Thursday, 3 October 2013

Other uses for champagne

I expect that most of you know that only sparkling wines produced in the Champagne region of France are technically allowed to be labelled as champagne. Here in Australia, locally produced wines in this style are called sparkling wines instead.  Once, at the Forest Lodge Hotel, the menu described them as sparkly. I think this is a wonderful mental image, although it did make me worry about swallowing glitter.

Mmm, these guys take their sparkly seriously... (Photo linked through from here).

As it turns out, the term champagne has at least one other use - it's a version of the SLC36A1 (solute carrier family 36, member 1) gene that interacts with the basic coat colour genes to product unusual and, most of the time, beautiful coat colours.

 Now, the important things to remember when discussing genes are:
  1.  Your horse has two copies of each gene*, one inherited from either parent; 
  2. There are many different versions of each gene in the horse population, some of which can produce identical or nearly identical appearance and biological function, while other versions can produce a different coat colour or cause disease; and 
  3. Each physical characteristic of your horse, including coat colour, results from the combined effects of the two copies of each gene, AND the interactions between a large number of different genes.
Champagne... or sparkly? A: chestnut, B: gold champagne, C: bay, D, amber champagne, E, black, F, classic champagne. Pic linked through from here.
The version(s) of the SLC36A1 gene called champagne interact with basic coat colours to create either gold champagne (chestnut plus champagne), amber champagne (bay/brown plus champagne) or classic champagne (black plus champagne). The colours in the picture above are good examples, but there is a lot of variation between individuals. They can be darker or lighter, and the mane and tail colour can vary widely. In practice, there is a whole golden rainbow of champagne shades.

So how come they look that way? Basically, the champagne gene reduces the amount of pigment that your horse or pony produces. Both the red (pheomelanin) and black (eumelanin) pigments are affected. As with the cream coat colours, the mane and tail are often affected differently to body hair. As a bonus, the change in colour is often accompanied by a beautiful gleam - maybe this champagne should be called sparkly too!

Weird and wonderful. Foals with the champagne gene are born with blue eyes. Pic linked through from here.
Champagne coat colours are accompanied by unusual skin and eye colour. Foals are born with blue eyes, which mature into green, pale hazel or amber. Horses and ponies that have inherited a version of the SLC36A1 gene that creates the champagne coat colours also have less pigment in their skin than normal, resulting in a pinker skin that often appears slightly mottled or freckled. It is easiest to see this unusual skin in places where the the hair is thin or missing, like around the eyes, nose, udder or sheath, and under the tail.

Palomino or golden champagne? Now you've read this blog entry, you'll spot those dark eyes and make the call easily! (Please don't share this picture, it's licensed to me rather than the world in general).
The effect of champagne can be very similar to cream... when we are describing a horse, that is! (I like to think that my wise readers could spot the difference in the way they feel after drinking those two liquids.) This is especially true for golden champagne coat colouring (chestnut base colour) which can be very similar to palomino, and in some instances for amber champagne (bay/brown base colour) which can be very similar to buckskin. In these instances the horse's eye colour may provide a clue, or you could ask for a genetic test to confirm which genes are present.

EB's Wind Dancer, a stallion advertised as homozygous champagne (that means both copies of his SLC36A1 gene are versions that cause champagne coat colouring). Picture linked from here.
So, I hear you wonder, what about the difference between one copy of the champagne gene and two copies? Well, when it comes to the way your horse or pony looks, there are no definite colour differences. As you can see from the picture above, the two copies of the champagne gene can cause the skin and eyes to be quite pale, but given how much colour variation there is when just one copy of the gene is inherited, this isn't a sure-fire way to tell. The main difference is that when a horse has two copies of the champagne version(s) of SLC36A1, then all of their offspring will inherit the gene.

Would you like to get your horse tested for champagne? Practical Horse Genetics has just added champagne testing to the list of DNA testing that we offer.

The version(s) of the SLC36A1 gene that create champagne coat colours were discovered by a team of scientists in the USA: Deborah Cook  - who did the experiments, Samantha Brooks, Rebecca Bellone, and Ernie Bailey (links go to author publications on Pubmed and can include publications by other people with the same name). The full article is here, free of charge (bless 'em). This discovery came shortly after the sequencing of the horse genome. Thank-you, everyone involved in this research!

* Except for genes on the X and Y chromosomes in male horses, where there may be only one copy.

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