The neuronal ceroid-lipofuscinoses (Batten disease): comparative aspects

Screening and Carrier Rate of Neuronal Ceroid Lipofuscinosis in Chihuahua Dogs in Japan

Neuronal ceroid lipofuscinosis (NCL) is a group of rare lethal neurodegenerative lysosomal storage diseases that occur in a range of dog breeds, including Chihuahuas. Recently, a homozygous single base-pair deletion (c.846delT), which causes a frame shift generating a premature stop codon (p.Phe282Leufs13*) in the canine CLN7/MFSD8 gene, has been identified as a causative mutation for NCL in Chihuahuas. The objective of this study was to determine the frequency of the mutant allele and/or carrier rate of NCL in Chihuahuas in Japan using a newly designed real-time PCR assay. Samples of saliva were randomly collected from 1007 Chihuahua puppies during physical examinations prior to the transportation to pet shops. Screening results revealed a carrier rate of 1.29%, indicating a mutant allele frequency (0.00645) that is considered sufficiently high to warrant measures for the control and prevention of this lethal disease. The genotyping assay designed in this study could make a valuable contribution to the control and prevention of NCL.

ATP13A2 missense variant in Australian Cattle Dogs with late onset neuronal ceroid lipofuscinosis

The neuronal ceroid lipofuscinoses (NCLs) are lysosomal storage disorders characterized by progressive neurodegeneration and declines in neurological functions. Pathogenic sequence variants in at least 13 genes underlie different forms of NCL, almost all of which are recessively inherited. To date 13 sequence variants in 8 canine orthologs of human NCL genes have been found to occur in 11 dog breeds in which they result in progressive neurological disorders similar to human NCLs. Canine NCLs can serve as models for preclinical evaluation of therapeutic interventions for these disorders. In most NCLs, the onset of neurological signs occurs in childhood, but some forms have adult onsets. Among these is CLN12 disease, also known as Kufor-Rakeb syndrome, PARK9, and spastic paraplegia78. These disorders result from variants in ATP13A2 which encodes a putative transmembrane ion transporter important for lysosomal function. Three Australian Cattle Dogs (a female and two of her offspring) were identified with a progressive neurological disorder with an onset of clinical signs at approximately 6 years of age. The affected dogs exhibited clinical courses and histopathology characteristic of the NCLs. Whole genome sequence analysis of one of these dogs revealed a homozygous c.1118C > T variant in ATP13A2 that predicts a nonconservative p.(Thr373Ile) amino acid substitution. All 3 affected dogs were homozygous for this variant, which was heterozygous in 42 of 394 unaffected Australian Cattle Dogs, the remainder of which were homozygous for the c.1118C allele. The high frequency of the mutant allele in this breed suggests that further screening for this variant should identify additional homozygous dogs and indicates that it would be advisable to perform such screening prior to breeding Australian Cattle Dogs.

Tracking sex-dependent differences in a mouse model of CLN6-Batten disease

Background

CLN6-Batten disease is a rare neurodevelopmental disorder characterized pathologically by the accumulation of lysosomal storage material, glial activation and neurodegeneration, and phenotypically by loss of vision, motor coordination, and cognitive ability, with premature death occurring in the second decade of life. In this study, we investigate whether sex differences in a mouse model of CLN6-Batten disease impact disease onset and progression.

Results

A number of noteworthy differences were observed including elevated accumulation of mitochondrial ATP synthase subunit C in the thalamus and cortex of female Cln6 mutant mice at 2 months of age. Moreover, female mutant mice showed more severe behavioral deficits. Beginning at 9 months of age, female mice demonstrated learning and memory deficits and suffered a more severe decline in motor coordination. Further, compared to their male counterparts, female animals succumbed to the disease at a slightly younger age, indicating an accelerated disease progression. Conversely, males showed a marked increase in microglial activation at 6 months of age in the cortex relative to females.

Conclusions

Thus, as female Cln6 mutant mice exhibit cellular and behavioral deficits that precede similar pathologies in male mutant mice, our findings suggest the need for consideration of sex-based differences in CLN6 disease progression during development of preclinical and clinical studies.

Electronic supplementary material

The online version of this article (10.1186/s13023-019-0994-8) contains supplementary material, which is available to authorized users.

