Talk:Gray horse

Lethal white
I removed this incorrect fact:


 * Unlike the frame overo gene, which causes all-white foals to die shortly after birth (called "lethal white syndrome"), sabinos can be born entirely white and be perfectly healthy.

See lethal white syndrome. The "lethal white is homogeneous frame overo" theory was an unsubstantiated theory predating the blood test; in fact the lethal white gene is not carried by all frame overos, and is even carried by non-overos. Deco 20:44, 2 September 2005 (UTC)

I'm going to peruse the UC Davis web site on this and see if we can straighten this mess out. Bottom line is that there are no true albino horses. Never happens, never has happened, and not sure what theories are all out there, but I guess we all just try to cite the state of the art research.Montanabw 22:11, 6 June 2006 (UTC)
 * See the references in the Lethal white syndrome article, in particular this one. Lethal white is not caused by a homozygous frame overo, and this has been definitively established by accredited research; Laurie Fio's theory, which was never substantiated by experiments, has been discredited by new research. I also normally trust the VGL as a reliable resource, but there's no way they can reconcile their own statement that "not all overos are carriers" with this homozygous overo model. Moreover, lethal white foals are not "born dead" - they typically live for up to a few days after birth before they die. Deco 21:44, 6 June 2006 (UTC)

I'll tweak that they aren't born dead...I guess it's the WW foals that are born dead. The UC Davis site seems to be standing behind Fio's research, but I'll look at the APHA site too, double check against the Lethal White Wiki page and see if we can merge the competing theories together, or at least explain that there is more than one view on this. (Looks like the APHA article cites research at U Minnesota from 1998, can you locate a direct cite to that research so we can have "dueling universities?"

I don't breed Paints, so I don't have a horse in this race, which I HOPE will keep me neutral on this issue.Montanabw 22:11, 6 June 2006 (UTC)
 * The link I gave above summarizes some of the U Minn research, although I don't have access to the original article. It is true that there's a single gene responsible for it, but that gene certainly doesn't cause overo coloring if non-overos carry it, as both VGL and U Minn assert. In the U Minn article they refer to the allele using "L". I've contacted VGL for clarification on Fio's theory a couple times, but they haven't responded yet. If you think Fio's theory deserves to be treated as equally credible, I guess that's okay, but please don't give the impression that all overos or only overos are carriers, which could lead to dangerous breeding practices. Deco 22:41, 6 June 2006 (UTC)


 * Oh, by the way, I agree with the current wording, so if you're happy with that we're settled. :-) Deco 22:54, 6 June 2006 (UTC)

Check my last sets of tweaks. I'm done being a Wikipedian for the day, so if I haven't destroyed anything since your last check, life is good. Someone (maybe me, maybe not) should just create a white (color) horse page, move all this stuff over there and just link to it from the gray page...that way they can also put the fleabitten gray stub back into this article. Montanabw 23:01, 6 June 2006 (UTC)
 * I think that's a good idea. The only obvious connection between them is the final visual appearance of their coats. The article on white horses could also mention a variety of other "white" horses that aren't really white, like cremellos, perlinos, maximally-expressed sabinos and so on. Deco 23:07, 6 June 2006 (UTC)

Deco, didn't the APHA article also show a photo of a "maximally-expressed" Paint of some sort--a genetic Overo or Tobiano?? If I get motivated to do the White horse page, it is probably worth adding in ALL the ways a horse can wind up white (other than peroxide bleach! ) Montanabw 15:18, 7 June 2006 (UTC)

Lethal White controversies
Broke out the lethal white stuff into its own section. Anything--pro or con-- on this controversy needs to be cited and sourced. Please read material carefully before editing on this topic, and if anything currently there is wrong, then please cite SCIENTIFIC sources, and preferably phrase it as a controversy instead of doing any wholesale deletion or broad statements.

