D Locus (Dilution locus), allele d2

For an overview of dog coat color hierarchy continue to the article Introduction into coat color in dogs.

The MLPH gene (melanophilin gene) is responsible for dilution of the dark pigment eumelanin which turns the original black colour to blue (grey) or the original brown (liver) colour to lilac. There have been identified three different MLPH gene variants so far – each variant is tested separately:

• allele d1: variant c.-22G>A of MLPH gene – is the most common variant and occurs in many dog breeds.

• allele d2: variant c.705G>C of MLPH gene – occurs in Chow Chow, Sloughi, Thai Ridgeback, French Bulldog – in these breeds, a combination of the alleles d1/d2 may occur – these dogs may also have dilute coat colour → continue here to order double test for locus D (alleles d1 + d2).

• allele d3: variant c.667_668insC of MLPH gene – occurs in Chihuahua, Hungarian mudis, Hungarian pumis, Italian greyhound, Pekingese, Shetland sheepdog, Shih-tzu, Tibetan mastiff, Yorkshire terrier – in these breeds, a combination of the alleles d1/d3 can be found as well – these dogs will also have dilute coat colour → continue here to order double test for locus D (alleles d1 + d3).

Each variant has a recessive mode of inheritance – the dog must inherit the dilution allele from both parent so that the dilute colour becomes expressed.

There will probably be found other variants responsible for dilute coat colour as there still are breeds with dilute coat colour that is caused by none of the alleles d1, d2 or d3.

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Reference:

Van Buren, S.L., Minor, K.M., Grahn, R.A., Mickelson, J.R., Grahn, J.C., Malvick, J., Colangelo, J.R., Mueller, E., Kuehnlein, P., Kehl, A. : A Third MLPH Variant Causing Coat Color Dilution in Dogs. Genes (Basel) 11:, 2020. Pubmed reference: 32531980.

Bauer, A., Kehl, A., Jagannathan, V., Leeb, T. : A novel MLPH variant in dogs with coat colour dilution. Anim Genet 49:94-97, 2018. Pubmed reference: 29349785.

Drögemüller, C., Philipp, U., Haase, B., Günzel-Apel, A.R., Leeb, T. : A noncoding melanophilin gene (MLPH) SNP at the splice donor of exon 1 represents a candidate causal mutation for coat color dilution in dogs. J Hered 98:468-73, 2007. Pubmed reference: 17519392.