Canine neuronal ceroid lipofuscinoses: Promising models for preclinical testing of therapeutic interventions

The neuronal ceroid lipofuscinoses (NCLs) are devastating inherited progressive neurodegenerative diseases, with most forms having a childhood onset of clinical signs. The NCLs are characterized by progressive cognitive and motor decline, vision loss, seizures, respiratory and swallowing impairment, and ultimately premature death. Different forms of NCL result from mutations in at least 13 genes. The clinical signs of some forms overlap significantly, so genetic testing is the only way to definitively determine which form an individual patient suffers from. At present, an effective treatment is available for only one form of NCL. Evidence of NCL has been documented in over 20 canine breeds and in mixed-breed dogs. To date, 12 mutations in 8 different genes orthologous to the human NCL genes have been found to underlie NCL in a variety of dog breeds. A Dachshund model with a null mutation in one of these genes is being utilized to investigate potential therapeutic interventions, including enzyme replacement and gene therapies. Demonstration of the efficacy of enzyme replacement therapy in this model led to successful completion of human clinical trials of this treatment. Further research into the other canine NCLs, with in-depth characterization and understanding of the disease processes, will likely lead to the development of successful therapeutic interventions for additional forms of NCL, for both human patients and animals with these disorders.

Retinal Degeneration In A Mouse Model Of CLN5 Disease Is Associated With Compromised Autophagy

The Finnish variant of late infantile neuronal ceroid lipofuscinosis (CLN5 disease) belongs to a family of neuronal ceroid lipofuscinosis (NCLs) diseases. Vision loss is among the first clinical signs in childhood forms of NCLs. Mutations in CLN5 underlie CLN5 disease. The aim of this study was to characterize how the lack of normal functionality of the CLN5 protein affects the mouse retina. Scotopic electroretinography (ERG) showed a diminished c-wave amplitude in the CLN5 deficient mice already at 1 month of age, indicative of pathological events in the retinal pigmented epithelium. A- and b-waves showed progressive impairment later from 2 and 3 months of age onwards, respectively. Structural and immunohistochemical (IHC) analyses showed preferential damage of photoreceptors, accumulation of autofluorescent storage material, apoptosis of photoreceptors, and strong inflammation in the CLN5 deficient mice retinas. Increased levels of autophagy-associated proteins Beclin-1 and P62, and increased LC3b-II/LC3b-I ratio, were detected by Western blotting from whole retinal extracts. Photopic ERG, visual evoked potentials, IHC and cell counting indicated relatively long surviving cone photoreceptors compared to rods. In conclusion, CLN5 deficient mice develop early vision loss that reflects the condition reported in clinical childhood forms of NCLs. The vision loss in CLN5 deficient mice is primarily caused by photoreceptor degeneration.

Australian Cattle Dogs with Neuronal Ceroid Lipofuscinosis are Homozygous for a CLN5 Nonsense Mutation Previously Identified in Border Collies

Background

Neuronal ceroid lipofuscinosis (NCL), a fatal neurodegenerative disease, has been diagnosed in young adult Australian Cattle Dogs.

Objective

Characterize the Australian Cattle Dog form of NCL and determine its molecular genetic cause.

Animals

Tissues from 4 Australian Cattle Dogs with NCL‐like signs and buccal swabs from both parents of a fifth affected breed member. Archived DNA samples from 712 individual dogs were genotyped.

Methods

Tissues were examined by fluorescence, electron, and immunohistochemical microscopy. A whole‐genome sequence was generated for 1 affected dog. A TaqMan allelic discrimination assay was used for genotyping.

Results

The accumulation of autofluorescent cytoplasmic storage material with characteristic ultrastructure in tissues from the 4 affected dogs supported a diagnosis of NCL. The whole‐genome sequence contained a homozygous nonsense mutation: CLN5:c.619C>T. All 4 DNA samples from clinically affected dogs tested homozygous for the variant allele. Both parents of the fifth affected dog were heterozygotes. Archived DNA samples from 346 Australian Cattle Dogs, 188 Border Collies, and 177 dogs of other breeds were homozygous for the reference allele. One archived Australian Cattle Dog sample was from a heterozygote.

Conclusions and Clinical Importance

The homozygous CLN5 nonsense is almost certainly causal because the same mutation previously had been reported to cause a similar form of NCL in Border Collies. Identification of the molecular genetic cause of Australian Cattle Dog NCL will allow the use of DNA tests to confirm the diagnosis of NCL in this breed.

