Brindle (k^br)

Brindle (k^br) is a color pattern causing black, blue, brown or lilac stripes on a red or yellow base color. Here we look at the variations and genetics of brindle coat in dogs.

What is Brindle?

Brindle appears in dogs that express an A-Locus pattern (clear sable, shaded sable, agouti, saddle back or tan point). Brindle adds random vertical stripes of eumelanin-pigmented coat running from top to bottom over the red base color pigmented by phaeomelanin. Learn more about pigment types here.

While brindle stripes often seem quite irregular they often follow some basic direction with a V-shape along the back and stripes running vertically and loosely following the shape of the body.

Both eumelanin and phaeomelanin are visible in this pattern and many traits like merle, greying, color dilution, liver, white spotting, ticking, intensity or countershading can have an influence on how a brindled dog actually looks.

And there might also be some yet unknown modifiers that affect the expression of different brindle patterns.

The k^br-Allele

There are three alleles at the K-Locus: K^B (dominant black), k^br (brindle) and k^y (normal expression).

The wild type allele k^y causes normal production of eumelanin and phaeomelanin in all patterns. The dominant allele K^B causes a dominant black coat with only eumelanin.

k^brindle is recessive to K^B but dominant over k^y. The k^br allele causes a mix between these phenotypes with stripes of eumelanin on all coat areas pigmented by phaeomelanin.

k^br causes a somewhat random variegated expression of the K^B allele on red coat. And this is hardly surprising if we consider that the k^br orignated from a recombination event between a K^B and a k^y allele. So the brindle allele essentially is a duplication of the K-Locus on one chromosome.

The brindle stripes give us a clue about the pathways the pigment cell precursors (melanoblasts) traveled across our dog’s body. During embryonic development, they migrate from the neural crest along the body all the way to the extremities. And in brindle dogs, some cells produce a solid black coat (K^B) and some produce a solid yellow coat (k^y) creating a striping pattern.

And since brindle is already present in breeds of ancient origin like Akita, Shiba and other Asian spitz breeds the first brindled dog likely lived several thousand years ago. Today brindle is found in dogs from all breed groups like Dachshund, Mastiff, Irish Wolfhound or Cairn Terrier.

By the way, at the moment there is no commercial test available testing for brindle. Instead, K^B/k^br, k^br/k^br or k^br/k^y will all be reported as K^B/k^y since elements from both alleles are present.

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There seems to be more to brindle than we currently understand. Newer research by Vetgenomics Russia from 2023 indicates that brindle alleles can change between generations.

And this could explain some weird observations breeders made over the years. And hopefully, it will help in finally producing a reliable testing method.

During the formation of germ cells, there is some pairing and reshuffling of homologous sequences between chromosomes, called recombination.

Brindle is a fusion of a K^B and a k^y sequence sitting on the same chromosome (K^B+k^y or k^br). During recombination, a brindle allele can lose one of these sequences and revert back to either K^B or k^y.

Recombination can also produce brindle alleles with more than one copy of K^B (K^B+K^B+k^y or k^br+). And again, brindle alleles with a duplicated KB sequence can also sometimes revert back to normal brindle (K^B+k^y or k^br).

Actually, there seem to be at least a few known cases of brindle dogs producing solid offspring with a k^y/k^y partner. Meaning, some dogs that are visibly k^br/- seem to pass on a surprise K^B to their offspring…

All of this would explain how breeders can easily select for extra-dark brindle coats (unknowingly selecting for K^B+K^B+k^y or k^br+). Or how some offspring has an unusually light or dark pattern compared to the rest of the breed (when k^br turned into k^br+ or k^br turned into K^B or k^br+ reverted to k^br). Also, think of almost black “reverse brindle” or “seal” in breeds such as French Bulldogs or Boxers.

When will a dog be brindled?

To have a brindle pattern with alternating stripes of eumelanin on phaeomelanin a dog has to be able to produce both types of pigment and to switch from one to the other.

So brindle won’t be expressed in dogs that are either recessive red (phaeomelanin only), dominant black (which would be K^B/k^br anyway) or recessive black (eumelanin only).

And of course, the coat has to be pigmented at least in some areas. If a dog is all white e.g. due to extreme piebald we can’t observe the brindle pattern.

Brindle Patterns

Brindle can affect different agouti patterns and can itself be affected by a variety of different genes explaining the many different looks on brindle dogs!

Brindle Density

The brindle pattern in some dogs is very minimal with only some sparse stripes here and there.

Minimal brindle can be found in many breeds from Great Dane to Bulldog and is often seen in sighthound breeds like Whippet, Galgo Español or Greyhound. Sometimes stripes even seem to be missing from the pattern.

But brindle can also get very heavy up to the point where the dog looks almost completely black.

Since a very dense striping pattern gives the impression the dog had actually red stripes on black coat this is sometimes called black brindle or reverse brindle. But there is no such thing and technically all brindle dogs express black stripes on a red coat.

