Using sequencing techniques, Brazilian scientists have revealed the genomic regions that may be responsible for hair curls. These regions not only code for follicle growth but also for neurological and behavioral functions, suggesting a genetic-biological link between whorls and temperament, said Gregório Miguel Ferreira de Camargo, PhD, of the School of Veterinary Medicine and of Animal Sciences from the Federal University of Bahia, in Salvador, Brazil.
The results confirm what many riders have long suspected about the various swirling patches of hair on horses’ heads and necks, he said.
“It has been previously reported that horses with whorls above the eye line are more difficult to handle than those with whorls in the eye line or below,” said Ferreira de Camargo, citing previous studies. . “The traits and behavior of the spire are associated. This correlation, in genetics, could be caused by two factors: linkage (two distinct genes are inherited together) and/or pleiotropy (a single gene codes for two distinct traits).
Ferreira de Camargo and colleagues genotyped partial genomes of 342 Quarter Horses to find candidate genes responsible for the number and location of whorls on the head and neck. They found genomic “windows” – regions likely to be linked to these traits – which together explained up to 80% of whorled genetic differences in individual horsesdepending on the character.
These windows included many genes linked to hair follicle growth, Ferreira de Camargo said. But interestingly, he said, some of those same genes also had known neurological and behavioral functions. For example, the KLF5 gene on chromosome ECA17 appears to be associated with the location of whorls on the head (above, at, or below eye level). In humans, this gene controls the repair and regrowth of hair follicles, but it is also known to be associated with chronic schizophrenia. And the number of whorls on the head appears to be at least partially determined by the SIRT1 gene on the ECA1 chromosome. This gene is expressed in the hair follicle and has been linked to depression and schizophrenia in previous studies. Other candidate genes in windows related to whorl number correlate with neurological disorders such as Parkinson’s disease, he said.
“These genomic regions are definitely associated with whorl formation,” said Ferreira de Camargo. Horse. “We are sure because we used whorled phenotypes and not follicular growth phenotypes. So, we specifically addressed the turns-based variation.
The results came as no surprise to Ferreira de Camargo and his team, he added. “In fact, we expected to find genomic regions that could be used to explain association by linkage or pleiotropy,” he said. “Fortunately, we were able to cast some hypotheses on the physiology behind the association of whorls and behavior.”
Future research should aim to realize genome-wide associations between whorls and temperament and detail the genomic regions identified in the current study, Ferreira de Camargo said.
Studies correlating whorls with performance characteristics — running, jumping or dressage ability, for example — could also be an important avenue of research, he added. Such research “could provide more practical results on whorls and even the development of genetic tests for selection,” Ferreira de Camargo said.
Lima DFPA, da Cruz VAR, Pereira GL, Curi RA, Costa RB, de Camargo GMF. Genomic regions associated with position and number of hair whorls in horses. Animals (Basel). 2021;11(10):2925. Published October 10, 2021. doi:10.3390/ani11102925