Discovery Alert: Join the Nerd Herd to Learn about Eden Whites

Unleash your inner scientist in the world of equine genetics. In this episode, we're joined by our very own Aiden McFadden, Katie Martin, and Dr. Robin Everts to learn about the HPS5 gene. This isn't your everyday discovery - this gene is a key player in the white markings observed in horses. We dissect the different alleles of this gene and extrapolate the physical phenotypes one could potentially observe in horses that have them. Groundbreaking discoveries like this haven't happen for a decade in the equine world, making this not just a thrilling revelation for us, but for equine enthusiasts and professionals alike. 

We also take the reins to discuss depigmentation in horses and the role of EDX Whites. Delving into our understanding of this gene, its function in melanogenesis, and the intriguing connection to depigmentation found in other species like zebrafish and humans.  As we wrap up this episode, we hope you come away with not just a newfound appreciation for horse color genetics but an understanding of its significance in revealing the appearance, history, and potential health issues of horses. So why wait? Immerse yourself in the exploration of equine genetics!

Transcript

Lauren 0:07

Welcome back to another episode of Dynetics Unbridled. On this episode, our very own nerd herd is in the studio to tell you all about our latest discovery.

Christa 0:17

So wait, hps 5, it's not MITF, it's not KIT, it's not PAP. Is this new Do?

Aiden 0:26

we know that, you guys know.

Lauren 0:33

That was our very own researcher, aiden McFadden. He is ready to give you all the nitty-gritty details about Aiden Whites. We're also joined by our head of quality control and data management, katie Martin, and our head of research and laboratory operations, dr Robin Evers. Here's what he had to say on the lasting impact of this discovery.

Robin 0:53

A ton of horses out there that have white markings and we don't know what it is with the current methods and current assays. So here is now a new gene that will kind of explain why these horses have white. And the other thing is also, as Katie said, it's like in all kinds of different breeds. It's not like only in quarter horses or only in paid horses, it's in a whole gamut of horses, like from Shire and Clyde, seal or whatever, to Shetland Pommies.

Lauren 1:19

Keep listening while we unload all the deep science and explain what this does for the equine industry. I'm Lauren McDevitt, and with me, as always, is our fearless leader, crystal Lafayette. What do you think, crystal? Should we just jump right in?

Christa 1:32

Yeah, let's not check the girth, let's just get on, okay so we're going to start with what is an Aiden. White Aiden. Do you want to talk about Aiden White?

Aiden 1:42

Yes, I would love to. Tons of genes are already implicated in white spotting in horses, so we already have Kit, mitf, hax 3. The list goes on and on, and now we can add one more gene to that list and that's HPS5. And there are three different alleles that we saw that we kind of termed Aiden White, and it's basically just another gene that's associated with white spotting in horses.

Lauren 2:06

Okay. So as one of the horse people in the room, I always have to ask this question what does this mean for my horse? So talk about the phenotype a little bit. If I'm looking at my results and I see EDX, w12 or 3, what can I expect to see physically on my horse?

Aiden 2:23

So it's already pretty similar to what we've seen Kit, especially the more subpoena like Kit phenotypes. So we're talking blazes, snips, stars, you know those kind of facial markings. It's possible for them to have blue eyes, sometimes when that deep augmentation is extending beyond the eyes, and then really tall white socks and then we also see in more. So Aiden White 1 and Aiden White 2, a more drastic phenotype, so more extensive white markings and then also some markings on the abdomen, sometimes on the back, but more like spots, white spots.

Katie 3:02

Could Aiden White's cause a partial blue eye?

Aiden 3:05

I've seen fully blue eyes. I don't know if I've seen a full or a partial blue eye. I'm not going to say it's not possible, but I'm also not going to confirm it.

Christa 3:16

TBD. Yeah, further into the research. So if there's deep pigmentation and blue eyes and, I'm assuming, a white head, do we see any? Is there any reported deafness, like with some of the splashes?

Aiden 3:29

So we have no reported deafness, but it's, yeah, it's very situational.

Aiden 3:35

Not only do you have to have the genotypes of the horse, but you also have to have an owner that's telling us hey, this horse has hearing problems. And then even then, that doesn't mean it's due to this mutation. It could be due to something else that we don't see. It would take a lot of horses to be reported as deaf or near deaf to really make that association or really studying the melanocytes in the ear to see if there's actually something going on there. I haven't even really seen white markings really extend behind the ears, behind the eyes, yes, but not like a splash white which really can cover the entire face consistently.

