Spongiform Leukoencephalomyelopathy
Gene : CYTB
Transmission : Mitochondrial DNA
Mitochondrial DNA is inherited from the mother. An affected mother transmits the disease to all of her descendants. An affected father does not transmit the disease.
Mutation : Substitution, mitochondrial gene CYTB; c.14474 G>A, p.(V98M)
Medical systems: Neurological, neuromuscular
Breeds : Australian Cattle Dog, Shetland Sheepdog
Age of onset of symptoms: between 6 to 12 months of age
Spongiform leukoencephalomyelopathy is a genetic neurological disease seen in the Shetland sheepdog and Australian cattle dog. Symptoms are first seen between 2 to 9 weeks of age and include tremors, ataxia, paresis/paralysis, spasms and cranial nerve dysfunction. Within nerve cells, myelin is not formed properly thus preventing the normal communication between nerve cells. Heredity of the disease is unusual because the defective gene is found in the mitochondrial genome. Since mitochondria are passed on only from the mother, an affected female passes the disease to all her offspring, while an affected male does not pass on the disease.
The term “spongiform” refers to the affected brain which looks like a sponge when viewed under a microscope. Leuco- refers to white matter in the brain; encephalo- refers to the brain, while myelo- refers to the spinal cord.
References:
OMIA link: [2684-9615]Tkaczyk-Wlizło A, Kowal K, Ślaska B. (2022) Mitochondrial DNA alterations in the domestic dog (Canis lupus familiaris) and their association with development of diseases: A review. Mitochondrion 63:72-84. [pubmed/35134592]
Li F-Y, Cuddon PA, Song J, et al. (2006) Canine spongiform leukoencephalomyelopathy is associated with a missense mutation in cytochrome b. Neurobiology of Disease 21 (1): 35–42. [pubmed/16026996]