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SEAL Brown - discussion.

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duncentralstation
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Re: SEAL Brown - discussion.

If Michal knows about this site and is offended by what is/was being said, he could also come here, get a user name, and engage in a dialog with us. He would not be the first geneticist to come and rub elbows with the common folk here. ;)

Ah, he rubbed plenty of common folk elbow on one of the Morgan related Yahoogroups. I don't think he has any qualms about rubbing elbows with "us". :D

Just too busy to be on too many forums is all. In fact, he has been too busy to participate on the Morgan group in a long time. He has probably gone to no mail delivery on it.

ACC, yeah, it wasn't that HE was offended. But he did appreciate that I wanted to make sure inaccuracies about his research were "corrected".

'Night everyone!!

Nancy Castle
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rabbitsfizz
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Re: SEAL Brown - discussion.

Well, I am reserving judgement on the Dominant White thing as a lot of the animals I have seen labeled as such are not, in fact, white, which does make me wonder....and I have never been one to accept anything without proof.
The "At" thing is unproven and whilst you may well see a classic seal brown, I see a Black Bay. ;)

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Re: SEAL Brown - discussion.

Dominant white IS proven... unless you don't trust that lab either. They fully admitted the horses DON'T have to be white. Where is the problem? Just what they call it?

RF, as much as you hate the word "tovero" I hate the term "black bay". I also hate "black chestnut". It's a total misnomer and can thoroughly confuse most people, especially the newbies you try so hard not to confuse (by not using overo, tovero, etc).

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duncentralstation
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Re: SEAL Brown - discussion.

RF,

The other day I posted the link to the published study on the four Dominant White mutations that have been documented thus far.

Dominant White is proven and has been since November 9, 2007 when the study was published. Authored by a number of very reputable researchers, including Samantha Brooks of Cornell, who was also one of the main researchers who found the Sabino 1 and Tobiano mutations.

Here's the link again. Peer reviewed journal. Open access, so the full article is available to everyone.

PLoS Genetics: Allelic Heterogeneity at the Equine KIT Locus in Dominant White (W) Horses

Nancy Castle
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duncentralstation
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Re: SEAL Brown - discussion.

RF, as much as you hate the word "tovero" I hate the term "black bay". I also hate "black chestnut". It's a total misnomer and can thoroughly confuse most people, especially the newbies you try so hard not to confuse (by not using overo, tovero, etc).

I'm with you, especially on terms that are contradictory.

Black bay/smoky buckskin - Yes, they are black based, but they are not "blacks". Smoky should be reserved for "E? aa" cream dilutes. Not "E? A?" cream dilutes.

Black chestnut is a term commonly used for the very darkest shade of chestnut in the Morgan breed. I admit that I've become rather numb to it, but that doesn't mean I like it. Like you, I have seen some very confused newbies on this one. :?

Another I don't like is seal grulla (have only rarely seen this one), used for those dark seal brown based duns that look close to grulla, but the owner/breeder knows they are brown + dun, not black + dun.

There are others, but I cannot think of them at the moment. And I need to feed the kids and the dogs.

Nancy Castle
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Maigray
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Re: SEAL Brown - discussion.

I absolutely understand your point here. Let me just say that the only reason all of this "secrecy" on my part ever got started is because someone on this forum had heard through some "grapevine" that what Michal found was not a mutation involving agouti. And this was being accepted here as fact.

This lead me to believe that Michal may have told someone else a little bit about what he found, and it ended up getting relayed incorrectly or incompletely through that grapevine, leading to him being kind of trashed in a way. The responses were something to the effect of "If it's not agouti then how can he call it 'At'. That's just wrong!" I'm not literally quoting what was written, but just how I basically remember it.

Those comments were, IMO, causing people to come to the conclusion that he might be ... shall we say ... less than intelligent enough to be doing any sort of research.

I don't understand any of this.

I actually don't believe many people care about the actual mutation in this situation. The conflict here is how it is being handled. They are upset over exactly the same things that appear to upset you - unproven, secondhand rumors and a total lack of openness about the test. Calling people gutless because they are questioning rumors and secrecy and providing only rumors and secrecy to actually convince them of that fact is...possibly not the best course of action. People don't actually need to contact researchers to figure out what they've done. They just read the research. It speaks for itself.

