Description: The locus is responsible for the presence of white, unpigmented areas on the coat. These can occur in many different patterns. The locus S is located with the Microphthalmia Associated Transcription Factor (MITF) gene encoding a transcription factor that controls the development and migration of melanocytes. MITF protein expression is an essential factor for hair pigmentation. The absence of pigment is due to the absence of melanocytes, not the failure of the biochemical reactions necessary for pigment synthesis.
As a result of the mutation, the SINE element (short interspersed nuclear element) is inserted. Dogs with SINE embedded show either extreme white spots or coloring of Piebald. In Irish spotting dogs and in dogs without white spots, the SINE element does not occur.
Several mutations have been identified in the MITF gene at the S locus. The correlation of these mutations is not fully understood.
Among the three mutations associated with white spotting, the presence of SINE insertion is detected. A non-SINE state is called del (as a deletion), a SINE state is called ins (as insertion). Thus, there are three combinations: S/S, S/s and s/s (ins/ins). In some breeds (Collie, Great Dane, Sheltie, Italian Greyhound) there appears to be a codominant inheritance. The heterozygous S/s genotype causes a typical pseudo-Irish spotting. In most other breeds, S (No white spotting, solid, monochromatic) is dominant over s (ins) (white mottled).
In most breeds, dogs heterozygous for SINE insertion (genotype S/s) single-colored or only minimally white, for example on toes. In some breeds, heterozygotes have white undersides, often with a white-collar called pseudo-Irish.
All dogs without SINE advertising (genotype S/S) are solid – plain colored.
Inheritance: autosomal codominant
Mutation: g.21836232_21836427ins>del at the MITF locus, SINE insertion in MITF gene CFA20
Sample: EDTA whole blood (1.0 ml) or 2 buccal brushes. For official purposes, the confirmation of the dog’s identity by Veterinarian is recommended.
The analysis is suitable for the following breeds: American Cocker Spaniel Basset Hound, Beagle, Border Collie, Boxer, French Bulldog, Cavalier King Charles Spaniel, Chihuahua, Chinese Shar-Pei, Dachshund, English Cocker Spaniel, French Bulldog, German Longhaired Pointer, German Shorthaired Pointer, German Wirehaired Pointer, Goldendoodle, Havana Silk, Havanese, Labradoodle, Newfoundland/Landseer, Pointer, Poodle, Portuguese Water Dog, Shar Pei, Saint Bernard, Whippet, Yorkshire Terrier
Notes: This test is specific for the insertion of SINE in the MITF gene known to be associated with random white dots – piebald. This analysis is not suitable for testing Irish spotting and symmetrical white marking.