In other words, instead of saying "UC Davis is wrong," say something like, "there are two views on this issue. On one hand, original research at UC Davis says X, while on the other hand, a more recent study at U Minn says Y." And cite source. I tried to do this with earlier material.

This whole bit on white horses really needs its own article, not to be the unwanted stepchild of the Gray article. But I haven't had the time to do it. Be easy--just cut and paste Montanabw 21:21, 17 July 2006 (UTC)

Genetics stuff to work into article
Article needs to be read and accurately put into gray article (moved from Lipizzan article):


 * Monika Seltenhammer of Vienna's University of Veterinary Medicine, and Leif Andersson of Sweden's Uppsala University  (in a study published on July 20, 2008 in Nature Genetics) found that: "the white coat of the Lipizzan is caused by a mutated gene. White and grey horses, including Lipizzans, are born with a darker coat but lose their colour between the age of 6 and 8 due to chromosome mutations, which cause pigment-producing melanocyte cells to be produced more rapidly in these horses so that the stock is quickly used up and the horses lose their pigmentation. The same chromosome was responsible for the horses' heightened risk of melanoma skin cancer. 70 to 80% of grey and white horses aged 15 or older develop skin disease. But the horses are hardly at risk, as the disease cells do not spread as quickly as in humans."


 * Related Comment from other talk page: I think the "error" in the edit comes from a lack of understanding that gray isn't "special." I read that blip and think "Yeah, so? Everything's a mutation." But clearly they are referring to improved understanding of the mutation that causes gray. Lips don't have a weird form of gray, or at least not significantly weird. I looked up the study that this blip refers to and it is called "Comparative Histopathology of Grey-Horse-Melanoma and Human Malignant Melanoma" by Monika Seltenhammer, et al. in Pigment Cell Research. 17(6):674-681, December 2004.

The IMPORTANT part of the study is that melanomas associated with gray coats are less prone to malignancy than human melanomas. In light of this, yes, this article ought to be part of the Gray article, as it clarifies what may be perceived as a cavalier attitude towards a known cancer-linked phenotype. Perhaps you knew this. Countercanter (talk) 19:58, 21 July 2008 (UTC)

Probably relevant to this article, needs sandboxing, wordsmithing and then a place to go. Montanabw (talk) 17:46, 22 July 2008 (UTC)

Some sources
J. C. Patterson-Kane, L. C. Sanchez, E. W. Uhl and L. M. Edens. Disseminated Metastatic Intramedullary Melanoma in an Aged Grey Horse (2001). Journal of Comparative Pathology. 125(2-3):204-207.

Beth A. Valentine. Equine Melanocytic Tumors: A Retrospective Study of 53 Horses (1988 to 1991) (2008). Journal of Veterinary Internal Medicine. 9(5):291-297.

Countercanter (talk) 13:03, 9 April 2009 (UTC)

Most white horses
"However, most White[sic] horses have pink skin and some have blue eyes. A horse with dark skin and dark eyes under a white hair coat is gray."

I think that this sentence needs to be rewritten as:
 * "However, white horses have pink skin and some have blue eyes. A horse with dark skin under a white hair coat is gray."

--PBS (talk) 15:28, 26 December 2012 (UTC)


 * So go ahead and fix it, don't need permission to fix typos.  Montanabw (talk) 21:57, 26 December 2012 (UTC)

Need breed in caption
In the picture of the gray mare and foal it would be better if the picture caption gave their breed. I would guess they are Welsh ponies of Section A or B but I can't be positive. White Arabian mare (talk) 14:54, 17 August 2015 (UTC)

I mean the photo at the top of the 'changes in color of gray horses' section. White Arabian mare (talk) 15:05, 17 August 2015 (UTC)


 * If you click on the photo, it usually brings up a description that mentions the breed. That photo didn't, and we can't take wild guesses - the image is from a German uploader, so Welsh pony is unlikely.   Montanabw (talk)  07:55, 18 August 2015 (UTC)

Alright. I just thought it might be better if the breed could be added but I guess it's not possible. White Arabian mare (talk) 01:59, 28 August 2015 (UTC)

Move discussion in progress
There is a move discussion in progress on Talk:White (horse) which affects this page. Please participate on that page and not in this talk page section. Thank you. —RMCD bot 13:00, 3 November 2019 (UTC)

Fleabites and somatic events
How is this for wording:

Researchers suggest the speckles on "fleabitten" grays may be caused by a somatic loss or inactivation of the duplicated copy, as that would explain why the speckles are more common on heterozygous grays than homozygotes.