There were huge discussions about the dominant white study on the old board. Many people questioned whether calling it "dominant white" was really accurate.

duncentralstation
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Re: SEAL Brown - discussion.

I find this so frustrating.

Some say publish it and we'll believe it.
But they fail to include that they'll believe it ONLY if it's what they want to hear, rather than something different.

Well, once again, if you (the general you) don't like or understand why these mutations are being called Dominant White ... ASK!! And ask the right people, for Pete's Sake.

It isn't rocket science folks. You just type an email and hit send.

If I'm offending anyone, so be it. I thought this forum was about color genetics, not "just the color genetics we want to believe and accept".

There is an email address for Tosso Leeb within the published W study. Email him or Samantha Brooks (her email addy is on the Cornell site) and ask why those mutations are called Dominant rather than some form of sabino.

I did it. I wanted to learn! I initially contacted Samantha, then eventually Tosso, and was able to get more info than I had even anticipated. So I know the answers.

But, to be bluntly honest, it wears me out trying to convince people who don't want to be convinced or won't do the leg work themselves, then gripe that it's not right.

So, to anyone who wants the answer to why DW and not Sabino ... go ask the researchers like I did, so you can get it straight from the source. I would rather spend my time working on the article I've been trying to finish for the past couple of weeks.

Nancy Castle
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Jenks
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Re: SEAL Brown - discussion.

Does anyone think that pangare and At/seal are the same? That would be why I'd be interested in seeing chestnuts with pangare tested for it.

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Re: SEAL Brown - discussion.

Jenks, my understanding is that that was what the French study disproved. I could be wrong though.

As far as Michal goes, I continue to find the secrecy odd. The horse color genetics world is small and at this point everyone on the planet knows (or should) about his project. I can't imagine it would be stolen and passed off as someone else's... or am I completely misunderstanding something?

I'm not saying that I don't think his study is valid or invalid... just that this is the first time I can recall a situation like this. Again, I could be wrong since I only follow coat color genetics on very much the level of a layperson.

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Re: SEAL Brown - discussion.

I don't believe it was a queston of not understanding. It was discussed. Some people simply disagreed. They were not dumb, they understood what was going on, we debated the points, discussed the pros and cons, analysed the strengths and weaknesses of the study. And some people disagreed.

horsegen
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Re: SEAL Brown - discussion.

I don't think anyone here is trying to disprove Michal's work or discredit him. I think that people here are asking a lot of questions because they simply don't have the answers. There's absolutely nothing wrong with that. They should be asking questions, because Michal is offering a test for something he hasn't published. That means that people are paying money for something that hasn't been validated by anyone but him. Some people are okay with that, and some aren't. Both are fine.

When you offer a test for something that isn't published, people are going to speculate, and some of those speculations are going to be wrong. That's just nature, and it's the price you pay for not publishing. I'm sure he knows that, and I'm also sure that he's not really bothered by anything anyone is saying on an internet forum. I hear inaccuracies about my research on the internet sometimes and while I have no idea where people get some of their stuff, it's not a big deal. My research hasn't been published...when it is, people can read about it and answer questions.

It's great that Nancy is working so hard to defend Michal's research based on what he's told her, and obviously what he's told her has convinced her that he's really found "brown." But no one else has this information, so certainly we can't expect anyone to be convinced simply because she is. And as a geneticist, I will certainly not be convinced until I see the reviewed paper. While it's certainly possible that Michal has found brown, there are certain things about the research that make me (as a geneticist) very nervous. For example, it has been cited here that about 95% of horses that look brown test for this "At". The assumption made here is that those other 5% must have some other mutation. But as a geneticist, I have to ask whether this "At" might not be the brown mutation at all, but a linked mutation that just travels with brown. It is very dangerous, when you have an animal displaying a phenotype that does not carry the mutation you this causes that phenotype, to just assume that those horses must not really be that phenotype. Then you're twisting your data to fit your hypothesis.

