There’s something special about grey horses (six Lipizzaners pictured). They’re born with a distinct coat colour, but speckling and dappling begins soon after birth, progressing to near white as years go by. This all-over grey is caused by mutation in a gene called STX17. It’s been selected for because it brings beauty. But it’s accompanied by a beast – at 15-years most greys will have melanoma [a skin cancer]. And a proportion also develops vitiligo [skin depigmentation] – a condition that may be linked with melanoma in some people. STX17 is activated in the melanoma tumours of grey horses, suggesting its involvement in the cancer. With the possibility of the noble grey as a disease model, STX17 mutation was sought in human melanomas. It wasn’t apparent; but understanding the complex equine genetic linkage between hair colour, melanoma and vitiligo may yet yield clues to the human disease.
Written by Lindsey Goff
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