The Splashed White Gene in Horses

Splashed white is another spotting gene in horses. It resembles tobiano in that the pattern is usually crisp-edged, and there is no tendency for the kind of uneven roaning often seen in sabino. Splashed white is more common in Europe than in North America, but is becoming common in Paints.

The best description of splashed white is that the horse looks as if it had been dipped feet-first in white paint with its head lowered. Minimal white markings may not be recognized as due to a spotting gene. The next stage includes a blaze that widens toward the muzzle and may extend up the sides of the head, white extending above the knees and hocks, and possibly a belly spot. With stronger grades of spotting the entire head is often white, as well as the entire underbody, and eventually only the ears may retain pigment. Eyes are usually blue or have blue chips. Splashed white can be confused with very crisp sabino markings without roaning, but sabino-1, at least, can be identified through genetic testing.

I am sorry I have no photographs of this pattern, but it is rare in North America. Even Sponenberg’s photos are of Icelandic horses. Splashed white can be very difficult to tell from a crisply marked sabino without roaning. The amount of head white would be unusual for a tobiano. In general tobiano markings look as if white paint was dripped over the horse from the top, while the white in splashed white gives more the appearance of coming up from the bottom. The pattern occurs and is being selected for in Paints, and is known in Icelandic horses,  Welsh Ponies, and Finnish Draft Horses. It also is known in the Appaloosa.

Splashed white appears to be associated with deafness in horses, though many splashed whites have normal hearing.

Splashed white is believed to be due to a dominant or incompletely dominant gene, though the wide range of patterns produced by this gene makes genetic studies difficult. There is evidence of at least one white horse being homozygous for splashed white. At the present time, a DNA test for this gene is not available. There is conflicting evidence as to whether this pattern is associated in any way with the KIT locus.

North Pole Weather 1/21/13

White ice, or rather snow on its way to being white ice. This is the road I live on.

The sun will rise at 10:09 this morning and set at 3:57 this afternoon, giving us 5 hours 47 minutes of “daylight.” I actually saw the sun from my window last Thursday, and we’ll be up to 6 hours of daylight by Wednesday. It’s still not what you’d call warm – temperature back and forth around 0°F – but it’s warm enough for us at this time of year. The rain a week ago we can do without!

That rain is still here, as far as the effects are concerned. Roads are covered with white ice and gray ice, though very little black ice. They’re all covered, though, and correspondingly slick. I found myself fishtailing a little going around corners, after staying home for several days. And how many places do you know where they cancel school because the temperature is above freezing? They did, a week ago. But the seed catalogs are starting to pile up! Spring should be coming sometime!

The darker lanes are gray ice. If you look closely, you can see where bits have chipped off, giving a much darker color.

I got another batch of slides in for digitizing, including a couple of hundred I took when I took the long way around returning to Alaska (the first time I drove the Alaska Highway, back when only the first hundred miles were paved.) As I recall, I managed to hit quite a number of parks and monuments going north from the Grand Canyon to the Canadian border between the Rockies and the Sierra Nevada, all the time traveling with two Siamese cats who started yowling the minute we got off the pavement and continued until we crossed the Alaska border and got back on pavement. I hope the photos aren’t too faded; I might share some of my memories of that trip.

P.S. about 2:30 pm. I just picked up the digitized slides, but haven’t looked at them yet. I did get some pictures of white and gray ice, though. (And I no doubt annoyed cars behind me by driving under the speed limit. It will be a long time before it’s safe to drive at normal speeds.)

The Frame Gene in Horses

Chestnut paint. This particular horse appears to have the frame allele rather than sabino, judging from the face and lower legs, in spite of the ragged appearance of the spots.

Frame is another type of spotting gene in horses, formerly lumped into overo and sometimes called frame overo. It has nothing to do with the KIT locus, unlike tobiano and sabino-1.

Frame involves patterns of white which do not usually include roaning, though frame may occur in conjunction with other genes that cause roaning. In frame, the white areas tend to be arranged horizontally on the sides of the horse, and almost never cross the back. Frame is also almost the only pinto pattern in which the legs remain pigmented, though normal leg markings may occur.

Like all spotted horses, frame horses may vary from mostly colored to predominantly white. A frame horse will almost always have a wide blaze or bald face, and an apparently unspotted horse with a bald face but no white leg markings is likely to be a minimally marked frame. As the white expands the head may become mostly white and the white areas on the sides may expand to cover most of the horse, with the spine and legs being the last areas to lose color.

