Shirayukihime (Japanese: シラユキヒメ, Hepburn: Shirayukihime; 4 April 1996 – 5 May 2019) was a Japanese Thoroughbred racehorse and broodmare. She competed in 2001, recording no wins in nine starts. She is notable for being a white-coated horse born from a spontaneous KIT gene mutation (designated W14), and for establishing a lineage of white-coated racehorses as a broodmare. Her descendants include Sodashi, the first white horse to win a Japanese Classic, and Hayayakko, the first white horse to win a JRA graded stakes race.
Background Shirayukihime was a white mare bred in Hayakita (now Abira), Hokkaido, by Northern Farm. She was sired by Sunday Silence and her dam was Wave Wind, a bay mare by the American stallion Topsider. Despite both parents being dark-coated (Sunday Silence was dark bay, Wave Wind was bay), Shirayukihime was born white due to a spontaneous mutation in the KIT gene. The mutation, designated W14, is a 54-base-pair deletion in exon 17 (c.2392_2445del) that causes an 18-amino-acid deletion in the tyrosine kinase domain II of the stem cell factor receptor (SCFR). This disrupts melanocyte precursor cell migration, resulting in a white or spotted coat. The probability of such a spontaneous white mutation occurring is estimated at 1 in 10,000 to 1 in 20,000. Her racing name is derived from the Grimm's Fairy Tales character Snow White. She was owned by Makoto Kaneko and sent into training with Yoshiyuki Goto at the JRA's Miho Training Center.
Racing career Shirayukihime debuted on February 3, 2001, in a 5-million-yen allowance race on the turf at Kokura Racecourse, finishing eleventh. She ran in eight subsequent races through September 2001, all in the 5-million-yen or 9-million-yen allowance classes. Her best finish was third in a 5-million-yen allowance race over 2000 meters at Fukushima Racecourse on May 13, 2001. This was the first time a white-coated horse finished in the top three in a JRA race. She did not win any of her nine starts and earned ¥1,900,000 in total.
Statistics The following table details all 9 starts of Shirayukihime's racing career based on official netkeiba and JBIS records.
Date Course Race Class Distance (Condition) Odds(Favourite) Field Finish Time Winning(Losing)Margin Jockey Winner(2nd Place) Ref2001 – five-year-old season Kokura 4YO+ Allowance 1 Win Turf 1200 m (Firm) 13.0 (5th) 16 11th 1:11.0 0.8 Yoshiyuki Aoki Sky Jump Kokura 4YO+ Allowance 1 Win Turf 2000 m (Firm) 14.6 (5th) 16 12th 2:05.0 1.3 Yoshiyuki Aoki Jin Perfect Chukyo 4YO+ Allowance 1 Win Dirt 2300 m (Muddy) 20.2 (8th) 16 14th 2:05.0 5.2 Koshiro Take Eishin Jordan Fukushima Iwaki Tokubetsu 1 Win Turf 1700 m (Firm) 32.3 (10th) 13 8th 1:44.2 1.2 Yoshikazu Yokoyama Noble Derby Fukushima 4YO+ Allowance 1 Win Turf 2000 m (Firm) 6.5 (4th) 16 2:03.0 0.2 Masaki Katsura Silver Meteor Hakodate Okushiri Tokubetsu 1 Win Turf 2000 m (Firm) 15.6 (5th) 15 10th 2:05.0 0.8 Norihiro Yokoyama Daiichi Line Hakodate Yunokawa Tokubetsu 1 Win Turf 2000 m (Firm) 28.0 (5th) 15 9th 2:03.2 1.5 Masaki Katsura New England Sapporo Niseko Tokubetsu 1 Win Turf 1200 m (Firm) 59.7 (11th) 11 8th 1:10.8 0.5 Yūichi Shikato Delikit Sapporo Eniwadake Tokubetsu 1 Win Turf 2000 m (Firm) 25.1 (7th) 12 9th 2:04.1 1.2 Yūichi Shikato Soun Senpu
Broodmare career Following her retirement from racing, Shirayukihime became a broodmare at Northern Farm. Because the W14 white mutation is dominant over other coat colours, approximately 50% of her foals were born white or spotted, following Mendelian inheritance. She was mated with three stallions owned by Makoto Kaneko: Black Hawk, Kurofune, and King Kamehameha. Her broodmare registration was cancelled on February 7, 2017. She died on May 5, 2019.
