Em, Eg, E, e
The two pigments eumelanin aka black, and pheomelanin aka red/yellow is determined by the MC1R Gene. The MC1R gene is also known as Extension. There are six known alleles of the MC1R Gene.
1. EM-Melanistic mask
4. e1-Red or Yellow
6. e3-Pale Yellow or White
Em produces a eumelanin mask on the muzzle and sometimes the ears, which is only visible on sables, tan points, and agoutis. It can sometimes be seen on the tail and the front chest.
Eg also known as grizzle. In some breeds is called domino. It is a modifier of tan points, so can only be expressed when the dog is also atat on the A locus.
E has no effect on phenotype.
e is recessive red. This turns all eumelanin to phaeomelanin. Recessive red dogs are solid red, except in white areas, no matter what other alleles are present on the other locus. Recessive red can cover even merle. A recessive red dog cannot have any visible black, chocolate, blue, or lilac. Eumelanin in the eyes and nose is usually not unaffected.
Em/Em 2 copies of mask
Em/Eg 1 copy of mask and 1 copy of grizzle
Em/E 1 copy of mask and 1 copy of black
Em/e1 1 copy of mask and 1 copy of red/yellow/cream
Em/e2 1 copy of mask and 1 copy of red/yellow/cream
Em/e3 1 copy of mask and 1 copy of red/yellow/cream
Eg/Eg 2 copies of grizzle
Eg/E 1 copy of grizzle and 1 copy of black
Eg/e1 1 copy of grizzle and 1 copy of red/yellow/cream
E/E 2 copies of black
E/e1 1 copy of black and 1 copy of red/yellow/cream
E/e2 1 copy of black and 1 copy of red/yellow/cream
E/e3 1 copy of black and 1 copy of red/yellow/cream
e1/e1 2 copies of red/yellow/cream
e1/e2 2 copies of red/yellow/cream
e1/e3 2 copies of red/yellow/cream
e2/e2 2 copies of red/yellow/cream
e3/e3 2 copies of red/yellow/cream
The Em allelle
Dogs that are black, blue or brown may have the mask but may be hidden because of the body color. White will also hide the mask.
Red or Yellow is widespread and found in many dogs that are uniformly yellow, red, or cream. The pale cream color is produced by the e2 variant.
There are two new alleles that have been discovered on the E locus. They are Eg and Eh. Some have unknowingly called this gene Sable.
The Eg Allelle
Grizzle is a pattern of dark pigment on the back of the head, body and tops of the legs. Light pigment is present on the lower legs, undersides, up the face around the eyes. Grizzle cannot be expressed if the K Locus is present. Grizzle is sometimes called Domino, and looks very much like a shaded sable or saddle back. The shading can vary from black to grey to brown.
Grizzle is dominant over all E locus alleles except for Em, which means a grizzle dog can never have a mask, so an EmEg dog would have a mask but would not look grizzle. Grizzle is visible only on dogs that are atat at Agouti. So Eg is a modifier of tan points.
The effect of brindle on grizzle is another thing to consider. Grizzle produces an opposite of brindle presentation. As we know, Brindle affects the red areas as in tan points on an atat dog. But, with Grizzle, the red areas are not affected, the black areas are.
This suggests that the red or tan areas on a grizzle are essentially the same as recessive red. It may be that the grizzle pattern has a fault in the allele. If true, grizzle may considered at least partial recessive red.
Extra Masking- Etching
Some masked dogs may have large amounts of shading on the chest and legs. This could be a modifier extending the mask, or some other unknown variation of the masking allele. This extra shading shows on the underside, which is definitely different from the shading on the top of the dog. There is a possible connection between the extra masking and the look of etching, which is seen when the spots on a sable pied looks to have dark etching around its edges. It may be that the extra masking may cause the eumelanin producing melanocytes to spread out to the edges of any phaeomelanin areas on the dog. On a dog without white, this would be on the legs, feet and chest.
The Eh Allele
Dogs with this allele are known as sable. This is not the same as the ay some call sable. Eh is almost identical to Eg, and is also considered a modifier of tan points.
It is found that Eh works differently than Eg in the fact that it appears to override dominant black.
The remaining two E locus alleles are E (black), and e (recessive red). The E extension allows the other genes on a dog to express as they normally would. e produces a much more visible effect.
An ee dog will be completely red. The nose, eyelids, lips, and footpads will remain black, or if diluted, chocolate, blue, or lilac, the coat will be solid red, or red with white markings. This is because the recessive red gene stops the cells from producing eumelanin.
Recessive red is dominant over almost all other locus, and is therefore at the TOP of the Hierarchy of genes. Dominant black, sable, tan points, merle…ALL patterns with black, will be turned to solid red by the ee gene.
DNA is necessary to know if a recessive red dog carries any of the A or K allelles, and would thus be able to pass those on to its offspring. One very important fact is that the recessive red dog could be merle, even though it appears to be just red. The only indicator would be the striking blue or partially blue merled eyes…not all merles have merled eyes! A clear, unmasked sable can look identical to a recessive red, another reason to DNA ee dogs, so as to determine whether they are sables or recessive reds. Some dogs do carry and express both sable and recessive red.