Christa 4:15

Yeah, so at this point we it's remains unknown, but at this point we have no cases of animals who have this, who have reported deafness. But we'll have to update that as things go forward.

Lauren 4:26

Yeah, okay, I want to backtrack here for a second. So you talked about kit, which most of our horse people are more familiar with the term dominant white, also MITF or packs three is something most of us more commonly refer to as splash white. Our equine genetic folks are pretty familiar with naming variants after the horse that played a role in the discovery. But now we're dealing with HPS five, which Edelon has the ability to name. Why are we even able to name it to begin with?

Robin 4:52

Well, I've led to believe it's at least 10 years, at least a decade, since there was another gene discovered that caused white spots on a horse. I think the main importance of this discovery is that, you know, there are a ton of horses out there that have white spots on them and we, with the current known variants, we don't or we cannot describe what they are and how they came to that. And so this is a new gene in horses that actually will tell us something about why that horse is white.

Lauren 5:25

Okay, I wanna make sure that we don't skim over the fact that you just said it's been 10 years since a new variant causing white markings was found in an entirely new gene. That just makes me really impressed with the direction that equine genetic discovery is going, and then that future impact that it's gonna have on breeders and registries. So I'm sure, since this is such a big deal, that there was a lot of thought put behind the name. So can you guys talk a little bit about the inspiration of where that name came from?

Robin 5:56

Aiden has done such tremendous work as it's an absolute fabulous analysis of all the data. We thought maybe in a wash to him we combine etalon and Aiden together and come into Aiden.

Lauren 6:08

That totally makes sense because Aiden's passion and the entire team's dedication for these discoveries is clear to just about anybody we speak with. So I'm glad we're able to sit here and highlight the discovery process and share the hard work each of you are doing behind the scenes. It'll be really interesting to see when people start testing for Aiden whites and getting those results back. I wonder how many horses will have it, because a lot of times people go. My horse has this weird white marking, but I'm not seeing it on the allele summary, and that right there is why we encourage all of our users to reach out. If your horse has a distinct white marking and you don't see it in your results, you might have one of these new discoveries or something entirely different that hasn't even been discovered yet.

Christa 6:55

Yeah, that's always interesting to explain to people when they run a diagnostic panel in their horse and it comes back with no known whites and it's got a huge blaze and, like in this case, tall white stockings and they go. Well, your panel doesn't work, oh God. No, we have to explain this again. There are a bunch of unknown whites out there but thanks to Aiden, we now have Aiden, there's three more. But to your point, Lauren, what breeds have we found this in so far?

Lauren 7:26

Katie, do you wanna take a moment and talk about what you've seen, looking at all the data?

Katie 7:31

So we have actually found this in gypsy horses that's what we've seen from our cover horses, of course, and a lot of quarter horses and paint horses, minis, morgan's, saddlebred's, chinca-tinkponies, welsh.

Christa 7:46

So it's all over the place All over. So it's probably pretty old. Is that a good assumption? It's an old mutation.

Aiden 7:52

Good assumption to me, yeah.

Christa 7:54

And no one found it, nobody's looking for it. Until now.

Robin 7:59

Exactly.

Lauren 8:00

Okay, so talking about nobody else being able to find this, or nobody was even looking for it in general, does this discovery affect how new white markers are gonna be looked for in the future? Will it impact how others are going about their own discovery process?

Robin 8:16

Well, I'm hoping that if other people find other mutations in these genes, that they keep on using the same nomenclature and it's gonna be edx w four, five, six. But yeah, I mean, it really shows that you know, when we do the way we are looking at this by using comparative genetics and looking at other species for same phenotypes, hopefully there are other genes that people start looking at also because there are more genes than what we have right now with KIT, mitf and Bax3 and HPS5. So there's also SOX10 and some other ones out there that potentially have effect on white and yeah, there are so many horses which still that are unknown why they have white spots. Maybe those are candidates for those genes.

Christa 9:00

Or maybe some of the newer ones will be, because mutations happen all the time.

Lauren 9:04

Okay, so looking around this table, we have a special opportunity to get really nerdy. Can we take a turn and kind of talk about the deep science? Aiden, can you talk a bit about genomics in general and why discoveries are just a bit challenging?

