that albinism explains white coat color in the White German Shepherd, White Shepherd and White Swiss Shepherd breed lines.

* - Stephanitz, accompanied by his friend Artur Meyer, attended the April 3, 1899 Karlesruhe Dog Exhibition, one of the largest all breed dog shows to date, in the Rhineland town of Karlesruhe.  Stephanitz and Meyer saw a herding dog name Hektor (Linksrhein) von Sparwasser and immediately realized he had found his ideal foundation dog.  Hektor was born the 1st of January 1895 along with litter brother Luchs von Sparwasser, later registered SZ-155.  The breeder of Hektor and Luchs was Herr Friedrich Sparwasser of Frankfort.  Horand whelped in Friedrich Sparwasser's Frankfort kennel in (as Hektor von Sparwasser) together with litter brother Luchs.  Hektor is sometimes referenced as Hektor Linksrhein with Linksrhein referring to the Rhine region of his kennel.  Frankfort is close to the Rhine river on the Rhine’s Main tributary and is considered to be in the Rhine region.  

Stephanitz at once bought Hektor and renamed the dog Horand von Grafrath.  Horand is the first entry in the German Shepherd Dog Club of Germany or Der Verein für Deutsche Schäferhunde, or SV, Stud Book as “Horand von Grafrath, SZ-1.

”Horand’s and Luchs’ maternal grandfather was a white-coated German herding dog named Greif von Sparwasser, whelped in Friedrich Sparwasser's Frankfort kennel in 1879.  George Horowitz, renowned English Judge, German Shepherd (Alsatian) columnist, author and historian documents the background of Hektor Linksrhein (a.k.a. Horand von Grafrath) in his 1923 book, “The Alsatian Wolf-Dog.” In his book Horowitz documents that Greif von Sparwasser was presented at the 1882 and 1887 Hanover Dog Shows.   Horowitz also documents Greif's white progeny entered in shows in succeeding years.

Greif von Sparwasser was mated with female Lotte von Sparwasser who whelped a litter that included a wolf-grey colored female named Lene von Sparwasser, later registered SZ-156.  Both Greiff and Lotta had the distinctive 'up right' ears and a similar body conformation that we see in the modern German Shepherd Dog breed.  In Lene's mating to dog Kastor (Rüde) von Hanau SZ-153 she whelped a litter that included the wolf colored Hektor (a.k.a. Horand von Grafrath SZ-1) and his wolf colored litter brother Luchs, SZ-155.  Friedrich Sparwasser obviously had both white and wolf (sable) colored herding dogs of the same body conformation in his kennel and he was pairing white and colored dogs in his breeding program.  Sparwasser's herding dogs are described as originating from the German Thuringia highland region.

Horand von Grafrath, whelped in Friedrich Sparwasser's Frankfort kennel in January 1895 as Hektor von Sparwasser.  Hektor is sometimes referenced as Hektor Linksrhein with Linksrhein referring to the Rhine region of his kennel.  Frankfort is close to the Rhine river on the Rhine’s Main tributary and is considered to be in the Rhine region.