Merle

Quick Summary

Merle is an incompletely dominant coat color pattern characterized by irregularly shaped patches of diluted pigment and solid color.

Miniature Australian Shepherd puppy with merle pattern
Miniature Australian Shepherd puppy with merle pattern.

Phenotype: The merle pattern is characterized by irregularly shaped patches with diluted pigment while other patches on the coat are fully pigmented in color.

Mode of Inheritance: Incomplete dominance

Alleles: N = Non-merle, ### = Merle allele present, size is provided

Breeds appropriate for testing: Many breeds including but not limited to: American Bully, American Pit Bull Terrier, American Staffordshire Terrier, Australian Shepherd, Beauceron, Bergamasco, Border Collie, Cardigan Welsh Corgi, Catahoula Leopard Dog, Chihuahua, Cockapoo, Cocker Spaniel (American), Collie, Dachshund, Dunker, French Bulldog, Great Dane, Koolie, Mudi, Old English Sheepdog, Pomeranian, Pyrenean Shepherd, Shetland Sheepdog, Crossbred

Explanation of Results:

  • Dogs with N/N genotype are not expected to display a merle pattern. They cannot transmit this merle variant to any of their offspring.
  • Dogs with N/### or ###/### (### = any number from 200-280) may display a merle pattern. This pattern varies along a continuum. The amount of dilute patches is dependent on which merle allele(s) are present AND if the dog will show black/brown pigment (eumelanin) = NOT e/e at MC1R. In brief, eumelanic dogs with two copies of smaller allele sizes (lower numbers) display little to no merle pattern often referred to as "cryptic merle". Eumelanic dogs with 1 or 2 copies of larger alleles (higher numbers) are expected to display the merle pattern. Eumelanic dogs with one or two copies of the highest numbers (~270-280) display a dramatic dilution/white pattern referred to as harlequin. This is NOT the phenotype resulting from the gene variant identified as Harlequin (H) in the Great Dane. Breeding two dogs that possess any of the merle variants may produce "double merle" offspring (homozygous) which may be prone to health problems. Double merle dogs may have auditory, ophthalmologic, skeletal, and other defects and will transmit a merle variant to all of their offspring.
  • Dogs with N/###/### or ###/###/### (### = any number ranging from 200-280) have an additional merle allele likely resulting from the propensity of the repetitive DNA causing the merle phenotype to increase or decrease in size. Each individual cell still only has two copies. However, different cells of the body may have different sizes of alleles. The phenotypic impact of the additional allele cannot be predicted as distribution throughout the body may be variable. Similarly, it is possible for all alleles to be transmitted to offspring but depends on the alleles present in the egg and sperm cells, thus the heritability cannot be predicted.

Results of this test can be submitted to the OFA (Orthopedic Foundation for Animals)

Price

$45 one test per animal
$65 two tests for coat color/fur type/bobtail (same animal) (excludes Cocoa)
$85 three tests for coat color/fur type/bobtail (same animal) (excludes Cocoa)
+ $15 each additional test if ordering more than three coat color/fur type/bobtail tests on the same animal (excludes Cocoa)

Additional Details

Merle coat pattern on a mixed breed dog
Merle coat color pattern on a mixed breed dog. Image credit: Dr. Jennifer Campbell-Smith/Spothound Photography

The merle pattern is characterized by irregularly shaped patches with diluted pigment while other patches on the coat are fully pigmented in color (solid). Merle only dilutes eumelanin (black) pigment; dogs with an MC1R e/e genotype do not produce black pigment and thus do not express merle, but can produce merle offspring depending on the genotype of the mate. Merle is governed by a SINE insertion in the PMEL17 or Silver (SILV) gene. SINEs are defined as short interspersed nuclear elements. These are repetitive DNA sequences that can copy and insert into different locations in the genome. The impact of the insertion depends upon the location: they can impact gene expression and function and, if inserted into the germ line cells, can be passed down to future generations.

The presence or absence of the merle SINE insertion determines the possibility of observing the merle phenotype while the length of the end of the SINE insert sequence, which is composed of the nucleotide A (poly-A tail), correlates to the extent of the merle pattern observed. Only one copy of the merle associated variant is necessary to see the effects but the length of the tail directly influences the phenotype.

The length of the poly-A tail can vary by as much as 80 nucleotides. When originally identified, range of sizes were grouped into three categories with 4 results: no SINE insertion= N, short poly-A tail= Mc (cryptic merle aka phantom or ghost and merle phenotype may or not be observed), longer poly-A tail = M (the merle pattern always observed), and an undefined region between long and short where merle pattern prediction was inconsistent. Until September 9, 2020 the VGL reported these as N, Mc, or M.

