Dilute Coat Color D-Locus and New D2-Locus
The MLPH gene codes for a protein called melanophilin, which is responsible for transporting and fixing melanin-containing cells. A mutation in this gene leads to improper distribution of these cells, causing a diluted coat color. The mutation causing color dilution is recessive, and two copies of the mutated gene (the D allele or the D locus) are needed to produce the diluted coat color.
The MLPH mutation affects both eumelanin and phaeomelanin pigments. These pigments control the color of the dog. Black, brown, and yellow dogs can all be affected by the D locus. However, the effects of the dilution are more pronounced in black dogs. A diluted black dog becomes known as a blue dog. Names for this color trait vary across the different breeds, with blue, charcoal, slate, or grey being common names. A diluted chocolate dog is often referred to as a lilac or isabella and a diluted yellow dog is offten called champagne. Dogs that express the diluted phenotype have a d/d or d2 genotype. They are coded as B/B, B/b, or b/b and E/E, E/e, or e/e respectively, with regards to the E and B loci, which determine coat color.
Because the mutations responsible for the dilution phenotype are recessive, a dog can carry one of the two dilution variants and still express a normal coat color. These dogs can pass on either the full-colored genes or the diluted traits' alleles to any offspring. This means that two dogs that are full-colored can have a diluted puppy. This makes DNA testing for the D locus an important breeding tool, whether breeding for a dilute coat, or to avoid it.
Animal Genetics now offers a test for a second recessive mutation affecting dilution of coat color. This mutation was identified in a number of dog breeds where individual dogs had a diluted coat color, yet tested non-dilute. The additional variant works with the MLPH variant to dilute hair and skin in the same way. A diluted dog can be d/d, d/d2, or d2/d2. When a dilute test is requested, Animal Genetics tests for both d and d2 alleles.
|Chocolate||Dilute||Basic Color Description|
|B/B or B/b||D/D||Black|
|B/B or B/b||d/d or d2||Blue|
|b/b||d/d or d2||Lilac|
|e/e||d/d or d2||Champagne|
D Locus Testing:
Animal Genetics currently offers testing for two different types of dilute tests that can determine how many copies of the recessive MLPH allele a dog carries. Dogs can be have their DNA tested at any age.
Animal Genetics accepts buccal swab, blood, and dewclaw samples for testing. Sample collection kits are available and can be ordered at Canine Test Now.
Testing Is Relevant for the Following Breeds:
Animal Genetics offers DNA testing for 2 different types of dilute. The genetic test verifies the presence of the mutations and presents results as one of the following:
Additional causes of this trait may exist. A negative result for this mutation does not eliminate the possibility that an additional, yet unidentified, mutation or mutations in the genome may lead to a similar trait.
|D/D||Non-dilute||The dog carries two copies of the non mutated MLPH allele. In most cases the dog will express a normal, non-dilute coat color and will always pass on a copy of the "D" allele to all offspring.|
|D/d||Carrier of dilute||Both the dominant and recessive MLPH alleles detected. In most cases the dog will have a normal, non-dilute coat and is a carrier of the dilute coat color. The dog can pass either MLPH allele on to any offspring.|
|d/d||Dilute||The dog has two copies of the recessive mutated MLPH allele. In most cases the dog will have a dilute colored coat. He will always pass on a copy of the MLPH allele on to any offspring.|
|D/d2||Carrier of dilute||Both the dominant non mutated MLPH allele and recessive d2 mutated MLPH alleles detected. In most cases the dog will have a normal, non-dilute coat and is a carrier of the d2 dilute coat color. The dog can pass either MLPH allele on to any offspring.|
|d2/d2||Dilute||The dog has two copies of the d2 recessive mutated MLPH allele. In most cases the dog will have a dilute colored coat and will always pass on a copy of the MLPH allele on to any offspring.|
|d/d2||Dilute||The dog carries one copy of d and one copy of d2 mutated MLPH allele. In most cases the dog will have a dilute colored coat and will always pass on a copy of either MLPH mutated allele on to any offspring.|