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083-088-GeneticSeries_Part1 Modifi ed: December 10, 2015 10:58 AM Files:Publications:PHJ:01.16 Journal:01.16-Sent to Rip:083-088-GeneticSeries_Part1.indd APHA FILE PHOTO A Paint owner’s guide to demystifying IQ the genetics of spott ing patt erns. Part 1 of 2 By IRENE STAMATELAKYS

efore DNA testing became com- it’s challenging to keep up with the latest be thought of as strings of —the mon—before we downloaded developments. building blocks in all living organisms Bforms and pulled hairs and With that in mind, the Paint Horse that determine visible traits, like hair received results via email—Paint Horse Journal has developed a two-part series color, and non-visible traits, like relied on collective wisdom and to increase your genetics IQ. For nov- type. A horse has 64 pairs, trial and error in their quest to produce ices, we’ll bring you up to speed on the inheriting half from the sire and half those all-so-desirable colored . - essentials. For genetics buff s, we’ll shed from the dam. ers needed to experiment for years before light on some of the latest developments Each has an address—a spe- confi rming a horse was a good, great or and challenges facing researchers and cifi c site on a specifi c chromosome. poor color producer. Foaling time brought breeders. And for everyone, we’ll attempt We call this address a , with the lots of pleasant surprises, along with some to answer the question, “How can these plural being loci. Quite often, geneti- disappointment and occasional heartache. genes enhance my Paint cists use the locus name to refer to a While the arrival and development of program?” gene. And when a gene comes in diff er- DNA testing has eliminated a lot of the ent forms, those variations are called guesswork, many of us have a limited Genetics Jargon . understanding of the tools science has to Before we get into spotting specif- For example, the locus has off er. Others have a good handle on Paint ics, let’s start with some basic genet- two alleles: a tobiano (TO) and a Horse genetics, but advances and discov- ics terminology you probably learned non-tobiano allele (n). Either can occur at eries are happening at such a fast rate that in biology class. can the Tobiano locus, but each chromosome

