The Genetics of Seal Brindle in the Cane Corso … Probably
Editor's Note: Stefanie Henneboehl runs the popular Coats and Colors website (www.coatsandcolors.com). When I contacted her about clarifying my understanding of seal brindle in the Corso, she sent back a very detailed explanation of the genetics behind this color phenomenon in the breed.
Those who find genetics articles to be a bewildering minestrone soup of lower- and upper-case letters will not find relief here: Those same annotations figure centrally Stefanie’s explanation. But they are worth the time to decipher them. Stefanie has such a clear and accessible way of describing genetic concepts — complete with adorable cartoon Corsos to illustrate the various coat patterns and colors — that I immediately asked her permission to publish an edited version of it. And she graciously agreed.
Stefanie based the following comments on the Embark coat-color results of a Cane Corso that is identifiable in photos as a seal brindle.
Photographs accompanying this story were chosen primarily for how clearly they showed this often ambiguous color, not for the typiness of the dogs themselves.
There are still quite a few unknowns involving what causes seal or brindle seal.
I'll try to explain, with one caveat: The following reﬂects my current understanding. It might not hold up if one day researchers ﬁnd whatever actually causes seal.
First of all, many breeds have their own lingo for seal and brindle phenotypes that don't always reﬂect color genetics. Terms such as “black brindle,” “reverse brindle” and “sealed brindle” are breed terms that can mean diﬀerent things, depending on who you talk to.
With a seal brindle, what you have is a dog with a sable pattern and black stripes (brindle causes the layer of black stripes on top of the sable pattern).
But since the dog also has the secret seal ingredient, his black stripes are not solid black.
Instead, they are somewhat transparent and look very coppery-brownish when viewed in bright daylight or compared to a normal black brindle.
Seal brindle. Note how comparatively "flat" this black color appears. For pedigree buffs, this is Bayron del Dyrium.
Let's talk about this example ...
This dog is B/B D/D, making his eumelanin (mask + stripes) non-diluted black.
He is Ay/at, so he has a sable pattern Ay, causing a solid yellow/red coat. (But he carries tan points at). He is also Em/Em, which adds a black mask on top of his muzzle.
He also is brindle, which adds black stripes on top of all the yellow/red pigment in his pattern.
If he was KB/- instead of brindle, he would be solid black. If he was ky/ky, his sable pattern would be unaﬀected.
Now the interesting part … This dog tested as KB/ky.
But he is not solid black (KB) carrying normal pattern (ky). Instead, he is visibly brindle, which in fact makes him kbr/kbr or kbr/ky.
This is expected. So far, there is no reliable testing method for brindle (kbr).
The brindle allele is literally just a 2-in-1 K-locus with one copy of ky "glued" to one copy of KB.
Any dog with at least one kbr will come back as KB/ky (which is the lab report saying, “We found both KB and ky”). Testing companies can't distinguish between a real "KB/ky" and any combination with brindle in the mix (KB/kbr, kbr/kbr or kbr/ky).
kbr is a middle ground between dominant black (KB/- in solid black dogs) and the wild type (ky/ky in non-brindled sables). It adds some black (the stripes) on top of the sable coat.
The black stripes express the dominant black KB portion of the brindle allele; the unaﬀected areas in between express the ky portion of the brindle (these areas are just sable with no added black).
But the dog is not just brindle with normal black stripes. He is supposed to be seal brindle with coppery seal stripes.
So, what does seal do?
To get any kind of "ghost markings" such as seal, a dog has to express dominant black (KB).
Seal is an unknown modiﬁer that makes eumelanin-pigmented coat (the black in solid black dogs or the black stripes in a brindled dog) a little transparent.
Seal is sometimes called "incomplete dominant black."
This is very common in the Cane Corso and easy to see on solid black dogs (KB/KB or KB/ky).
It causes the tan from the hidden sable pattern to bleed through the dominant black KB layer. This causes faded black with a copperish "ghost sable."
Seal often comes with darker extremities, a darker face and a darker stripe down the spine. In longer- haired breeds, it causes pale hair roots on the neck, shoulders and trousers.
Compare to this true black Cane Corso.
You can also ﬁnd dogs with "ghost tan points" on dogs that are seal + dominant black (KB/-) with a tan point pattern underneath (at/at). In this case, the yellow portions that can bleed through from the hidden pattern are restricted to the tan markings.
But seal does not only aﬀect the KB expression in solid black dogs: It can also aﬀect the KB portion (the stripes) in a brindle pattern.
So you get a dog with a normal sable coat and leaky black stripes on top that can look quite reddish- brown or coppery.
I would call this seal brindle.
Seal can be hard to spot in images.
A gallery of what appears to be seal brindle:
Then there are cases where dogs that are seal+KB/kbr express seal and seal brindle at the same time. In some dogs, this causes a weak brindle pattern between the incomplete black layer and the tan bleed-through.
I would probably call this ghost brindle.
All the phenomena above also happen in dogs with blue pigment. But there are no separate terms for gray seal or gray brindle seal. I guess the blue pigment often does not have enough contrast against a yellow or red background to be sure if stripes are faded or not.
Blue seal puppy.
What is called “sealed brindle” in Boxers (or "ultra brindle" in Boerboels) might be something else.
In Boxers, a "sealed brindle" is a dog that tests as KB/ky and is expected to be brindle by parentage, but has little to no visible stripes and is completely black or seal.
The most common explanations so far are: 1) These dogs have something weird going on; 2) Their brindle is so dense that dogs just look black (or seal), or 3) These dogs are actually KB/- (solid or seal) from being mixed with something else.
Newer research from Vetgenomics Russia indicates that there might be another explanation:
Remember, the kbr allele is just a combination of a KB and a ky allele. That makes it impossible to test if a dog really is KB/ky or if he is KB/kbr, kbr/kbr or kbr/ky.
The Russian company now claims that they can distinguish between these genotypes.
They do this by not only looking for the presence of KB and ky, but counting how many KB and ky a dog has!
• A dog that is KB/ky will have one copy of each.
• A dog that is kbr/ky will have (KB+ky)/ky
• A dog that is kbr/kbr will have (KB+ky)/(KB+ky)
• A dog that is KB/kbr will have KB/(KB+ky)
While doing their research, they claim to have discovered two interesting things:
The brindle allele predisposes a dog for more recombination events. A dog’s brindle allele can consist of more than one K; they call this kbr+. They found a dog whose brindle allele was KB+KB+KB+KB+ky+ky. This would lead to interesting testing possibilities if it wasn’t in Russia. Maybe the more KBs, the darker the brindle might be?
A brindle allele can fall apart. This would result in a kbr dog possibly producing KB oﬀspring if his kbr allele lost its ky portion. So black Boxers might be KB/- after all!