Ooooooooh !
just wanted to add in spotted horses/ponies that DON T display "LP ROAN" ......the horses/ponies who coat patterns remain on the whole UNCHANGED/STABLEfrom thier birth colour /pattern throughout thier lives ( other than the slight seasonal changes that can be obsevered fairly universaly through out horse solid , coloured ,dilutes as well as spotties )thier areas of ""STABLE" colour / pattern MAYBE ? a product of KIT ?
as All KITS "paterns" seem to be on the whole "STABLE " & NON -PROGRESSIVE in thier nature
only another thought

IF ? ........any totally "STABLE" coat patterns still exsist in "apaloosa" colour .......idon t know ?

_________________
life without horses & chocolate just wouldn t be worth living!
sarah x

i ve been going over & over the CAT & TORCH analogy in my mind while doing the horses
and i MAY well be wrong & have misread the Genetic study stating LP lp & LPLP both display "spotted" coat patterns where as lplp didn t display any "spots"
it suddenly dawned on me that in other genetic reports i ve read "spotted" reffers to areas of white within a base coat colour ......not "spots " of base colour that show through the white
so i ll see if i can get clarification on exactly what is ment in this instance by the term "spots"
as i may have got confused ( in which case i appologise Steph )
HOWEVER it doesn t alter the fact LP lp tested & LPLP tested horses could not be told apart by coat pattern which leads me to question Shiela s THEORY on NIGHTBLINDNESS
AS it states horses with LPLP coat patterns ARE PRONE TO NIGHT BLINDNESS
WHERE AS horses with LP lp coat patterns remain UNEFFECTED
UNLESS i ve misunderstood the findings completely ( which i m not ruling out ! ) i don t see how this can be IF as i ve read the results theres no consistant differences visually between the 2 ?

i ll try & E-MAIL Paul Szauter from MOUSE GENOME INFORMATICS to see if he can offer clarification on the results of the study

_________________
life without horses & chocolate just wouldn t be worth living!
sarah x

_________________
Dan Reeves, Animal Genetics UK - Always happy to talk about horse DNA and colour genetics - but don't expect me to know anything about dressage!!

http://www.facebook.com/profile.php?id=525383847

Paul was ( so i believe ) involved in mapping of the LP gene in appaloosa coat pattern in horses i contacted him after reading his report on comparison studies between LP & KIT n which it was conclued that there was no link (highly unlkely )i did post the study for everyone to view earlier in this thread .so the comments Paul made about LP reffered to horse coat patterns in this instance not mice .i ll look bck for a quote off Paul s posting

Quote:

