The Pinto Patterns:
Tobiano, Frame Overo, Splash, and Manchado
This page is under construction.It will contain extensive information on the various horse pinto patterns. We are looking for pictures of horses that are representative of the various amounts of white that can be found in each pattern. For a photo to be chosen the horse must be clean, unclipped, and standing in a conformation type stance that best shows off the colour.
Tobiano (To): is the most common of the large spotting patterns that are referred to as “pinto”. A typical Tobiano horse has white feet and legs from the hocks and knees down and a dark/ coloured head with no more than typical horse markings on the head (star, strip, snip, normal blaze). If there is more than typical white face markings this is an indicator of other white pattern factors. The coloured body spots are generally smooth and rounded looking not jagged edged. The white spots typically have a vertical orientation, cross the top line at least once and have sharp, clean edges. Coloured areas remain on the flanks, chest and head on horses with greater areas of white. A highly expressed Tobiano may only have a dark head with the remainder of the body white. A very minimal Tobiano may only have white socks, similar to a non-Tobiano horse. Tobiano can also cause “roaning” in the coloured areas and “mapping” on the edges of the coloured areas. Mapping is when there is a narrow band of roan colour on the coloured part of a spot tracing the edge. Homozygous Tobiano horses also tend to have more “ink spots” or “cats paws” than a heterozygous Tobiano. Theses markings are small coloured spots in the white areas that look like ink spots or paw prints. Eye colour is normally brown but blue or part blue eyes may occur when white marks cross the eye. Tobiano (To) is the most common colour test at the University of Kentucky.
Genetics:. Tobiano is caused by a large chromosomal inversion, 70 kb downstream from the KIT gene that is believed to disrupt the normal functioning of the KIT gene (Brooks et al, 2007). Dr Kathryn Graves describes the inversion as “it’s like the chromosome came out, flipped around, and went back in”. There is also a SNP within the KIT gene that is closely linked to the Tobiano pattern as well as additional markers that are associated with the Tobiano spotting pattern (Brooks et al, 2002).
Breeds: Many, not inclusive of: Paint Horse, Shetland Pony, Miniature Horse, Gypsy Cob
Frame Overo (O/o): Historically Overo referred to any white spotting pattern that wasn’t Tobiano, but now is used solely for Frame Overo. Frame Overo is a highly desired white spotting pattern. Many of its features appear as the opposite of Tobiano. The white is generally in irregular patches on the sides of the body and neck that look as if they are “framed” in colour. White marks rarely cross the back between the ears and tail and tend to have a vertical orientation. Feet and legs are usually dark unless combined with another white spotting pattern. White areas have sharp edges but may also have a halo of pigmented skin under the white hairs at the colour boundary similar to the mapping seen with Tobiano. Blue eyes are often seen in Frame horses as well. All Frame Overo horses are heterozygous as in its homozygous form the mutation is lethal. A homozygous horse will be born nearly white to completely white and will die within 72 hours if not humanely euthanized. The foal is born with an inability to defecate/ pass manure as a result of undeveloped nerves in the digestive system referred to as “ileocolonic aganglionosis” or “Megacolon”. The condition is known as LWO (lethal white overo) or OLWS (overo lethal white syndrome).
Genetics: The Frame Overo gene, EDNRB (endothelin receptor type B) is located on chromosome 17 and has 8 exons. Frame Overo is caused by a mutated Ile118Lys on the EDNRB gene.
NCBI: Gene ID: 100033875; Location: Chr 17 NC_009160.2 (50601395…50625930, compliment); Length: 24,536 bp
Ensembl: Gene ID: ENSECAG 00000024851; Location: compliment (50604167…50625930); Length: 21,764
Breeds: mainly found in American breeds with Spanish horse ancestry.
Tovero: This is not a specific colour pattern but is a term used by the APHA (American Paint Horse Association) to describe horses with both Tobiano and any other white spotting pattern.
Splashed White (SW1-5+): Splashed White is a group/category of white spotting patterns where the horse is often described as looking as if it was dipped in white paint from the feet up. The white covers the head, legs, underbelly and under the neck before moving higher up the body. The white is usually crisply delineated with no roaning but can also be very Sabino-like as well. The white markings can also be more Tobiano-like rather than Overo-like. Many horses also have blue eyes. A highly expressed horse tends to have no colour on the topline, a solid white head and some small amounts of body colour remaining. Splashed White has been noted to cause deafness when the inner ear is white (depigmented). Splash in Traditional Cobs may be a form of Sabino-like White Spotting Pattern that they call Splash.
Genetics: Caused by multiple mutations on the MITF and PAX3 genes
Splashed White 1 (SW1)- MITF gene mutation, Homozygous viable. Found in many breeds, including Quarter Horse, Paint Horse, Trakehner, Miniature Horse, Shetland Pony, Icelandic Horse.
Splashed White 2 (SW2)- PAX3 gene mutation, Homozygous lethal, Founding Quarter Horse mare bornIn 1987.
Splashed White 3 (SW3)- MITF gene mutation, Homozygous lethal, 2 known Quarter Horses
Splashed White - (SW-)- MITF gene mutation causing white patterns, colour dilution, and deafness. Found in the Frances-Montagne horse Apache du Peupe. Known as Macchiato within the breed and given this colour designator as there is a colour dilution present. Due to low sperm motility the horse has been gelded.
Splashed White 5 (SW5)-