Large animal models of rare genetic disorders: sheep as phenotypically relevant models of human genetic disease

Animals that accurately model human disease are invaluable in medical research, allowing a critical understanding of disease mechanisms, and the opportunity to evaluate the effect of therapeutic compounds in pre-clinical studies. Many types of animal models are used world-wide, with the most common being small laboratory animals, such as mice. However, rodents often do not faithfully replicate human disease, despite their predominant use in research. This discordancy is due in part to physiological differences, such as body size and longevity. In contrast, large animal models, including sheep, provide an alternative to mice for biomedical research due to their greater physiological parallels with humans. Completion of the full genome sequences of many species, and the advent of Next Generation Sequencing (NGS) technologies, means it is now feasible to screen large populations of domesticated animals for genetic variants that resemble human genetic diseases, and generate models that more accurately model rare human pathologies. In this review, we discuss the notion of using sheep as large animal models, and their advantages in modelling human genetic disease. We exemplify several existing naturally occurring ovine variants in genes that are orthologous to human disease genes, such as the Cln6 sheep model for Batten disease. These, and other sheep models, have contributed significantly to our understanding of the relevant human disease process, in addition to providing opportunities to trial new therapies in animals with similar body and organ size to humans. Therefore sheep are a significant species with respect to the modelling of rare genetic human disease, which we summarize in this review.

Recent studies of ovine neuronal ceroid lipofuscinoses from BARN, the Batten Animal Research Network

Studies on naturally occurring New Zealand and Australian ovine models of the neuronal ceroid-lipofuscinoses (Batten disease, NCLs) have greatly aided our understanding of these diseases. Close collaborations between the New Zealand groups at Lincoln University and the University of Otago, Dunedin, and a group at the University of Sydney, Australia, led to the formation of BARN, the Batten Animal Research Network. This review focusses on presentations at the 14th International Conference on Neuronal Ceroid Lipofuscinoses (Batten Disease), recent relevant background work, and previews of work in preparation for publication. Themes include CLN5 and CLN6 neuronal cell culture studies, studies on tissues from affected and control animals and whole animal in vivo studies. Topics include the effect of a CLN6 mutation on endoplasmic reticulum proteins, lysosomal function and the interactions of CLN6 with other lysosomal activities and trafficking, scoping gene-based therapies, a molecular dissection of neuroinflammation, identification of differentially expressed genes in brain tissue, an attempted therapy with an anti-inflammatory drug in vivo and work towards gene therapy in ovine models of the NCLs. This article is part of a Special Issue entitled: "Current Research on the Neuronal Ceroid Lipofuscinoses (Batten Disease)".

Neuronal ceroid lipofuscinosis in Border Collie dogs in Japan: clinical and molecular epidemiological study (2000-2011)

Neuronal ceroid lipofuscinosis (NCL) is an inherited, neurodegenerative lysosomal disease that causes premature death. The present study describes the clinical and molecular epidemiologic findings of NCL in Border Collies in Japan for 12 years, between 2000 and 2011. The number of affected dogs was surveyed, and their clinical characteristics were analyzed. In 4 kennels with affected dogs, the dogs were genotyped. The genetic relationships of all affected dogs and carriers identified were analyzed. The survey revealed 27 affected dogs, but there was a decreasing trend at the end of the study period. The clinical characteristics of these affected dogs were updated in detail. The genotyping survey demonstrated a high mutant allele frequency in examined kennels (34.8%). The pedigree analysis demonstrated that all affected dogs and carriers in Japan are related to some presumptive carriers imported from Oceania and having a common ancestor. The current high prevalence in Japan might be due to an overuse of these carriers by breeders without any knowledge of the disease. For NCL control and prevention, it is necessary to examine all breeding dogs, especially in kennels with a high prevalence. Such endeavors will reduce NCL prevalence and may already be contributing to the recent decreasing trend in Japan.

Novel rapid genotyping assays for neuronal ceroid lipofuscinosis in Border Collie dogs and high frequency of the mutant allele in Japan

Neuronal ceroid lipofuscinosis (NCL) constitutes a group of recessively inherited lysosomal storage diseases that primarily affect neuronal cells. Such diseases share certain clinical and pathologic features in human beings and animals. Neuronal ceroid lipofuscinosis in Border Collie dogs was first detected in Australia in the 1980s, and the pathogenic mutation was shown to be a nonsense mutation (c.619C>T) in exon 4 in canine CLN5 gene. In the present study, novel rapid genotyping assays including polymerase chain reaction (PCR)-restriction fragment length polymorphism, PCR primer-induced restriction analysis, mutagenically separated PCR, and real-time PCR with TaqMan minor groove binder probes, were developed. The utility of microchip electrophoresis was also evaluated. Furthermore, a genotyping survey was carried out in a population of Border Collies in Japan using these assays to determine the current allele frequency in Japan, providing information to control and prevent this disease in the next stage. All assays developed in the current study are available to discriminate these genotypes, and microchip electrophoresis showed a timesaving advantage over agarose gel electrophoresis. Of all assays, real-time PCR was the most suitable for large-scale examination because of its high throughput. The genotyping survey demonstrated that the carrier frequency was 8.1%. This finding suggested that the mutant allele frequency of NCL in Border Collies is high enough in Japan that measures to control and prevent the disease would be warranted. The genotyping assays developed in the present study could contribute to the prevention of NCL in Border Collies.

