Piebald colouring pattern

Piebald coloration in the coat is characterized by the presence of white spots or patches distributed all over the body.

Definition

The piebald colouring pattern refers to a phenotype characterised by the presence of white patches or spots. The size of the patches can vary from a small amount of white markings on the chest or legs to an almost completely white coat. The variant is located in the MITF gene (also known as the S-locus) which encodes a protein involved in the control of the development and function of melanocytes, the cells responsible for pigment production.

Genetic basis

The piebald variant is also known as "sp" for "spotting". The presence of one copy of the variant will be sufficient for the expression of the trait but, in this case, spotting will be more limited. This effect is due to the co-dominance of the S and sp alleles. If the dog has two copies of the variant it is possible that the white spots are large and can occupy almost the entire coat of the dog. This coloration pattern is imposed independently of the color of the dog's coat, except in albinos. It should be noted that the appearance and extent of the white patches can be influenced by multiple genes and vary greatly between breeds.

Other relevant information

The trait arises as a result of a problem in the development of pigment cells, thus reducing the number of melanocytes and the production of pigment in certain areas of the body. This damage affects not only the pigment cells in the hair follicle but also those located in the ears. In fact, a link has been found between the presence of the sp allele and the development of congenital deafness in several breeds. On the other hand, the presence of white patches is often associated with pink markings on the skin and nose and blue eyes. The described variant may be called by other names such as "flash" colour, "parti" colour or extreme white. Breeds commonly showing white markings are American Eskimo Dog, Australian Cattle Dog, Bichon Frise, Bluetick Coonhound, Brittany, Chihuahua, Chinese Crested Dog, Dalmatian, English Setter, English Springer Spaniel, French Bulldog, German Wirehaired Pointer, Japanese Chin, Maltese and Saint Bernard.

Bibliography

Baranowska Körberg I, Sundström E, Meadows JR,et al. A simple repeat polymorphism in the MITF-M promoter is a key regulator of white spotting in dogs. PLoS One. 2014 Aug 12;9(8):e104363.

Karlsson EK, Baranowska I, Wade CM,et al. Efficient mapping of mendelian traits in dogs through genome-wide association. Nat Genet. 2007 Nov;39(11):1321-8.