COAT COLOUR INHERITANCE PATTERNS ASSOCIATED WITH THE LEOPARD COMPLEX IN HORSES (A REVIEW)

The aim of the study is to summarize the published results of studies on the inheritance patterns of the piebald coat color in domestic horses. Objectives: to analyze scientific papers aimed at studying the variability of the piebald coat color and its genetic determination. In preparing the review, publications of leading research groups working in the field of equine genetics were used. The search for scientific publications was performed using the following electronic library resources and databases: Wiley (https://onlinelibrary.wiley.com), PubMed Central (https://pmc.ncbi.nlm.nih.gov), ResearchGate (https://researchgate.net), OMIA – Online Mendelian Inheritance in Animals (https://www.omia.org). The list of references included 7 monographs and 55 scientific articles. Among horses with traits of the leopard complex, an extremely wide variety of phenotypes in color is observed. The LP (Leopard) mutation in the TRPM1 gene plays a key role, causing unique depigmentation patterns in horses. The LP mutation appeared in ancient horse populations long before their domestication and was caused by a retroviral insertion into intron 1 of the TRPM1 gene. To date, two loci have been identified whose mutations are associated with the control of leopard skin color variation in domestic horses: the incompletely dominant mutant LP allele (ECA1:g.108297929_ 108297930ins1378) and the dominant modifying allele PATN-1 (SNP ECA3:g.23658447T>G). It is important to note that, as a rule, only heterozygosity for the LP allele in combination with the presence of the dominant modifier PATN-1 in the horse's genotype leads to the preferred, well-defined leopard skin color phenotype. The LP mutation is the main factor determining the presence of various depigmentation variants observed in piebald horses. Heterozygous horses (with the LP/lp genotype) typically exhibit classic piebald patterns, such as leopard spots on a white background, or a roan color. The nature and intensity of depigmentation signs can vary significantly depending on additional genetic factors.