c = colt, f = filly
Foaled Name Sex Colour Sire Record / Major wins 2003 Shirokun c White Black Hawk 5 starts, 0 wins 2004 White Vessel c White Kurofune 17 starts, 3 wins. First white horse to win a JRA race (2007). 2005 Yukichan f White Kurofune 17 starts, 5 wins. Kantō Oaks (JpnII), Queen Sho (JpnIII), TCK Ōi Hai (JpnIII). First white horse to win a graded race. 2007 Mama's Dish f Gray Kurofune 10 starts, 0 wins 2008 Shirobee c White Kurofune Unraced. Lead pony at Kyoto Racecourse. 2009 Marshmallow f White Kurofune 12 starts, 2 wins. First white horse to win a JRA maiden race (2011). Dam of Hayayakko. 2010 Blanc Manger f White Kurofune 3 starts, 0 wins. Dam of Danon Harlock. 2011 Marble Cake f White King Kamehameha 17 starts, 3 wins 2012 Buchiko f White King Kamehameha 16 starts, 4 wins. Dam of Sodashi and Mama Cocha. 2014 Shironii c White King Kamehameha 49 starts, 4 wins. First white stallion to run in a GI (2021 Tennō Shō Spring). 2015 Shirayukihime 2015 f Bay King Kamehameha Unraced 2016 Butchini f White King Kamehameha 18 starts, 3 wins
Notable descendants Shirayukihime's white-coated lineage includes the following graded stakes winners:
Hayayakko (2016, c, white, by King Kamehameha, out of Marshmallow) – Leopard Stakes (GIII, 2019). First white horse to win a JRA graded stakes race. Sodashi (2018, f, white, by Kurofune, out of Buchiko) – Sapporo Nisai Stakes (GIII, 2020), Hanshin Juvenile Fillies (GI, 2020), Oka Shō (GI, 2021), Victoria Mile (GI, 2022). First white horse to win a GI and a Japanese Classic. Meikei Yell (2018, f, bay, by Mikki Isle, out of Shiroinger) - Kokura Nisai Stakes (GIII, 2020), Fantasy Stakes (GIII, 2020), Tulip Sho (GII, 2021), Silk Road Stakes (GIII, 2022), Keio Hai Spring Cup (GII, 2022), Centaur Stakes (GII, 2022) Mama Cocha (2019, f, bay, by Kurofune, out of Buchiko) – Sprinters Stakes (GI, 2023). Amante Bianco (2021, c, white, by Henny Hughes, out of Yukichan) - Haneda Hai (JpnI, 2024)
White coat genetics The white coat of Shirayukihime and her descendants is caused by the W14 mutation in the KIT gene. This mutation is a 54-base-pair deletion in exon 17 (c.2392_2445del), resulting in an 18-amino-acid deletion in the tyrosine kinase domain II of the stem cell factor receptor (SCFR). Because the mutation occurs in the intracellular domain, it reduces SCFR activity by up to 75%, producing a more severe white phenotype than mutations in the extracellular domain. Horses carrying one copy of W14 may be fully white, spotted (buchi), or have partial white markings. Horses homozygous for W14 are presumed non-viable.
Pedigree
Shirayukihime is inbred 4 × 5 to Almahmoud. Her dam Wave Wind was unraced. Her granddam Storm and Sunshine won a Grade 2 race in the United States.
See also Thoroughbred racing in Japan Sodashi White (horse)
References