Posted: Thu Mar 06, 2008 9:20 pm Post subject: -------------------------------------------------------------------------------- Sarah wrote to me directly at Mouse Genome Informatics. I am posting my reply for all. _____ Dear Sarah, Thank you for directing me, through your postings in the thread that you cited, to many interesting and informative web sites. By reading these, I have a basic understanding of some of the major genes involved in coat color in horses. I find the current research very interesting also. Here is the best summary that I have found (for a geneticist): http://en.wikipedia.org/wiki/Equine_coat_color_genetics To address your question, I will give you a very basic explanation of the genetics of coat color. The appearance of the coat of a horse (or a mouse) is the end product of the action of many genes. We call this appearance the phenotype (which roughly translates as "the form that is shown"). The phenotype allows us to make certain inferences about the genetic makeup of that horse (or mouse). To use a simple example, consider the case of breeding a pair of black horses. Suppose that one of the foals produced is chestnut. We know that black is either EE (homozygous) or Ee (heterozygous), and that chestnut is ee (homozygous). We can look at the chestnut foal and tell its genotype (ee), but until the black parents produced a chestnut foal, we couldn't tell whether they were EE or Ee. Now we know that they are both Ee. The Lp ("Leopard complex") gene found in Appaloosas is an interesting case. We cannot tell LpLp from Lplp by looking at them; they both have Appaloosa spotting. The black and chestnut horses in the prior example are lplp. One of the studies that you cited showed that LpLp horses are nightblind (congenital stationary night blindness or CSNB), while Lplp horses have normal vision. The Lp gene has been located to a specific region on chromosome 1 using linkage analysis. I will give you a very brief explanation of this. If two different genes are located on different chromosomes, they will assort independently in crosses. Let us use hypothetical genes A and B. If we cross Aa Bb to aa bb, there will be four genotypes: Aa Bb aa Bb Aa bb aa bb Each of these will occur with equal frequency if the genes are on different chromosomes. Independent assortment means that the probability that a sperm or egg is A (as opposed to a) does not influence the probability of it being B (as opposed to b). The production of gametes (sperm or egg) is frequently compared to games of chance using dice or cards. If I roll a pair of dice, the probability that I will roll a six on one die is not influenced by the number that comes up on the other die. The situation changes if A and B are on the same chromosome ("linked"). Here, the four types in the example above will not be produced in equal frequency. Two types (the parental types) will be more frequent than the other two types (the nonparental or recombinant types). The extent of linkage (departure from independent assortment) depends on the distance between the genes on the chromosome. In the studies of Lp on the web pages that you cited, hundreds of genetic markers that can be scored in the laboratory were followed to see if any of them displayed linkage to Lp. Using this technique, the gene causing Appaloosa spotting (Lp) was located to a region of chromosome 1. We know that Lp produces Appaloosa spotting, and we know that it is located in a specific region of chromosome 1. We also know many other genes in that region. Many of those genes are known by their DNA sequence, which usually gives us an idea of the normal function of the protein that is the product of those genes by comparison to the sequences of proteins whose function is known. We would like to know whether the Lp gene, as identified by spotting in Appaloosa horses (a phenotype), corresponds to any of the known genes in the specific region of chromosome 1. All of the genes in that region are potential candidates, so additional studies are necessary to identify the gene that corresponds to Lp. One of the studies that you cited demonstrated that the phenotype caused by Lp is not a result of mutations in the Kit gene. Kit is a gene known in mouse, humans, and other mammals that is known to produce white spotting. In the old literature on mouse genetics, this was known as dominant white or W. It has since been found to be a variant of a gene known to be involved in cancer (an oncogene) called Kit. The gene that started the thread that you cite is another interesting gene, Grey or G. This is described as a modifier gene, meaning that horses that have the Grey allele (GG or Gg) might have any other coat color genotype, and therefore could have a wide range of coat colors. As they age, they go grey at different tempos and in different patterns, depending on the individual. There are some interesting ideas about whether homozygous GG horses go grey faster than Gg, and some speculation on the various patterns (dappled, flea-bitten, etc.). There does not appear to be a solid scientific basis for any of the speculation, but everyone agrees that horses that are GG or Gg are affected by greying to some extent over several successive sheddings of the coat. In your posts on the sixth page of the thread, you have asked about turning on and turning off of genes, and how that might affect the color of the coat. The color in mammalian hairs is produced by two pigments, eumelanin (black or brown) and phaeomelanin (yellow or red). These pigments are synthesized in a series of enzymatic steps from tyrosine, an amino acid. The pigments become incorporated into pigment granules that are smaller than individual cells before being deposited in growing hairs. Many genes affect coat color by affecting different steps of this process. White hair may be produced by alleles that block the synthesis of tyrosine (this is the cause of albinos in mice and humans), or alleles of different genes that interfere with the migration of melanocytes (pigment-producing cells) in the skin. Brown hair, as opposed to black, can be caused by alleles that change the size and shape of pigment granules. Grey hair, as opposed to black, can be caused by alleles of different genes that cause the clumping of pigment granules. Red or yellow hair is caused by alleles of other genes that cause the production of phaeomelanin over eumelanin. It is not very important to remember all of these specifics; I just cite them to point out that coat color is a complex process, and that many genetic variations affecting a wide range of cellular processes can alter coat color. The phenotypic effect of the Grey allele is to cause a gradual loss of the ability of a pigment cell to produce pigment. This might occur at any of several different biological steps, but we can rule out some of the possible causes because of the presence of pigment initially. For example, we know that the migration of pigment cells in the skin is normal, because these horses are born with a normal coat color pattern that changes over time. We also know that the enzymes involved in the synthesis of melanin are also not affected directly, for the same reason. Because we understand much of the biology of pigment production, we can definitely say that Grey causes a cessation of production of pigmented hair by affecting an important step in that process. It is extremely unlikely that the Grey allele causes the production of a chemical bleaching agent. While that cannot be entirely ruled out at this point, there is a principle in science that we should not use exotic explanations when simple ones will suffice. The other question that you ask is why Grey is associated with an increased incidence of tumors and a decreased lifespan. There are many possible explanations for this. Several well-studied coat color genes in mice are pleiotropic, which is a fancy way of saying that they produce several seemingly unrelated phenotypes. Usually, when these genes are analyzed in detail, an explanation for the diverse effects emerges. For example, there is a coat color mutation in mice originally called dilute (d) because it "dilutes" pigment. Mice that would otherwise be black are gray, mice that would otherwise be brown are cinnamon or lilac, and so on. One of the alleles of the dilute locus causes demyelination of nerves, resulting in convulsions and early death. We now know that this gene encodes a protein necessary for the transport of subcellular components along microtubule trackways in nerves. This same function is responsible for dispersing pigment granules in melanocytes. I hope that this explanation is helpful to you. Here are a couple of resources that I think you will find useful. We have posted a glossary of many terms in genetics that can help you to understand the vocabulary of this science: http://www.informatics.jax.org/javawi2/servlet/WIFetch?page=glossaryIndex&printFormat=footer We have also created an online version of The Coat Colors of Mice, a very detailed book exploring the genetics and biology of coat color in mice. This will have application to the problem of coat colors in horses: http://www.informatics.jax.org/wksilvers/ Good luck in your research on this interesting subject! Yours, Paul Szauter Mouse Genome Informatics