Genetic Mutations and Phenotypes in Humans and Horses

Aiden 9:19

There's a lot that's still not perfectly understood about, you know, horse genetics and just genomics as a whole across all species. And this exact gene HBS5, isn't very well understood compared to something like KIT or MITF. So it's really these novel findings that help to build up the foundational knowledge for these new genes or these more recently discovered genes that really aren't characterized as well. So finding something in horses that causes depigmentation, it's really going to help build up also desire to figure out what this exact does, or what this protein does in the cell. It's implicated in melanogenesis, which is the formation of your pigment, but the exact role it does no one really knows right now.

Christa 10:10

Is there sorry, go ahead.

Robin 10:12

Yeah, Aiden. So why did you then look at HBS5? If there was like really unknown what it did, Like how did you get to the idea to look at HBS5?

Aiden 10:21

So this isn't the first time, you know, an HBS gene has come up in equine research. So previously HBS1 and some other proteins that interact with that protein have been implicated in kind of the shade of a bay horse or a chestnut horse or you have maybe a more intense or a lighter chestnut color. So that's kind of some indication that it might. You know those proteins HBS5 proteins might have something to do with pigment in horses and then in other models, so specifically zebrafish and humans, mutations in HBS5 cause depigmentation. It's mostly ocular, so they have depigmented eyes. But in humans we see very similar albumisms. As you know, different genes like kit or MITF might do.

Christa 11:16

So this is a known active gene in other mammals.

Aiden 11:19

Oh yeah, for sure.

Christa 11:20

But not extremely well known, clearly, because no one knows what else it does Do it humans.

Aiden 11:25

So the name of the gene actually takes on the name of the syndrome Hermansky-Pudlock syndrome, hps. And not only does albumism characterize this syndrome, but also prolonged bleeding times, so it takes longer for your blood to coagulate. We don't really know if that happens in horses, so if you notice it, let us know.

Christa 11:47

That's where crowdsourcing comes in right, when people are testing their horses. To date, we have no reported side effects, but maybe there are, we just don't know yet.

Aiden 11:56

Just like we talked about deafness earlier, this could be another one, but you know, time tells.

Christa 12:01

And that can be said for any of the genetics, right? I mean we look at all these different genes and they do different things in different animals. The base function tends to be similar but you can say good or bad about anything. Myostatin at speed and too much muscling on some cows and they have trouble birthing them, but it makes great race horses and court horses. So, it depends on what you're looking for and what you're seeing in your individual animal, and it also depends on the exact mutation.

Aiden 12:29

If it's a large deletion of a lot of the gene or stop game mutation that truncates the size of the protein, depending on where that mutation is, all these factors kind of play a part in determining what that phenotype is and how severe that phenotype might be. So it could be that the mutations that cause a Hermansky-Powelluck syndrome in humans is a super big deletion. There's different isoforms or for mancipula syndrome. So you know, I'm kind of speaking out of my depth here. I don't know all of them, I don't know what the mutations that cause all of them are.

Christa 13:05

No one knows what isoforms is anyway, so you're fine.

Aiden 13:09

But there's a lot of factors that are playing into the severity of a phenotype.

Christa 13:14

So what kind of mutation is EDXW1, 2, and 3? Are they different types?

Aiden 13:20

So they're all SNPs, single nucleotide polymorphisms. So it's one base pair. That's swapping from one base pair you know your A, t, g, cs to just another one. So one and two are missense mutations. So those are actually changing your protein sequence. But EDXW3 is actually a mutation in a putative splice site. So that's where your different exons would meet up to form your protein and a mutation there can cause here's the word again that you love isoforms, different isoforms of that protein to be expressed.

Robin 14:00

So in principle it just excludes some part of the coding sequence or it puts some non-coding sequence into the strength of DNA.

Aiden 14:09

And that could cause a different form of the protein to be in your cell.

Katie 14:15

That's where it should change the function.

Aiden 14:17

And is that something we know? No, we don't know if it's actually changing the protein sequence there. Like I said, it's a putative splice site, so it's generally considered to be a splice site, but it's just a marker that's strongly associated with this phenotype. We don't know if it actually causes that different splicing, but it's likely.

Lauren 14:41

Let's circle back to horses. So you mentioned that three is a different type of mutation than one and two. So if you have an isoform versus just a SNP change, can you look at those horses phenotypes like the amount of white or white pattern and suspect that they're different, or are they just completely indistinguishable?

