NCL5 in Border Collies and Australian Cattle Dogs

Neuronal ceroid lipofuscinosis (NCL) is a neurodegenerative disorder which affects people, dogs and other animals (e.g. cattle, sheep, horses). In some animals the causal mutation leading to NCL has not been described yet. In connection with NCL in animals and people mutations in six different genes CLN 1,2,3,4,5,6,8 (Daly et al. 1998, Gupta et al. 2001) have been described for now. Each mutation in the given gene causes a unique form of NCL.

In the breed of border collies and australian cattle dogs causal mutation was found in connection with NCL in the position 619 coding the sequences of exon 4 of CLN5 gene. It is a single-base substitution (c.619C >T) which leads to formation of preliminary termination codon in position of 206 of CLN5 protein, resulting in shortening of the final protein by 144 amino acids (Melville et al. 2005). This shortening has probably very significant impact on the protein's function.

Typical for neuronal ceroid lipofuscinosis is accumulating of lipopigments (ceroid and lipofuscin) in lysosomes. Clinical symptoms can be observed quite early, around 15th month of a dog age. The beginning and clinical course of the disease vary greatly and are very individual. The rate of neurodegeneration increases together with the age, with psychical abnormalities and ataxy usually developing in all affected dogs. Increased restlessness, aggression, hallucinations, hyperactivity and epileptic attacks can be observed as well. Accompanying symptom is damaged retina due to lipopigment storage. Most affected dogs lose their ability of normal muscular coordination during training, walking and feeding. Affected young dogs rarely survive more 28th month of age (Studdert et al. 1991).

Occurrence of mutated allele in the population of border collies is rather rare (approximately 3,5%).

It is quite difficult to distinguish individual forms of NCL in individual dog breeds. NCL5 described in border collies and australian cattle dogs is very similar, with the range of symptoms and age of dog at onset of disease, to the NCL form diagnosed in English setters (NCL in English setters is caused by mutation in CLN8 gene, Katz et al. 2005).

NCL is inherited autosomally recessively which means that the disease develops only in those dogs who inherit mutated allele from both parents. Carriers of mutated allele (heterozygotes) are clinically healthy but transmit the mutation on their descendants. In case of mating two heterozygous dogs there is a theoretical chance that 25% of descendants will be absolutely healthy, 50% will be carriers a 25% will inherit from both parents mutated allele and therefore will be NCL affected.

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References:

Melville SA, Wilson CL, Chiang CS, Studdert VP, Lingaas F, Wilton AN. A mutation in canine CLN5 causes neuronal ceroid lipofuscinosis in Border collie dogs. Genomics. 2005 Sep;86(3):287-94

M.J. Daly, et al., GENEHUNTER 2.0-A complete linkage analysis system, Am. J. Hum. Genet. Suppl. 63 (1998) A286.

V.P. Studdert, R.W. Mitten, Clinical features of ceroid lipofuscinosis in Border collie dogs, Aust. Vet. J. 68 (1991) 137- 140.

P. Gupta, et al., Disruption of PPT1 or PPT2 causes neuronal ceroid lipofuscinosis in knockout mice, Proc. Natl. Acad. Sci. USA 98 (2001)13566-13571.

M.L. Katz, et al., A mutation in the CLN8 gene in English setter dogs with neuronal ceroid-lipofuscinosis, Biochem. Biophys. Res. Commun.327 (2005) 541- 547.