Further investigations by multiple, independent, researchers have refined the phenotypic correlation with the poly-A tail length. The following figure shows the allelic ranges and nomenclature defined by each research study. The nomenclature differs by study. Many variables likely contributed to the varied ranges and nomenclature some of which is dependent on sample sizes, breeds used, ascertainment bias, etc.

Given the variation that exists in the scientific literature for allele nomenclature the VGL now reports merle alleles based on size instead of by allele designation (please see Figure 1). This allows animal owners to utilize these numbers with the naming scheme they prefer.

Figure showing the merle allelic ranges and nomenclature defined by each research effort.

Figure 1: Merle Allele Nomenclature Defined by Multiple Scientific Studies. The VGL reports merle as the size of the detected allele. The allele can be any number from 200-280), The figure demonstrates the different proposed nomenclature based on the reported allele size.

Dogs with cryptic merle (also called phantom or ghost merle) typically display little to no merle pattern and some may be misclassified as non-merles. The cryptic merle alleles occur in the lower end of the range (typically from 200-255, however, this range and designation varies by study). As the length of the poly-A tail increases, the degree of eumelanin dilution increases to produce the merle pattern with the highest end of the range producing a phenotype that can be completely white (around 280 bp). In dogs with merle, this has been referred to harlequin or merlequin. It is important to note that the merle derived “harlequin” is distinct and caused by a different genetic mechanism from Great Dane Harlequin (H).

The merle poly-A tail is genetically unstable and, although uncommon, parents and offspring may have different sizes and thus different genotypes. Despite claims to the contrary, exhaustive sampling and testing at the VGL has identified heritable expansion and contraction of the merle insert in offspring where parentage testing has been confirmed. Also, in rare cases, the poly-A tail may expand in some cells leading to the appearance of three alleles in one animal. The distribution throughout the body of cells with differing allele sizes depends upon the timing of the origin of the expansion or retraction of the poly-A during development. If early in development, two distinct populations of cells may be present throughout the dog. If later, the appearance of two populations of cells may be restricted to specific tissues.

A white double merle Australian Shepherd
A double merle (M/M) Australian Shepherd with visual and auditory defects

Blue and partially blue eyes are typically seen with merle, and merle dogs may possess a wide range of auditory and ophthalmologic defects. Dogs with two copies of any of the size variants consistent with merle (alleles other than N) are called double merles and often can have an all white coat accompanied by multiple abnormalities of skeletal, cardiac, and reproductive systems, therefore breeding two merle dogs is discouraged to avoid producing double merle offspring. However, it is important to consider that many double merle dogs with ophthalmic and auditory defects often have a white spotting component and double merles in a breed with low piebald spotting allele frequency such as Catahoula leopard dogs, have fewer noted auditory and ophthalmologic defects.

Because of the complexities of merle inheritance and potential health concerns, DNA testing is recommended to establish the genetic makeup of dogs for the merle gene for those breeds where this color dilution pattern is present.

