Genetic basis of Dilute - The dilute coat color in cats is caused by a mutation in the MLPH gene (melanophilin), located at the D locus. The critical mutation identified is a single-base deletion (c.83delT) causing a frameshift and truncated protein product that affects normal pigment distribution. This mutation is inherited in an autosomal recessive manner: cats must inherit two copies of the dilute allele (d/d) to express the diluted coat color. Heterozygous cats (D/d) are carriers without dilute phenotype, and homozygous wild-type (D/D) cats show non-diluted coats.
Pathophysiology - Melanophilin is essential in the intracellular transport and even distribution of pigment granules (melanosomes) within hair shaft melanocytes. The MLPH mutation causes clumping and uneven distribution of pigment granules along the hair shaft. This leads to an optical dilution of coat color since pigment density per hair is reduced. Examples include Black pigment is diluted to gray (“blue” in breeder terminology), Chocolate diluted to lilac, Cinnamon diluted to fawn, Red/orange diluted to cream. This affects both main pigment types: eumelanin (black/brown shades) and phaeomelanin (red/orange shades).
Complications - There are no health complications associated with dilute coat color or the MLPH mutation itself; the effect is purely cosmetic. Coat color dilution sometimes correlates with a softer or fluffier coat texture but this varies by breed. Some breeds (e.g., Russian Blue, Korat, Chartreux) are fixed for the dilute allele, while others carry various D/d genotypes.
Why This Matters to Breeders and Vets - Breeders use genetic testing to determine carrier status and predict dilute coat color in litters, allowing informed breeding decisions, especially in breeds where dilute color is desirable or to manage coat color diversity. Veterinarians may use the genetic information to explain coat color inheritance to owners; no direct medical relevance beyond coat phenotype.
Summary - Dilute coat color in cats is an autosomal recessive trait caused by a pathogenic single-base deletion mutation in the MLPH gene. This mutation leads to clumping and uneven pigment distribution causing dilution of all base coat colors (black to blue, chocolate to lilac, red to cream, etc.). It is important for breeders interested in coat color genetics and for understanding inheritance patterns. The mutation has no adverse health effects.
