I-Locus Dog (Intensity)

I-Locus (Intensity)

The Intensity-locus (I-Locus) in dogs is linked to the gene encoding the Major Facilitator Superfamily domain-containing protein 12 (MFS12), which plays a role in phaeomelanin production (light pigment). In dogs with the wild-type genotype, hair expressing only phaeomelanin displays as a red, gold, or tan coat. Conversely, a recessive mutation in MFS12 leads to a reduction in phaeomelanin production, resulting in a lighter colour spectrum from cream to white.

Inheritance

The wild-type I-Locus allele is denoted as I, while the recessive allele responsible for pigment dilution is marked as i. The allele displays semi-dominance, implying that dogs with the I/I genotype are unaffected, while those with I/i will exhibit less pigment dilution compared to dogs with i/i.

The impact of the I-Locus dilution is most noticeable in dogs with the recessive red mutation on the E-Locus (e/e), as it influences the entire coat. Furthermore, in dogs with patterns like black-and-tan or saddle tan, the tan portions of their coat will also undergo dilution to cream or white.

Relevant tests

• H821