A melanistic mask (also referred to as a mask or masking) is a dog coat pattern that gives the appearance of a

mask A mask is an object normally worn on the face, typically for protection, disguise, performance, or entertainment, and often employed for rituals and rites. Masks have been used since antiquity for both ceremonial and practical purposes, ...

on the dog's face. The hairs on the muzzle, and sometimes entire face or ears, are colored by

eumelanin Melanin (; ) is a family of biomolecules organized as oligomers or polymers, which among other functions provide the pigments of many organisms. Melanin pigments are produced in a specialized group of cells known as melanocytes. There are ...

instead of

pheomelanin Melanin (; ) is a family of biomolecules organized as oligomers or polymers, which among other functions provide the Biological pigment, pigments of many organisms. Melanin pigments are produced in a specialized group of cells known as melan ...

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 Mahogany is a straight- grained, reddish-brown timber of three tropical hardwood species of the genus ''Swietenia'', indigenous to the AmericasBridgewater, Samuel (2012). ''A Natural History of Belize: Inside the Maya Forest''. Austin: Universit ...

. The trait is caused by M264V (''E^M''), a completely dominant

allele An allele is a variant of the sequence of nucleotides at a particular location, or Locus (genetics), locus, on a DNA molecule. Alleles can differ at a single position through Single-nucleotide polymorphism, single nucleotide polymorphisms (SNP), ...

(form) of the

melanocortin 1 receptor The melanocortin 1 receptor (MC1R), also known as melanocyte-stimulating hormone receptor (MSHR), melanin-activating peptide receptor, or melanotropin receptor, is a G protein–coupled receptor that binds to a class of pituitary peptide hormon ...

gene In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...

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 is a coat (animal), coat coloring pattern in animals, particularly dogs, cattle, guinea pigs, cats, and, rarely, horses. It is sometimes described as "tiger-striped", although the brindle pattern is more subtle than that of a tiger's co ...

, 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 ''E^M'') at the

(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 The melanocyte-stimulating hormones, known collectively as MSH, also known as melanotropins or intermedins, are a family of peptide hormones and neuropeptides consisting of α-melanocyte-stimulating hormone (α-MSH), β-melanocyte-stimulating ...

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-signaling protein is a protein that in humans is encoded by the ASIP gene. It is responsible for the distribution of melanin pigment in mammals. Agouti interacts with the melanocortin 1 receptor to determine whether the melanocyte (pigment ...

is responsible for all pheomelanic hairs. Although Clarence Cook Little proposed in 1957 that

was caused by another allele at the same locus, known as ''e^br'', his hypothesis was refuted in a 2007 study.

Gallery

File:Deutscher Schäferhund- portrait.JPG, German Shepherd dog with black mask File:Whippet długowłosy głowa suki MB 01.jpg, Longhaired

whippet The Whippet is a British breed of dog of sighthound type. It closely resembles the Greyhound and the smaller Italian Greyhound, and is intermediate between them in size. In the nineteenth century it was sometimes called "the poor man's raceh ...

with black mask File:French Mastiff 001.jpg, Red dogue de Bordeaux with liver mask File:AlpineMastiff0077.JPG, St. Bernard with black mask and white markings File:Kerry blue terrier pl2.jpg, Kerry blue terrier with black mask. Although the coat on the body has lightened in color in a process known as "clearing" or "greying", the mask has retained its original color. File:Vilda1.jpg,

Border collie The Border Collie is a British list of dog breeds, breed of herding dog of the collie type of medium size. It originates in the region of the Anglo-Scottish border, and descends from the traditional Sheep dog, sheepdogs once found all over the ...

puppy with black mask, tan points, and white markings. On the front portion of the muzzle, the points on the cheeks are partially "covered up", or inhibited in expression, by the mask.

References

{{reflist Dog anatomy Animal hair Animal coat colors