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can only carry one allele. Because chro- A recessive gene is only expressed with how we think that gene should look The Dominant Whites mosomes come in pairs, a horse carries in the homozygous state. Lethal phenotypically. All of these are found on two alleles at a particular locus. White Syndrome, for example, is a Now that you’ve reviewed the lingo, the KIT gene, located on Chromosome The Dominant Whites If a gene is dominant, like Tobiano, recessive condition; none of the known let’s take a look at the known mutations 3. Researchers named them Dominant Position on the horse only needs one copy of the allele spotting patterns are fully recessive. responsible for Paint Horse spotting pat- White, although horse breeders might Name KIT Gene Breed from one parent to have a tobiano spot- Finally, is what some- terns: “The Big Six” and “The Dominant use other terms to describe the patterns. 1 (W1) 15 Franches-Montagnes Horse: White ting pattern. For instance, a heterozygous thing looks like on the outside—for our Whites.” It’s important to note that these The alleles are dominant, meaning a trace to Cigale, a foaled in 1957 tobiano (n/TO) has one Tobiano allele; a purposes, that’s the outward expres- genes do not determine whether or not horse only needs to inherit one copy Dominant White 2 (W2) Exon 2 : White horses trace back homozygous tobiano (TO/TO) has two. sion of a white spotting pattern in Paint skin cells can produce , which of the to produce to KY Colonel, a with extensive white markings, foaled in 1946. Some genes are incompletely domi- Horses. refers to the horse’s is a class of pigment that’s responsible that range from slightly increased face nant. This means that heterozygotes genetic makeup. Sometimes a horse can for the dark color of skin, hair and more. and leg markings to sabino-like to com- Dominant White 3 (W3) Exon 4 Arabian: Spotted horses trace back to R Khasper, a near-white foaled in 1996. do not look the same as homozygotes. carry a spotting pattern gene, but not Rather, these genes infl uence the migra- pletely white. We’ve bolded the entries Dominant White 4 (W4) Exon 12 Camarillo : White horses Sabino 1 is one example, which we’ll express it in a way that’s consistent tion of (melanin pigment- for three Dominant White genes known trace back to Sultan, a stallion foaled in 1912. describe later. producing cells) in the . to exist in the Paint , and Dominant White 5 (W5) Exon 15 Thoroughbred: Horses trace back to show examples of each below. (see photo at left ) Puchilingui, a stallion foaled in 1984 with a sabino-like coat pattern, and his offspring. Dominant White 6 (W6) Exon 5 Thoroughbred: Identifi ed in a single white The Big Six horse. Dominant White 5 (W5) Dominant White 7 (W7) Intron 2 Thoroughbred: Identifi ed in a partially white fi lly. Dominant White 8 (W8) Intron 15 : Identifi ed in a partially white horse with mottled phenotype. Dominant White 9 (W9) Exon 12 : Identifi ed in a completely white horse. Dominant White 10 (W10) Exon 7 Paint/Quarter Horse: Horses trace back (see photo at left ) to GQ Santana, a stallion foaled in 2000, CASSIDY COBARR CASSIDY COBARR CASSIDY COURTESY LAUREN BORK LAUREN COURTESY and his offspring; expression ranges from nearly all-white to horses with face/leg white and belly spots. Dominant White 11 (W11) Intron 19 South German : Identifi ed in a DON TROUT completely white stallion and three white offspring. Dominant White 10 (W10) Dominant White 12 (W12) Exon 3 Thoroughbred: Identifi ed in a single horse with sabino-like pattern. Dominant White 13 (W13) Intron 17 Quarter Horse/: Identifi ed in a crossbred family with two white animals. Dominant White 14 (W14) Exon 17 Thoroughbred: Identifi ed in a completely white horse. Dominant White 15 (W15) Exon 10 Arabian: Identifi ed in a single horse with partial depigmentation. Dominant White 16 (W16) Exon 7 Oldenburg: Identifi ed in a family with three almost completely white horses. Dominant White 17 (W17) Exon 12 Japanese Draft Horse: Identifi ed in a com- pletely white horse with one blue eye. KELLY GRAPHICS LLC KELLY Dominant White 18 (W18) Intron 8 Swiss : Identifi ed in a single Dominant White 20 (W20) horse with extended white speckled areas. CASSIDY COBARR CASSIDY SUSANNA COURTESY MARINELLI COURTESY BAR K 2 BAR COURTESY Dominant White 19 (W19) Exon 8 Part-Bred Arabian: Horses have bald faces, extended white legs and irregular belly spots. Dominant White 20 (W20) Exon 14 Multiple : Very common mutation; (see photo at left ) incomplete dominant trait. Markings might include a wide blaze, leg markings and small belly spots. Has a subtle effect on depig- mentation with a stronger effect on bays than sorrels. Living homozygotes have been found and tend to have more white. Dominant White 21 (W21) Exon 17 Icelandic Horse: Identifi ed in a single horse with a sabino-like pattern. COURTESY KRISTEN MEYERS KRISTEN COURTESY

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One of the biggest challenges facing researchers and Paint Horse breeders alike is the nomenclature of spotting patterns. CASSIDY COBARR COBARR CASSIDY GAIL SHAW CASSIDY COBARR COBARR CASSIDY

