Identification of a new quantitative trait locus on equine chromosome 18 responsible for osteochondrosis in Hanoverian warmblood horses.

This research identifies a new gene location related to the development of a joint disease called osteochondrosis in Hanoverian warmblood horses. It utilized a specific set of microsatellites within equine chromosome 18 and found evidence suggesting one particular gene could be contributing to the disease.

Research Objectives

• This study aimed to identify gene locations, or quantitative trait loci (QTL), associated with osteochondrosis in Hanoverian warmblood horses. Osteochondrosis is a disease affecting the joints, and is common in equine species.
• The researchers specifically looked at a chromosome in horses (equine chromosome 18, or ECA18) using the horse genome assembly EquCab2.

Methodology

• A set of 27 highly polymorphic (variable) microsatellites, including 11 newly developed ones, was used. Microsatellites are short, repetitive DNA sequences that can be helpful in genetic mapping.
• The selected microsatellites were found to be highly polymorphic, with an average polymorphism information content of 62.1%, and were evenly distributed on ECA18 at an average spacing of three megabases (Mb).
• Genotyping of these markers was done using 14 paternal half-sib families, identical to the family pool used in a previous whole-genome scan.

Findings

• Through chromosomal-wide linkage analysis, a QTL for osteochondrosis was discovered between 74.94 and 82.25 Mb. This pertains to horses that had osteochondrosis in fetlock, hock, or both joints, as well as horses suffering from a more severe version of the disease, called osteochondrosis dissecans, in their hock joints.
• Within this newly discovered QTL, the parathyroid hormone 2 receptor gene emerged as a potential candidate causing osteochondrosis. This gene may play a significant role in bone development and its mutation could possibly lead to bone disorders like osteochondrosis.

Conclusion

• This research study contributes to our understanding of the genetic causes behind osteochondrosis in horses. The newly uncovered QTL on ECA18 and its potential association with the disease brings us a step closer to identifying the exact genes responsible for this common equine disorder. This could help in developing strategies for prevention, treatment, and selective breeding in the future.