Another Frame. Note minimal leg markings with wide blaze and white spots on sides.

Frame is due to a single allele, frame (Fr), at a locus called endothelin receptor b (EDNRB) on equine chromosome 17. The locus has two known alleles, frame (Fr^Fr) and wild-type (Fr⁺). Frame horses, some of which are so minimally marked as to look solid, have one frame and one wild-type allele.

Breeding two frame horses together may produce lethal white foals, with two frame alleles. Such foals are born white, and the part of their nervous systems that controls the lower intestinal tract does not develop properly. They normally die within 72 hours of birth, though most are euthanized as soon as they are recognized. Most breeders avoid mating two frame horses together in order to avoid the production of such foals.

The frame allele can be tested for. Such testing has demonstrated that some genetically frame horses appear to be solid colored. Whether this is due to a suppressor gene or genes or is simply the extreme end of random variation of amount of white is unknown.

(If you’re here because you like horses, my story, Horse Power, is free today on Kindle. Click on the cover in the sidebar.)

North Pole Weather 1/14/13

We don’t need this! As of 3 pm it’s raining. In North Pole, Alaska, in January. Pity the poor voles. And the snow “curtains” in the second photo have collapsed.

As of 8:37 the temperature is at the freezing point and we have intermittent freezing rain and snow. It is way too warm for this time of year!

The sun will “rise” at 10:30 this morning and “set” at 3:30 this afternoon for a whole 5 hours 5 minutes of alleged daylight. We’re gaining almost 6 minutes a day, now, and the sun is 8 times its diameter above the horizon at noon. I should be able to see the sun from the south windows, once the clouds clear up. Like maybe the end of the week?

We’ve finally had a little snow, though not enough to make up for the settling. It’s also turned warm – too warm for this time of year. No actual icicles yet, but my thermometer was up to 30°F yesterday, which is far too warm when the roads are covered with snow and the forecast calls for mixed rain and snow. I stayed home. Sadly, because yesterday was my critique group – but it’s half an hour away, and the driving conditions were too bad to risk.

The moderate warmth last week caused the thin piles of snow on the raised bed hoops to start clinging together and at the same time weakened it enough that it gradually began to sag over and hang from the underside of the hoops. It didn’t look quite as striking yesterday, as the new snow on the beds just about eliminated the space between the bottom of the hanging snow curtain and the top of the snow beneath it. It’s hard to see from the photo, but the snow here falls so vertically that those thin plastic tubing hoops leave grooves in the snow on the actual beds, as they keep the snow from reaching the bed beneath them. The snow on the two by fours atop the lattice has leaned over on both sides of the lattice this year, giving a scalloped look.

I received the second round of slide digitizations, and once again found out how poorly sorted my slides are. And how much some, but not others, have faded or developed blurriness. I tried to clean this one up with iPhoto, as it’s one of the few I have of Chanty (Deryni Enchantress.) She was only about 6 months old in this one.

Sabino Spotting in Horses

“Chico”, owned by Charlotte Rowe

For many years two types of “pinto” spotting were recognized—tobiano and overo. Overo has now been broken into a number of distinct spotting genes—frame, splash, sabino-1, other sabinos, polygenic sabino, some types of dominant white, and manchado. Sabino now seems to be as much a grab-bag of genetically different types of white markings as overo once was. Here I will concentrate on Sabino-1, while noting that several other genetic types of sabinos and dominant whites seem to be associated with mutations at nearly the same locus.

Sabino with near minimum markings.

The sabino pattern has a wide variety of expressions, and some can be easily confused with other types of spotting, or even with roan. Sabinos not infrequently have areas of roaning as well as white spots, or flecks of color within the white areas. Almost all have white feet and facial markings, and the minimally marked ones can sometimes be detected by narrow extensions of the white up a leg or down the throat. The horse in the photograph to the right, for instance, has extensions of the high stockings in points up the legs as well as small white belly spots.

Sabino head, showing white underside.

In contrast, tobianos tend to have white legs but relatively plain faces, while frame horses have heavily marked faces with generally dark legs. It is unlikely that a sabino would have a completely plain head or completely dark legs, but sabino can certainly mimic any of the other pinto patterns combined with normal face and leg markings.