A missense mutation in canine CLN6 in an Australian shepherd with neuronal ceroid lipofuscinosis

The childhood neuronal ceroid lipofuscinoses (NCLs) are inherited neurodegenerative diseases that are progressive and ultimately fatal. An Australian Shepherd that exhibited a progressive neurological disorder with signs similar to human NCL was evaluated. The cerebral cortex, cerebellum, and retina were found to contain massive accumulations of autofluorescent inclusions characteristic of the NCLs. Nucleotide sequence analysis of DNA from the affected dog identified a T to C variant (c.829T>C) in exon 7 of CLN6. Mutations in the human ortholog underlie a late-infantile form of NCL in humans. The T-to-C transition results in a tryptophan to arginine amino acid change in the predicted protein sequence. Tryptophans occur at homologous positions in the CLN6 proteins from all 13 other vertebrates evaluated. The c.829T>C transition is a strong candidate for the causative mutation in this NCL-affected dog. Dogs with this mutation could serve as a model for the analogous human disorder.

Accumulation of glial fibrillary acidic protein and histone H4 in brain storage bodies of Tibetan terriers with hereditary neuronal ceroid lipofuscinosis

The neuronal ceroid lipofuscinoses (NCLs) are inherited neurodegenerative diseases characterized by massive accumulation of autofluorescent storage bodies in neurons and other cells. A late-onset form of NCL occurs in Tibetan terrier dogs. Gel electrophoretic analyses of isolated storage body proteins from brains of affected dogs indicated that a protein of approximately 50 kDa was consistently prominent and a 16 kDa component was present in some brain storage body preparations. Mass spectral analysis identified the 50 kDa protein as glial fibrillary acidic protein (GFAP), isoform 2. GFAP identification was supported by immunoblot and immunohistochemical analyses. Histone H4 was the major protein in the 16 kDa component. Specific accumulation of GFAP and histone H4 in storage bodies has not been previously reported for any of the NCLs. Tibetan terrier NCL may be the canine correlate of one of the human adult-onset NCLs for which the genetic bases and storage body compositions have not yet been determined.

Neuronal ceroid lipofuscinosis: clinical and morphologic findings in nine affected Polish Owczarek Nizinny (PON) dogs

OBJECTIVE

The aim of this study was to characterize the clinical and morphologic features of neuronal ceroid lipofuscinosis (NCL) in the Polish Owczarek Nizinny (PON) breed of dog.

ANIMALS

Nine Swedish PON dogs of both sexes were included in the study.

PROCEDURE

All dogs underwent a detailed clinical evaluation, with emphasis on ophthalmic exams. Histopathology and electron microscopy were performed on the eyes, brain and various internal organs. Immunohistochemical staining for detection of sphingolipid activator proteins (SAPs) and mitochondrial ATP synthase (SCMAS) was performed on the eyes and brain.

RESULTS

The dogs showed behavioral abnormalities, motor disturbances and visual impairment or blindness. Pupillary responses were abnormal while fundus changes varied from normal to severe retinal atrophy. Electroretinography (ERG) showed variable changes, from slight alterations in the process of dark adaptation to severely reduced or nonrecordable ERG a- and b-wave amplitudes. Histopathology revealed intracytoplasmic storage bodies within neurons of the brain and in retinal cells, especially the retinal pigment epithelium (RPE). Round to oval granular type of inclusion bodies, known as granular osmiophilic dense deposits (GRODS), were found in neuronal cells in the brain and in the retina. Immunohistochemistry identified the storage material in the brain and retina as consisting of SAPs.

CONCLUSION

The presently described NCL disease in PON dogs shows similarities to previously recorded cases in the Miniature Schnauzer. The closest human equivalent to this disease is infantile NCL (CLN1), in which the major stored proteins are SAPs and the ultrastructure of the inclusion bodies of neuronal cells is granular.

