| | | A cis-acting regulatory mutation causes premature hair graying and susceptibility to melanoma in the horse.
In horses, graying with age is an autosomal dominant trait associated with a high incidence of melanoma and vitiligo-like depigmentation. Here we show that the Gray phenotype is caused by a 4.6-kb duplication in intron 6 of STX17 (syntaxin-17) that constitutes a cis-acting regulatory mutation. Both STX17 and the neighboring NR4A3 gene are overexpressed in melanomas from Gray horses. Gray horses carrying a loss-of-function mutation in ASIP (agouti signaling protein) had a higher incidence of melanoma, implying that increased melanocortin-1 receptor signaling promotes melanoma development in Gray horses. The Gray horse provides a notable example of how humans have cherry-picked mutations with favorable phenotypic effects in domestic animals.
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Montag, 21. Juli 2008
That's why Lipizzans are grey!!!
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Yahoo News Lipizzan horses' white colour due to mutated gene: study The white coat of the Lipizzan horses performing at Vienna's prestigious Spanish riding school is caused by a mutated gene, a new study showed Sunday, solving a decades-old mystery over the horses' colour. White and grey horses, including Lipizzans, are born with a darker coat but lose their colour between the age of six and eight due to chromosome mutations, Austrian and Swedish researchers found in the study published Sunday in the scientific journal Nature Genetics. These genetic changes 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, according to one of the study's co-authors, Monika Seltenhammer of Vienna's University of Veterinary Medicine. The study also found that the same chromosome was responsible for the horses' heightened risk of melanoma, a serious skin cancer. Between 70 and 80 percent of grey and white horses aged 15 or older develop skin disease, said Leif Andersson of the department of medical biochemistry and microbiology at Sweden's Uppsala University. But the horses are hardly at risk, as the disease cells do not spread as quickly as in humans, said Seltenhammer.
AntwortenLöschenAnother link, this time auf Deutsch.
AntwortenLöschenwww.oe24.at
Click on Wissen and scroll down to the article titled
Darum sind Lipizzaner weiss.
Karen Mac.
Good evening Andreas and everyone in H and D,
AntwortenLöschenHere is a quotation from a feature in todays Daily Mail [ a UK newspaper..] on 21st July 2008. I have abridged this from the lengthy article by David Derbyshire.
WHY EVERY WHITE HORSE CAN TRACE ITS ROOTS BACK TO JUST ONE ANCESTOR THOUSANDS OF YEARS AGO.
They have been favoured by kings and emporers, in the form of Desert Orchid they became the housewives' choice and in Billy the police horse they helped clear the Wembley pitch and make history.
Now scientists have identified the genetic mutation that turns horses grey and then white - and it could mean that they all trace their ancestors back to just a single mare or stallion more than 2,500 years ago.
Grey horses are typically descended from Arabian ancestors, including the famous purebred Lipizzaner stallions that are trained for classical dressage, and have been selected by humans for their striking appearance. Born with dark hair greys gradually lose pigmentation. As their hair becomes white between six and eight years old they take on a grey appearance due to their black skin underneath.
Dr Leif Andersson and colleagues at Uppsala University, Sweden, found mutated genes in more than eight hundred grey horses from eight different breeds. Crucially the variants are not present in horses of other hues and through further DNA mapping the phenomenon was nailed down to the over expression of two neighbouring genes, known as STX17 and NR4A3. It is not known if one, or both of the genes is responsible for the loss of hair pigmentation, according to the study published online in Nature Genetics.
Dr Anderssons team also point out between 70 and 80 percent of grey horses older than 15 years have melanomas, the most serious form of skin cancer that reduces their lifespan. They believe the defective genes trigger both the disease and the loss of hair colour through reducing protective pigment containing cells in the skin and hair follicles.
Dr Andersson analysed the coat colours and skin of thoroughbreds from five national studs in Austria, Croatia, Hungary, Slovakia and Slovenia. He said the grey provides a notable example of how humans have cherry-picked mutations that produce attractive appearances in domestic animals. He said, " The manifestation of this mutation as a white horse has had a strong impact on human culture and has left numerous traces in art and literature from Asia and Europe, such as Pegasus and the unicorn."
The oldest written record is by the Greek historian Herodotus, who describes the Persian emporer Xerxes who reigned from 485 to 465 BC as keeping sacred white horses.
Dr Andersson said, " The prestige of riding a white horses has thus led to the selection of the grey causing mutation by humans. This mutation is by far the most common cause of white colour in horses."
For the full article and pictures [ Desert Orchid / Billy / Lipizzan in Courbette / Saxon horse carvings ] please go to
http://www.dailymail.co.uk/sciencetech/article-1036871/Why-white-horse-trace-roots...
Karen MacKenzie,
Manchester, England.
For those, like me, who were not quick enough to go to the link Karen's shared with us, here's the link to the Mail article - http://www.dailymail.co.uk/sciencetech/article-1036871/Why-white-horse-trace-roots-just-ancestor-thousands-years-ago.html Here's the link to a study undertaken by the University of Veterinary Medicine, Vienna, Austria - Equine melanoma in a population of 296 grey Lipizzaner horses - http://www.ncbi.nlm.nih.gov/pubmed/12638791?dopt=Abstract - that I found some time ago. I've always been aware that it's thought greys are disposed to melanomas - poor Rags (Ragyogo!) ,,, she's now so used to having her tail lifted & an inspection done that she accepts it with dignity ,,, rather than worry about it, as she did in her early days when she came moved here. Neither information relating to greys nor the incodence of melanoma's in greys that I've come across gives information as to why the Lipizzaner has a predominantely black skin. Is there any information about this fact, anywhere? Jos챕 Wales UK
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