I once, in my research, found a mutation in a gene that I thought for sure was the one I wanted. It was in a coding region of the gene, it made a significant amino acid change, and it was located in a very important region of the gene. That's very strong evidence! But as I tested more horses with my trait, I found some that I knew had the trait, but NOT that mutation. So I was wrong, and I didn't know that till I disproved myself. This was easier for me, because my trait is not subjective like a coat color shade, so I knew I was wrong. How does Michal know if he's wrong or not? It's actually VERY hard to prove that a mutation you have is the one you want...so hard that most of us in this field don't actually do it. We really should make knock-out mice that carry the mutation of interest and look at their phenotypes, but that's expensive and time-consuming. So usually we just make a really good case for our mutation, and part of that is showing that we've tested lots and lots of horses and they all hold up. But when you have something subjective, like brown, that can get very, very tricky. So obviously I will not be jumping on the At bandwagon until I see a paper.

Yes, most times everyone in this field knows what everyone else is doing. We work together on projects, we all attend the same meetings, and we hear people present their current research. Michal does not attend any of the equine genetics meetings, so no one really knows what he's found or how good the research is. That air of "unknown" makes more people skeptical. People don't discredit the dun test too often because our lab is pretty open about what the test is and how it works. And we have published the research behind it, just not in a paper. It has gone to meetings and been presented, so that other researches have a chance to review it. That makes things "feel" a little better to people. It doesn't make Michal wrong...just more likely to be questioned.

Certainly many people e-mail and call with questions all the time. We have a customer service office on the front line for easy questions, and more difficult ones come back to the researchers. No one should be shy about asking.

And yes, the "Triple Dun Bun Salute" is very cute, Nancy. It's hanging on the wall of our office/lab. :D

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Re: SEAL Brown - discussion.

My problem with "Dominant White" is simply and completely the name, not the existence, although, honestly, I would like to see a few more, and some consistency in the breeding.
What is the point of labelling something "White" when a fair percentage of the animals are not white??
I am happy to call a horse "Dark Bay" or even "Sooty Bay" if that is what it is, I have no problem with not using Black Bay, and Sooty Buckskin and Black bay are not the same thing, and I have never used them that way, nor heard of them being used that way, it is not a European thing (that is reserved for calling Buckskin, "Dun"!!! :laugh1 )
It was a habit I got into when dealing with TBs as that is how the colour is described, here at least.
I am completely suspicious of the "Brown" thing and shall be until the paper is published!!

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NZ Appaloosas
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Re: SEAL Brown - discussion.
Understood, but whereas with other studies there has been either lack of interest in the proceedings and/or an openness that seems to be missing here. (note, I am saying "seems"). There was an "openness of discussion" in other genetics research that just isn't apparent with the research into brown (and not just colour), and that "secrecy" gets reinforced with comments like yours earlier, about not being able to speak openly.

I absolutely understand your point here. Let me just say that the only reason all of this "secrecy" on my part ever got started is because someone on this forum had heard through some "grapevine" that what Michal found was not a mutation involving agouti. And this was being accepted here as fact.

I think (and know that this is true in at least my case) that a lot of it has to do with Gower's theory of "At", the agouti research done by the French (think that was the nationality of the researchs, but don't quote me), and then this popping up and coming across originally as being a springboard to promote Gower's theory despite the agouti research. I know I stated it on the previous board that part of my resistance does stem from what seems like a direct connection to Gower's theory, and that I personally would have been a lot "happier" if he had used other nomenclature.

And yes, there has been major confusion as to whether the test is for markers near agouti (a la dun zygosity test) or a totally different/new "agouti".

This lead me to believe that Michal may have told someone else a little bit about what he found, and it ended up getting relayed incorrectly or incompletely through that grapevine, leading to him being kind of trashed in a way. The responses were something to the effect of "If it's not agouti then how can he call it 'At'. That's just wrong!" I'm not literally quoting what was written, but just how I basically remember it.

That part I don't know about, but as stated above, a lot of my own personal "unhappiness" with "At" has to do with connotations to Gower. And I'm not overly fond of her book/theories, and I have seen where a lot of people get confused by her book, albeit accepting it as total gospel, despite research to the contrary of what she claimed.

Those comments were, IMO, causing people to come to the conclusion that he might be ... shall we say ... less than intelligent enough to be doing any sort of research.

