D Locus (D-LOCUS)
Dilution, Dilute Coat, Coat Color Dilution
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 leading to a dilute coat color. This mutation is recessive so two copies of the mutation are needed to produce the dilute coat color. This mutation affects both Eumelanin and Pheomelanin pigments, so black, brown, and yellow dogs are all affected by the dilution with the effect being more pronounced in black dogs. The mutation responsible for a diluted coat is recessive so a dog can be a carrier and still appear to have an undiluted coat color. A diluted yellow dog is often referred to as a champagne. It is important to note that certain breeds have exhibited an association between carrying two copies of the D Locus mutation and a dermatological condition called Color Dilution Alopecia (CDA) or Black Hair Follicular Dysplasia (BHFD). These conditions are characterized by hair loss and potential recurring skin infections. The effect is variable within and between breeds so not all dogs that carry two copies of the D-Locus mutation will exhibit symptoms. It is likely that additional mutations or environmental factors are involved so the dilute status of a particular dog can be used as a guide in determining potential disease susceptibility. It is also important to note that additional breed-specific mutations exist for dilute coat color that is not detected by this test.
Reading Your Results
These dogs have two copies of the normal gene, will have an undiluted coat and will not pass the mutation to their offspring.
B. (CARRIER/NOT AFFECTED):
These dogs have one copy of the normal gene and one copy of the mutation associated with dilute coat coloring. They will have an undiluted coat but will, if bred, pass the mutation to 50% of its offspring, on average.
C. (AT RISK/AFFECTED):
These dogs have two copies of the mutation associated with a diluted coat color which results in blue, charcoal, grey, lilac or champagne coat dependent on other coat color loci.
Drögemüller C, Philipp U, Haase B, Günzel-Apel AR, 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. 2007; 98(5):468-73. [PubMed: 17519392]