Turnaround Time
3-6 business days

Species

Dog

Breed

Crossbred Affenpinscher Afghan Hound Africanis Aidi Ainu Dog Airedale Terrier Akbash Dog Akita: American type Akita: Blend, Other Akita: Japanese type Akita: Unregistered Alaskan Husky Alaskan Klee Kai Alaskan Malamute Alaskan Sled Dog Alpine Dachsbracke AMB/AMBOR American Bandogge Mastiff American Blue Gascon Hound American Bulldog American Bully American Eskimo, Miniature American Eskimo, Standard American Eskimo, Toy American Foxhound American Hairless Terrier American Pit Bull Terrier American Staffordshire Terrier American Water Spaniel Anatolian Shepherd Dog Anglo-Francais de Moyen Venerie Anglo-Francais de Petite Venerie Appenzeller Ariegeois Armant Aryan Molossus Aussiedoodle Australian Cattle Dog Australian Cobberdog Australian Domestic Dog Australian Kelpie Australian Labradoodle Australian Shepherd Australian Shepherd, Miniature Australian Terrier Austrian Black & Tan Hound Austrian Pinscher Austrian Shorthaired Pinscher Austrian Smoothhaired Hound Azawakh Bali Street Dog Barbet Basenji Basque Sheepdog Basset Artesian Normand Basset Bleu de Gascogne Basset Fauve de Bretagne Basset Hound Bavarian Mountain Hound Beagle Beagle Harrier Bearded Collie Beauceron Bedlington Terrier Belgian Griffon Belgian Laekenois Belgian Malinois Belgian Mastiff Belgian Sheepdog Belgian Tervuren Bergamasco Berger de Pyrenees, Smooth Muzzled Berger du Languedoc Berger Picard Berner Laufhund Berner Neiderlaufhund Bernese Mountain Dog Bichon Frise Biewer Biewer Terrier Biewer Yorkshire Terrier Biewer, Biro Billy Black & Tan Coonhound Black Forest Hound Black Mouth Cur Black Russian Terrier Bloodhound Blue Lacy Bluetick Coonhound Bolognese Border Collie Border Collie Cross Border Terrier Borzoi Bosnian Roughhaired Hound Boston Terrier Bouvier Des Ardennes Bouvier Des Flandres Boxer Boykin Spaniel Bracco Italiano Braque d'Auvergne Braque de l'Ariège Braque du Bourbonnais Braque Dupuy Braque Francais, de Grande Taille Braque Francais, de Petite Taille Braque Saint-Germain Brazilian Terrier Briard Briquet Griffon Vendeen Brittany Broholmer Bruno Jura Laufhund Brussels Griffon Bull Terrier Bulldog Bullmastiff Ca De Bestier Cairn Terrier Canaan Dog Canadian Cur Canadian Eskimo Dog Cane Corso Canis lupus Cardigan Welsh Corgi Carolina Dog Catahoula Leopard Dog Catalan Sheepdog Caucasian Ovcharka Cavalier King Charles Spaniel CB Romanesc Carpatin Central Asian Shepherd Cesky Fousek Cesky Terrier Chart Polski Chesapeake Bay Retriever Chien d'Artois Chien Francais Blanc et Noir Chien Francais Blanc et Orange Chien Francais Blanc et Tricolore Chihuahua Chinese Crested Chinese Foo Dog Chinook Chortaj Chow Chow Cimarron Uruguayo Cirneco dell'Etna Clumber Spaniel Cockapoo Cocker Spaniel, American Cocker Spaniel, Unknown Variety Collie Cook Island Feral Dog Coton de Tulear Coyote Croatian Sheepdog Curly-Coated Retriever Czech Wolfdog Czechoslovakian Vlcak Dachshund Dalmatian Dandie Dinmont Terrier Danish Broholmer Danish/Swedish Farmdog Denmark Feist Deutsch Kooiker Deutsch-Drahthaar Deutsche Bracke Deutscher Wachtelhund Dingo Doberman Pinscher Dogo Argentino Dogue de Bordeaux Drentse Patrijshond Drever Dunker Dutch Malinois Dutch Shepherd, Longhaired Dutch Shepherd, Roughhaired Dutch Shepherd, Shorthaired Dutch Smoushond East European Shepherd East Siberian Laika English Bulldog English Cocker Spaniel English Coonhound English Foxhound English Mastiff English Setter English Shepherd English Springer Spaniel English Toy Spaniel English Toy Terrier Entlebucher Epagneul Bleu de Picardie Epagneul Breton Epagneul Francais Epagneul Picard Epagneul Pont-Audemer Estonian Hound Estrela Mountain Dog Eurasian Farm Collie Fell Hound Fell Sheepdog Field Spaniel Fila Brasileiro Finnish Hound Finnish Lapphund Finnish Spitz Flat-Coated Retriever Fox Fox Terrier, Smooth Fox Terrier, Wire French Bulldog Galgo Espanol German Drahthaar German Hunt Terrier German Longhaired Pointer German Pinscher German Sheeppoodle German Shepherd German Shorthaired Pointer German Wirehaired Pointer German Wolfspitz Giant German Spitz Giant Schnauzer Glen of Imaal Terrier Golden Retriever Goldendoodle Gordon Setter Gr Ang-Fr Tricolor Hound Gr Ang-Fr W & B Hound Gr Ang-Fr W & O Hound Grand Anglo-Francais Grand Basset Griffon Vendeen Grand Bleu de Gascogne Grand Gascon-Saintongeois Grand Griffon Vendeen Great Dane Great Pyrenees Greater Swiss Mountain Dog Greek Harehound Greek Sheepdog Greenland Dog Greyhound Griffon Bleu De Gascogne Griffon Fauve de Bretagne Griffon Nivernais Haldenstovare Hamiltonstovare Hanoverian Hound Harlequin Pinscher Harrier Havana Silk Havanese Hawaiian Poi Dog Heading Dog Hertha Pointer Hovawart Huntaway Hygenhund Ibizan Hound Iceland Dog Inca Hairless Dog Inuit Sled Dog Inuit Sled Dog Mix Irish Red & White Setter Irish Setter Irish Terrier Irish Water Spaniel Irish Wolfhound Islandsk Farehund Istrian