G-Locus

Progressive graying causes a dog’s eumelanin pigment color to fade over time. Black fades to gray or silver gray while brown fades to a beige, sandy reddish-cream shade.

What is Progressive Graying?

In some dog breeds, puppies are born with regular black or brown eumelanin pigment but over time the coat color fades to a lighter and paler shade.

This phenomenon is called progressive graying or progressive fading. It usually starts in young puppies but can take up to several years until complete.

Progressive graying only affects bearded dogs and is found in many wirehaired or curly dog breeds. Graying begins at the hair base and is influenced by hair age. It causes a gradual decrease of pigment density in the cortex of the growing hair shaft.

Since the coat in many furnished breeds grows continuously the color in the hair tips grows out over time. And shaving these dogs can speed up the perceived loss of color when we cut off all of the darker and older hair.

As a rule of thumb, eumelanin in any pattern will fade from black to blue-gray or to a silver-white gray, from brown to beige or to a pale cream color/café au lait.

Graying on dilute colors (blue and lilac) might not be as prominent at first glance but will further lighten even these colors.

Nose and skin pigment will not fade and keep their original color. Phaeomelanin doesn’t seem to be affected in many cases but the influence of fading on phaeomelanin intensity remains unclear^[1].

The Graying-Locus

The potential allele causing a pigment fading phenotype is thought to be found at the theoretical G Locus. But the Graying Locus has not been identified with certainty yet. So for now, we don’t know what mechanism is responsible for color fading in some bearded dog breeds.

One candidate for explaining graying is the KITLG gene on dog chromosome 15. In a recently published study variation in KITLG seemed to be associated with pigment intensity along the hair shaft, phaeomelanin intensity in some breeds but also with color variation in eumelanin-based Poodles^[2].

But for now, we can only theorize how graying works from a breeder’s perspective. Progressive graying seems to be an incomplete dominant trait that causes a dose-dependent effect on all eumelanin in a dog’s coat.

Dogs with a g/g genotype don’t develop graying and keep their original color.

Dogs with a G/g genotype will fade to some degree.

But the strongest effect can usually be observed in dogs that are G/G. Homozygous dogs seem to fade quicker and more dramatically.

Since this is a dominant trait a dog can not be a carrier without actually expressing graying. But graying will only affect dogs with furnishings and at least some eumelanin in their coat.

Graying will not be visible in dogs with smooth facial hair or dogs with extensive white spotting, clear sable or a recessive red phenotype. But these dogs can still pass graying on to their offspring if they are in fact G/G or G/g.

Some long-haired dogs with a graying factor are said to have a lighter hair base even without furnishings.

Graying Examples

The coat pigmentation of dogs with progressive graying lightens as a dog reaches adulthood.

But this process can take some time and sometimes takes years until complete. In some cases, the coat will even periodically get darker when new hair growth happens.

Usually, puppies are born with normal pigment (“black born gray“) but can have lighter paws or a lighter muzzle even at birth.

Solid Coat Colors

Many dog breeds with graying have a solid coat color from dominant black (or in some rarer cases recessive black, e.g. in Pumis).

Interestingly, in breeds with dominant black, the hidden pattern on the A-Locus can temporarily become visible during the graying process, e.g. as faint tan markings on the muzzle or reddish hair on the back.

Dogs with solid coat color and graying can be found in some Poodles, Labradoodles, Bedlington Terriers, Briards, Kerry Blue Terriers or Pyrenean Shepherds.

Usually, a black coat will fade to blue or silver and a brown coat will fade to beige or café au lait. Areas with a shorter coat like the ears or tail can hold pigment better and appear darker than leg furnishings or a fluffy topknot.

But the range of colors caused by fading is pretty variable. Minimal graying is sometimes perceived as “bad pigment” since it only loses some of its rich and full color.

Graying and White

Many dogs with fading pigment have white markings, e.g. Bearded Collies, Spanish Water Dogs, Portuguese Water Dogs or some parti Poodles.

Graying and Masks

In dogs with an E^m allele, the eumelanin on the muzzle doesn’t seem to fade like the eumelanin in the rest of the coat. This gives a gray phenotype with a black mask or a sandy beige coat with a brown mask.

This can happen in many breeds with graying, e.g Kerry Blue Terrier, Bouvier des Flandres, Briard, Tibetan Terrier or Pyrenean Shepherd.

