• About This Guide
  
• How This Guide is Being Developed
  
• Philosophy of this guide
  
• Using this Guide
  
• Thinking Scientifically
  
• About the Author
  
• Documented Genes
  
• What is a documented gene?
  
• Black/Red (MC1R)
  
• Bay (ASIP)
  
• Cream/Pearl (SLC45A2)
  
• Dun (TBX3)
  
• Gray (STX17)
  
• Silver (PMEL17)
  
• Champagne (SLC36A1)
  
• Roan/Tobiano/Sabino/White Spotting (KIT)
  
• Splash White (MITF/PAX3)
  
• Leopard Complex (TRPM1/ECA3P)
  
• Frame (EDNRB)
  
• Tiger Eye (SLC24A5)
  
• Height Regulation (HMGA2/LCORL)
  
• Mushroom (MFSD12)
  
• Eden White (HPS5)
  
• Hypothetical Genes
  
• What is a hypothetical gene?
  
• Borrowed Genes
  
• Glossaries
  
• Glossary of Colors
  
• Glossary of Terms
  

Eden White (HPS5)

• Last updated: 2026-03-24

  Common Names: Eden White, HPS5 White Factor in HGG

  Scientific Name: Hermansky-Pudlak Syndrome 5

  Equine Chromosome: 14

  General Overview:

  
  

  HPS5 is the first new gene to be associated with white markings in horses discovered since MITF and PAX3 (splash white) in 2019. The full impact of HPS5 in horses is unknown but it appears to act as a white booster.[1] In other species mutations of this gene are known to cause albinism and bleeding disorders.[2,3]

  
  

  Both EDXW1 and EDXW3 have been confirmed to be impacted by MC1R status, with E/? horses having smaller white markings than e/e horses. This is a known phenomenon with most white marking genes, but it is neat that this study was able to document it scientifically. This study also tested horses with both EDXW1 and W20 and found significant white boosting when the two mutations were paired.
  
  All three HPS5 variants discovered so far have been found in a wide variety of breeds and seem to be quite common. 

• Specific Alleles:

  EDXW1, also called Eden White 1 or “Cruz White”, is a mutation said to “ increase average depigmentation by 5.56 points”. This makes it similar in strength to EDXW3.

  
  

  EDXW2, also called Eden White 2 or “Dream White”, “increased depigmentation by 9.5 points” making it the strongest white booster of the three discovered so far. 

  
  

  EDXW3, also called Eden White 3 or "Irish White”, “increased white by 5.59 points on average”. This makes it similar in strength to EDXW1.

• In HorseGeneticsGame:

  When HorseGeneticsGame.com was first founded, I predicted that there would be a large number of untestable mutations that impacted the overall amount of white. These untestable genetics were abstracted into a single number I called white factor. With the discovery of a fifth gene that promotes white spotting, I now feel confident enough to quantify that abstract number into something specifically inheritable and testable. While undoubtedly there is still much more for geneticists to discover about white spotting control, there is now enough for me to put something concrete in the game. 

  
  

  The WF# alleles of HPS5 are hypothetical and found only in game. While they are based on real scientific mechanisms they have not been found or named this in real life. Named WF1, WF2, and WF3 they add 1, 2, or 3 “points” of white boosting respectively. Wild type -/- results in no white boosting, while W1/- has a small amount of white boosting. WF3/WF3 would be the loudest amount of white boosting. They can combine in any pairing.

• Lethality:

  There is no evidence that the HPS5 mutations known in horses are embryonic lethal or contribute to lethal foals. It is possible that they contribute to poor health outcomes or lethality in individuals with very high white amounts caused by other mutations.

  
  

  In HorseGeneticsGame.com HPS5 alleles are never directly lethal in any combination. In some combinations of KIT mutations, and some combinations of splash mutations HPS5 status may be enough to push a foal into the excessive white range causing it not to survive. When pursuing high white crosses, with high risk, sticking to HPS5 -/- can reduce negative outcomes.

• Citations:

  1. Aiden McFadden, Katie Martin, Micaela Vierra, Holly Robilliard, Erica W. Lundquist, Robin E. Everts, Samantha A. Brooks, Christa Lafayette, Three HPS5 mutations associated with depigmentation in diverse horse breeds. Livestock Science. ISSN 1871-1413, 2024 April https://doi.org/10.1016/j.livsci.2024.105454 
  2. Introne WJ, Huizing M, Malicdan MCV, O'Brien KJ, Gahl WA. Hermansky-Pudlak Syndrome. 2000 Jul 24 [updated 2023 May 25]. In: Adam MP, Bick S, Mirzaa GM, Pagon RA, Wallace SE, Amemiya A, editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993–2026. PMID: 20301464. https://pubmed.ncbi.nlm.nih.gov/20301464/ 
  3. Daly CM, Willer J, Gregg R, Gross JM. snow white, a zebrafish model of Hermansky-Pudlak Syndrome type 5. Genetics. 2013 Oct;195(2):481-94. doi: 10.1534/genetics.113.154898. Epub 2013 Jul 26. PMID: 23893484; PMCID: PMC3781975. https://pubmed.ncbi.nlm.nih.gov/23893484/ 

• Examples:

  -/-, WF1/WF2, WF3/WF3

  

  
  

  Het Sabino-1 with -/-, WF1/WF2, WF3/WF3