I sincerely hope I'm not part of that list...as I have stated time and again, I do not question his credentials, his intelligence or his ability...my unease about his research is based on a) what comes across as secrecy, b) payment for a test that he admits is not 100% accurate (and I can't say if I've ever seen info on whether it gives false negatives, false positives, or both, with this inaccuracy), and c) what has come across as a "not interested in" testing horses that may well disprove the basis of his theory--a why bother complicating things cuz I may not get the results I want sort of attitude. (Again, NOT saying that this IS his attitude, I am saying that this is what I am perceiving from the info I take in).

I am not a personal friend of his as some have referred to me in the past. But he has been published over 60 times in reputable medical journals. So my assumption is that he most likely knows how to conduct research. So, I found that whole thing very distasteful. And I did something about it.

I went directly to the source. I told him what had been said and asked if he was free to clarify it for me, and if I could post the gist of his response to the forum. At that point, he told me more than what I had expected (surprising since it would seem someone else leaked it and it passed around incorrectly), asking for my promise of confidentiality regarding the most technical part of it. But at the same time, giving me permission to at least say publicly that, yes, what he found does involve agouti and can legitimately be deemed "At".

Sometimes if people would simply grow a set, have the kahunas to contact the person who can *legitimately* answer their questions, much of this crap could be so easily avoided. They may not be able to tell you every detail of their ongoing research, but if at all possible, they will try their best to clarify for you. And what's the worst that can happen if you email them?

They reply? ;) Or they don't?

I have never, ever, ever had a researcher cause, or threaten to cause me bodily harm for asking a question ... I swear! :hammer Without exception, I have found them to be very congenial, and they do try to answer the questions to the extent that they can when it's ongoing research.

Some of us don't have the time...I've had a whole plateful of some serious sh*te handed to me recently in real life that requires most my time, energy and effort. Other researchers for which I've had interaction have gone to lengths to make themselves available in an easy-to-access format, i.e., yahoo email lists, this forum, etc.

I have had direct contact with Dr. Penedo and Stephanie Bricker at UC Davis regarding the dun study. Even made them both "Triple Dun Bun Salute" certificates for some test results they provided us (myself and owners) on some possible dunalino Morgan foals before the test was offered, and they loved them! In fact, they requested the high res versions so they could print and hang them.

Samantha Brooks, formerly with U of Ky, now with Cornell, is a gem! Super, super person and enjoyable, as well as very tolerant of my questions.

Tosso Leeb, Univeristy of Bern, Switzerland is the latest to go on my personal Wall of Fame for his generosity, trust, and patience!

And then there is Michal at Pet DNA Services. We have exchanged many emails, he has been super kind and generous, as well as very supportive of my desire to learn some of the more technical side of things. Of the Morgan people I know who have had contact with him regarding the At study, he has been good to communicate with them as well.

My point here being ... ask the person who knows the answer. Don't rely on hearsay if you don't have to. Don't rely on what I post. Ask him. He's a nice guy from my experience. As are all the others I've pestered.

See above ;)

Yes, that is pretty much what I meant, and I guess my unease comes from the fact that a paid-for test became available while the research seems to be still at the early stages of gathering information.

But usually that digging occurs before having to pay for tests and what is coming across as a "This Is It And It Has Been Proven So" by adherents of this "At" theory.

So, you probably aren’t on board with UC Davis offering the dun zygosity test, either, right? [/quote]

Define "onboard"...have I paid for any such testing, no. Do I accept that they have found markers that travel with dun, ayup, cuz I've had easy access (i.e., I haven't had to go looking for them) to people who were in a position to outline the information needed--and actually in more detail than I had expected.

No, you have pretty much hit the nail on the head. It just keeps coming across to me that there has been too much blanket acceptance of the "At" theory too early in the game, where the steps to disprove the theory haven't even been started (my science teachers always said that a researcher needed to attack the problem from both sides--to prove and disprove a theory for the research to be solid).

And we know the steps to disprove it have not been taken yet, because …. ??? Rhetorical question, because the answer is obvious ... we have not seen the published study. But, do we know what controls he has used in his study? Do we know that he has not used controls? Have you asked him? Has anyone?

The whole "he's not testing anything that doesn't phenotypically match the criteria" thing points in that direction. Again, might be just a perception thing, but without any sort of paper to turn to, perception is all we have to go on (and again, perhaps due to my own professional background, I have a problem with relying on perception).

