Quick Summary

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Phenotype: Base coat colors are lightened (diluted) to paler shades. For example, black becomes a gray-blue color (often called "blue" by breeders) and chocolate brown becomes a pale silvery red (in some breeds, this can be called "lilac"; in the French Bulldog, this is typically referred to as "isabella" - other breeds may have different names for this dilution).
Mode of Inheritance: Autosomal recessive
Alleles: D = Non-dilute, d1 = Dilute (variant 1, common), d2 = Dilute (variant 2), d3 = Dilute (variant 3, rare)
Breeds appropriate for testing: Many breeds
Explanation of Results:
- Dogs with D/D genotype are not expected to display dilute coat colors; they have no known dilution variants. They cannot produce dilute offspring or transmit any of the known dilution variants to their offspring.
- Dogs with D/d1, D/d2, or D/d3 genotype are not expected to display dilute coat colors, but they are carriers of dilution variants. They will transmit the dilution variant they carry to 50% of their offspring. Matings between two carriers of dilute variants are expected to produce 25% puppies with dilute coat colors.
- Dogs with d1/d1, d2/d2, d3/d3, d1/d2, d1/d3, or d2/d3 genotype are expected to display dilute coat colors. They will transmit a dilution variant to all of their offspring.
Results of this test can be submitted to the OFA (Orthopedic Foundation for Animals)
Dog Coat Color - Basic Panel (All breeds)
$100 per animal
Additional coat colors $15 per test
Dog Coat Color - French Bulldog Panel
$105 per animal
Additional coat colors $15 per test
Dog Coat Color - Bulldog Panel
$80 per animal
Additional coat colors $15 per test
Dog Coat Color - Great Dane Panel
$80 per animal
Additional coat colors $15 per test
Dog Coat Color and Type - Havanese Panel
$115 per animal
Additional coat colors $15 per test
Labrador Retriever Health Panel 2
$180 per animal
Nova Scotia Duck Tolling Retriever Health Panel
$140 per animal

A recessive mutation d1, previously named d, in the melanophilin (MLPH) gene (g.48121642G>A, c.-22G>A) was identified as the cause of color dilution phenotypes in several dog breeds (Drögemüller et al. 2007). However, this mutation alone does not account for all dilute color phenotypes. In 2018, Bauer et al. identified a second dilution in MLPH, variant d2 (c.705G>C, p.Gln235His) in the Sloughi, Chow Chow, and Thai Ridgeback dogs. Analysis at the Veterinary Genetics Laboratory (VGL) determined that the d2 variant is present at a frequency of less than 1% in phenotypically dilute French Bulldogs, thus suggesting that additional variants also cause this phenotype. Subsequent research at the VGL identified a third, very rare dilution variant d3 (c.667_668insC, p.His223Profs*41). The d3 variant has been detected in the Italian Greyhound, Chihuahua, Mudi, Pumi, Shih Tzu, Pekingese, Tibetan Mastiff, Yorkshire Terrier, Shetland Sheepdog, indigenous dogs, and wolf-dog hybrids (Van Buren et al. 2020).
Two copies of any of the three dilution variants, or any combination of two of these variants, are necessary to lighten the color. The d1 mutation is known to cause a reduction in the amount of full-length protein product, thus producing less pigment. The effect of the d2 mutation on the resultant protein is unknown, although in the homozygous state it dilutes color. The phenotype produced by two copies of the d3 variant is unknown, but this mutation is predicted to shorten the MLPH protein and likely disrupt function. Dogs that are compound heterozygotes d1/d2, d2/d3, or d1/d3 have a dilute phenotype. This diagnostic DNA test can detect all three known variants of the MLPH gene.