The exact phrasing from the paper is "The pigmented spots (speckling) may represent somatic events in which the duplicated copy has been lost or inactivated, considering that in homozygotes both chromosomes must be affected whereas a single event is sufficient in heterozygotes." (editing to add, later on it also says "Somatic revertants are expected to cause pigmented spots and, notably, speckling is common in G/g but not in G/G horses. The rare occurrence of blood marks in Gray horses is also consistent with a somatically unstable mutation.")

(PDF) A cis-acting regulatory mutation causes premature hair graying and susceptibility to melanoma in the horse. Available from: https://www.researchgate.net/publication/51415732_A_cis-acting_regulatory_mutation_causes_premature_hair_graying_and_susceptibility_to_melanoma_in_the_horse [accessed Apr 20 2020].

Iamnotabunny (talk) 01:36, 19 April 2020 (UTC)


 * Duplicated copy of what? The gray gene?  We need to explain this because it’s gibberish the way they wrote it. Our readers don’t know what a somatic event is, either. (Heck, I’m trying to figure out what it is...)  Montanabw (talk) 17:28, 20 April 2020 (UTC)


 * A somatic mutation is just a mutation that happens in a body cell (like the skin) rather than a reproductive cell (like an egg cell) and so affects the animal but isn't passed on to the next generation. A somatic event is them being vague because they're not sure and saying maybe it's a somatic mutation or maybe the gene is just deactivated in those cells, or maybe it's something else specific to some somatic cells. The thing about duplicated comes from the gray allele being a duplication, out of the different types of mutations it could be ...and I just realized there's nothing in there about that so of course readers are going to get confused, oops. Well anyway it's a 4.6 kb duplication, which means in the DNA there's a series of about 4600 of those little letters A, T, C, and G, and in gray horses all that DNA is repeated an extra time. That's also what the other study was talking about when it said the melanoma tissues had more copies than the other tissues. Some of the worst melanomas had that section of DNA repeated a third or fourth time, maybe more, but just in the melanomas and not in the whole horse. Iamnotabunny (talk) 22:48, 20 April 2020 (UTC)
 * Ok, should be fixed now. Thanks for pointing these things out, since I can't see them on my own. Iamnotabunny (talk) 22:57, 20 April 2020 (UTC)


 * Your edits worked. No need to get super complicated so long as we have a good source citation to the details for those who want to know more. Montanabw (talk) 01:06, 22 April 2020 (UTC)

Gray and melanomas
So, studies on gray and melanoma. This one (the original study that found the gray allele):