The sabino-1 allele is due to a single base-pair change in intron 6 of the KIT locus on equine chromosome 3. This means it is very tightly linked with tobiano and roan, both of which are also associated with the KIT locus. There are actually a number of mutations at the KIT locus that can produce sabino-like patterns.

Note the ragged, flecked appearance of the white.

Sabino-1 is incompletely dominant to the wild-type allele. This means that a horse with one sabino-1 allele and one wild-type allele will be a typical sabino. A horse with two sabino-1 alleles may be mostly white, often with a pattern approximating the “War bonnet” pattern—color in a head bonnet, chest patch, flanks and tail base. This pattern, however, can also be produced by combining the tobiano and frame genes. Sabinos sometimes come from two parents that appear to be non-spotted, but as with tobianos, one parent is generally a minimally marked sabino.

Some of the other KIT-related sabino alleles may be lethal when the foal inherits them from both parents, but this is still being investigated. There is also the problem that it may not be possible to determine visually whether a sabino may have more than one spotting gene.

The sabino-1 allele is well known and a genetic test is available.

“Horse Power”

Well, I did it.

I just clicked the “save and publish” button on Amazon Direct for my short story, “Horse Power.” It should be available for purchase at $.99 by this evening — I’ll update and link the cover to Amazon when it goes live. Update 10 pm: it’s live at Amazon.

I firmly believe that e-books should be less expensive than mass-market paperbacks, especially for new authors. I’ve been fighting with iUniverse on this (they want to price e-books at $9.99) and finally got Homecoming and Tourist Trap down to $4.99 each in e-book form at their site. The e-books should be even less at Amazon and Barnes and Noble, but it will probably take a while. (If they don’t show a lower price by the end of the month, complain to them.) Meanwhile, I have a story between the end of Tourist Trap and the start of the trilogy I’m editing now, so why not get it out, and learn to use Amazon direct at the same time? Thus “Horse Power.”

If you’ve read Tourist Trap, you may have wondered what happened to Timi and Amber after the end of that book, and this is their story, 22 years later. To quote from the blurb I’ve put up, “Rumors have reached the Inner Council of the Jarnian Confederation that the Horizon Company is illegally exploiting the colonists. Roi has been sent to find out what’s happening, and he asks his old friends, colonists Timi and Amber, for help. But the Company’s behavior is legal, if immoral. Can the three find a solution to the problem?”

The trilogy will be about a future war between the Confederation and Horizon, and the events in this story will be pivotal to that future, innocent as they seem at the time.

The cover, which I’m showing here for the first time (Ta-da! Cover reveal!) was done by Tomomi.ink. Like it? I do!

P.S: I’d love reviews on any of my books — especially if you like them!

The Tobiano Gene in Horses

Tobiano was the first type of white body spotting in horses recognized as being genetically distinct. Like other white markings, it varies widely in extent, with tobiano horses ranging from white with a colored head to normally colored with white hooves and lower legs, and perhaps a white area in the mane or tail. A few tobianos have blue eyes which are apparently produced by the tobiano gene.

The tobiano pattern has relatively crisp-edged white spots that cross the topline. The arrangement tends to be vertical, though not to the extent of a striped pattern. The head normally remains dark, though the white markings seen on non-spotted horses may be present. At times the dark skin extends under the edges of the white patches, giving a “halo” effect. Portions of the mane and tail growing from white areas are normally white, and in fact this may be the only obvious expression of tobiano in a minimally marked horse.

The pattern is due to a dominant allele, tobiano, at the tobiano locus, To. This locus is near but not at the KIT locus on chromosome 3, and a marker test is available. A horse with two copies of the tobiano allele is perfectly viable and not usually whiter than one with one tobiano and one wild-type allele. It is, however, more likely to show “paw prints” or “bear paws”–roan or spotted areas within the white patches.

Tobiano can occur on any base color: intense, dilute, or with interspersed white hairs. It does occasionally have an odd effect in the presence of one copy of the cream gene. The colored part of the coat “breaks up” into patches of dilute and non-dilute hair. This variation of the pattern is called calico. Calico is thought to be due to a dominant gene at a third locus which can only be detected if both tobiano and cream alleles are present. Theoretically, smoky calico should occur with areas of smoky, black, and white, but I cannot find any reference to this color in Sponenberg.