The only completely dominant white spotting gene isTobiano , which means a horse only It stands to reason that homozygosity increases the amount of While many Splash White carriers might look phenotypically similar, the needs one copy of the gene to inherit the trait. white markings—that seems to be the case for this 2015 cropout three known genes are very different. Hello Big Chex, a 2012 chestnut overo by A Splash Of Silver (QH) and out of Dun Gone Classy (QH). stallion by Big Chex To Cash and out of Custom Princess (QH), carries a Both parents are n/SW1 and minimally colored; this loud colt car- single copy of the SW1 gene and is negative for other known white-spotting ries two copies of the Splash White 1 gene. patterns. The Nomenclature a dominant form of white spotting, which Nightmare ranges from extended face and leg mark- Color Genetics One of the biggest challenges fac- ings to a completely white coat. mutation. But other W mutations vary talk to horse people, and they call it some- ing researchers and Paint Horse breed- Researchers decided to call the gene greatly in their expression—not all look thing entirely different.” Bookshelf ers alike is the nomenclature of spotting Sabino 1 for two reasons, Samantha like GQ Santana; they can range from a patterns. Over the years, this system of explains. First, the idea was to better nearly all-white horse to a mostly solid- The Mystical Modifier Free Live names used to designate a particular pat- match the terminology used by horse colored horse with a blaze and socks to It can be curious to ponder why one Want to learn more? Here are tern has grown increasingly complex and breeders. Second, they didn’t want to horses that look like what most horsemen horse might have more or less “color” two books to add to your equine Seminar: library. clumsy. scare or confuse people with connotations would call sabino. than another when both carry the same Horse Genetics (2013, 2nd Samantha Brooks, Ph.D., is assistant based on the lethal dominant white genes “One that comes to mind is W20,” spotting pattern mutation. Breeders Edition) by Ernest Bailey and professor of equine physiology at the Uni- found in mice or the overo lethal white Samantha said. “You’ll see a lot of W20 have often wondered about the existence “Paint Horse Samantha Brooks versity of Florida. Her genetics research gene in horses. in the reining horses. It’s a very frequent of an “enhancement” gene or perhaps a Genetics” This is the textbook Saman- led to the discovery of the Tobiano and Things got a little more complex when allele, and we know horses can be homo- gene that suppresses white. tha uses for her equine genetics Sabino 1 genes. Bianca Haase, a research fellow at the zygous for it. They are perfectly healthy, “[Enhancement] is a word I don’t 2016 APHA Convention class at the University of Florida, “The nomenclature is a mess,” Saman- University of Sydney in Australia, began and homozygotes rarely have more than like,” Samantha said, “in part because Richmond, Virginia but she says anyone who sur- vived high school biology can tha said. “It’s honestly my pet peeve.” discovering more genes based on the 30 percent white on the body. And yet it’s been applied to some known genes February 26, 2016 follow along. It covers the basic The problem is multi-dimensional. On Dominant White locus. that allele got a Dominant White acro- where it doesn’t belong.” 1:30–2:30 p.m. genetics of the horse including the one , you have researchers find- “When Bianca started finding her nym because it is in the KIT gene and The idea of a modifier gene comes coat color, parentage, medical ing the mutations and, from a scientific white mutations, many of those were [researchers wanted] to stick strictly to from genetics. If you’re fascinated by equine color genetics or want and population genetics, cyto- perspective, wanting to follow standard homozygous lethal, and many of those murine nomenclature. The scientific con- “In , we have two genes genetics, performance, breeding to learn more ways to improve naming conventions so that the names are completely white, but not all of them,” vention doesn’t take into consideration that control white spotting,” Samantha systems and genetic conserva- your through make sense to fellow researchers. On the Samantha said. “She found a couple in the issues that nomenclature can cause explained. “We have the main LP locus, tion, and new advances such as , don’t miss this micro-satellite testing. other, you have breeders who the series­—[some] that were potentially us. W20 is one a lot of horse people would which is present in horses with any- unique learning opportunity Equine Color Genetics don’t necessarily use the same terms. viable as homozygous and some [that call a splash white.” thing from a completely white coat with at the 2016 APHA Convention (2009, 3rd Edition) by D. Phillip Sabino 1 is a good example. were] heterozygous—that looked similar Three mutations designated Splash just a few spots to a horse who has in Richmond, Virginia. Saman- Sponenberg “We struck out on our own when we to sabino, but she chose to keep with the White can be confusing, too. Appaloosa characteristics but no body tha A. Brooks, Ph.D., assistant professor of equine physiology Now in its third edition, named Sabino 1,” Samantha said, “Based W symbol based on laboratory “My issue there is a scientific one spots. On top of that you add the Pattern this work is an encyclopedia of at the University of Florida, will on the murine (mouse) nomenclature, we research. Perhaps some of those should because you have two different genetic locus, which we call PATN1. It controls genetics, with enlighten attendees with her should have called it W for the Dominant have been pulled out and called sabino loci that have the same acronym: SW. the amount of white, from one percent to in-depth yet accessible explana- knowledge and research regard- tions and color photos illustrat- White locus.” instead of dominant white, for the sake That’s too confusing,” Samantha said. “At 99 percent.” ing Paint Horse genetics in this ing each example. It’s an excel- The term “dominant white” is not par- of limiting confusion among breeders of the very least, they should have been split PATN1 doesn’t produce a visible free seminar. Plan to get an lent resource for the Paint Horse ticularly descriptive either. It’s easy to spotted horses.” up and given two different names. But that spotting pattern itself, but it does control education on genetics and all it and equine color genet- imagine the gene produces an all-white In the Paint world, the most famous is the nightmare that is nomenclature in the expression of other spotting genes. has to offer the APHA. To learn more or to register online, visit ics enthusiast. horse—not exactly what Paint breeders dominant white horse is GQ Santana, the scientific community. And then you And to get the desired Appaloosa phe- apha.com/events/convention. are aiming for. The name actually refers to who was the founding animal of the W10 notype, you need both the LP and PATN1