Hound, Smoothhaired Istrian Hound, Wirehaired Italian Greyhound Italian Hound Jack Russell Terrier Japanese Chin Japanese Spitz Japanese Terrier Jindo Dog Jura Neiderlaufhund Kai Dog Kangal Dog Kangaroo Dog Karakachan Karelian Bear Dog Karelo-Finnish Laika Kayo Inu Keeshond Kerry Beagle Kerry Blue Terrier King Shepherd Kintamani Dogs Kishu Komondor Kooikerhondje Koolie Korean German Shepherd Kraski Ovcar Kromfohrlander Kuvasz Kyi Leo Labradoodle Labrador Retriever LabxGolden Laekense Lagotto Romagnolo Lakeland Terrier Lamalese Lancashire Heeler Landseer Lapinporokoira Lapponian Herder Large Munsterlander Large Spanish Hound Latvian Hound Leonberger Leopard Cur Leopard Hound Levesque Lhasa Apso Lithuanian Hound Llewellin Setter Lowchen Lundehund Lurcher Luzerner Laufhund Luzerner Neiderlaufhund Magyar Agar Majestic Tree Hound Maltese Manchester Terrier Manchester Terrier, Toy Maremma Sheepdog Maremma Sheepdog Mastiff Matthes Lion Hound McNab Middle Asian Owtcharka Mi-Ki Miniature American Shepherd Miniature Bull Terrier Miniature Goldendoodle Miniature Pinscher Montenegrin Mountain Hound Moscow Longhaired Toy Terrier Moscow Watchdog Mountain Cur Mudi Mullins Feist Native American Indian Dog Neapolitan Mastiff New Guinea Singing Dog Newfoundland Norfolk Terrier Norrbottenspets North American Shepherd Northeasterly Hauling Laika Norwegian Buhund Norwegian Elkhound Norwegian Elkhound, Black Norwegian Lundehund Norwich Terrier Nova Scotia Duck Tolling Retriever Old Danish Bird Dog Old English Sheepdog Olde English Bulldogge Otterhound Owczarek Podhalanski Papillon Parson Russell Terrier Patterdale Terrier Pekingese Pembroke Welsh Corgi Perdiguero de Burgos Perdiguero Navarro Perdiguero Portugueso Perro de Pastor Mallorquin Perro de Presa Canario Perro de Presa Mallorquin Peruvian Hairless Dog Peruvian Inca Orchid Petit Basset Griffon Vendeen Petit Bleu de Gascogne Petit Brabancon Petit Gascon-Saintongeois Petit Griffon Bleu de Gascogne Phalene Pharaoh Hound Pit Bull Plott Hound Podenco Canario Podengo Portugueso Grande Podengo Portugueso Medio Podengo Portugueso Pequeno, Smooth Podengo Portugueso Pequeno, Wirehaired Pointer Poitevin Polish Hound Polish Lowland Sheepdog Polish Owczarek Podhalanski Polski Owczarek Nizinny Pomeranian Pomsky Poodle, Miniature Poodle, Standard Poodle, Toy Poongsan Dog Porcelaine Portuguese Cattle Dog Portuguese Pointer Portuguese Sheepdog Portuguese Water Dog Posavac Hound Prager Ratter Pudelpointer Pug Puli Pumi Pyrenean Mastiff Pyrenean Shepherd Rafeiro do Alentejo Rat Terrier Red & White Setter Redbone Hound Rhodesian Ridgeback Ridgeback Cross Rottweiler Rumanian Sheepdog Russell Terrier Russian Harlequin Hound Russian Hound Russian Samoyed Laika Russian Spaniel Russkiy Toy Russo-European Laika Saarlooswolfhond Sabuesos Espanol de Monte Sabuesos Espanol Lebrero Saint Bernard Saint Hubert Jura Laufhund Saint Usage Spaniel Saluki Samoyed Sanshu Dog Santal Hound Sapsaree Sarplaninac Schapendoes Schillerstovare Schipperke Schnauzer, Miniature Schnauzer, Standard Schweizer Laufhund Schweizer Neiderlaufhund Scottish Collie Scottish Deerhound Scottish Terrier Sealyham Terrier Segugio Italiano a Pelo Forte Segugio Italiano a Pelo Raso Seppala Siberian Sleddog Serbian Hound Serbian Tricolor Hound Shar Pei Shetland Sheepdog Shiba Inu Shih Tzu Shikoku Shiloh Shepherd Dog Shiloh Shepherd, ISSA Siberian Husky Silken Windhound Silky Terrier Skye Terrier Sloughi Slovak Cuvac Slovakian WH Pointing Dog Smalandsstovare Small German Spitz Small Munsterlander Soft Coated Wheaten Terrier South African Boerboel Mastiff South Russian Ovcharka South Russian Steppe Hound Spanish Alano Spanish Mastiff Spanish Water Dog Spinone Italiano Sporting Lucas Terrier Springer Spaniel Sri Lankan Dog Stabyhoun Staffordshire Bull Terrier Standard German Spitz Stephens Stock Stichelhaar Strellufstover Stumpy-Tail Cattle Dog Styrian Roughhaired Mountain Hound Sudanese Dog Sussex Spaniel Swedish Elkhound Swedish Lapphund Swedish Vallhund Tahltan Bear Dog Taigan Tamaskan Tasy Teddy Roosevelt Terrier Telomian Tengger Dog Tenterfield Terrier Thai Ridgeback Thornburg Feist Tibetan Mastiff Tibetan Spaniel Tibetan Terrier Tosa Inu Tosa Ken Toy Fox Terrier Toy German Spitz Transylvanian Hound, Long Transylvanian Hound, Short Treeing Feist Treeing Tennessee Brindle Treeing Walker Coonhound Turkish Feral Dog Turkish Greyhound Tyrolean Hound Tyroler Bracke Vasgotaspets Vizsla Volpino Italiano Walker Coonhound Weimaraner Welsh Hound Welsh Sheepdog Welsh Springer Spaniel Welsh Terrier West Highland White Terrier West Siberian Laika Westphalian Dachsbracke Wetterhoun Whippet Whippet, Longhaired Whippet, Longhaired Cross White Shepherd Wirehaired Pointing Griffon Wirehaired Vizsla Wolf Wolf Hybrid Working Dog X-Bred Coonhound Xoloitzcuintli Xoloitzcuintli, Toy Yorkshire Terrier Unknown
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Type of Test