Although tobiano is dominant, tobiano foals are now and then produced by parents that appear non-spotted. On close examination one of these parents is generally a minimally marked tobiano, with extensive leg white and vary little face white.

The tobiano in the video is a good example of the pattern. Note the way the white markings on the neck are carried into the mane, and the way the white patches cross the topline.

Plans for 2013

Ever start a project you’ve been putting off and find it leading you in totally new directions?

This one was taken when I was a postdoc at NCAR in the early 70’s.

I did a lot of photography at one time. I have stacks of 35 mm slides taken with my old Nikon through-the-lens reflex and older 2 ¼ x 2 ¼ slides taken on 620 film. I’ve wished before I could use them on the blog, though sadly many were lost in the fire, as was the camera. I did get a batch of what I thought were wildflower photos converted to digital at Sam’s to see how good a job they did. (Some of the digitized photos from the first round are on this blog, and as you can see they weren’t all wildflowers, and included some I knew I’d taken but thought were lost.)

I decided to get the rest of the slides digitized. This has involved going through a number of poorly-labeled boxes, in the course of which I discovered that while none of my finished, spliced-together super 8 movies had survived the fire, a number of bits from the late 60’s and early 70’s have. I haven’t been able to view them yet (no projector) but I have some ideas on that.

(3 pm update: a friend loaned me a super 8 projector, which is currently warming up enough that the condensation on it evaporates. Also a screen. Remember those? I should know by this evening if I have anything left on the film.)

(Not quite 4 update: I definitely have content, and some looks good enough to put on YouTube–if I can just get it digitized!)

Thought I’d lost this one. My first two Shelties, Derry and Bonny, with their obedience trophies from the 1978 National Specialty.

The first step is to see what’s there, and then I hope I can get the good ones digitized. And if I can, why not make them into videos and share them on YouTube? I have iMovie and GarageBand on my Mac, but I’ve never used them. So I fired them up a few days ago, and discovered that I had video clips on iPhoto. Mostly they’re accidents when I hit the video switch on my camera without realizing it, but a few with the iPhone were deliberate. I can’t seem to view them on iPhoto, but iMovie lets me go through them just fine. I also confirmed that iMovie will accept still pictures, even giving me a sort of movie when I put individual burst shots together.

Then there was the flower garden I planted while I was living at Wynfromere Farms in the early ’70’s. Again, I knew I’d taken pictures, but didn’t know where they were.

Then I started thinking. Didn’t I have a video camera somewhere? A Flip I got a couple of years ago, tried out on several subjects, and then put away when I couldn’t figure out how to do anything with the video? That was before I got iLife ’11 installed, and when I found the Flip and plugged it into the Mac to charge it, it proceeded to open iPhoto and download itself, giving me numerous clips I’d totally forgotten I had from the dog show a year and a half ago.

At the moment, I think I need something to bring me up to speed on iMovie and GarageBand, so I’ve ordered the iLife ’11 Portable Genius. Paper. I don’t really like manuals on-screen, particularly if I may need to be flipping back and forth between several pages. But I think I might be able to do something with snowflake images and “Six-Pointed Snowflakes,” just to get my feet wet. And learn how to post on YouTube, of course.

On internal evidence, this was taken in the ’70’s. Good example of the pink and blue effect I’ve been talking about. I think from the angle I probably took this from the back of my horse, Challenge.

Guess I know what I’m going to be doing new this year besides writing, editing, and uploading a short story to Amazon direct!

White Body Markings on Horses

Any color horse, full color, dilute, or with intermixed white hairs, can have white body markings. These have long been recognized as falling into two categories: leopard (Appaloosa in North America) and pinto (or paint, piebald, skewbald, or parti-colored.) I’ll leave the leopard complex for later, beyond noting that the horses in Tourist Trap have leopard complex markings. For today, I’ll just give a brief overview of the paint/pinto nomenclature.

Tobiano

In British usage, a piebald was a black and white horse, and a skewbald was red and white. This distinction is rarely made today. Rather, the color of the horse—bay, black, palomino, red dun roan silver, or whatever—is followed by the pattern of marking. And there are a lot more patterns recognized today, often due to quite distinct genes, than was the case when I first became interested in horse genetics!

Paint and pinto are in fact synonyms when they are used as descriptive terms, though they have separate breed registries. In North America the word pinto may be more common in the east and the word paint in the west, but either may include any of the patterns of white body spotting.

