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Discussion Starter · #1 ·
So I joined a group on Facebook and when someone posted a photo of a homozygous tobiano Saddlebred with one blue eye (blatantly tobiano but has star and trianle snip on face) as well as a heterozygous tobiano Saddlebreds with two blue eyes (and an almost completely white face that looked definity frame or splash), I was informed that the rules about splash/frame causing blue eyes are out the door, that homozygous tobianos are proving to be more likely for blue eyes than heterozygous and that it was obvious that untestable strains of sabino were causing blue eyes.

This really intrigued me, apparently despite looking blatantly splash or frame, none of the usual overo patterns are common in Saddlebreds and one line in particular is known for tobiano and blue eyes and testing negative for any other pattern.

Basically I was informed new research shows that every single "rule" we thought we knew about pinto patterns is completely out the door and not valid any longer.

I just found this highly intriging and was hoping to get some input from our fellow color experts and enthusiats as clearly I am lagging behind with this new research and would love to hear any new info!
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Did they provide a link to any of this "new research"? Or any testing saying that these Saddlebreds were negative for splash or frame?

A tiny snip could be the only obvious hint at splash on a tobiano because tobiano also causes white legs. And a tobiano with a bald face? Not only tobiano there. I call BS on them.
 

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Discussion Starter · #3 · (Edited)
One of them is the owner of Equine Tapestry I believe and has travelled a lot researching color. Apparently they're discovering all these new mutations on the extension of tobiano?

Not going to lie, I love color but I suck at math and proper terminology so when people start throwing extension and locus and gene names and abbreviations at me, I get confused.
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Discussion Starter · #4 ·
This is what I was told:

"Throw the whole "3 overo patterns" thinking out the window - genetic research has proven it is no longer valid. There are over 20 known mutations at KIT and at MITF we are fast approaching 10. All of these mutations cause white. We've learned in the last two years that there is a heck of a lot we don't know and that a lot of what we thought we knew isn't actually true. That there are "3 overo patterns" and they are responsible for all face markings is one of those things we know is no longer even remotely close to true."

"It is less important if a "breed" carries a pattern, than if the horses in that specific pedigree carry them. I had high hopes, early in my study of splashed white (SW1, really) that the Chubasco family would prove to have that pattern, but never found one with the classic expression (homozygous SW1). That could be chance, of course, so I would still love to see a blue-eyed horse from that line tested. Still, I would not be surprised at all if the test came back negative. That line is not, to my knowledge, related to the line that *has* produced the classic pattern."

"And yes, we really do need to stop looking at this as "three (or four or five) overo patterns". It is so, so much more complex than that. Given the consistency that this line produces blue eyes, I would not be surprised if there is some kind of addition mutation involved, but here is the thing; it is *not* splitting off from tobiano. That is, if this was a MITF or PAX3 mutation (which is what from the look one might expect), then why don't we see it popping up on the solids? And that question is not just one that applies here, with the Chubasco horses, but with a variety of breeds where this kind of thing has been found in a family."


It kind of went totally over my head so I was just hoping for some more info as this was news to me!
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We've never had her DNA tested, but our Paint tobiano mare has 2 blue eyes.



 

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Discussion Starter · #6 ·
Her face is also a strong indication that she carries splash or frame as well though PHM. Homozygous tobianos can have blue eyes, but it's a common belief that it's never cause by tobiano but rather the presence of additional genes such as splash and frame. The reason for believing this is that the vast majority of blue eyed tobianos tested would also test positive for an overo gene. But now they're saying they're finding tobianos that test negative for every other pattern, so the blue eyes are being caused by an untestable for of splash or sabino, or its the tobiano itself causing blue eyes.
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I do agree with them that there has been a significant amount of research done in the last 10 years that has made a difference in what we currently know about different gene mutations and locations, but I'd just like to see some kind of scientific paper or evidence from them.

I'm not saying they're wrong or anything because they clearly know more than I do, I'm just skeptical of their whole "Well just erase everything you've ever thought. It's different now" stance when the rules we currently use for each pattern works 9.8 times out of 10.
 

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Discussion Starter · #8 ·
That's how I felt, but a few of these people think EVERYTHING is tobiano + Sb1 and I don't undersand it. Why would you automatically think that every time you see a tobiano with blue eyes when they show face white extremely typical to frame and/or splash? I would really like to see these horses tested.

And I understand th Chubasco line not testing positive for SW1, but what about frame? I would have said frame for all of the Saddlebreds face white based on the angularness of it.

What member here has a black mare with blue eyes? She's a TWH or similar gaited breed and I thought she tested positive for frame?
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