NB. i only copied & pasted the whole post as i didn t want to quote Paul out of contect incase i tainted it with my perception as others may read it differently to me .......and i ll readily admit i regularly get confused & lost thats why experts such as Paul & Dan have been such a God send in setting me straight!

_________________
life without horses & chocolate just wouldn t be worth living!
sarah x

reposting this post made by myself ......for easy refference as it holds the links to the studies reffered to above

Quote:

Joined: 12 Jan 2008 Posts: 686 Posted: Sun Mar 02, 2008 8:13 pm Post subject: -------------------------------------------------------------------------------- i m trying to find info on "Lp" GENE! no luck REALLY so far found this for the mega brain boxes! .........meana JACK SH*T to me! other than apparently the "Lp" Genne in Appaloosa coat pattern has no link with WHITE MICE BOTTOMS ? ANYWAY ITS PAGE 64 0F 71 !.......GOOD LUCK! www.isag.org.uk/pdf/COMP.PDF THESE LINKS ARE TOO IN DEPTH FOR ME ( THEY RE FOR YOU BRAINY ONES? ) i think this link just accepts THEORY A about" Lp ROANING" &" Lp" GENES ????? It again mentions "KIT" and rules it out and APARENTLY the DNA link is made between the WHITEPATTERNIG GENE IN MICE /PIGS & SOMETHING ELSE I CAN T REMEMBER! "KIT" AND THE "TABIANO" &" OVERO" PATTERNS IN COLOURED HORSES ???? www.cababstractsplus.org/fts/Uploads/PDF/20000107754.pdf SO AS I UNDERSTAND IT NO DNA "MARKER" (if thats the correct term? ) HAS BEEN FOUND FOR EITHER THE "GREY GENE" NOR "Lp GENE" SO NOTHING SCIENTIFICLY PROVED OR DISPROVEN .........YET!!!!!!! ......INTERESTINGLY THOUGH .......the "ROAN "gene has asl been "MAPPED" & "LINKED" to "KIT" (as was BOTH OVERO & TOBIANO ......remembering ALL of these 3 "PATTERNS" are"STABLE"( ie NON PROGRESSIVE IN NATURE) where as "Lp" or "GREY" are BOTH "CONSIDERED "UNSTABLE IN NATURE" Hmmmmmmmmmm the study mentions a possible link to VITTILIGO ......Hmmmmmmm that would make it different GREY as with GREY it s BELIEVED the skin remains unchanged?( by pure coincedence both my Mum & sister have this condition but whats interesting is her IDENTICALTWIN sister does NOT? www.vitiligosociety.org.uk/

hope that helps

_________________
life without horses & chocolate just wouldn t be worth living!
sarah x

i was looking at Bill wet today
and he s like one of those "magic painting books !"
just add water and look what you get!