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Genetic Testing Find out exactly which colors and patterns your stallion or mare carries before the breeding season begins. APHA’s official genetics testing part- ner, the Veterinary Genetics Labora- tory at the University of California– Davis, offers a Comprehensive Coat Color test for $125. This simple pro- cedure, done with 30 to 50 hairs (with intact roots) from your horse, tests for the presence of red factor, agouti, cream, pearl, champagne, dun, silver, gray, Tobiano, Frame Overo, Sabino 1, Splash White 1, 2 and 3, and Dominant White 5, 10 and 20. Results, sent by email, take seven to 10 business days. Order the test by calling APHA at 817- 222-6423, and learn more online at COURTESY SUSANNA MARINELLI SUSANNA COURTESY vgl.ucdavis.edu. The SW3 gene is relatively rare; one known carrier (n/SW3) is TD Celebri Te, a 2009 chestnut overo stallion by TD Kid and out of Te Time Playmate (QH).

genes. Samantha notes researchers have “With some of these W mutations— of genes—his phenotype and the extent not yet documented any PATN1 effect on a particularly the ones that look like splash of his white markings—is dependent on pattern other than LP. white or sabino—that gene alone is not multiple factors, including the interac- “Really, Appaloosa is the product of enough to bump a horse from solid Paint- tion of different spotting patterns. It’s two loci, not just one,” Samantha said. “We bred up to Regular Registry,” she said. also possible that environmental or attribute it to one, but you have to have two “Folks have not attributed that gene as even randomly determined factors play to get the pattern people want. a spotting pattern—they’ve just got this a role as well. We still have much to “The analogy [for Paints] is that LP horse with socks and a blaze, when it might learn in the area of equine color genetics; is like Tobiano and PATN1 is your mythi- actually have a good spotting gene there. the benefits of increasing our knowledge cal enhancement gene,” she said. “The “They tend to get called enhancement and understanding, however, are clear: reality is that because Paint Horses work genes because any time you add two spot- improving the percentage of foals born with so many different patterns, we prob- ting patterns together, you typically get with a desirable color pattern and safe- ably don’t have an enhancement gene. more white. People are giving the credit to guarding the health of the horses we raise. But why else would you get some horses the more notable of the two patterns—let’s Coming up next month, ride along that are 80 percent white and others that say Tobiano—but they are also ignoring the with the Paint Horse Journal to the lead- have four socks and one white tuft in fact the horse is actually multi-patterned. ing animal DNA parentage verification their mane, but both are genetically Tobi- What people are calling an ‘enhancer’ is laboratory in the world, the Veterinary ano? You can imagine that there might just another spotting pattern that has a dis- Genetics Laboratory at the University be a modifying locus that’s contributing tribution that doesn’t perfectly align with of California–Davis. There, we’ll inter- to that. Part of this variation is simply the APHA threshold for Regular Registry. view VGL Director Cecilia Penedo, Ph.D., due to chance. If there was a second gene The horse might possess a perfectly valid about the importance of equine color test- essential to the expression of a key Paint spotting pattern that can act and produce ing, how these tests are conducted and pattern [like tobiano], I think we would color entirely on its own. I would categorize the results of a small, informal study of have found it by now. these genes as a more minimal spotting a randomly selected group of Paints— “There are certainly genes that create pattern, not an enhancer or modifier.” both Regular Registry and Solid Paint- more white when added to Tobiano and per- In other words, that mythical modi- Bred horses—to see how many carried a haps some that create less white. I like the fier or enhancement gene is probably just known pattern gene, as we continue our term ‘modifying’ because it doesn’t imply a another spotting pattern—either known or investigation on how these genes can be particular type of effect. Modifiers are not unknown—that is increasing the amount used to enhance Paint Horse breeding yet described genetically, and at this point of white on your Paint. programs. they are kind of mythical.” Samantha’s theory is that some of The Potential to Produce Irene Stamatelakys is a special contributor these mythical modifiers are actually white While a horse’s genotype tells one for the Paint Horse Journal. spotting patterns. story, the expression of that combination [email protected]

88 January 2016 | PAINT HORSE JOURNAL 087-092-GeneticSeries_Part2 Modified: January 11, 2016 10:06 AM Files:Publications:PHJ:02.16 Journal:02.16-Sent to Rip:087-092-GeneticSeries_Part2.indd APHA FILE PHOTO A Paint Horse owner’s guide to the power Genetics IQ and potential of genetic testing for spotting Part 2 of 2 patterns.