Graying and Sabling

Dogs with heavy sable shading have enough eumelanin that graying can be visible. Examples can be found in breeds like Pyrenean Shepherd, Irish Wolfhound, Tibetan Terrier, Löwchen or Skye Terrier.

Some sable dogs only have dark pigment on their ear tips which will turn gray over time.

Graying and Brindle

Many dogs breeds with progressive graying have a brindle pattern.

But since all of the affected breeds are long-haired, wiry or curly the darker stripes in their coat give a less distinct pattern compared to short-haired dogs. And graying obscures a brindle pattern even more.

Brindle with graying is found in breeds like Skye Terriers, Bouviers, Glen of Imaal Terrier, Deerhound or Irish Wolfhound.

Graying and Tan Points

On a tan point pattern, the black or brown eumelanin will fade to gray, silver, beige or sandy cream shades. Sometimes there is not too much contrast left between lighter tan markings and a fully faded base coat color.

Some dog breeds with a tan point pattern and graying are phantom Poodles, Cesky Terriers, Bedlington Terriers or Dandie Dinmont Terriers.

Graying and Saddle Tan

In dogs with a saddle pattern and graying the tan markings grow while the saddle becomes lighter and lighter. Prominent examples of dogs with a gray saddle are Yorkshire Terrier or Australian Silky Terriers.

Some other examples are Otterhounds, Lakeland Terriers, Griffon Nivernais, Petit Basset Griffon Vendéen or Grand Basset Griffon Vendéen.

Graying and Merle

Typical breeds with progressive graying are not breeds that traditionally come in merle. But in some crosses like Aussiedoodles, lurchers or terrier mixes these traits can meet.

A classic merle pattern causes a random mixture of pigmented and diluted patches on eumelanin-pigmented areas. Graying will cause even the once fully colored patches to fade and make any merle pattern less distinct or barely visible.

Graying Look-Alikes

Not all dogs with blue or gray coats got their color from progressive graying:

• Dilution can turn black to blue and brown to lilac. But these dogs are already born with a diluted coat color and diluted skin and nose pigment.
• White phaeomelanin intensity in A-Locus patterns can look very grayish, e.g. pepper-and-salt in Schnauzers.
• Atypical Merle sometimes causes a uniform grayish color instead of a more patchy merle pattern.
• Domino and Grizzle cause pale hair roots, less eumelanin and it lightens phaeomelanin. The actual phenotype depends on a dogs original pattern but many dogs with domino look grayish.

Dog Breeds with Progressive Graying

Graying is present in many bearded dog breeds:

• Australian Silky Terrier
• Australian Terrier
• Bearded Collie
• Bedlington Terrier
• Bergamasco Shepherd Dog
• Biewer Terrier
• Bolonka Zwetna
• Bouvier des Flandres
• Briard
• Cairn Terrier
• Catalan Sheepdog
• Cesky Terrier
• Dandie Dinmont Terrier
• Deerhound
• Glen of Imaal Terrier
• Grand Basset Griffon Vendéen
• Griffon Nivernais
• Havanese
• Irish Wolfhound
• Jack Russell Terrier
• Kerry Blue Terrier
• Lagotto Romagnolo
• Lakeland Terrier
• Lhasa Apso
• Löwchen
• Old English Sheepdog
• Otterhound
• Parson Russell Terrier
• Petit Basset Griffon Vendéen
• Poodle
• Polish Lowland Sheepdog
• Portuguese Water Dog
• Puli
• Pumi
• Pyrenean Shepherd
• Sealyham Terrier
• Skye Terrier
• South Russian Shepherd Dog
• Spanish Water Dog
• Tibetan Terrier
• Yorkshire Terrier

Learn More

Links

[1] Slavney AJ, Kawakami T, Jensen MK, Nelson TC, Sams AJ, Boyko AR (2021) Five genetic variants explain over 70% of hair coat pheomelanin intensity variation in purebred and mixed breed domestic dogs. PLoS ONE 16(5): e0250579. https://doi.org/10.1371/journal.pone.0250579

[2] Weich K, Affolter V, York D, Rebhun R, Grahn R, Kallenberg A, Bannasch D. Pigment Intensity in Dogs is Associated with a Copy Number Variant Upstream of KITLG. Genes. 2020; 11(1):75. https://doi.org/10.3390/genes11010075

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