Hyperekplexia (Startle disease) in Galgo

The disease is characterized by an involuntary startle response associated with generalized or intermittent muscle rigidity. The startle reaction is triggered by unexpected input, such as noise or touch. Clinical signs are present from birth. Puppies are unable to walk or stand properly. Neonatal death is not uncommon due to the complications of feeding and breathing during hypertonic episodes of respiratory muscle hypertonicity/startle responses.

In the Spanish Galgo breed, hyperekplexia is caused by mutation c.1379_1380delCT in the SLC6A5 gene, encoding a neurotransmitter transporter. The mutation leads to the premature introduction of a stop codon and to the truncation of the protein to one third.

The mode of inheritance of the mutation is autosomal recessive. This means that only individuals who inherit the mutated gene from both parents will develop the disease. Carriers of the mutated gene are clinically healthy but pass the mutation on to their offspring. In the case of a mating between two heterozygous individuals, theoretically 25% of the offspring will be completely healthy, 50% of the offspring will be carriers and 25% of the offspring will inherit the mutated gene from both parents and will therefore be affected by the disease.

The genetic test can clearly reveal the genotype of the animal and is a useful tool for breeders to prevent unintentional breeding of affected puppies.

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References:

Murphy, S.C., Recio, A., de la Fuente, C., Guo, L.T., Shelton, G.D., Clark, L.A. : A glycine transporter SLC6A5 frameshift mutation causes startle disease in Spanish greyhounds. Hum Genet 138:509-513, 2019. Pubmed reference: 30847549