By IRENE STAMATELAKYS

ast month, we shed some light group of Paints—both Regular Regis- in the 1960s to include horses, offering on the genetics behind the white try and Solid Paint-Bred—to see how identity and parentage testing via blood Lspotting patterns common to many carried a known pattern gene. typing. Today, it is the leading animal the Paint Horse breed: Tobiano, Frame We’ll also take a closer look at the W20 DNA parentage verification laboratory Overo, Sabino 1, Splash Whites 1, 2 and mutation, which is relatively unknown in the world, serving as the official labo- 3, and Dominant Whites 5, 10 and 20. but highly prevalent in Paints. And we’ll ratory for 120 horse registries, in addi- We covered the essentials and touched discuss the importance of color testing tion to offering genetic disease and coat on some of the latest developments with breeders and researchers as we color testing to the general public. and challenges facing researchers and continue our investigation on how these While Paint Horse owners could breeders, specifically the naming sys- genes can be used to enhance Paint choose one of several private labora- tem and “mythical modifiers.” Horse breeding programs. tories for equine coat color testing, a This month, we go inside the Vet- significant percentage use VGL. erinary Genetics Laboratory at the Welcome to my Laboratory “For the last three years, we’ve University of California–Davis to learn Originally established in the 1950s to seen a significant increase in both coat more about the lab, how DNA tests are provide parentage verification for color and disease panel testing done conducted and the results of a small, registries, UC–Davis’ Veterinary Genet- via APHA and a decrease in orders for informal study of a randomly selected ics Laboratory expanded its services individual tests,” VGL Director Cecilia

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The University of California–Davis’ Veterinary From the minute Genetics Laboratory is APHA’s official genetic In the Roots: testing partner. Leaders in genetic testing, the Extracting DNA VGL offers a variety of coat color and pattern a test is ordered, tests along with genetic disease testing and

Y other services like parentage verification. precautions are Ever wonder what happens to your horse's mane hair sample once it arrives at UC-Davis for testing? Veterinary Genetics Laboratory Director Cecilia Penedo ORATOR B taken to ensure walked us through the process. 1. Hair samples delivered to the labora- results are both tory are given a unique VGL case GENETICS LA

Y number used to track each sample in the system. All information available accurate and for the sample (case number, horse VETERINAR Y ID, registration number, sex, date of timely. , name and registration number

