SDCA1 – Spongy degeneration with cerebellar ataxia Belgian Shepherd type
SDCA1 stands for spongy degeneration with cerebellar ataxia type 1 and it is a severe neurodegenerative disorder with an eary onset. The disease affects the Belgian Malinois (Belgian Shepherd) dog breed and it is caused by a mutation in the KCNJ10 gene. SDCA1 is equivalent to EAST syndrome in humans, characterized by epilepsy, ataxia, sensorineural deafness and renal salt wasting tubulopathy.
KCNJ10 gene encodes a potassium channel, which is expressed in the central nervous system (CNS), eye, inner ear, and kidney. These channels play a crucial role in modulation of neuronal cells’ membrane potential and neuron cell excitation.
Characteristics and Symptoms
Affected puppies start to display symptoms already before 2 months of age. Puppies show wide-based ataxic gait, which is more prominent in the hind limbs. Movement is accompanied with stumbling, staggering, intention tremor, bunny hopping, balance loss and falling. Exercise or stress may induce episodes of muscle spasms together with an aggravation of cerebellar symptoms. Affected puppies have seizures and rapid progression of clinical signs. Affected puppies are usually euthanized due to the severity of the symptoms.
Spongy degeneration with cerebellar ataxia in Belgian Shepherds SDCA1 is caused by a mutation in the KCNJ10 gene. The mutation is likely to occur in several other closely related breeds, i.e. Belgian Tervueren, Belgian Sheepdog (Groenendael), and Belgian Laekenois. The disorder is inherited in an autosomal recessive manner. Dog carrying one copy of the mutated gene is heterozygous and will not show the SDCA1 symptoms. When mating two carriers (heterozygotes) at conception each cub has a 25% chance of being affected, a 50% chance of being an asymptomatic carrier, and a 25% chance of being unaffected and not a carrier. Currently there is no cure for spongy degeneration with cerebellar ataxia in Belgian Shepherds.
Mauri, N., et al. (2016). A Missense Variant in KCNJ10 in Belgian Shepherd Dogs Affected by Spongy Degeneration with Cerebellar Ataxia (SDCA1). G3: Genes| Genomes| Genetics: g3-116.
Van Poucke, M., Stee, K., Bhatti, S. F., Vanhaesebrouck, A., Bosseler, L., Peelman, L. J., & Van Ham, L. (2017). The novel homozygous KCNJ10 c. 986T> C (p.(Leu329Pro)) variant is pathogenic for the SeSAME/EAST homologue in Malinois dogs. European Journal of Human Genetics, 25(2), 222-226.
Kleiter, M., Hogler, S., Kneissl, S., Url, A., Leschnik M. (2011). Spongy Degeneration with Cerebellar Ataxia in Malinois Puppies: A Hereditary Autosomal Recessive Disorder? J Vet Intern Med. 2011 May-Jun;25(3):490-6.