Researchers from Belgium and the Netherlands have found a gene that causes dwarfism in Friesian horses. The gene is a mutation on chromosome 14 (B4GALT7). This discovery will allow breeding horses to be tested for the gene in order to prevent two carriers from mating.
For years, Friesian horses have been plagued by a number of undesirable genetic characteristics. Dwarfism, for example, causes serious health problems for the horses. This condition is characterised by short limbs and poorly developed ribs, but the head usually develops normally.
Gene passed on by both parents
Researchers at the universities in Utrecht, Wageningen and Ghent have discovered the gene that causes dwarfism, and they hope to be able to determine how the condition develops in the horses. To accomplish this, they examined several dwarf Friesian horses and normal horses. According to the researchers, dwarfism is a recessive trait in the population, which means that the Friesian horses inherit dwarfism from both parents. The Friesian horse population in the Netherlands is very small, so the defective gene has a major impact on the current population. The researchers therefore recommend examining Friesian horses for the presence of the gene in order to prevent breeding two carriers of the gene together.
In humans, mutations in this gene cause two different rare diseases: Ehlers-Danlos syndrome and Larsen syndrome. These diseases result in defects and excessive flexibility in the limbs and joints.
The full research report is available here.