finds that gray homozygotes are more likely to have melanomas than horses heterozygous for gray. They also find that bay/black at agouti has a weak but highly significant effect, with black at agouti having more risk of melanoma. They speculate that the increased melanoma risk comes from increased MC1R signalling and would like to have tested if chestnut made a difference as well, but not enough of the lipizzaners carried chestnut. When they say 70-80% of gray horses over 15 get melanomas, they cite "Sutton, R.H. & Coleman, G.T. Melanoma and the Graying Horse (RIRDC  ResearchPaper Series) 1–34 (Barton, Australia, 1997)." and "Fleury, C.et al.The study of cutaneous melanomas in Camargue-type gray-skinnedhorses (2): epidemiological survey.Pigment Cell Res.13, 47–51 (2000)." As for the mechanism, they think more expression of STX17 and the neighboring gene NR4A3 causes both the gray color and the tumors by causing increased melanocyte proliferation. Probably NR4A3, because that one is involved in regulation of the cell cycle and is linked to carcinogenesis, plus the gray melanomas were expressing more of the cyclin CCND2, which is a target gene for NR4A3. Cyclins regulate the cell cycle and tumors often make more of them. And they cite "Smith, A.G.et al.Melanocortin-1 receptor signaling markedly induces the expressionof the NR4A  nuclear receptor subgroup in melanocytic cells.J. Biol. Chem.283,12564–12570 (2008)." for saying increased MC1R signalling causes increased expression of NR4A3, so I guess there's that link. So they propose that increased proliferation of melanocytes in the skin causes melanomas, and in the hair causes depletion of stem cells which leads to it turning white.

This one:



by mostly the same authors finds that while gray has a section of DNA that's repeated twice, in melanoma tumors that area is often repeated even more times with the more aggressive tumors having more repeats. So a non-gray horse would have two copies of this DNA, one on each of the pair of chromosomes, a heterozygous gray horse would have 3, and a homozyous gray horse would have 4, but some of the tumors had 5-8 repeats. Unrelated to melanomas they also mention that some connemaras go gray extremely slowly, with a picture of a 14 year old connemara who is still pretty dark, and they checked and found that they have the same gray mutation as any other gray horse.

This one:



tried to replicate the connection between ASIP and melanoma risk in gray horses that the first study found, and also look for a link to MC1R. They used 335 gray quarter horses while the first study had 694 gray Lipizzaners, and basically nothing came out as statistically significant. The homozygous grays were about twice as likely to have melanomas as heterozygous grays, but there were not enough of them for the result to be significant. Then for whether black/bay/chestnut base color and the underlying extension and agouti genes had any effect, they tried looking at it a bunch of different ways but didn't get anything statistically significant, though they did find the relation between agouti and melanomas trended in the expected direction. They think agouti had less effect than in the first study because the chestnut extension allele was much more common. At they end they compare melanoma prevalence and severity across different breeds and say that in the quarter horses they studied, 16% of all the horses had a melanoma, or 52% of only the horses at least 15 years old. This is compared to studies on other breeds which found a prevalence in 31.4% in the Camargue (68% in Camargues at least 15 years old), 50% in the Lipizzaner (75% in Lipizzaners at least 15 years old), and 89.6% in the Pura Raza Española and crosses (100% in PREs at least 10, not 15 but 10, years old). Here's the studies they cite for the other breeds: camargue, PRE, camargue again, lipizzaner.

I'll see if I can find any other studies on gray and equine melanoma later but this is enough for today. Iamnotabunny (talk) 13:14, 20 April 2020 (UTC)

I’m rereading the Pielberg studies. As for the gray and melanoma studies, I already cited one on a Thoroughbred, if you note the diffs to the changes I added. I think we probably should just link to the equine melanoma article to avoid content forking, and if needed, add more refs there explaining how much variation is in the studies. (It’s worth drilling down on, actually, but there, not here.) Here, we could summarize something like prevalence of melanomas in older horses varies from estimates of x% (cite) to x% (cite) with outlier studies showing 0% and 100%.(cite) I think it’s very much worth noting that very few studies had enough horses in them for results to be statistically significant. The Agouti (A) thing sounds very unproven—in particular, while it creates the bay color on a black coat (E), it can occur in chestnuts (ee), masked because of the absence of E. Montanabw (talk) 15:35, 20 April 2020 (UTC)

Oh, and for the “flea bites,” let’s say “pigmented speckles.” That is more accurate. As in “fleabitten gray horses are recognized by the development of pigmented speckles on the body.”  We need some sourcing, but on the grays I’ve known over the years, I’d say there’s definitely a link to heterozygosity, and what’s more, they increase as the horse ages...I’ve seen horses that are pure white at age 8 become totally freckled by age 15. Montanabw (talk) 15:35, 20 April 2020 (UTC)


