Appaloosa Pattern-1 is a modifier of the leopard complex spotting (LP) and controls the amount of white in the coat pattern.
Phenotype: Appaloosa Pattern-1 is a modifier of the leopard complex spotting (LP) and controls the amount white in the coat, increasing the amount of white present in horses that also have the LP mutation.
Mode of Inheritance:Autosomal dominant
Alleles: N = Normal, PATN1 = Pattern-1
Breeds appropriate for testing: Appaloosa, Appendix, British Spotted Pony, Australian Spotted Pony, Knabstrupper, Noriker, Miniature Horse, Pony of the Americas, among others
Explanation of Results:
Horses with N/N genotype will not have increased amount of white in their coat related to PATN1 and cannot transmit an Appaloosa Pattern-1 variant to their offspring.
Horses with N/PATN1 genotype that are also LP (N/LP or LP/LP) will have high amounts of white patterning (typically more than 60% at birth). They may transmit the Appaloosa Pattern-1 variant to 50% of their offspring.
Horses with PATN1/PATN1 genotype that also have at least one copy of LP (N/LP or LP/LP) will have high amounts of white patterning. They will transmit an Appaloosa Pattern-1 variant to all of their offspring.
*In order for high levels of white spotting to be visible on horses that inherit PATN1, LP must also be present.
Leopard Complex Spotting, a highly variable group of white spotting patterns, is controlled by the LP gene. LP determines if a horse will have a leopard complex spotting pattern while other genes determine the extent (or amount) of white patterning present. One of these genes has been identified and has been termed Pattern-1 for first pattern gene or PATN1 for short. A dominant mutation (PATN1) was identified that is associated with increased amount of white in horses that also have the LP allele. The amount of white pattering on horses with LP and PATN1 typically range from 60-100%. In horses with LP but without PATN1 the range is generally from 0-40% at birth. It is thought that additional modifiers help to explain the range in patterning observed.
In horses that are heterozygous for LP (N/LP), presence of the PATN1 mutation often produces a leopard or a near–leopard pattern. In horses that are homozygous for LP (LP/LP), the PATN1 mutation most often results in a few-spot or near few spot pattern.
The PATN1 mutation is present in breeds with LP, including the Appaloosa, British Spotted Pony, American Miniature Horse, Noriker, and Knabstrupper, among others. The PATN1 mutation has been found in other breeds but may not have an effect on phenotype in the absence of LP. Testing for both LP and PATN1 is recommended for breeders interested in producing Leopard Complex Spotted horses and ponies.
Holl, H. M., Brooks, S. A., Archer, S., Brown, K., Malvick, J., Penedo, M. C., & Bellone, R. R. (2015). Variant in the RFWD3 gene associated with PATN1, a modifier of leopard complex spotting. Animal Genetics,47(1), 91-101. doi: 10.1111/age.12375