Dog Coat Color - D Locus (Dilution; d3)

Acronym:	D3 locus
Gene:	MLPH
Mutation:	c.667_668insC
Inheritance:	Autosomal recessive
Sample type:	CHS (Cheek Swab), WBE (Whole Blood EDTA)

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Genetics and characteristics

Coat color in dogs is an important characteristic along with hair length, growth pattern, and curl. Coat color is determined by the expression of two melanin pigments, eumelanin (black/brown) and pheomelanin (yellow/red). The melanophilin (MLPH) gene commonly referred to as the D (dilution) Locus and mutations within it were identified as the cause of color dilution phenotypes in several dog breeds. The specific pigmentation phenotype in dogs with coat color dilution is caused by defective transport of melanosomes which leads to an accumulation of melanosomes around the melanocytes nuclei as well as large clumps of pigment in the hair shafts. There have been reported a few variants of the MLPH gene that are causing different color phenotypes – d¹, d², and d³. The cause of the d³ variant is a single base insertion resulting in shortened MLPH protein which likely disrupts its function.

Coat color dilution in dogs is inherited as an autosomal recessive trait meaning dogs are required to have both mutated MLPH genes to show dilution phenotype. Dogs that carry just one mutated gene do not show a change in the coat color but act as carriers of the specific mutation. Black dogs that carry both mutated genes become blue and liver dogs become isabella. The mutated MLPH gene also affects the nose and eye color. In blue dogs, the nose will be blue pigmented and in isabella dogs slightly darker than liver, whereas the eyes will be lightened to amber. Genetic testing can identify carriers and help breeders in future mating pairs selection.

 

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Results Reported As

 

 

 

 

 

 

 

 

 

 

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References:

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. (2020). A Third MLPH Variant Causing Coat Color Dilution in Dogs. Genes, 11(6), 639. https://doi.org/10.3390/genes11060639

Brancalion, L., Haase, B., Wade, C. M. (2022). Canine coat pigmentation genetics: a review. Animal genetics, 53(1), 3–34. https://doi.org/10.1111/age.13154