Phenotypic and Genetic Analysis of the Leopard Complex Spotting in Noriker Horses.

The study dives into a new method of quantifying leopard complex (LP) spotting patterns in Noriker horses using image analysis tools. With this method, the team discovered other factors, like sex, age, base color, and parents’ spotting phenotype, that seem to affect the LP spotting variation. The team analyzed images of 90 horses and also genotyped a sample of 191 Noriker horses.

Use of Image Analysis Tools

• The researchers used image analysis tools to numerically quantify variability of the LP spotting phenotypes.
• They used Generalized Procrustes analysis to minimize systematic errors that might occur during the imaging process.
• The team then normalized the images, converted them into binary form, and employed principal component analysis (PCA) on the pixel matrices obtained. This process converted pixel-level data into more manageable numerical data.

Investigation on Noriker Breed

• They applied the above method to 90 images to figure out the specific leopard patterns within the Noriker breed.
• A representative sample of 191 Noriker horses was genotyped for any known LP spotting associated loci.
• Most (97%) of the genotyped leopard-spotted horses were found to be heterozygous for LP – meaning that they had one copy of the LP gene variant and another different gene variant – and had at least one copy of the PATN1 allele, associated with LP spotting.

Diverse Factors Redefining the Expression of LP Spotting

• Despite the dominance of the PATN1 allele, there was still tremendous variation in the pattern, suggesting that other genetic and non-genetic factors might be affecting the expression of LP spotting.
• After analyzing the data, researchers estimated the effects of factors such as the modifier PATN1, sex, age, base color, and the spotting phenotype of parents on the LP spotting.

Results of Principal Component Analysis

• The PCA of the pixel matrix yielded two significant components that accounted for 51% of the variation.
• When a linear model was applied, significant effects on the first and second components were observed for factors such as age groups and base color.
• Sex and parents’ LP phenotype also showed significant effects on four additional components, hinting at their potential influence on the expression of LP spotting in Noriker horses.