Associations between candidate gene markers at a quantitative trait locus on equine chromosome 4 responsible for osteochondrosis dissecans in fetlock joints of South German Coldblood horses.

This study investigated the genetic factors affecting the occurrence of bone and joint disorders, specifically osteochondrosis dissecans (OCD), in South German Coldblood horses. Researchers found a connection between specific variations in the acyloxyacyl hydrolase (AOAH) gene and the prevalence of OCD in the fetlock joints of these horses.

Study Overview

• In order to further understand osteochondrosis (OC) and osteochondrosis dissecans (OCD) in South German Coldblood horses, the researchers conducted a full scan of the genome using 250 microsatellite markers. This allowed them to identify possible quantitative trait loci (QTL), which are regions of the DNA that correlate to the variation in a quantifiable trait.
• They discovered a significant QTL on equine chromosome 4q (ECA4q) that seemed to be linked to OCD in fetlock joints, the ankle joint in horses.

OCD-Related Gene Identification

• Their investigation turned to potential OC-related genes in the identified area, which they evaluated by looking at single nucleotide polymorphisms (SNPs), i.e., variations occurring in a single DNA building block (nucleotide). This analysis involved 32 affected horses and 64 unaffected ones.
• Significant associations between OCD in fetlock joints and three different SNPs located in specific regions of the acyloxyacyl hydrolase (AOAH) gene on ECA4q were found.

Analysis Model and Results

• In order to account for potential environmental influences and to further study the genetic effects, the researchers utilized a linear animal model.
• This approach confirmed the association of one particular SNP located in the 3′-untranslated region (UTR) of exon 21. A noteworthy additive genetic effect for fetlock OCD was reported, with an estimation of 0.42 (P = 0.002), along with a dominance effect of -0.32 (P = 0.03).
• It is important to note that this is the first reported case of a genetic marker in population-wide linkage disequilibrium – a situation where a particular gene variant (allele) is more frequently found with another allele than expected by chance – with OCD in equine fetlock joints.