Coat colour I locus / Intensity (MFSD12-related) - Dog

What does this test examine?

This genetic test analyses the MFSD12 variant c.151C>T at the canine I locus. The trait is known as I locus, Intensity, Intense, phaeomelanin dilution, red pigment intensity and cream or white dilution of red, yellow or tan pigment.

What does the I locus mean for the coat?

MFSD12 mainly influences the intensity of light pigment. Dogs with two i alleles can show dilution of red, yellow or tan pigment toward cream or white. The effect is often clearest in dogs that mainly show red or yellow pigment through the E locus, but tan points or saddle tan can also become visibly lighter.

Inheritance and result

The I locus is mainly interpreted as autosomal recessive, with the strongest effect in i/i dogs. A dog with I/I has normal pigment intensity for this variant, I/i carries one i allele and i/i gives the strongest MFSD12 contribution to light cream or white phaeomelanin.

Practical value of this test

• Helps breeders predict whether puppies may show deep red/yellow shades or lighter cream/white shades.
• Makes hidden i carriers visible before colour matings are planned.
• Gives owners and puppy buyers a clearer explanation of why a dog looks lighter than expected from other colour genes.
• Supports colour planning together with E locus, A locus, K locus, B locus, D locus and white pattern genes.