Researchers believe they have identified the gene that causes the deadly Naked Foal Syndrome (NFS).
It is a genetic disorder seen in Akhal-Teke horses for more than 75 years. Akhal-Tekes are popular for their speed, endurance, and distinctive metallic color with sheen. And it has been named as one of the most beautiful horse breeds in the world.
Naked Foal Syndrome is a monogenic autosomal recessive trait. The number of hairless foals derived from the Central Asia breed continues to grow.
The NFS horses are born hairless with dry, scaly skin and often die within days or months after birth. The reason for the early deaths is not known, although some hairless foals have survived for more than two years.
An international team of researchers based their findings on genome sequencing of two affected horses, two carriers, and 75 control horses from other breeds.
Researchers identified the ST14:c.388G>T nonsense variant as the most likely underlying genetic defect. When published in G3: Genes, Genomics Genetics, the scientists maintain genetic testing is the best way to avoid the breeding of foals with the condition.
They described the clinical and pathological phenotype of two Akhal-Teke horses with NFS. A male cremello foal was two years 10 months old and still alive at the time of the study’s revision. Compared to nonaffected horses of the same age, the colt had a growth delay and was small. The horse is bald, with only sparse and thin body hairs.
Mane and hairs at the tail are sparse or absent. Whiskers are present but sparse, curly, and abnormally short. And the horse’s eyelashes are missing.
The skin was dry and scaly in some body parts. The owner reported a persisting increase in tear flow. Multifocal scars and erosive lesions were present, possibly due to the missing physical protection of a normal hair coat. Researchers did not observe any abnormalities in the teeth or hooves.
The second horse was born in June 2016.
Veterinarians had to euthanize the filly at 21 days due to a “spontaneous leg fracture”. The skin and hair phenotype closely resembled the first horse. It also had normal teeth and hooves.
A necropsy revealed mild internal hydrocephalus, or fluid in the brain, a heart defect, and severely altered lymphoid organs. The histological findings in the lymphoid organs were consistent with a defect in primary immune organ development, and the specific immune response.
Researchers look at the ST14 gene, which has essential roles in the interfollicular epidermis by contributing to epidermal barrier formation as well as for hair follicle development.
The team is not clear why NFS affected foals have such a short, although varied life expectancy. Researchers say they need to study additional horses with NFS to characterize the pathologies leading to premature death in these horses.