And while I don't think that anything about the "At" research will ruin/destroy lives, etc., as stated above, I have seen incidents where the "facts" were as latched upon as this one seems to be, and the selectiveness wasn't really found/discovered until some 20+ years later. In that paricular situation, some 200+ people were jailed on what has since been found to be extremely flawed science. That's why complete research, on both sides of the equation, is so important.

I laughed at this, because I totally bypassed any commentary on lives being ruined in your first post, because I knew you didn’t mean the comparison literally. Again … peer review once he can (hopefully) wrap it up and submit it for publication. That is as “proven” as ANY color genetics study gets. And if you read some of them, you will see a lot of words like “predicted to”. But what gets relayed to the layperson is “proven to be”. So, how proven is any scientific finding … color related or otherwise … really? Rhetorical question, as you’ve already made that very point yourself. And it’s actually true!

I was merely stressing a point And it dawned on me, after I wrote that, there could well be someone who perceives me of believing that this whole At/not At thing is going to ruin peoples' lives. (See, there's that nasty "perception" thing again! :laugh1 ).

But let's focus on why you're personally "nervous" about this. Because of what you feel is a lot of secrecy, which I do understand. You already stated that you realize this has become an issue with At specifically because of what I've said. I accept that responsibility.

Not just you...there are others who go on (and tell others that they are flat-out wrong) with the same sort of abandon which people used to tell Christopher Columbus he was going to fall off the face of the earth if he tried to sail west to India...in fact, all that you have done/written/found out IS helpful, does bring a bit more sense to the issue (at least for me.)

Let us not lose sight of the fact that every ongoing study has its "secrecy". And let's put this studies secrecy in perspective. Blame or credit me with seeing inaccuracies via what seemed to be a seriously flawed grapevine being readily accepted as if it were fact, when it was not proven, either. And blame or credit me for taking the initiative post a correction from the one true legitimate source with his permission.

Again, not you, per se. But yes, there is definitely a flawed grapevine, a highly active one, and no apparent steps by Michael to correct/remove that flawed grapevine.

Had that misinformation not been posted, and had it not appeared that is was being accepted without question from a source other than the researcher of that study, this secrecy issue probably wouldn't have come about at all. Then again, had I just kept my mouth shut, it wouldn't have happened, either, right?

In that, you are wrong--keeping your mouth shut wouldn't have kept this from happening, because really this is a rehash of a thread from the previous board, and very possibly first arose more than a year ago (and I would say has been discussed/debated, along these very same lines more than once).

Diane

NZ Appaloosas
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Re: SEAL Brown - discussion.

RF, as much as you hate the word "tovero" I hate the term "black bay". I also hate "black chestnut". It's a total misnomer and can thoroughly confuse most people, especially the newbies you try so hard not to confuse (by not using overo, tovero, etc).

Now see, I see "black bay" merely as a descriptor rather than a genetic term, and means to me a horse that is so darkly bay, it takes a genetic test to make sure it's bay.

I've just had another thought (scary, ain't it?) but are we talking at cross purposes on "brown" and "seal brown"? To me, they are two very distinct phenotypes--seal being with the lighter muzzle and other soft bits, and theorised to be caused by pangare, and "brown" being, well, mud-coloured :laugh1 but uniformly from nose to toes (which would/could mean that a chestnut should be able to be genetically "brown" unless of course it can only exist in bays).

Diane

NZ Appaloosas
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Re: SEAL Brown - discussion.

I actually don't believe many people care about the actual mutation in this situation. The conflict here is how it is being handled. They are upset over exactly the same things that appear to upset you - unproven, secondhand rumors and a total lack of openness about the test.

BINGO!

Diane

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Re: SEAL Brown - discussion.

Does anyone think that pangare and At/seal are the same? That would be why I'd be interested in seeing chestnuts with pangare tested for it.

No, I don't think so (see my post above) Jenks, have you been reading my mind before I even think of things???? :laugh1

Diane

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Re: SEAL Brown - discussion.

Ha! What is the French study Sarah is talking about? I have not been able to read every page at once and must've missed something...

NZ Appaloosas
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Re: SEAL Brown - discussion.

