The Leopard Complex
This page is under construction.It will contain extensive information on the horse patterns that are part of the leopard complex. We are looking for pictures of horses that are representative of the progression of patterns in various horses and for sequential photos that show the progression of Varnish in a single horse. For a photo to be chosen the horse must be clean, unclipped, and standing in a conformation type stance that best shows off the pattern.
Appaloosa/ Leopard Complex (Lp): The spotting pattern made famous in North America by the Appaloosa breed is referred to correctly as the Leopard Complex because there are many related patterns classified as appaloosa/Leopard. It is thought that there may be over 10 different Leopard patterns. From historical records and even the analyses of cave paintings it is thought that the Leopard Complex is a very ancient mutation that may be older than 25,000 years. The Leopard gene is an incomplete dominant which expresses differently in heterozygous and homozygous forms, it also causes the companion pattern genes to express differently depending on various pattern interactions. The Leopard gene causes mottled skin around the nose, lips and genitals; also stripped hooves and white sclera around the eyes. Homozygous Appaloosas are affected by both Equine Recurrent Uveitis (ERU)/ Moon Blindness which causes the body’s immune system to attack eye tissue causing eventual blindness if severe enough, and Congenital Stationary Night Blindness (CSNB) which is a condition that makes it difficult or impossible to see in relatively low light. Other breeds are thought to have these conditions as well but there has been no extensive testing to date. Because Leopard Complex has so many variables that are not yet understood many horses can and will not fit into the currently established pattern identification.
Varnish Roan (Lplp or LpLp): is the most basic pattern. It is the Leopard gene (Lp) without any companion pattern genes. A horse starts out with a dark/ normal coat with maybe a few white hairs, as it ages the coat progressively “roans out”, creating a mottled appearance, with darker patches on the bony areas such as the hip bones and shoulder blades. Homozygous horses will varnish faster than heterozygous horses. Additional pattern genes will not show without the Lp gene being present, yet appear to be dominant in themselves.
Pattern 1 (Patn1): The first pattern gene has been identified and labelled Pattern 1 (PATN1), it causes what is referred to as Leopard Spotting. As the name implies the horse is spotted like a leopard. When a horse is heterozygous Leopard (LP/lp) and has Pattern 1, it will have a mostly white body with all over body spots of the base colour.
Few spot (PATN1): when a horse is homozygous Leopard (LpLp) and has pattern 1, it will have a mostly white body with smaller sized spots and few to no spots… Wait, less spots? This is a hard concept for most people because we automatically assume that there should be more spots. All coat modifiers are actually referring to the amount of white that is “added” to the coat. If we think of heterozygous as one dose and homozygous as two doses then it makes sense that heterozygous adds one dose of white, leaving lots of spots and homozygous adds two doses of white and covers more of the spots, leaving less visible.
Blanket Pattern: has not yet been located genetically but is often referred to as pattern 2 (Patn2). It causes a white pattern that looks like a white blanket with spots has been thrown over the horses back.
Snowcap: is a horse that is homozygous Leopard (LpLp) and has pattern 2 (Patn2). The blanket has few to no spots.
Snowflake: is a pattern where the horse is a Varnish Roan that has small white spots that look like snowflakes on its body that increase in numbers over the years.
Genetics: The Leopard Varnish Roan/ basic pattern (Lp) gene, TRPM1 (Transient Receptor Potential Cation Channel, subfamily M, member 1)
is located on chromosome 1 and has 5 exons.
NCBI: Gene ID: 100059740; Location Chr 1 NC_009144.2 (108196607…108299882, compliment); Length: 103,276 bp Length: 103,276 bp
Ensembl: Gene ID: ENSECAG00000007539; Location: 108196684…108303608; Length: 106,925 bp
Breeds: Tiger Horse, Knabstrup/Knabstrupper, Pony of the Americas, Appaloosa, Several gaited breeds, British Spotted Pony, Gypsy Cob
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