COURTES of sire and dam, client ID, etc) is logged into the computer database. 2. Samples are batched according to Penedo, Ph.D., said. “Panel testing for said. “Being part of the university and Of the nearly 300 Paints tested, the are still white-spotting mutations to be tests ordered. DNA is extracted from either disease or coat color for Paints is the School of Veterinary Medicine allows following results were noted: identified that we know are present in hair roots from each sample in a only available through APHA and for a our resident faculty to be engaged with • Frame Overo present in 37% of the the breed. More research is needed to batch. relatively low cost. Owners are recog- research, to keep abreast of latest develop- sample resolve some of these patterns. White 3. The DNA extracts are subject to the nizing the value and taking advantage ments and to teach and train students. All • Tobiano present in 32% of the spotting is a very complex trait, with Polymerase Chain Reaction (PCR) process, a laboratory technique of these membership services that are this translates to a better service provided sample many genes that cause depigmented used to make copies and to amplify clearly important and beneficial to the to our customers.” • SW1 present in 9% of the sample phenotypes, variable expression and the specific target DNA sequences breed.” VGL’s commitment to research is also • SW2 present in 2% of the sample influence of genetic and non-genetic for each test. For parentage analysis, From the minute a test is ordered, pre- key to their partnership with APHA. In • SW3 present in 1% of the sample factors.” the targets are the 21 markers used cautions are taken to ensure results are 2015, the association commissioned a • Sabino 1 present in 3% of the sample for this purpose. For the diagnostic both accurate and timely. Cecilia says small study looking at white pattern genes • W20 present in 39% of the sample W20: Subtle but Effective tests, such as coat color and genetic this is a fairly detailed process, with many in a randomly selected group of horses. • W10 present in a single horse in the Interestingly enough, four out of disease, samples are put through the checks along the way to safeguard accu- “We tested 298 Paints for all coat-color sample every 10 horses in the small APHA/ appropriate assays as ordered. All racy. [See “Extracting DNA” for an in- and white-pattern mutations—19 muta- • W5 not present in the sample VGL study were W20 carriers. But diagnostic test panels include ID and depth look at the process.] tions in all, not included,” Cecilia • Appaloosa not present in the sample what do we know about this mutation? sex markers that allow further track- “The breadth of genetic tests that we explained. “There is still some analysis of “The Paint Horse breed is clearly Located on the KIT gene along with 22 ing of each sample to ensure the have available, the high quality and accu- the data to be done, but the results give a very diverse in color mutations,” Ceci- other known white spotting patterns, it correct sample is being tested. All diagnostic tests are run in duplicate; racy of our results, our expertise and good broad view of coat color variation in Paint lia said. “The majority of known muta- was discovered in 2013 and is believed for each case, two independent DNA customer service set us apart,” Cecilia Horses.” tions can be found in the breed; there to have a subtle effect on pigmentation. extractions are done and their DNA Horses with W20 might have a wide types are matched. blaze, leg markings, small belly spots 4. DNA typing is done by capillary and/or roaning throughout the coat, electrophoresis to separate the fluo- but the gene might have an even greater rescence-labeled PCR products and impact in amplification of white mark- allow us to visualize the outcomes of ings caused by other genes. the PCR tests. DNA types are deter- “It has been associated with mined using computer software increased size of white markings and developed by the VGL. with extended amounts of white when 5. DNA types are placed in the VGL combined with other white-spotting database and analysts review results, prepare the information and send

ARR ARR mutations,” Cecilia said. “It will be B B reports to clients (registries or indi-

CO CO interesting to correlate the W20 results Y Y vidual owners). Reporting of results

SSID with white-spotting phenotypes for this is done electronically. CA CASSID group of Paints.” “The turnaround time at the VGL is quite short considering all the quality While we commonly think of frame that While it’s thought that homozygosity for a pattern likeSplash White 1 might increase the amount Kao Castle, Ph.D., is the director of checks that we do before releasing a result. The majority of reports are sent have large patches of white “framed” by areas of visible white, that’s not always the case. Both of these foals tested as SW1/SW1 carriers—homo- Practical Horse Genetics, a laboratory to APHA within three to four business days from receipt of sample, unless of color, the pattern can be expressed more zygous for the gene—but they display vastly different amounts of white. in Redfern, New South Wales, Austra- minimally, too. there is a need to retest. If results are needed for prospective sale or breeding lia. They began offering the W20 test contracts, owners should submit samples as early as possible,” Cecilia advised.