[img][/img]


[img][/img]

[img][/img]

what i find intriging is he hasn t retained all his birth pigment in his skin
he seems to have retained selected areas only or else he s also losing the pigment from his skin as well ? ......unless ......his coat is more dense in areas so the spots held in his skin can t show through

_________________
life without horses & chocolate just wouldn t be worth living!
sarah x

and Billy dry (&muddy )

[img][/img]


[img][/img]


[img][/img]

sorry he s looking so hanging !

_________________
life without horses & chocolate just wouldn t be worth living!
sarah x

i m posting this link to maintain balance in this debate

www.appaloosaproject.info/index.php?module=pagemaster&PAGE_user_op=view_page&PAGE_id=1&MMN_po...

Quote:

Implications: Isolation of LP will make possible the development of a DNA test. Breeders will be able to confirm if LP is present or not in young horses that do not immediately show the classic Appaloosa characteristics required for regular registration. It will also allow for the accurate identification of horses that are homozygous for LP.

another interesting topic to explore on this link
Night Blindness (CSNB)

2. Inheritance Information for Appaloosa-specific CSNB
- Diagrams showing various types of crosses and the probable outcomes, using Punnett Squares

_________________
life without horses & chocolate just wouldn t be worth living!
sarah x

There is usually (but not always) a visible difference in horses that are believed Lp/lp and those that are Lp/Lp - horses that are Lp/Lp tend to have fewer spots within the areas of white than those that are Lp/lp (hence the term fewspot), they also generally have amber colored hooves on solid coloured legs (solid here means without socks/stockings and/or associated white leg markings). It is more difficult to tell on those horses that have smaller areas of white or that are Lp/Lp without any significant PATN gene. Also Lp homozygous horses tend not to have spots on the top of the rump.

thanks Steph for explaining that ......but .....DNA testing is proving more & more asumptions made on phenotype studies ( observation of the apperance /coat pattern ) can be in accurate & misleading . I m equally as guilty of drawing conclusions from observations ...but as we both agree its DNA testing that will reveal the true answers
maybe Shelia will be right , maybe my theory will be right , maybe we ll both be partly right , or maybe we ll both be completely wrong
i think the genticists will get to the bottom of it in time & just hope whatever the results they are made PUBLIC as breeders have the right to know the actions behind these genes its so important on a much deeper level than just colour sometimes we try try to cheat nature in our favour too much as nature reasons for things are very often much deeper than we respect

_________________
life without horses & chocolate just wouldn t be worth living!
sarah x

i am also posting this link here as i find it fascinating & relevant to this topic

http://www.arabianrun.com/arguide.htm

some interesting observations

Quote:

The white horse, born white with black skin, is the result of abnormal action of the grey factor in which the basic color of the coat has been entirely replaced before birth. These foals are born in what would otherwise be considered the adult coat phase. MS Czarthan AHR#44054 was one of these rare and unique horses. Desert Name-Abyad The grey Arabian can start with any basic coat color, but is most common with dark horses. With the exception of the rose grey (a red chestnut that greys from the base coat to give it a rosy color), most greys go through several darkening phases where the horse eventually becomes near black before turning grey. It is impossible to tell what color the base coat of the horse actually was unless it was viewed as a foal. Greys usually dapple at some point in the greying process. All colors are capable of dapples as it is associated with good nutrition, however, the dapple effect is most noted on the sooty shade horse by contrast. Desert Name-Kurush (White spots on the grey during the color transitions are clear white with underlying black skin. They are not to be confused with dapples.) There are two basic types of grey: Those that lose pigment in the mane and tail and become white, known by the Desert Name-Safra bardah, and those that retain some black in the mane, tail, and sometimes the legs, Desert Name-Safra el jahra. Both types maintain the black skin pigment. Another form of grey is the fleabitten in which small flecks of color are viewed throughout the coat. These flecks are usually reddish but can sometimes be black or both. These colored flecks in no way represent the base color of the horse. Desert Name-Marshusha Bloody marks are distinctive large reddish patches on a grey horse that increase in size as the horse ages. They are independent of both background color and greying phases. Rarely, in a very aged horse, this coloration could appear uniformly red. This phenomenon appears to be a reversal of the greying process.

also i feel fascinating & possibly relevant to the GREY /LP ROAN debate

Quote:

One of the Abbas Pasha’s most celebrated mares was Faris Saouda, a parti-color (wildly spotted) horse. This ancient gene is not a sign of impurity but exactly the opposite. The true parti-color is not a common spotting pattern as seen today, but instead is the failure of pigmentation cells to spread throughout the body of the horse, a unique mutation occurring mostly in hotbloods. The Abbas Pasha set great store by this color and collected 11 mares with these attributes. Faris Saouda can be found in most of the bloodlines available in the U.S. today. The true parti-color is hardly ever seen today and is strictly hotblood in origin. Desert Name-Ablak This color is not related to the tobiano or the overo gene groups. Appaloosa type spots in the Arabian also seem to be a throwback to the parti-color. These horses are not eligible for the Appaloosa registry, even though some could be confused with the true Appaloosa.

_________________
life without horses & chocolate just wouldn t be worth living!
sarah x

a friend recently brought this reasuring (for any of us grey horse owners )study to my attention . thought i d share this comforting info with you as it is in stark contrast to Shiela Archers statement about greys
http://www.ncbi.nlm.nih.gov/pubmed/12638791?ordinalpos=5&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum

[/quote]Although melanoma-bearing grey horses were encountered up to stage 4, none of the affected individuals suffered any severe clinical effect or was handicapped in performance[quote]

this is further backed up by the number of OUTSTANDING grey performance horses across all disaplines both past & present day
i hope this helps put those of you with Grey horses minds at ease as it has mine .YES there is a proved link but its not all DOOM & GLOOM

_________________
life without horses & chocolate just wouldn t be worth living!
sarah x

_________________
Dan Reeves, Animal Genetics UK - Always happy to talk about horse DNA and colour genetics - but don't expect me to know anything about dressage!!

http://www.facebook.com/profile.php?id=525383847

Sarah J that is a great link thanks

came across this link to an article by Shiela Archer , and found it very interesting so i thought i d share it

www.members.aol.com/WinterSpringsTWH/RoanInfo.html

Quote:

One might argue that this horse isn't actually carrying classic roan (Rn), but has instead some other sort of roan-causing pattern gene. I suppose it is possible that there's more than one gene that can cause roan patterning of a kind similar enough to classic roan that they are hard to tell apart from each other by physical appearence alone. If there are other genes that cause similar kinds of roaning, there is no way of knowing for sure until the Rn gene has been isolated and can be DNA tested for. Right now, all we know is that Rn is most likely a mutation at the KIT locus, but that's all that is known at this time. The only way to find out if there's more than one type of roaning gene at work that makes similar looking horses that all sort of seem to be classic roan, but aren't genetically the same, would be through lab-based research to isolate the genes. To the best of my knowledge, no one is doing this right now.

it is refreshing to see her aknowledge it is unsafe to draw too many conclusions on a horses appearence alone ,as 2horses with coats strikingly similar ( at a particular point in time )could be very different genetically .i believe the link with ROAN & KIT has now been mapped & proved .lots of info & theories on this link to exlore

Quote:

The main gene responsible for Appaloosa patterning is called "leopard complex", symbolized by "Lp". This gene occurs in other breeds of horses and ponies, yet it is the "appaloosa" gene, in the sense that all breeds which have this mutation will show one or more of the patterns associated with the leopard complex. The following is a partial list of breeds in which Lp occurs: Spanish Mustang (also called the Spanish Colonial Horse) Knabstrupper (Denmark) Noriker (Austria) Fallabella (Argentina) British Spotted Pony (UK) Karabair (Turkmenistan) Altai (Russia) There are others, but these are some of the most common ones. There are also still a few undetected LP-carriers in the following breeds that once had many more of them, but have now outlawed that coat pattern gene in their registration rules: Andalusian (Spain) Lusitano (Portugal) Lippizan (Austria) Quarter Horse (N.America)

i find the 2nd list of breeds observed to have LP within them incredably interesting as they are mainly breds associated with a high %of GREY within them .......so they seem to be sucesfully managing to breed out LP & keep GREY surely then there is alot to learn off these breeders who ve achieved this as it may help LP breeders achieve the oposite ie. BREED UT GREY WHILST KEEPING LP .......unless LP is dependant on GREY to show itself where as MAYBE .....GREY is not dependant on LP so it is possible to exclude the horses that display LP from the gene pool while sustaining GREY

just a thought

_________________
life without horses & chocolate just wouldn t be worth living!
sarah x