Neuronal ceroid lipofuscinosis in Rambouillet sheep: characterization of the clinical disease

Manifestation of neuronal ceroid lipofuscinosis in Australian Merino sheep: observations on altered behaviour and growth

Neuronal ceroid lipofuscinoses (NCL) is an inherited neurodegenerative disorder in children. Presently there is no effective treatment and the disorder is lethal. NCL occur in a variety of non-human species including sheep, which are recognised as valuable large animal models for NCL. This experiment investigated the progressive postural, behavioural and liveweight changes in NCL-affected lambs, to establish practical, non-invasive biomarkers of disease progression for future preclinical trials in a CLN6 Merino sheep model. A flock of eight lambs at pasture was studied, with the observer blind to the disorder status. Three genotypes were compared: homozygous affected NCL; n = 4), clinically normal heterozygous (Carrier; n = 2) and homozygous normal (non-carrier control (Normal); n = 2). Direct observation during daylight and continuous accelerometer measurements over 72 h were used to quantify lamb posture and behaviour in 11 sessions between 26-60 weeks of age, conducted at 3-5 week intervals. There was a Genotype (G) × Age (A) interaction (P = 0.001) for liveweight of the lambs in the experiment, with NCL, Carrier and Normal lambs gaining 11.8, 16.5 and 23.4 kg, respectively, between 26 and 60 weeks of age. G×A interactions were also found for walking behaviour (means for NCL, Carrier and Normal genotype groups at 26 and 60 weeks, were 1.7 and 7.9%, 3.3 and 3.1%, and 2.5 and 1.9% of observations, P = 0.008) and a composite variable of key behaviours identified in the principal components analysis (P < 0.001), with mean values for NCL lambs increasing three-fold compared to non-affected lambs as age increased. Similarly, NCL lambs became less responsive to visual and auditory stimuli as they aged. Mean responsiveness scores (out of 3) to visual stimuli for the NCL, Carrier and Normal genotypes at 26 and 60 weeks of age were 2.7 and 1.4, 2.8 and 2.9, and 3.0 and 3.0, respectively (G × A, P < 0.001). Changes in response to auditory stimuli were similar to visual stimuli. NCL lambs took more (P = 0.015) steps per 24 h than Carrier and Normal genotype lambs, but there was no G × A interaction. At 26 and 60 weeks of age respectively, NCL lambs took 2724 and 4121 steps per 24 h, compared to Carrier (1708 and 3105 steps) and Normal genotype lambs (2109 and 3506 steps). NCL lambs also performed less (P = 0.018) grazing behaviour than Carrier and Normal genotype lambs (66.5, 72.3 and 72.5% of observations for NCL, Carrier and Normal lambs, respectively). A number of behavioural changes identified in the experiment could form the basis for a protocol for monitoring and evaluation of disease progression.

Use of model organisms for the study of neuronal ceroid lipofuscinosis

Neuronal ceroid lipofuscinoses are a group of fatal progressive neurodegenerative diseases predominantly affecting children. Identification of mutations that cause neuronal ceroid lipofuscinosis, and subsequent functional and pathological studies of the affected genes, underpins efforts to investigate disease mechanisms and identify and test potential therapeutic strategies. These functional studies and pre-clinical trials necessitate the use of model organisms in addition to cell and tissue culture models as they enable the study of protein function within a complex organ such as the brain and the testing of therapies on a whole organism. To this end, a large number of disease models and genetic tools have been identified or created in a variety of model organisms. In this review, we will discuss the ethical issues associated with experiments using model organisms, the factors underlying the choice of model organism, the disease models and genetic tools available, and the contributions of those disease models and tools to neuronal ceroid lipofuscinosis research. This article is part of a Special Issue entitled: The Neuronal Ceroid Lipofuscinoses or Batten Disease.

Lysosomal storage diseases of animals: an essay in comparative pathology

A wide variety of inherited lysosomal hydrolase deficiencies have been reported in animals and are characterized by accumulation of sphingolipids, glycolipids, oligosaccharides, or mucopolysaccharides within lysosomes. Inhibitors of a lysosomal hydrolase, e.g., swainsonine, may also induce storage disease. Another group of lysosomal storage diseases, the ceroid-lipofuscinoses, involve the accumulation of hydrophobic proteins, but their pathogenesis is unclear. Some of these diseases are of veterinary importance, and those caused by a hydrolase deficiency can be controlled by detection of heterozygotes through the gene dosage phenomenon or by molecular genetic techniques. Other of these diseases are important to biomedical research either as models of the analogous human disease and/or through their ability to help elucidate specific aspects of cell biology. Some of these models have been used to explore possible therapeutic strategies and to define their limitations and expectations.