Genetic basis - caused by a 12-base pair in-frame deletion in the EPS8L2 gene on canine chromosome 18 (CFA18). The specific mutation is c.1033_1044del12nt, p.(Val345_Leu348del) in exon 12 of EPS8L2. EPS8L2 is important for the maintenance and integrity of inner ear hair cells, crucial for hearing. The mutation disrupts EPS8L2 function, leading to progressive hearing loss.
Pathophysiology - The in-frame deletion likely alters protein structure, impairing its ability to maintain inner ear hair cells. This causes progressive degeneration of auditory function, resulting in deafness. Unlike other congenital deafness types, affected dogs show normal hearing at birth that declines during early life.
Complications - Progressive hearing loss affects communication and quality of life. Complete deafness may necessitate environmental adaptations for safety and well-being. No known association with other health problems.
Clinical Presentation - Dogs typically have normal hearing early postnatally. Hearing loss can be noticed as early as 4 months of age, progressing to complete deafness by 1 to 2 years of age. Both males and females are affected, with males sometimes showing earlier onset. The deafness is bilateral, progressive, and not linked to coat color or pigmentation.
Inheritance - The disorder follows an autosomal recessive inheritance pattern. Affected dogs are homozygous for the EPS8L2 deletion. Carriers have one copy of the mutation and do not show symptoms but can pass the mutation to offspring.
Why This Matters to Breeders and Vets - Early onset adult deafness in Rhodesian Ridgebacks is a distinct genetic disorder different from congenital or pigment-associated deafness. Understanding the genetic basis enables development of DNA tests to identify carriers and affected individuals. This has important implications for breeders, owners, and veterinary care, allowing for informed breeding strategies and earlier management.