Last summer an important correction was issued to the paper where the first three splashed white patterns were identified.
There are errors in the identification of an allele, PAX3C70Y, arising by a de novo mutation event in a Quarter Horse mare born in 1987. The authors discovered a sample mix-up concerning the erroneously claimed Quarter Horse founder mare, labeled QH095 and genotyped PAX3+/+. Through analysis of an independent sample of QH095, the authors identified the genotype PAX3C70Y/+ in the new sample. Therefore, QH095 is not the founder animal for the PAX3C70Y allele.
The 1987 Quarter Horse mare referenced was assumed to be Katie Gun. The original study identified her as being homozygous for the wild-type allele, which would indicate that the mutation arose in her reproductive cells. That would mean it would be found in her offspring, while she was not herself splashed white.
This finding was called into question when a later study found the PAX3C70Y allele in three Lipizzans and seven Norikers. The error in the original samples was discovered, and the above correction was issued.
I’ll post more about the study involving the Norikers in the future. However, since the Paint Horse Journal published an article on the (newer) Splashed White 5 allele and a sixth allele was announced at a recent conference, it seemed that passing this along for those who were not yet aware might be helpful.
The image above is from the original article, “Mutations in MITF and PAX3 Cause “Splashed White” and Other White Spotting Phenotypes in Horses,” published in 2012.