French Bulldog Coat Color Genetics, In Depth

Brindle, Cream, Pale Cream, Fawn Pied - Four French Bulldogs, Four different colors

I’m about to begin a series of posts about French Bulldog coat colors. This can be taken as a warning, for those of whose eyes glaze over whenever this topic comes up. I’m most definitely a layperson, and not a geneticist, so bear that in mind when reading.

It will be broken down into the following sections:

Brindle (which is a coat pattern, not color)
Pied (see above, with pied being a marking, not a color or a pattern)
Black Masked dogs
Fawn and creams (an attempt to decipher the mysteries of the ‘e’ allele)
“Mystery Alleles” – everything else, and then some, from ticking to agouti to Dilute Colors

I’m basing a lot of this on the new, updated coat color genetic information research being done around the world, but in large part on the work of Dr. Schmutz, of the University of Saskatchewan. She writes that DNA and breeding research has identified the following alleles definitively —

Alleles known to exist at the 8 genes mapped in dogs, using DNA.

* A (agouti) = agouti signalling protein (ASIP) Examples with photos
o ay = fawn (cream to yellow to red with darker tips)
o sable (some solid black hairs intermingled amongst reddish hiars) aw = wild color of sable (black tips on cream to red hairs)
o at = black-and-tan or brown-and-tan
o a = recessive black
* B (brown) = tyrosinase related protein 1 (TYRP1) Examples with photos
o B = black eumelanin
o b, including (bs,b d,bc) = brown eumelanin
* E (extension) = melanocortin receptor 1 (MC1R) Examples with photos
o EM = melanistic mask Examples with photos
o E = eumelanin or phaeomelanin can be produced in hair
o e = only phaeomelanin produced in hair
* D (dilutes or pales eumelanin pigment to blue, and phaeomelanin subtly) = (MLPH) Examples with photos
o D = not diluted
o d = diluted pigmentation
* K (from black, “dominant black”) = Beta-defensin 103 Examples with photos
o KB = solid black, brown or blue (eumelanin pigmentation only)
o kbr = brindle (on body region that would be phaeomelanin pigmented otherwise)
o ky = expression of agouti alleles that express phaeomelanin possible
* M (Merle) = (SILV) Examples with photos
o M = Merle apparent on dogs that are not e/e
o m = wild type, no merle
* S (Spotting) = (MITF) Examples with photos
Note that this gene is certainly involved in piebald spotting, but may or may not be involved in Irish spotting
o S = Solid, or more correctly, minimal to no white markings
o s = piebald or randmon spotting, also called particolor
* H (Harlequin) = (gene not yet identified, but trait mapped to chromosome 9) Examples with photos
Note that for the Harlequin pattern to occur, at least one H allele and one M allele must be present.
o H = Harlequin pattern of Great Danes
o h = wild type, no Harlequin pattern

Additional alleles postulated to exist based on breeding data

* G (Progressive Greying) = (gene not yet identified) Examples with photos
This gene causes gradual greying of black or brown hair and paling of red hair, prior to geriatric age.
o G = Progressive greying
o g = wild type, no premature greying
* I (Intense) = (gene not yet identified) Affects only phaeomelanin pigment
o I = intense red, not diluted
o i = co-dominant, so i/i dogs are paler than I/i dogs
* C (Colored) = (gene not yet identified)
o C = full pigmentation
o ca = albino
* T (Ticked) = (gene not yet identified) Ticks are small pigmented flecks of color in white spots. Ticking is not visible on a solid colored dog. It is possible that there is a second gene causing Roaning, but that is not clear at this time.
o T = ticked
o t = not ticked