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![]() | Text and/or other creative content from this version of gray (horse) was copied or moved into white (horse) with this edit on 17 July 2006. The former page's history now serves to provide attribution for that content in the latter page, and it must not be deleted as long as the latter page exists. |
I removed this incorrect fact:
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)
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)
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)
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!<grin>) Montanabw 15:18, 7 June 2006 (UTC)
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)
Article needs to be read and accurately put into gray article (moved from Lipizzan article):
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)
References
[1] 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.
[2] 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)
"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:
-- PBS ( talk) 15:28, 26 December 2012 (UTC)
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)
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)
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)
@ Montanabw: 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].
Pielberg, Gerli Rosengren; Anna Golovko; Elisabeth Sundström; Ino Curik; Johan Lennartsson; Monika H Seltenhammer; Thomas Druml; Matthew Binns; Carolyn Fitzsimmons; Gabriella Lindgren; Kaj Sandberg; Roswitha Baumung; Monika Vetterlein; Sara Strömberg; Manfred Grabherr; Claire Wade; Kerstin Lindblad-Toh; Fredrik Pontén; Carl-Henrik Heldin; Johann Sölkner; Leif Andersson (2008). "A cis-acting regulatory mutation causes premature hair graying and susceptibility to melanoma in the horse". Nature Genetics. 40 (8): 1004–1009. doi: 10.1038/ng.185. PMID 18641652.
Iamnotabunny ( talk) 01:36, 19 April 2020 (UTC)
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:
{{
cite journal}}
: CS1 maint: unflagged free DOI (
link)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)
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.
Name | Image | Description |
---|---|---|
Foals |
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Horses in their first year begin to show a few white hairs as their foal coat sheds. Some foals show gray hairs around their eye, muzzle and other “soft” areas at birth, others do not show white hairs until they are almost yearlings. |
Iron gray, rose gray, “salt and pepper” |
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White hairs are mixed with the dark birth color. This is typically seen in young horses. If the underlying coat is bay or chestnut, the reddish tinge is called a “rose” gray. If the horse shows mostly black and white mixed hairs, a darker individual is sometimes called “iron” gray or described as “salt and pepper”. |
Dapple gray |
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Light and dark areas form a dappled pattern. Not all grays dapple, and it is an intermediate stage, usually seen in young adult horses. The horse will continue to become lighter. |
Complete depigmentation |
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Nearly all hairs are white. A horse at this stage may be done changing color, or may begin to develop fleabitten pigment. |
Fleabitten gray |
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Most hairs are white but pigmented specks of color develop, usually all over the body. Amount of speckling varies between individuals and density of speckling may increase as the horse ages. More often seen in heterozygous grays. |
Iamnotabunny ( talk) 14:20, 22 April 2020 (UTC)
How about placing all the relevant text into the table? Maybe play with photos?Thoughts? Montanabw (talk) 05:11, 30 April 2020 (UTC)
Name | Image | Description |
---|---|---|
Foals |
![]() |
Horses in their first year begin to show a few white hairs as their foal coat sheds. Some foals show gray hairs around their eye, muzzle and other “soft” areas at birth, others do not show white hairs until they are almost yearlings. |
Young gray horses |
![]() ![]() |
An intermediate stage typically seen in young horses in the early stages of turning gray is when white hairs are mixed with the dark birth color. In horses born black or dark bay, the horse shows mostly black and white hairs intermingled on the body. This is sometimes called "salt and pepper," "iron gray," or "steel gray." This is the most common intermediate form of gray, which can give a silvery look to the coat. A reddish tinge, called a “rose gray", describes this intermediate stage for a horse born a chestnut or bright bay. Young horses just starting to gray out are sometimes confused with roans, but a gray continues to lighten with age, while a roan does not. Roaning also causes fewer white hairs on the legs and head, giving the horse the appearance of dark points, which is usually not true of gray. |
Dapple gray |
![]() ![]() |
Light and dark areas form a dappled pattern of dark rings with lighter hairs on the inside of the ring, scattered over the entire body of the animal. Not all grays dapple, and it is an intermediate stage, usually seen in young adult horses, often considered highly attractive. The horse will continue to become lighter. Dappled grays should not be confused with the slight dappling "bloom" seen on horses of other colors that are in excellent condition, as "bloom" dapples disappear should the horse lose condition. |
Late stage graying |
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As grays become lighter with age, a few areas, especially around the flanks and legs, retain some color |
Complete depigmentation |
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Nearly all hairs are white. A horse at this stage may be done changing color, or may begin to develop fleabitten pigment. Gray horses with a completely white coat can be distinguished from a white horse by their underlying black skin, particularly around the eyes, muzzle, and genital area. |
Fleabitten gray |
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Flea-bitten gray is a color consisting of a white hair coat with small pigmented speckles or "freckles". The flea-bitten pattern is seen primarily in heterozygous Grays. [1] Most horses who become flea-bitten grays still go through a brief period when they are pure white. The amount of speckling varies between individuals and density of speckling may increase as the horse ages. Some horses may appear almost pure white, with only a few speckles observed on close examination. Others may have so many speckles that they are occasionally mistaken for a roan or even a type of sabino. |
Blood marks |
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One unique form of gray, genetically related to flea-bitten gray, are “blood marks” or a "bloody shouldered" horse. This is an animal that is so heavily pigmented on certain parts of the body, usually the shoulder area, that it appears as an irregular, almost solid pattern—as if blood had been spilled on the horse, hence the name. Blood marks can change size and shape as the horse ages. Arabian horse breeders claim the Bedouin people considered the "bloody shoulder" to be a prized trait in a war mare and much desired. [2] |
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)
References
pielberg-2008
was invoked but never defined (see the
help page).