Robin 15:00

It doesn't have to change that much because if the point mutation is something that causes, stop mutation in the protein, so it truncates the protein or makes the protein much smaller, it might have the same effect of having something like a splice site donor, as Aiden talked about, where there is an introduction of weird sequence like non-coding sequence or an exclusion of part of the coding sequence. So you cannot really say just by it being a SNP or a missens mutation or a splice site donor, you can by definition say there is a difference there or not.

Christa 15:35

So what you're telling me is I can't go, I want three instead of two because I'll get higher socks.

Robin 15:40

No.

Katie 15:41

Dang it so one of the other things that Aiden found, though, is that you will likely have more white on a red base horse than a black base horse. The word epistatic.

Christa 15:53

Can you talk about epistatic Katie? No, it's one, two, three, not it. So that's another interesting thing that's mentioned in a couple of our publications and that's where a white mutation will have a greater or lesser effect on a specific base coat color. What have you seen?

Aiden 16:15

So in EDXW1 and 3 we see more extensive white markings, typically on those chestnut base horses.

Katie 16:25

We've actually seen horses that have one, two and three on our black base and might have just a star.

Christa 16:34

Wow, so wait, you can have one, two and three, so you can have more than two of these mutations in a single horse.

Robin 16:43

That's a dangerous road to go down.

Lauren 16:47

To be continued. Yeah, yeah, well, and that's really interesting to talk about too, because I know like, looking at the photos we were looking at too, the discovery horse play, it's not like anything like super unique looking. I think people here knew white marker and they think, oh, it's going to have, you know, a white spot at the top of its neck somewhere really random or something different. But maybe explaining a little bit more of like that what the phenotypes can be, it can be very different depending on how it expresses right.

Aiden 17:13

Yeah, so the word again. Melanogenesis is a very random process, right? So even horses with the exact same genotypes end up looking different.

Christa 17:23

So what you're saying is any other blaze by any other name is still a blaze, like you can get a blaze from any number of mutations, because the underlying process is very similar.

Discovering and Understanding Horse Color Genetics

Aiden 17:37

Yeah, and the extent of that blaze, how wide it is, how thin it is, it changes from horse to horse. Even with the same genotype. It can be the same or look very similar to some of those kit mutations like W30 to 34, 35. But yeah, it's hard to tell just by looking at the horse which mutation it might be, just because it's such a random process.

Katie 18:00

And of course there's combination of the mutations Right the combos.

Christa 18:04

Oh my God.

Katie 18:05

Yeah, and also the cool thing is that one, two and three. We have a handful of horses that have all three, but they're across different breeds, so it's back to we need 10,000 horses to see what happens. Well, the variants are older, so they could be everywhere in combinations.

Robin 18:23

And these horses probably have also kit or MITF mutations in addition to those.

Katie 18:29

Some don't, some do.

Robin 18:31

Yeah, so there's a whole bunch of different things there that all vary the whiteness of the horse. So it's really hard to predict, because if you have a horse there it might have EDX1, but then it might have MITF or kit also.

Katie 18:46

Yeah, we have ones that are homozygous Splash.

Robin 18:48

White 1.

Katie 18:49

They have lethal white Tobiano. Splash White 1, splash White 2.

Christa 18:53

So I'm just curious. I know that in rat coat colors that there are studies showing various shades and patterns can be influenced by the diet and temperature of the mother during gestation. Is there any possible theory about that in horses?

Aiden 19:17

Not that I've read about that exact theory, but a lot of the research that has been collected over the years has alluded to many other factors influencing my white markings. So the variance in phenotype, so the differences in phenotype from horse to horse, is really only partially explained by these alleles. And, like Rob was saying earlier, you have a lot of different genes, a lot of different alleles playing into the phenotype of your horse. It's not just one or two spots, it's upwards of 10, 15, 20 different working parts of this machine that are making your horse look like what it looks like. And it's possible. We can't say no, but we also can't say for sure.

Robin 20:07

We could test for it, but it costs a lot of money because horses only give one full a year, whereas rats do like six or eight siblings several times a year.

Christa 20:18

Yeah, I think it would be interesting, but it's a bigger chunk to bite off for research for sure.

Robin 20:22

Right, I'm happy to do that and have a bunch of horses like in Alaska versus like the tropics. I spent all my time on it.

