The origin of the degenerative and painful equine disease has so far remained elusive to scientists. However, it is known to appear quite frequently in Thoroughbreds, Warmbloods, and purebred breeds such as Paints and Quarter Horses. It is also more prevalent in tall horses, and previous research has shown that it is hereditary. Together, these data indicate a genetic link, said Christa Lafayette, CEO of Etalon Diagnostics in Menlo Park, California.
Lafayette, a biotech and equestrian scientist, was inspired to discover that connection during a dinner conversation at the 2019 American Association of Equine Practitioners (AAEP) meeting in Denver, Colorado.
“I was sitting with some amazing equine vets at AAEP, and I literally wrote on a napkin what we hoped to be able to fix within the next year, and the genetics behind the kissing thorns was at the top of the list,” Lafayette said.
Shortly after returning from AAEP, Lafayette partnered with Beau Whitaker, DVM, of Brazos Valley Equine Hospital, in Salado, Texas, and Kent Allen, DVM, of Virginia Equine Imaging, at The Plains, who were also at that table. dining room of the AAEP – and many other engineers and researchers to take on the task of finding the “kissing thorn gene”.
The team performed genotyping on 155 Warmbloods and stock horse breeds that had presented to participating veterinarians’ clinics due to back pain and / or poor performance. Veterinary evaluations of the horses revealed that they ranged from having severe grade 4 backbones to none at all.
Genetics: an extra degree of severity for each copy
The team identified an associated variant, or allele, for kissing spines on chromosome 25. This BIEC2-668062 single nucleotide polymorphism (SNP) is linked to an average increase in the severity of a kiss for each of two copies of the kiss. allele of the horse (one for each parent).
This allele was unrelated to the height of the horses, which appears to be a separate and unique factor for kissing thorns, Lafayette said.
It was, however, in close proximity to a gene already known in other species to be associated with the proliferation of chondrocytes (a cell that produces cartilage), a sign sometimes observed histopathologically (under the microscope) with kissing spines, said Laura Patterson Rosa. , DVM, PhD, scientific consultant at Etalon Diagnostics and first author of the group’s study publication. “It was reassuring that one of the genes ‘close’ to our best marker was actually implicated earlier,” she said.
The discovered allele is not a causative to kiss the thorns, however. It’s just one of many factors linked to the development of the disease, including exercise, rider ability and weight, riding equipment and fit, core muscle strength, head and neck position, injury and lameness, Lafayette said.
“We believe this (genetic) correlation is a variant risk for a higher degree or severity of kissing spines and possibly for the development of the disease itself,” Lafayette said. The horse. “So instead of kissing grade 1 thorns, for example, they’re more likely to have grade 3 or 4.”
Smarter breeding and competition with kissing thorns
Armed with this new knowledge, breeders and owners can make informed decisions about horses carrying the risk variant, Lafayette and Patterson Rosa said.
“For example, if I have a stallion and I know he has a high risk of transmitting a spinal-related variant of the kiss, then I may not mate him with a mare who has the same disposition, because then my chances are much higher than that. the resulting foal will have high-quality kissing spines, ”he said.
As research continues, scientists may even find a causal mutation that could “provide the power to ‘stir up’ kissing thorns,” Patterson Rosa said.
As for saddle horses that have one or two copies of the endangered variant of kissing spines, Lafayette suggested taking a proactive and protective approach. Having the variant doesn’t mean they can’t keep working.
“Now suppose you have a horse that you bought for an event or for Western riding or whatever you plan on doing, and you find that it has a high risk of kissing thorns,” he explained. “So you’ll probably spend a little more time doing some back building exercises, maybe a little more dressage, maybe a little lighter on the back. You will pay a little more attention to the saddle fit and may even do the X-rays a little more proactively, because you know that horse is more likely to suffer from spines. “
The researchers stressed the importance of being able to work with real-world cases in veterinary clinics, with the collaboration of professionals and owners. “We immensely appreciate the way the community has embraced this effort,” said Patterson Rosa.
I study, Genomic loci associated with performance-limiting equine spinous processes (spines kissing), first appeared in Research in veterinary sciences in June 2022.