Melanistic mask
Encyclopedia
A melanistic mask is a dog coat
pattern that gives the appearance of a mask
on the dog's face. The hairs on the muzzle
, and sometimes entire face or ears, are colored by eumelanin instead of pheomelanin pigment. Eumelanin is typically black, but may instead be brown, dark gray, or light gray-brown. Pheomelanin ranges in color from pale cream
to mahogany
. The trait is caused by M264V (EM), a completely dominant allele
(form) of the melanocortin 1 receptor
gene
.
A mask is visible in conjunction with a variety of coat patterns, such as tan points and sable. Nonetheless, it may be difficult to see with certain others, such as brindle
, and will not be visible on a completely eumelanic coat. Any white markings on the coat, caused by a lack of pigment, will appear to be layered over the mask and other markings.
(MC1R) locus
, also known as the extension locus. It is completely dominant to the other alleles of the gene, and causes the melanocyte-stimulating hormone
to bind to and activate melanocortin 1 receptors (located on melanocytes) in the mask's area, causing those melanocytes to produce eumelanin. Another allele, known as E, is responsible for "normal extension", which allows eumelanin to be produced as usual. e, completely recessive to the other alleles, suppresses all eumelanin production in the coat—the resulting color is sometimes known as recessive red, clear red or Australian red. Therefore, if a dog appears clear red or fawn but has a mask, the agouti gene
is responsible for all pheomelanic hairs. Although Clarence Cook Little
proposed in 1957 that brindle
was caused by another allele at the same locus, known as ebr, his hypothesis was refuted in a 2007 study.
Coat (dog)
The coat of the domestic dog refers to the hair that covers its body. A dog's coat may be a double coat, made up of a soft undercoat and a coarser topcoat, or a single coat, which lacks an undercoat...
pattern that gives the appearance of a mask
Mask
A mask is an article normally worn on the face, typically for protection, disguise, performance or entertainment. Masks have been used since antiquity for both ceremonial and practical purposes...
on the dog's face. The hairs on the muzzle
Snout
The snout, or muzzle, is the protruding portion of an animal's face, consisting of its nose, mouth, and jaw.-Terminology:The term "muzzle", used as a noun, can be ambiguous...
, and sometimes entire face or ears, are colored by eumelanin instead of pheomelanin pigment. Eumelanin is typically black, but may instead be brown, dark gray, or light gray-brown. Pheomelanin ranges in color from pale cream
Ivory (color)
Ivory is an off-white color that resembles ivory, the material out of which the teeth and tusks of animals is made. It has a very slight tint of yellow....
to mahogany
Mahogany (color)
Mahogany is a reddish brown color. It is approximately the color of the wood, mahogany. However, the wood itself is not uniformly the same color, and "mahogany" is not a standard HTML color with a standardized RGB value....
. The trait is caused by M264V (EM), a completely dominant allele
Allele
An allele is one of two or more forms of a gene or a genetic locus . "Allel" is an abbreviation of allelomorph. Sometimes, different alleles can result in different observable phenotypic traits, such as different pigmentation...
(form) of the melanocortin 1 receptor
Melanocortin 1 receptor
The melanocortin 1 receptor , also known as melanocyte-stimulating hormone receptor , melanin-activating peptide receptor, or melanotropin receptor, is a G protein-coupled receptor which binds to a class of pituitary peptide hormones known as the melanocortins, of which include adrenocorticotropic...
gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
.
Appearance
At minimum, a melanistic mask will appear on the muzzle, and may also be visible on the eartips, entire ears, or entire face. Hairs in those areas will be colored by eumelanin instead of pheomelanin pigment, making it look as though the dog has a mask on its face. Eumelanin is usually black, but may instead be liver (also known as chocolate; dark brown), blue (also known as slate; dark grey), or isabella (also known as lilac; light grey-brown); accordingly, a mask may be any of these colors. Pheomelanin occurs in shades of red ranging from ivory to mahogany, which include cream, gold, and tan.A mask is visible in conjunction with a variety of coat patterns, such as tan points and sable. Nonetheless, it may be difficult to see with certain others, such as brindle
Brindle
Brindle is a coat coloring pattern in animals, particularly dogs, cats, cattle, guinea pigs, crested geckos and, rarely, horses. It is sometimes described as "tiger striped", although the brindle pattern is more subtle than that of a tiger's coat...
, and will not be visible on a completely eumelanic coat. Any white markings on the coat, caused by a lack of pigment, will appear to be layered over the mask and other markings.
Genetic basis
The melanistic mask is caused by the M264V allele (known as EM) at the melanocortin 1 receptorMelanocortin 1 receptor
The melanocortin 1 receptor , also known as melanocyte-stimulating hormone receptor , melanin-activating peptide receptor, or melanotropin receptor, is a G protein-coupled receptor which binds to a class of pituitary peptide hormones known as the melanocortins, of which include adrenocorticotropic...
(MC1R) locus
Locus (genetics)
In the fields of genetics and genetic computation, a locus is the specific location of a gene or DNA sequence on a chromosome. A variant of the DNA sequence at a given locus is called an allele. The ordered list of loci known for a particular genome is called a genetic map...
, also known as the extension locus. It is completely dominant to the other alleles of the gene, and causes the melanocyte-stimulating hormone
Melanocyte-stimulating hormone
The melanocyte-stimulating hormones are a class of peptide hormones that are produced by cells in the intermediate lobe of the pituitary gland...
to bind to and activate melanocortin 1 receptors (located on melanocytes) in the mask's area, causing those melanocytes to produce eumelanin. Another allele, known as E, is responsible for "normal extension", which allows eumelanin to be produced as usual. e, completely recessive to the other alleles, suppresses all eumelanin production in the coat—the resulting color is sometimes known as recessive red, clear red or Australian red. Therefore, if a dog appears clear red or fawn but has a mask, the agouti gene
Agouti gene
The Agouti gene is responsible for determining whether a mammal's coat is banded or of a solid color . The chief product of the Agouti gene is Agouti signalling peptide , but there are a number of alternative splice products....
is responsible for all pheomelanic hairs. Although Clarence Cook Little
C. C. Little
Clarence Cook "C.C." Little was an American genetics, cancer, and tobacco researcher and academic administrator.-Biography:...
proposed in 1957 that brindle
Brindle
Brindle is a coat coloring pattern in animals, particularly dogs, cats, cattle, guinea pigs, crested geckos and, rarely, horses. It is sometimes described as "tiger striped", although the brindle pattern is more subtle than that of a tiger's coat...
was caused by another allele at the same locus, known as ebr, his hypothesis was refuted in a 2007 study.