E Locus · MC1R

E Locus: Extension

The master switch that decides whether a dog's coat shows black-based pigment (eumelanin) or red/yellow pigment (phaeomelanin) — and whether a black facial mask is present.

Alleles

Em: Melanistic mask: Produces the dark facial mask seen on fawn French Bulldogs, Pugs, and many other breeds. Dominant over E and e — a single copy shows. Affects eumelanin in the face only.
Eg: Grizzle / domino: A rare patterning allele found in some sighthound breeds (Afghan, Saluki, Borzoi). Produces a distinctive shading pattern. Uncommon in toy breeds and doodles.
E: Normal extension: Allows eumelanin to be produced normally. Whether any black shows depends on the K and A loci. Most common allele in working and sporting breeds.
e: Recessive red: Two copies (e/e) completely block eumelanin in the coat — the whole coat becomes red, apricot, cream, gold, or near-white regardless of any other color gene. The most powerful masking allele in canine genetics.

What the E locus does

MC1R is a receptor on melanocyte (pigment cell) surfaces. When it receives a signal, cells produce eumelanin — the black-to-brown pigment family. When the signal is blocked, cells default to phaeomelanin — the red-to-cream pigment family.

The E locus is where that switch lives. It does not create a pattern by itself; it decides whether the black-based patterns coded by the K and A loci are even allowed to appear in the coat.

The dominance order is Em > Eg > E > e. Em is the most dominant — one copy is enough for a mask. e is fully recessive — only e/e blocks eumelanin.

e/e recessive red — the great masker

A dog with two copies of e (e/e) cannot deposit any black or brown pigment into its coat hairs. The entire coat becomes some shade of red, apricot, cream, gold, or near-white — regardless of what the A, K, and M loci say. e/e is epistatically dominant over all of them.

This is why so many of our Toy Poodles are apricot to deep red and our Maltese and Maltipoo lines carry e/e — it produces those gorgeous, even, clear coats. The e/e genotype is cosmetic only; it carries no health defect.

The critical catch: because e/e hides everything else, a gold or red dog can secretly be a sable, tan-point, brindle, or even a merle carrier. You cannot tell from the coat alone. Only DNA testing reveals what is hidden — and in the case of hidden merle, that matters enormously for safe breeding.

The black mask (Em) and how it works

Em restricts extra eumelanin production to the muzzle, ears, and sometimes the forehead, creating the dark 'mask' look. It is dominant — one Em copy is enough to show a mask, even in dogs that are otherwise red or fawn.

On an e/e dog the mask cannot appear on the coat (no eumelanin production at all in coat hairs), but the dog can still carry and transmit Em to offspring — making it possible for an e/e dog to produce masked puppies.

Em is especially recognizable in fawn French Bulldogs, Pugs, and Mastiff-type breeds, where the body is warm fawn and the muzzle is solidly dark.

How the E locus interacts with other loci

E is epistatic over the A and K loci: if a dog is e/e, agouti patterns and dominant black simply cannot be seen in the coat. Those genes are still inherited and can be passed to offspring — the dog just expresses none of them visually.

E also visually hides the M locus (merle). A red e/e dog carrying a merle allele is a 'cryptic red merle' — it looks entirely solid-colored but can produce merle or even double-merle puppies. This is one of the most dangerous scenarios in dog breeding, which is exactly why we DNA-test every breeding dog.

The B and D loci still influence the dog's nose, paw pads, and eye rims even when the coat is e/e — that is why a red dog can have a brown (liver) nose (b/b) or a blue-grey nose (d/d) even though the coat looks uniformly red.

E locus in toy breeds we work with

Toy Poodles: Red and apricot Toy Poodles are almost universally e/e. The deep red comes from modifier genes acting on the phaeomelanin shade. Silver and blue Poodles are not e/e — they are dilute (d/d) black-based dogs. Cream Poodles are also e/e, just at the pale end of the phaeomelanin spectrum.