Results Reported As
Test Result Merle

N/N

No copies of the merle associated SINE insertion.

N/###

One copy of the merle associated SINE insertion. See attachment (last page) for additional information.

###/###

Two copies of the merle associated SINE insertion. See attachment (last page) for additional information.

N/###/###

Two copies of the merle associated SINE insertion and one copy without the insertion. The impact of this may not be resolved. See attachment (last page) for additional information.

###/###/###

Three copies of the merle associated SINE insertion. The impact of this may not be resolved. See attachment (last page) for additional information.

### = merle alleles are reported by size (200- 280) so that any of the proposed nomenclature schemes in Figure 1 can be utilized.

References

Clark, L.A., Wahl, J.M., Rees, C.A., & Murphy, K.E. (2006). Retrotransposon insertion in SILV is responsible for merle patterning of the domestic dog. Proceedings of the National Academy of Sciences of the United States of America, 103(5), 1376-1381. doi: 10.1073/pnas.0506940103

Kaelin, C.B., & Barsh, G.S. (2013). Genetics of pigmentation in dogs and cats. Annual Review of Animal Biosciences, 1, 125-156. doi: 10.1146/annurev-animal-031412-103659

Murphy, S. C., Evans, J. M., Tsai, K. L., & Clark, L. A. (2018). Length variations within the Merle retrotransposon of canine PMEL: correlating genotype with phenotype. Mobile DNA, 9, 26. PMID: 30123327, PMCID: PMC6091007, doi: 10.1186/s13100-018-0131-6

Langevin, M., Synkova, H., Jancuskova, T., & Pekova, S. (2018). Merle phenotypes in dogs - SILV SINE insertions from Mc to Mh. PloS one, 13(9). PMID: 30235206, PMCID: PMC6147463, doi: 10.1371/journal.pone.0198536

Ballif, B. C., Ramirez, C. J., Carl, C. R., Sundin, K., Krug, M., Zahand, A., Shaffer, L. G., & Flores-Smith, H. (2018). The PMEL Gene and Merle in the Domestic Dog: A Continuum of Insertion Lengths Leads to a Spectrum of Coat Color Variations in Australian Shepherds and Related Breeds. Cytogenetic and Genome Research, 156(1), 22-34. doi: 10.1159/000491408

License Info

The Veterinary Genetics Laboratory is licensed to offer the merle test.