This post first appeared on January 27, 2012
Some of the first test results from the new Splash White tests have started trickling in, and they are proving really interesting. Here is some of what we have learned so far.
As far as I am aware, those horses that have tested positive have all had the SW1 gene. That means the exact nature of the other two versions (SW2 and SW3) is still a mystery.
So far, with really limited results, it does look like in identifying SW1 researchers may have found the gene responsible for Classic Splash. That was the pattern originally described by Klemola in the 1930s. Even more exciting is that the one horse known to have tested as homozygous does have the classic pattern. That horse can be seen here.
Another interesting horse in that group is the homozygous tobiano. There had been rumors that the KIT gene had been ruled out as a location for Splash White. I had explained why the KIT location was important in limiting the number of color mutations in this previous post, “Location Matters.” If the general rule that was explained there – that a horse should only have two mutations on any given gene – holds true, then finding a horse carrying two KIT mutations and splash white should tell us that splash white is not on KIT. The two tobiano genes would already take the two KIT slots. It is my understanding that there have been at least two horses tested as homozygous for tobiano that also have the Splash White gene.
That opens the door to the idea that there may be a lot more tobianos out there carrying SW1 than we might have previously expected because it isn’t an either/or situation. A horse could carry and pass along both patterns. What is also interesting is that tobiano has a way it sometimes skews that creates a dark patch with an odd “point” that drops from the croup. Some of us have long wondered if that might come from Splash, and now a horse with that kind of pattern has tested to be a carrier. It will be interesting to see if more horses with that kind of “point” also test positive, especially those that do not have such splash-like facial markings.
The other big news out of the early results is that there are horses that are coming back with blue eyes that test negative for all three of the Splash genes. It is really too early to know exactly what that means. Obviously more things cause blue eyes than just Classic Splash because they found those two other genes. It may be that there are still more versions, or it may be that one of the many yet-to-be-identified sabino patterns are involved. What we can say is that blue eyes are not caused by just one or two things. The situation is more complex than that. But then if pinto tests have told us anything, it is that it is all more complex than anyone originally thought!