An important English Thoroughbred stallion named Dark Ronald, who had an important influence on German horse breeding, is off the hook for the spread of Warmblood fragile foal syndrome, according to researchers.
Researchers from the universities of Göttingen and Halle in Germany have been able to prove that the disease did not stem from Dark Ronald, which had been the assumption until now.
Warmblood fragile foal syndrome is a severe, usually fatal, genetic disease that manifests itself after birth in affected horses. It leaves connective tissue is unstable. Under force, the skin can tear from the tissue underneath and the joints can suffer dislocation.
Scientists took an important step in 2012 toward solving the mystery of the defect when they identified the gene responsible.
It is called PLOD1 and normally ensures that collagen molecules in the skin and connective tissue can bind to form a stable network. The mutation in the PLOD1 gene prevents the “cross-linking” needed for stable collagen.
However, the exact origin of the mutation remained unclear.
Since the spread of the genetic defect is a problem in horse-breeding in Germany, more work was done in this area.
The Verden-based Vereinigte Informationssysteme Tierhaltung (IT-Solutions for Animal Production) determined the possible origin of the genetic defect last year after conducting tests on about 2000 horses and examining their pedigree records.
Its investigation concluded that the genetic defect was probably through Dark Ronald, who lived from 1905 to 1928, or his father, Bay Ronald. The defect was then spread through their offspring.
However, current research, led by the University of Göttingen, calls this theory into question.
“We have now succeeded in proving that Dark Ronald was not a carrier of the PLOD1 mutation and can, therefore, be excluded as the original source of this genetic defect,” says Professor Bertram Brenig, who is the director of the Institute of Veterinary Medicine at the University of Göttingen and lead author of the study.
Doubts about whether the mutation descended from Dark Ronald were first raised soon after the publication of the findings, and further investigation pointed to a Hanoverian stallion born in 1861.
Dark Ronald was an important Thoroughbred stallion in German breeding. He was sold to Germany in 1913 and was used as a stallion, first in Graditz and later in Altefeld.
In 1928, he was brought to the veterinary clinic of the University of Halle for treatment for intestinal colic, and he died there.
Since then his remains – including his skeleton, heart and skin – have been kept in one of the natural science collections of the Martin Luther University Halle-Wittenberg.
“This is most fortunate,” explains Brenig, “as it has allowed us to examine Dark Ronald directly for the presence of the PLOD1 mutation.”
The scientists were able to examine small pieces of Dark Ronald’s skin.
“Examining the DNA from the nearly 100-year-old skin of Dark Ronald was not easy,” said co-author Dr Renate Schafberg, from the University of Halle, “because we knew nothing about the tanning or other preservation treatments of the skin.”
The disease itself probably originated in the middle of the 18th century.
Breeding animals in Germany are now consistently tested for the genetic defect.
There is a comparable genetic disease in humans, known as Ehlers-Danlos syndrome, which shows similar symptoms.
Xuying Zhang et al. Skin exhibits of Dark Ronald XX are homozygous wild type at the Warmblood fragile foal syndrome causative missense variant position in lysyl hydroxylase gene PLOD1. Animal Genetics (2020). DOI: https://doi.org/10.1111/age.12972