Probably frame, based on the wide blaze and generally dark legs.

The first breakdown came when tobiano was recognized as being genetically distinct from overo. Then it turned out that there were several genetically distinct patterns being lumped together as overo—just about everything that wasn’t tobiano, in fact. The latest version of Sponenberg gives no less than seven patterns of white body markings, not including the leopard complex or the dark-eyed solid white of the American Albino. I’ll give a very short summary of the seven here, and cover specific patterns and what is known of their genes in later posts.

Tobiano is a relatively clean, crisp spotting with white legs but generally dark heads. White markings tend to be vertical and generally cross the back in all but minimally marked animals.

The frame pattern was once considered typical overo. It is horizontal, tends to affect the head first and the legs last, and white rarely crosses the spine. Frame to frame breeding can produce white foals that die shortly after birth.

Sabino, showing both the ragged outlines and the roaning typical of this pattern.

Sabino-1 horses normally have both face and leg markings, and often have roaned areas as well. They are usually not as crisply marked as tobianos, but they vary widely and confusion with almost any of the other patterns is possible. Roaning often occurs and is an expected part of the pattern.

Splashed white gives the appearance of the horse being splashed with white paint from below. The legs are normally white, and so is the belly area. In addition, white is normally present on the head, often to such an extent that the head is entirely white.

Polygenetic sabino and the form of dominant white that sometimes produces colored areas are not well characterized genetically. but are apparently distinct from the other forms of white spotting.

The final pattern, which is very rare, is called manchado, and has been seen in several breeds in Argentina. In this pattern, white first appears along the top line, and can produce a white mane on an otherwise colored horse. The head and legs tend to stay dark as the white areas grow larger, and there are often dark spots in the white, giving a superficial similarity to some leopard patterns.

All of these patterns vary widely in the amount of white, and all have pink skin under the white portions of the coat. I’ll take them one at a time in later posts.

Other Patterns of White Hairs in Horses

Rabicano under saddle

This week will be a bit of a catch-all, covering a variety of patterns of white hairs that are neither grey, classic roan, face and leg markings, or associated with white spotting. (Varnish roan, for instance, is a leopard gene pattern, and sabino and dominant white may also produce roaning as part of the pattern.) The genetics of none are well understood. Following Sponenberg, I will list and describe them here. Sorry for the lack of photos, but I haven’t even seen all of these patterns myself.

The first, frosty, may be a variant of classic roan, as it is found in the same breeds. In this pattern, the roaning is most pronounced over bony areas such as the hips, and roaning may affect the mane, tail and head as well as the body. “Squaw manes” and “squaw tails” with white hair mixed in often indicate the frosty pattern. Although there is little doubt that the pattern is genetic, it is not well understood.

“Roaned” is used to refer to horses with a scattering of white hairs not due to the roan or grey genes. It is not always possible to distinguish them from minimal classic roans, but they do occur in breeds where roan does not occur.

Rabicano horse, showing the white at the tail base.

White ticking is a much more specific pattern, involving the base of the tail and the flank. It is not progressive and may occur on any base color. Tails with the base white are sometimes referred to as “skunk tails” or “coon tails.” In Spanish the pattern is called rabicano. This pattern is one of the few “roan” patterns to occur in Arabians. Inheritance is thought to be dominant.

Birdcatcher spots are small white spots scattered over a horse’s body. They are named for a Thoroughbred horse, Irish Birdcatcher, who had such spots. They run in families so probably are genetic, but no studies have been carried out.

Rabicano, showing how white hairs are arranged in stripes on the sides.

White striping is very rare in horses. The vertical white stripes may be a form of roan, as seen on the rabicano photos. Or it may simply be an accident of gestation. One striped Thoroughbred in Australia, Catch a Bird, is himself striped but is producing as a classic roan.

Finally, minor white markings may occur as a result of scarring. These are most common with freeze branding or saddle sores, but one pattern, called white lacing, is commonly due to a skin problem called reticulated leuktricia. Most often the growth of white hair in a net-like pattern over the hips and back is preceded by the formation of crusts in the skin, but not always. Both genetic and environmental causes seem to be involved. If you have an Amazon account, you may be able to see Sponenberg’s photos here.

Next week I’ll start discussing the patterns usually called paint or pinto.

This information is an update of an earlier post.