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"One of the advantages “The only way that was possible,” Sonny has sired a few multi-pat- she said, “was if the mare was not terned foals that are completely white, of coat-color panel homozygous for black and carried other as has the Shaw’s newest stallion, Free Live spotting genes. So I tested her, and Hello Big Chex, who tested heterozy- testing is that Paint sure enough she came back positive gous for Splash White 1. This season Seminar: for Splash White 1. It’s an example of “Big Chex” sired a that is all white “Paint Horse breeders have more how genetic testing can also surprise out of a multi-patterned mare. They you sometimes, even when you think think the foal may be homozygous Genetics” complete information you have it all figured out. SW1 and plan to test when he’s older. 2016 APHA Convention “I have a couple of in my pro- “I always tell potential breeders to Richmond, Virginia about their horses and gram that I’ve tested who carry Splash get their mares genetically tested prior February 26, 2016 White 1, and all they have is a star to breeding to Sonny or Big Chex. Just 1:30–2:30 p.m. are better equipped on their heads. One of my babies this because they are mostly solid in their year is homozygous for Splash White coat patterns doesn’t mean that they do If you’re fascinated by to make informed 1 and only has four stockings and a not carry some color genes,” Gail said. equine color genetics or want bald face, which is really common; I From a health perspective, there to learn more ways to improve decisions." MEG MARTEL also have a colt who is really obvious are other compelling reasons to test all your breeding program through that he’s homozygous splash because breeding animals for white pattern muta- genetic testing, don’t miss this Researchers think W20 might impact the expression of other white spotting genes. Oh Im unique learning opportunity he was so excessive compared to his tions—and that goes beyond avoiding Awesome [AUS], for example, carries SW1 and W20 and displays more ragged edges to his at the 2016 APHA Convention markings than what’s typically found on horses with only SW1. parents, who were very minimal.” matings between Frame Overo carriers. in Richmond, Virginia. Saman- Cassidy says testing is worthwhile “I recommend that breeders avoid tha A. Brooks, Ph.D., assistant compared to the investment needed to matings between horses carrying SW2 professor of equine physiology commercially about six months after it W20, Kao found two horses that car- without W20 and Sabino 1 with W20, produce a foal. or SW3 and between horses that have at the University of Florida, will was discovered. ried a Splash White mutation and W20 and those horses are pretty obvi- “It just really takes the gamble out W5 or W10,” Cecilia said. “There is enlighten attendees with her “It’s well-known that if you have a that looked different from a typical ously sabino. It’s really an odd one. of the color when you breed something no hard evidence based on outcomes knowledge and research regard- ing Paint Horse genetics in this frame overo stallion, and you are look- splash white overo. Research-wise, it was a of luck. that’s not homozygous,” Cassidy said. from such matings, but we expect free seminar. Plan to get an ing to breed foals with lots of white “There seemed to be a little bit “The in the KIT gene While not all of her buyers care about them to cause health problems. The education on genetics and all it markings, you should look for solid more white, and it changed the nature in horses must be unusually high. I coat color genetics, some do. “My clients prediction is that these could result in has to offer the APHA. To learn mares with a fair bit of white—a blaze of the markings,” she said, describ- don’t think there are any other ani- that are looking for a breeding pros- homozygous foals [for example, foals more or to register online, visit and decently-high socks,” Kao said. ing the edges as more ragged and mal species where there are so many pect—to them it’s very important, so I with SW2/SW2, SW3/SW3, apha.com/events/convention. “That’s a pretty good description of a roany than a traditional splash white mutations in the KIT gene. It’s very like to have that available. It also helps W5/W5, W10/W10] that would not be horse with W20.” pattern. She also thinks W20 boosts interesting from a genetics or research me price the animal because rarity plays Curious to see the effects of the the amount of white on a horse with standpoint.” a big factor in price.” mutation, Kao requested a photo of Sabino 1. Australians Gail and Rod Shaw of any horse that tested positive for As luck would have it, a W20 test Should You Test? Woodstock, New South Wales, have Frame Overo and W20. The main chal- led to a rare discovery. If you are still debating the value of been breeding and showing Paint lenge was finding horses that carried “I had someone send a sample for a coat color testing, just talk to Cassidy Horses for 30 years. They quickly just the two genes because so many filly who was homozygous for Sabino Cobarr, owner of Shining C Grulla Horses embraced genetic testing when it were multi-patterned. 1 that was completely white, and the in Wolfe City, Texas. A firm believer in became available. “One of the first things I noticed owner insisted that I test for W20 genetic testing, she tests all the horses in “In 2003, we purchased Artful was horses that were frame overo as well,” Kao recalled. “I said there her breeding program; Cassidy learned Gunner,” Gail said. “At the time there and also had W20 seemed to be the really is no point—the two are alterna- the hard way a few years ago about trust- wasn’t any genetic testing for Splash more loudly marked frame overos,” tives to one another. If your horse has ing hearsay when she got a surprise from White, only Frame Overo. ‘Sonny’ did Kao said. “With the relatively small two Sabino 1 alleles, it can’t possibly a mare she was told was homozygous for test positive for Frame Overo, and all numbers that have come through, it have a W20.” the Tobiano and black genes. our solid Paint mares tested negative. looks like it does increase the odds of But the owner insisted, and much “I went ahead and bred her to my “When testing for Splash White getting a loud frame overo with a nice to Kao’s surprise, the filly carried solid grulla Quarter Horse stallion became available, we found out that amount of white. But it’s definitely W20 as well. who is heterozygous black and homo- Sonny carries SW1 and SW2 as well; GAIL SHAW not a rule. I have seen two instances “There has been a genetic recom- zygous dun, and I thought I would at the time, we didn’t know that this Y where a horse has been positive for bination within the KIT gene,” she be guaranteed a grulla tobiano baby,” was common for Gunner-bred horses.

