Coat colour dilution / D locus 3 / dilution d3 (MLPH-related) - Dog

What does this test analyse?

This genetic test analyses the MLPH variant c.667_668insC, also referred to as d3, for D locus 3 / dilution d3 in dogs. The trait is known as the D locus, coat colour dilution, dilution, color dilution alopecia, CDA, Blue Doberman Syndrome and, depending on the base colour, as blue, charcoal, lilac, Isabella, silver or champagne.

What does D-locus dilution mean?

MLPH is involved in transport and distribution of pigment granules in the hair follicle. When a dog carries two D-locus dilution alleles, normal pigment distribution is disrupted and the visible coat colour becomes lighter. Black pigment can become blue, grey or charcoal, brown or liver can become lilac or Isabella, and red, yellow or cream can become lighter or champagne-coloured. Nose and eye colour can lighten as well.

This d3 variant is especially relevant in breeds where this specific D-locus allele has been described, including Chihuahua, Italian Greyhound, Mudi, Pekingese, Pumi, Shetland Sheepdog, Shih Tzu, Tibetan Mastiff and Yorkshire Terrier. Because coat colour is controlled by multiple loci, the final visible colour also depends on the E locus, B locus, K locus, A locus and other coat-colour genes.

Inheritance and result

The trait is inherited as autosomal recessive. A dog with two copies of this variant has a dilute D-locus genotype for this tested allele. A dog with one copy is a carrier: one copy alone usually does not cause a dilute coat, but it can produce dilution when the other copy carries another D-locus dilution variant.

Practical value

• Breeders can identify carriers and dogs with two copies before planning matings.
• The test helps explain why a dog may show blue, grey, lilac, Isabella, charcoal, silver or champagne-coloured shades.
• The result makes it easier to combine D-locus information with other coat-colour tests for a realistic colour expectation in puppies.
• In breeds where color dilution alopecia occurs, the result helps include risk and follow-up more deliberately in breeding selection.