I'm not sure if anyone linked it, but basically they studied agouti, and found only "A" and "a". Maybe one of our genetics-schooled folk can get a link to the actual paper? (or English translation of it, if it was not written in English).

Diane

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Re: SEAL Brown - discussion.

OH- the old one? I thought there was a new one or something....I just don't remember it disproving that pangare was seal. I do remember it proving that seals tested bay - same study - right?

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Re: SEAL Brown - discussion.

I thought I remembered something about pangare but I could be mistaken. It was a while ago.

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Re: SEAL Brown - discussion.

Yes, the French study was done to prove that all seals were actually black with pangare' (no agouti). They found that all seals in fact do carry agouti. They also DID NOT find 'A', they only found 'a'. That is how the current test works, it only counts the number of agouti negative ('a') mutations. Thus regardless of what the French study found, they CLEARLY missed something or they WOULD have found at least one 'A'. This leaves the door wide open for any number of other mutations within agouti.

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NZ Appaloosas
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Re: SEAL Brown - discussion.

So, does anyone have (or can get) an English version of the seal brown/agouti study?

Diane

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Re: SEAL Brown - discussion.

I think I've read it somewhere... if someone doesn't beat me to it I'll try to dig it up tonight.

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Re: SEAL Brown - discussion.

I'm not sure how (or even if) I can get the full article, but there's the abstract:
http://www.ncbi.nlm.nih.gov/pubmed/11353..." onclick="window.open(this.href);return false;

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Daylene Alford
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Re: SEAL Brown - discussion.

Well my school has a subscription but it only goes back to 2003...online at least...:BH

EDIT: I found it email me for a copy....

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Re: SEAL Brown - discussion.

Hi everyone,
I've been a longtime lurker on this forum and have enjoyed it hugely. I'd like to add a couple of thoughts to the Brown debate.

Over on the allbreed forum there's been a lively debate on appy colors/expression. And there are several folks that have solid horses with very, very minimal appy characteristics. --Like a couple of freckles where the sun don't shine minimal.
This started me thinking along the lines of expression and bell curves, where the gene has variable expression.

What if we're seeing the same phenomenon with brown horses?
Agouti works by pushing the black pigment to the outside edges of the horse, replacing black pigment producing cells with red pigment producing cells.

There does seem to be a range of expression from high black on the legs to low black, and Wild Bay with brown legs and short dark socks. Might brown be the maximal expression of Agouti, with the black pigment pushed all the way off the edges of the horse? With Black Bay being the minimal expression?

Seal brown could be Maximum Agouti + some other modifier like pangare ?

This could explain the horses at the start of the thread, where two browns produced a bright bay foal. Lets say A(max) is more dominant that A, so a brown horse could be A(max) A , breeding two browns could result in AA.

Love to hear thoughts on this idea.

duncentralstation
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Re: SEAL Brown - discussion.

It's important to understand that Agouti does not replace black pigment producing cells with red pigment producing cells.

ALL horses are capable of producing red pigment, regardless of what their color is visually or genetically. But not all of them are capable of producing black pigment. Only horses that have at least one "E" mutation can produce eumelanin (black pigment).

But ALL horses can produce red pigment ... this is why even an "EE" faded black horse can show red undertones in its coat. This is also why an "EE Aa" horse (bay that is homozygous for black) can still clearly show red pigment on its body.

Agouti acts as to block the production of black pigment, not to replace black pigment with red pigment. In the areas of the horse where agouti is blocking the production of black pigment, red pigment is visible because agouti is not blocking its production. The horse, even though "EE", was already producing the red pigment. But we couldn't see it because the production of black pigment was causing the red pigment to not be visible to us. But along came the agouti gene to block the black pigment from the body, unveiling the red pigment that was "hiding" under the black ... so to speak.

Brown is the result of a mutation of agouti that is genetically different from the bay form of agouti. The information is still "in research" and not yet published, so I cannot elaborate on it any further. But what I was told by the researcher who seems to have found it is that this is a mutation different from "clear bay" agouti.

Wild bay, is either the result of a mutation of agouti different from both bay and brown, or it could possibly be the result of another modifier causing further restriction of the black pigment. I would tend to think it's more likely another mutation of agouti, but I could believe either as the cause. In mice, there are several (over 20??, I can't remember for sure) mutations of agouti, so it wouldn't surprise me if there are multiple agouti mutations in horses as well.