Yorkies: Many gold or blonde Yorkies are e/e, which is why some lack the tan-point pattern typical of the breed. Traditional steel-blue-and-tan Yorkies are at/at (tan points) with D/d or d/d dilute — not e/e. Knowing which your Yorkie is requires a DNA test.

French Bulldogs: Fawn Frenchies are often Ay/– (sable) with Em mask — not e/e. True recessive-red Frenchies also exist. The mask (Em) is extremely common in Frenchies and can appear on fawn, sable, or even brindle backgrounds.

Maltese, Maltipoo, Bichon: These lines are typically e/e with minimal eumelanin, producing their characteristic white-to-cream coats.

E Locus FAQ

What does e/e mean in dogs?

e/e means the dog inherited two copies of the recessive red allele at the E locus (MC1R). It cannot produce black or brown pigment in its coat, so the coat is some shade of red, apricot, cream, gold, or near-white — regardless of every other color gene. The dog can still carry hidden tan-point, sable, merle, or chocolate genes that will appear only in offspring.

Can two red (e/e) dogs produce black puppies?

No. Two e/e parents can only pass the e allele to their offspring — every puppy will be e/e and also appear red or cream. Coat shade may vary from deep red to pale cream based on modifier genes, but none can be black-based, because e/e prevents eumelanin production in the coat entirely.

Why are so many Toy Poodles red or apricot?

Red and apricot Toy Poodles are e/e at the E locus. The recessive red genotype removes black pigment from the coat, and phaeomelanin (red/yellow pigment) shines through. Deeper red shades come from intensity modifier genes that concentrate phaeomelanin. This explains why two apricot parents can produce red or cream puppies — they are all e/e; only the intensity modifiers vary.

What is the difference between E/e and e/e in dogs?

E/e means the dog carries one normal extension allele (E) and one recessive red allele (e). Because E is dominant, the dog looks like a normal-pigmented dog — not red or cream — but it is a carrier and can pass the e allele to 50% of its puppies. e/e means both alleles are recessive red; the dog's coat is entirely red/apricot/cream with no black pigment expression.

Can a dog be e/e and still have a black nose?

Yes. The e/e genotype blocks eumelanin only from the coat hairs — it does not affect all pigment cells. Many e/e dogs have black noses, especially if they are B/B (no chocolate) and D/D (no dilute). However, an e/e dog that is also b/b will have a brown/liver nose, and an e/e + d/d dog may have a blue-grey or isabella nose. Nose color can provide a clue about B and D genotype even when coat color cannot.

Can a dog carry the Em mask allele and be e/e at the same time?

Yes. A dog can be Em/e genotype — heterozygous, with one mask allele and one recessive red allele. Whether the mask shows depends on the other allele. Em/e will show a mask because Em is dominant over e. But a dog can also be e/e and still carry Em as part of its genetic makeup — it would not show the mask in its own coat (because e/e suppresses all coat eumelanin) but it could pass Em to puppies.

Which dog breeds most commonly carry e/e?

e/e is especially common in breeds selected for red, apricot, gold, and cream coats: Toy Poodles (red/apricot), Golden Retrievers, Irish Setters, Vizslas, many Maltese and Bichon lines, some Cocker Spaniels, and many doodle crosses from those lines. It also occurs in Yorkies (producing all-gold individuals without tan points) and in French Bulldogs (producing red or cream Frenchies without fawn-plus-mask patterning).

Why is it important to DNA test a red or cream dog before breeding?

Because e/e hides all other color loci, a red or cream dog can carry hidden genes for sable, tan points, brindle, chocolate, dilute, or merle — none of which are visible in the coat. If a red dog secretly carries merle (M/m) and is bred to a merle partner, the resulting double-merle (M/M) puppies have dramatically elevated risk of deafness and blindness. DNA testing is the only way to know what a red dog is actually carrying.