Christa 20:31

I think you need to visit the ones in Alaska. We'll take care of the ones in the tropics.

Lauren 20:37

Well, the last thing I want us to cover, before we kind of wrap up here, is why this is so much more than a white marking. Can you guys talk about new discoveries and what they tell us and then just kind of the overall importance of research in horses?

Robin 20:52

It is a very old mutation that is in all the breeds, it seems like, so it can explain a lot of the whites that people currently can't explain.

Aiden 21:01

And you can also take that information, since it seems to be so much older, you know, if you look back at ancient horse DNA, you know that could allude to their different society selection patterns. You know what they wanted, what they wanted their horses to look like, like we see in Sabino and Tobiano. They kind of the frequency of those alleles kind of peak in valley throughout time as people go oh, I want this, no, I don't want this. So it's not only, you know, helping to better explain the horse, but it's also helping to explain the history of horses and why they look like the way they look now.

Katie 21:35

And, as Aiden and Chris were talking about, with the crowdsourcing and making connections in humans or other animals, that it could be changing the function. That's where we rely on our owners who know the horse is best, that if you know we start seeing a common misfunction or health issue, then we can start looking into that as well.

Christa 21:59

Yeah, a lot of times we get the question, especially recently why do you guys focus on whites so much Like? Why do you keep discovering whites? That's just a byproduct of us refining our process of finding genes, and that is what we're doing. That's the core of this mission is to understand how a horse functions and functions well in the environment that you're going to be working with it in, and so what we're trying to do is using whites, which is super simple. People send us photos, they run their diagnostics, they give us feedback and say, yes, this horse is fast, but it has a white blaze, it can hear, it can't hear, it has blue eyes. It doesn't. But under the surface, we're using that same process to find other things speed and gait and health and attributes that you want as a horse owner or maybe you don't, right.

Christa 22:44

So that's what's at the heart of it?

Aiden 22:45

It just happens to be that, you know, seeing the amount of light on your horse is a really easy thing to observe. You know, we'd love to be able to, you know, see everything, every phenotype, you know, but that's it's not always easy, right? We can't tell if a horse is deaf by looking at its hair, and even then, you know, a horse might act deaf, like it, you know, doesn't want to listen but that doesn't mean it's deaf, right?

Lauren 23:10

We all know a horse like that. That's why we're laughing.

Aiden 23:12

You know, a horse can't tell you it can't see. So why is it blind?

Christa 23:16

How do you?

Aiden 23:16

know, it's blind, you know.

Christa 23:18

Yeah, and maybe we can move on to other things that we're kind of toying with here in the lab. Things like okay, so we're looking at white markings in this horse. Does it have a convex or concave nose, right? What's its head shape look like? How big are its ears? What's the shape of the ears? All these things we can start to extrapolate and if we can apply the same platform that we have on the discovery for the whites, pretty soon that also becomes an autopilot. We can learn those things very quickly.

Katie 23:42

And, of course, a really good example is um lethal white. If you have two parents that are cares and you have a white foal that gives you a red flag that you need to you should have tested.

Lauren 23:54

Yes.

Christa 23:55

Yeah.

Lauren 23:56

Safer breeding practices is definitely a big pull for obviously a lot of people, because nobody wants to end up with a horse that doesn't make it. So that's definitely a good learning piece there. But I think, just going back to the more data and research we can do on these animals, long term what that means for the industry is you know, the breeding practices are going to be better, we're going to have better athletes, you'll be able to define what kind of animal best fits your program, and I think it's so much more than just a white marking on your horse that it means a lot in the future.

Christa 24:27

So, in conclusion, I'm just curious. So, aiden, do you think perhaps you could identify the gene for the horse that acts like it's deaf? Did you volunteer?

Katie 24:35

We're trying, we're trying.

Lauren 24:40

We can introduce you to a few that maybe we'll display that. Yeah Well, Aiden, Robin, Katie, we really appreciate you taking the time to talk about these discoveries with us. It's impressive to see all the tools we have at our fingertips. With more research and information on our animals, we only become better horse owners, and that impact has a chain reaction To our listeners. If you made it this far, consider yourselves honorary members of our nerd herd. If you liked this episode, make sure to give us five stars and leave us a review wherever you listen to podcasts. For more about Aiden White and the horses behind this discovery, visit our Facebook and Instagram at edelondx. You can also read the full story on edelondxcom. We'll see you next time.