Black brindle can be found in many breeds like French Bulldog, Boston Terrier, Boxer, Cairn Terrier or Kai Ken. Very dark brindle patterns are often accompanied by extended black masks.

Brindle and Coat Types

The distinct stripes in brindle patterns can be seen most clearly in shorthaired dogs. But of course, many breeds with very different coat qualities can sport a brindle pattern.

The brindle pattern on wirehaired and furnished, curly or longhaired dogs is less visible and often causes a muddy color with darker and lighter areas that seem to blend into one another.

Brindle on Sable

The most basic brindle pattern is a brindled sable. Sables have yellow coat all over the body with varying amounts of dark shading. Some of the sable pattern can be covered by white spotting or a melanistic mask, but usually, there is plenty of space where brindle can show.

Shaded sable and even clear sable with brindle can get quite dark especially along the dog’s back. This can obscure some of the brindle pattern.

Brindle on Agouti

Agouti causes alternating dark and light bands in single hairs and usually appears very greyish and can get quite dark. The combination of agouti and brindle is quite rare.

But the effect is nearly the same as in heavily shaded sables because brindle stripes become less visible or not visible at all on an already very dark coat.

Brindlepoint

In tan pointed dogs, black stripes will only be visible in the lighter tan markings. Such a brindled tan point pattern is often called brindlepont.

In dogs with already very sooty tan points, an extended dark mask, a white blaze or white spotting on the lower legs the tan points and thus the brindle pattern can become very small and barely visible.

Trindle

Tan pointed dogs with white spotting are commonly called tricolor (e.g. a black-tricolor would be black-and-tan-and-white). As in a normal tan point pattern, brindle will only affect the tan markings.

The combination of brindle with white markings on a black and tan dog is sometimes called trindle (as in tricolor-brindle).

Brindled Saddle Pattern

Since brindle only affects red coat. Only the lighter areas on a saddle-patterned dog get brindle stripes. The same goes for the intermediate pattern called creeping tan.

Brindle and Melanistic Mask

Brindle on the muzzle can be covered up by a melanistic mask. This is a common combination in breeds like Boxer, Mastiff, French Bulldogs, Great Danes or Dutch Herder.

Brindle and Phaeomelanin Intensity

While most dogs have a yellow to red pigment intensity under their brindle stripes their base color can be affected by intensity modifiers like the I-Locus. Phaeomelanin pigment color can actually vary from off-white to deep red.

Dogs with a very light base color are sometimes called silver brindle, cream brindle or other names.

Brindle and Countershading

Sometimes only the phaeomelanin on a sable, agouti, saddle or tan point pattern can get very light on the dog’s cheeks, eyebrows underside while keeping a normal color on the upper side of the dog.

This phenomenon is called countershading. In brindled dogs, it gives the impression of a color transition underneath the black stripes.

In some Asian spitz breeds, a similar effect is known as urajiro. This is just a Japanese breed term for countershading but these breeds are known to often have more crisp and bright light markings instead of a color gradient from lighter to darker coat.

Brindle Colors

The color of eumelanin in brindle stripes can be black, brown, blue or lilac.

A homozygous recessive genotype at the B-Locus (bb) causes brown pigment while a homozygous recessive combination at the D-Locus (dd) can dilute black pigment to blue or brown coat to isabella/lilac.

Brown Brindle

The combination of liver-colored eumelanin and brindle pattern (k^br/- b/b D/-) is quite rare. Besides, brown stripes on a yellow or red base color don’t give as much contrast as black stripes would.

Blue Brindle

In a dog with a diluted black brindle pattern (k^br/- B/- d/d) all eumelanin will turn a blue shade.

Since blue stripes o yellow or red coat again isn’t as rich in contrast as black stripes the striping often is not as distinct as it would be in a black dog.

Lilac Brindle

A brown dog with pigment dilution (k^br/- b/b d/d) will have lilac stripes on a yellow or red coat. This is a very rare combination and is often barely visible.

Brindle and Greying

Progressive Greying causes eumelanin intensity to fade over time in growing hairs.

Black stripes will turn grey and brown stripes will turn beige. Since this only affects wiry or curly coats it can make an already muddy brindle pattern even more washed-out.

Grey Brindle can be found in Irish Wolfhound, Scottish Deerhound and some terrier breeds like Cairn Terrier.

Brindle and White Spotting

White markings (from things like piebald or whitehead) are areas with a lack of pigmentation. Since neither phaeomelanin nor eumelanin is visible in the white coat the brindle will be hidden “under” the white spotting.

Many sighthounds like Whippet or Greyhound often come in brindle-white. This can also be observed in the trindle pattern (tricolor and brindle) mentioned above.

Brindle Ticking and Roan

Ticking only affects white coat where it shows as pigmented dots and speckles in the original color the coat would have had at this spot. So on a brindle patterned dog the spots would be brindled.

Roan is expressed as areas with many fully pigmented hairs growing in white coat. Roan can get quite dense and give the impression of an almost fully pigmented coat. But the combination of roan and brindle is rather rare.