 * I've gone ahead and made the fleabitten edits now. The source is again the Pielberg 2008 study that found the gray allele. Iamnotabunny (talk) 16:11, 20 April 2020 (UTC)


 * As for how much to put in this article and how much in the equine melanoma one, I think it would be worth having a section here explaining the connection to melanomas in basic terms, a note about how equine melanomas caused by gray are not usually so deadly as human melanomas, and possibly info about how common melanomas are in the different breeds. Details of the molecular biology not related to the coat color should probably go in the equine melanoma article. Iamnotabunny (talk) 16:26, 20 April 2020 (UTC)


 * Looking through the article, it hasn’t had a big update in a decade, and it shows. I just did a lot of wikignoming to clean up formatting, fix images, clarify phrasing and so on.  I made the melanoma bit into a new subsection, so if you want to build on it some, in terms of balance, I’d say we could add one more paragraph, but I’d prefer not to overwhelm the article with it, and I really don’t get into the weeds on prevalence within breeds here, because I think the studies are preliminary and it’s a minefield. I think we CAN talk about the studies in the melanoma article, because there we can get into the limits of the studies (i.e. “the only study on foo breed said x, based upon a sample size of y, and etc.” The two studies on breed foobar produced consistent or inconsistent results because one studied x and the other looked at y.”)   I compare this to the articles on soring and the Tennessee Walking Horse, where one article went into detail, summarized with wikilinks in the other.  Montanabw (talk) 17:24, 20 April 2020 (UTC)


 * Wow, that was a lot of changes! Lots of small improvements. But, you must have a narrower browser than me, because the images show up all in the wrong places now. Do you think we could make that top-left box shorter? That might help. Iamnotabunny (talk) 21:12, 20 April 2020 (UTC)


 * The infobox? It’s on the right on my screen... it’s also standardized to have a summary of info.  So we should keep it as is. But, I realized we didn’t really need the photo of the Andalusian, so I tossed it and tweaked the caption on one of the other images. That may help a little. I realize things got strung out when I moved all the images to default sizes and positions, so they might change with different browsers. If we ever wanted to prep this article for WP:GA or something, though, they’d want us to do it to conform to the MOS. There’s exceptions, of course, but the formatting gods of WP really hate “sandwiched” text.  Maybe the age stages or the “confused with gray” sections (or both) could be made into a table, like we did for the spotting patterns at Appaloosa and Leopard_complex, but I don’t really have the time and energy right now to do that kind of fussy formatting work... meh.  But if you want to mess with tables, that’s a possible solution.  Montanabw (talk) 01:18, 22 April 2020 (UTC)


 * Sorry, left and right are too similar. I've put the start of a table below.Iamnotabunny (talk) 14:23, 22 April 2020 (UTC)

Graying stages
Plopping this here for now since the descriptions could use some improvement. Should I add a foal picture as well? Should the article sections on individual stages just be moved to the description area, or should the table be in addition to those sections? And of course feel free to put it in yourself if you want to get to that before I do. Iamnotabunny (talk) 14:20, 22 April 2020 (UTC)


 * —We have the image of the pony mare and foal, which is good for showing how some gray foals, though not all, are born with a few white hairs. I wouldn’t call this “stages,” as color change is so highly variable (some grays never dapple, some never become fleabitten) I’d just describe the patterns, maybe “Variations?”  I’ll tweak, but recommend starting with the phrasing already in the article.  Montanabw (talk) 04:22, 30 April 2020 (UTC)

Idea
How about placing all the relevant text into the table? Maybe play with photos?Thoughts? Montanabw (talk) 05:11, 30 April 2020 (UTC)

Thanks, I think it's good enough to go in the article now. I'll change the pictures a bit and put it in. Iamnotabunny (talk) 13:34, 7 May 2020 (UTC)