The epitheliogenesis imperfecta locus maps to equine chromosome 8 in American Saddlebred horses.

The research focuses on a genetic disease in American Saddlebred foals called epitheliogenesis imperfecta (EI). The researchers traced the cause of the disease to a particular location on horse chromosome 8.

Research on Epitheliogenesis Imperfecta

• Epitheliogenesis imperfecta (EI) is a hereditary disease present in newborn American Saddlebred foals, a breed of horses.
• The disease is characterized by skin abnormalities and the symptoms closely match a similar disease in humans known as Herlitz junctional epidermolysis bullosa.

Linking Human and Horse Diseases

• The Herlitz junctional epidermolysis bullosa in humans is caused by a mutation in one of the genes (LAMA3, LAMB3, and LAMC2) coding the subunits of the laminin 5 protein.
• Similar to humans, the disease in horses is linked to these genes, with the LAMA3 gene being assigned to equine chromosome 8 and the LAMB3 and LAMC2 genes mapped to equine chromosome 5.

Examining the Genetic Cause

• The researchers analyzed the allele frequencies, or the rate at which certain gene variants appear in a population, at 11 locations in both affected and unaffected saddlebred horses.
• They found a significant difference in the allele frequencies at two specific points on horse chromosome 8 (ASB14 and AHT3) compared to the expected frequencies based on Hardy-Weinberg equilibrium (a principle used to measure genetic variation in a population).
• The researchers did not observe the same difference in allele frequencies at any points on horse chromosome 5, leading to the conclusion that the cause of the EI disease in these horses was most likely located on chromosome 8.

Conclusion

• The conclusion of the research is that the EI disease in American Saddlebred horses is linked to the LAMA3 gene, located on equine chromosome 8.
• This discovery could potentially aid in prevention and treatment strategies for affected horse populations, by providing a clearer understanding of the genetic cause of the disease.