Frame Overo and W20 and just had explained. “In this case, Sabino 1 Cassidy said. We had no idea that he could throw COURTES very minimal markings.” and W20 are on the same chromo- To her surprise, the mare foaled a red any combination of the genes. From Horses carrying multiple pattern genes seem to often express greater white markings. Artful While she hasn’t noticed a signifi- some together and are being inherited dun tobiano/splash white filly with a bald then on, we have color tested just Gunner is such an example: he carries the SW1, SW2 and Frame Overo genes and has sired foals cant difference on carrying together. So there now is Sabino 1 face and blue eyes. about all our foals.” carrying different combinations of those genes.

PAINT HORSE JOURNAL | February 2016 91 087-092-GeneticSeries_Part2 Modified: January 11, 2016 10:06 AM Files:Publications:PHJ:02.16 Journal:02.16-Sent to Rip:087-092-GeneticSeries_Part2.indd

Genetic Testing

Find out exactly which colors and patterns your stallion or mare carries before the breeding season begins. APHA’s official genetics test- ing partner, the Veterinary Genetics Laboratory at the University of Cali- fornia–Davis, offers a Comprehen- sive Coat Color test for $125. This simple procedure, done with 30 to 50 hairs (with intact roots) from your horse, tests for the presence of red factor, Agouti, Cream, Pearl, Cham- pagne, Dun, Silver, Gray, Tobiano, Frame Overo, Sabino 1, Splash White 1, 2 and 3, and Dominant White 5, SUSANNA MARINELLI SUSANNA

10 and 20. Results, sent by email, Y take seven to 10 business days.

Order the test by calling APHA at 817- COURTES 222-6423, and learn more online at Though there’s still more to discover, knowledge and understanding of your Paint’s genetics vgl.ucdavis.edu. can help you make more informed decisions with regard to breeding.

viable or those that could have severe can reveal with near-certainty if a horse author of the Journal’s monthly “Vet’s clinical problems. carries the genes for nine different spot- Bag” column, was the lead researcher. “It is possible that even combina- ting patterns—an amazing tool available He continues to investigate the genetic tions of these [compound heterozy- to the Paint Horse breeder. And yet, many link between white spotting patterns gotes]—for example, DNA genotypes questions remain. and deafness and has nearly completed SW2/SW3, or W5/W10—could be For example, some horses sport an a follow-up study. Stay tuned to future deleterious,” she explained. “Fortu- identifiable pattern—what we might issues of the Journal for complete nately, SW3, W5 and W10 are infre- call sabino or splash white—but don’t results and analysis. quent or rare enough to not cause test positive for any of the known white Though we still have a great deal to breed-wide concern, unlike OLWS. pattern genes. What causes those pat- learn about white spotting patterns in One of the advantages of coat color terns? And what are the other factors, horses, greater knowledge and genetic panel testing is that Paint breeders perhaps genetic or environmental, that tests available today offer breeders have more complete information about influence the quantity and placement valuable tools to increase the percent- their horses and are better equipped of white? Why are some horses solid or age of foals born with desirable spot- to make informed decisions about minimal white, and others who carry ting patterns. At the same time, this mate selection. This will minimize the same mutations are loudly marked? information also plays an important risks of producing affected foals that And finally, what impact do white role in equine health and welfare and are aborted or have to be euthanized spotting genes play on a horse’s health? in responsible breeding by limiting after birth.” One such example is deafness, found or preventing embryonic or neonatal with some frequency in frame overos loss. Paint Horse breeding will always The Breeder’s Toolbox and splash whites. involve an element of surprise, but Genetic testing for white spotting pat- In 2009, a small study evaluating genetic testing for white spotting pat- terns has come a long way. Until 2008, deafness in American Paint Horses was terns can help improve the odds that the only commercial test available ana- published, shedding some light on the those surprises will be good ones. lyzed blood samples for genetic markers question. K. Gary Magdesian, D.V.M., a for Tobiano but could not be used to offi- professor of medicine and epidemiology Irene Stamatelakys is a special contributor cially prove homozygosity. Today, testing at the University of California-Davis for the Paint Horse Journal. of about 40 mane hairs with intact roots School of Veterinary Medicine and [email protected]

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