Genetic basis of Bilateral deafness with vestibular dysfunction - also known as Deafness with Vestibular Dysfunction or DINGS2 in Dobermans is caused by a missense mutation in the MYO7A gene. The specific mutation identified is a c.3719G>A (p.R1240Q) missense mutation in exon 28 of MYO7A, which encodes the unconventional myosin VIIa protein. This mutation is highly conserved and strongly associated with the disorder, affecting cochlear and vestibular sensory cells. The MYO7A gene mutation is inherited in an autosomal recessive manner: dogs must inherit two copies of the mutated gene to be affected, and carriers with one copy are clinically normal but can pass the mutation on. MYO7A encodes myosin VIIa, a motor protein crucial for cochlear hair cell stereocilia development and function, necessary for hearing and balance. Unlike humans, affected Dobermans do not show retinal abnormalities, suggesting this mutation affects hearing and vestibular functions but spares vision.
Pathophysiology - The mutation results in defective myosin VIIa protein function, leading to abnormal development and progressive degeneration of cochlear outer and inner hair cells. Damage to these sensory hair cells causes sensorineural hearing loss (deafness) and vestibular dysfunction (balance problems). Affected dogs exhibit bilateral sensorineural deafness and vestibular signs such as uncoordinated gait and head tilt. The disorder is congenital or manifests within the first weeks of life.
Complications - Dogs suffer from complete bilateral deafness often accompanied by vestibular signs like unsteady walking, falling, head tilting, and "bobbing" movements. Vestibular dysfunction can cause balance issues and difficulty with coordination. Dogs can develop progressive hearing loss and worsening vestibular signs. The condition is non-progressive in terms of vision—affected dogs have normal retinal function.
Why This Matters to Breeders and Vets - Genetic testing for the MYO7A mutation allows breeders to identify carriers and avoid producing affected puppies. Early identification and breeding management can reduce incidence in the Doberman population. Veterinarians benefit from awareness of the genetic basis to confirm diagnosis via genetic testing and differentiate this disorder from other causes of deafness or vestibular disease. Managing affected dogs includes safety precautions due to deafness and balance issues.
Summary - Bilateral Deafness in Doberman Pinschers caused by a recessive missense mutation in the MYO7A gene results in congenital sensorineural hearing loss and vestibular dysfunction without vision impairment. The MYO7A protein plays a vital role in cochlear hair cell function, and its deficit causes deafness and balance issues from early life. DNA testing is available, enabling breeders and veterinarians to effectively manage this inherited disorder and improve breed health.