Genetic basis of Dilute D2 variant - is a rare form of the dilution gene found especially in Chow Chows, as well as Sloughis and Thai Ridgebacks. This variant is caused by a mutation in the MLPH (melanophilin) gene, specifically the c.705G>C mutation. Dilution genes affect the distribution and transport of melanosomes (pigment-containing organelles), resulting in diluted coat colors such as blue, silver, lilac, or cream, depending on the original pigment. The inheritance of the D2 variant is autosomal recessive, meaning a dog must inherit two copies of the mutation to express diluted coat color. The D2 variant acts independently or in combination with other dilute alleles (d1 or d3) to cause dilute phenotypes
Coat Colour Effects - Dogs homozygous for the D2 variant show diluted pigmentation, such as blue or silver shades depending on their original coat color. This differs from the more common D1 variant found in many breeds. The exact color shade may also be influenced by the presence of other dilute alleles combined with D2.
Why This Matters to Breeders and Vets - Dilute coat color is often associated with Color Dilution Alopecia (CDA), a hereditary disorder that causes hair thinning, brittleness, and alopecia. Understanding and identifying the D2 variant enables breeders to manage coat color genetics better and mitigate risk of CDA. Testing for the D2 variant is recommended in Chow Chows and related breeds to inform breeding decisions and avoid unintentional propagation of dilute coat color-associated health issues.
Testing and Inheritance - Testing requires a blood or buccal swab sample. The test detects the presence of D2 allele separately from the common D1 or other rare D3 dilute variants. Dogs with two copies of the D2 allele are dilute, those with one copy are carriers but have normal pigment