I believe the term "black bay" is a term used in some breeds (such as Arabians) to describe brown horses. Same color, different name.

Horses who appear brown but are known to have produced clear red bays ... most likely these horses are the < (less than) 5% whose phenotype is caused by something other than the "At" mutation of agouti.

Last I knew, this was more the rarity, though, as over 95% of the horses tested who appeared brown tested to have the "At" mutation.

So, I guess those that tested not to have "At" are kind of like the horses who looked like double cream dilutes, but ended up proving to be cream plus champagne or cream plus pearl. Same basic phenotype, but different genotype.

Nancy Castle
[url=http://www.duncentralstation.com]Dun Central Station[/url]

duncentralstation
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Re: SEAL Brown - discussion.

Hmmm ... maybe my understanding is not quite accurate??

From page 1, column 2 of the 2001 published study ....

"ASIP acts as an antagonist of MC1R by nullifying
the action of a-melanocyte-stimulating hormone (a-MSH). Loss of-
function of MC1R results in yellow pigment (pheomelanin),
whereas gain-of-function of MC1R or loss-of-function of ASIP
seems to result in the production of black pigment—eumelanin
(reviewed in Barsh 1996)."

Not that they sound terribly sure here ("... seems to result in ...."), either, though?

I don't think they are necessarily saying one type of cell is being replaced with another type, mind you, but I'm not really sure that my understanding was correct, either.

Maybe, if I can remember, tomorrow I'll have to email or call one of my geneticist contacts and ask her for a decent layperson's explanation. Because now I'm super curious to know how this would work ... how hairs that would otherwise have been black can be "switched" to be red?

On a breed specific forum about color genetics, there have been people who have asked how an "EE" horse can produce red pigment on their body when they don't have "a red gene". Typical responses from others have included "Because if it isn't black, it defaults to red." And this explanation has never actually answered the question. It does not *explain* anything. It's what some of us have been told, and we simply regurgitated it without necessarily understanding it.

What I posted above was how I have understood it to work for a while now. But, I need to find out if I have been off base all this time, and if so, how does it actually work. I'll try to find out.

Nancy Castle
[url=http://www.duncentralstation.com]Dun Central Station[/url]

NZ Appaloosas
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Re: SEAL Brown - discussion.

And there are several folks that have solid horses with very, very minimal appy characteristics. --Like a couple of freckles where the sun don't shine minimal.

Heehee, that's my Pearl! :rofl

This started me thinking along the lines of expression and bell curves, where the gene has variable expression.

What if we're seeing the same phenomenon with brown horses?
Agouti works by pushing the black pigment to the outside edges of the horse, replacing black pigment producing cells with red pigment producing cells.

Don't forget, black seems to have a suppressing 'factor' to it, at least in connection with white expression.

There does seem to be a range of expression from high black on the legs to low black, and Wild Bay with brown legs and short dark socks. Might brown be the maximal expression of Agouti, with the black pigment pushed all the way off the edges of the horse? With Black Bay being the minimal expression?

Seal brown could be Maximum Agouti + some other modifier like pangare ?

This could explain the horses at the start of the thread, where two browns produced a bright bay foal. Lets say A(max) is more dominant that A, so a brown horse could be A(max) A , breeding two browns could result in AA.

Love to hear thoughts on this idea.

Maybe black has suppressing factors on more than white?

Diane

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Re: SEAL Brown - discussion.

On a breed specific forum about color genetics, there have been people who have asked how an "EE" horse can produce red pigment on their body when they don't have "a red gene". Typical responses from others have included "Because if it isn't black, it defaults to red." And this explanation has never actually answered the question. It does not *explain* anything. It's what some of us have been told, and we simply regurgitated it without necessarily understanding it.

My first thought would be sun bleaching, my second thought (recently acquired) would be maybe copper deficiency? I have an acquaintance (internet friend) who breeds black angus cattle, and she's found that when angus cattle get reddish tinges on the face, chest, areas not normally reached by sun for bleaching, there's a copper deficiency in them. I don't know if this can be translated into horses, tho'...

Diane

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