I’m still searching for mottled or roaned dogs with an underlying brindle pattern. This dog shows extreme white spotting with some colored spots on his ears to illustrate the effect:

Brindle Merle

Merle deletes some of only the eumelanin in a dog’s coat. While the red or yellow coat is not affected all eumelanin will be a mix of fully pigmented and diluted patches.

Merle will only affect the eumelanin stripes on a brindled coat. This causes the stripes on a brindle merle to look broken, patchy or unusually irregular.

Brindlequin

Great Danes have a breed-specific merle modifier known as harlequin that only affects dogs with a merle genotype but will not be visible on non-merled Great Danes.

A H/h genotype at the H-Locus will cause all diluted areas in a merle coat to be fully deleted to white. This gives a distinct pattern with fully pigmented patches on a white coat.

The only desired harlequin color is black and white so most breeders try to plan accordingly.

But harlequin absolutely works on sable merle or brindle merle coats. These phenotypes are typically dubbed fawnequin or brindlequin.

Brindle Seal

Seal seems to make eumelanin transparent to some degree and lets the hidden agouti locus pattern shine through from underneath. But the exact mechanisms behind seal coloration are not yet identified.

Most often seal only affects heterozygous dominant black dogs (K^B/k^y). Black areas fade and reveal some of the normally hidden sable genotype (A^y/-). Seal dogs typically get a very brownish cast to their coat with a stripe of the black coat down the midline and black coat on the face and lower legs.

There are some rare cases known of brindle expressing on dogs with a seal phenotype.

In seal brindle dogs the black stripes seem to fade to a reddish bronze color and affected dogs can look almost brown with a very faint brindle pattern. Brindle Seal occasionally seems to happen in breeds like Boxer and bully breeds, Boston Terrier or Catahoula Leopard Dogs.

Brindle Domino

Domino is most often found in northern breeds (e^A) or sigthound breeds (e^G) where it modifies the original pattern a dog would have had.

Domino seems to restrict eumelanin production. It makes tan markings lighter and forms a large open facial mask on tan pointed dogs. Domino also causes light hair roots in an otherwise black coat.

Brindle with domino is quite rare and mostly happens in sighthounds like Afghan Hounds or Borzoi where it can do some interesting things.

On a sable brindle, the domino fades brindle striping. The brindle pattern almost disappears and leaves a light base color with some darker smudges.

And domino on a brindle point pattern will make the black coat on the dog’s back fade to some degree. The brindle can become visible in the black mantle while fading on the dogs face and legs.

Dog Breeds with Brindle

Brindle is a very common pattern in many dog breeds. In some of them it’s a very popular pattern (e.g. Boxer, Dutch Shepherd Dog), in others it’s quite rare (e.g. Border Collie):

• Afghan Hound
• American Akita
• Akita Inu
• American Bulldog
• American Staffordshire Terrier
• Azawakh
• Basenji
• Border Collie
• Borzoi
• Boston Terrier
• Bouvier des Ardennes
• Bouvier des Flandres
• Boxer
• Bullmastiff
• Bull Terrier
• Ca de Bou
• Cairn Terrier
• Cane Corso
• Cão de Castro Laboreiro
• Chihuahua
• Cimarrón Uruguayo
• Dachshund
• Dutch Shepherd Dog
• English Bulldog
• Fila Brasileiro
• French Bulldog
• Galgo Español
• Great Dane
• Greyhound
• Hanoverian Scent Hound
• Irish Glen of Imaal Terrier
• Irish Wolfhound
• Presa Canario
• Kai Ken
• Miniature Bull Terrier
• Neapolitan Mastiff
• Pyrenean Shepherd
• Scottish Deerhound
• Scottish Terrier
• Segugio Maremmano
• Sloughi
• Staffordshire Bull Terrier
• Taiwan Dog
• Welsh Corgi Cardigan
• Whippet

Learn More

Links

[1] Julie A Kerns, Edward J Cargill, Leigh Anne Clark, Sophie I Candille, Tom G Berryere, Michael Olivier, George Lust, Rory J Todhunter, Sheila M Schmutz, Keith E Murphy, Gregory S Barsh. Linkage and Segregation Analysis of Black and Brindle Coat Color in Domestic Dogs. Genetics, Volume 176, Issue 3, 1 July 2007, Pages 1679–1689, https://doi.org/10.1534/genetics.107.074237

[2] S. M. Schmutz, T. G. Berryere, N. M. Ellinwood, J. A. Kerns, G. S. Barsh. MC1R Studies in Dogs With Melanistic Mask or Brindle Patterns. Journal of Heredity, Volume 94, Issue 1, January 2003, Pages 69–73. https://doi.org/10.1093/jhered/esg014

[3] Dreger DL, Anderson H, Donner J, Clark JA, Dykstra A, Hughes AM, Ekenstedt KJ. Atypical Genotypes for Canine Agouti Signaling Protein Suggest Novel Chromosomal Rearrangement. Genes (Basel). 2020 Jul 3;11(7):739. doi: 10.3390/genes11070739. PMID: 32635139; PMCID: PMC7397341.