Ocular phenotype in a mouse gene knockout model for infantile neuronal ceroid lipofuscinosis

Mutations in the human protein palmitoyl thioesterase-1 (PPT-1) gene result in an autosomal recessive neurodegenerative disorder designated neuronal ceroid lipofuscinosis (NCL), type CLN1, or infantile NCL. Among the symptoms of the CLN1 disease are accumulation of autofluorescent lysosomal storage bodies in neurons and other cell types, seizures, motor and cognitive decline, blindness, and premature death. Development of an effective therapy for this disorder will be greatly assisted by the availability of suitable animal models. A mouse PPT-1 gene knockout model has recently been generated. Studies were performed to determine whether the mouse model exhibits ocular features of the human CLN1 disorder. A progressive accumulation of autofluorescent storage material in all layers of the retina was observed in the PPT-1 knockout mice. Accompanying the storage body accumulation was a modest loss of cells with nuclei in the outer and inner nuclear layers. As indicated by electroretinogram (ERG) responses, retinal function was only mildly impaired at 4 months of age but was severely impaired by 8 months, despite only modest changes in retinal morphology. The pupillary light reflex (PLR), on the other hand, was exaggerated in the knockout mice. The apparent anomaly between the ERG and the PLR findings suggests that disease-related PLR changes may be due to changes in extraocular signal processing. The pronounced ocular phenotype in the PPT-1 knockout mice makes these animals a good model for testing therapeutic interventions for treatment of the human CLN1 disorder.

A missense mutation (c.184C>T) in ovine CLN6 causes neuronal ceroid lipofuscinosis in Merino sheep whereas affected South Hampshire sheep have reduced levels of CLN6 mRNA

The neuronal ceroid lipofuscinoses (NCLs, Batten disease) are a group of fatal recessively inherited neurodegenerative diseases of humans and animals characterised by common clinical signs and pathology. These include blindness, ataxia, dementia, behavioural changes, seizures, brain and retinal atrophy and accumulation of fluorescent lysosome derived organelles in most cells. A number of different variants have been suggested and seven different causative genes identified in humans (CLN1, CLN2, CLN3, CLN5, CLN6, CLN8 and CTSD). Animal models have played a central role in the investigation of this group of diseases and are extremely valuable for developing a better understanding of the disease mechanisms and possible therapeutic approaches. Ovine models include flocks of affected New Zealand South Hampshires and Borderdales and Australian Merinos. The ovine CLN6 gene has been sequenced in a representative selection of these sheep. These investigations unveiled the mutation responsible for the disease in Merino sheep (c.184C>T; p.Arg62Cys) and three common ovine allelic variants (c.56A>G, c.822G>A and c.933_934insCT). Linkage analysis established that CLN6 is the gene most likely to cause NCL in affected South Hampshire sheep, which do not have the c.184C>T mutation but show reduced expression of CLN6 mRNA in a range of tissues as determined by real-time PCR. Lack of linkage precludes CLN6 as a candidate for NCL in Borderdale sheep.

Neuronal ceroid lipofuscinosis in Devon cattle is caused by a single base duplication (c.662dupG) in the bovine CLN5 gene

The neuronal ceroid lipofuscinoses (NCLs, Batten disease) are recessively inherited neurodegenerative disorders that affect humans and other animals, characterised by brain atrophy and the accumulation of lysosome derived fluorescent storage bodies in neurons and most other cells. Common clinical signs include blindness, ataxia, dementia, seizures and premature death. The associated genes for six different human forms have been identified (CLN1, CLN2, CLN3, CLN5, CLN6 and CLN8), and three other human forms suggested (CLNs 4, 7 and 9). A form of NCL in Australian Devon cattle is caused by a single base duplication (c.662dupG) in bovine CLN5. This mutation causes a frame-shift and premature termination (p.Arg221GlyfsX6) which is predicted to result in a severely truncated protein, analogous to disease causing mutations in human Finnish late infantile variant NCL (CLN5), and a simple genetic diagnostic test has been developed. The symptoms and disease course in cattle also matches CLN5. Only one initiation site was found in the bovine gene, equivalent to the third of four possible initiation sites in the human gene. As cattle are anatomically and physiologically similar to humans with a human-like central nervous system and easy to maintain and breed, they provide a valuable alternative model for CLN5 studies.

The neuronal ceroid-lipofuscinoses. Recent advances

The neuronal ceroid lipofuscinoses (NCLs) represent a group of neurodegenerative disorders characterised by progressive visual failure, neurodegeneration, epilepsy and the accumulation of an autofluorescent lipopigment in neurons and other cells. The main childhood subtypes are infantile (INCL;CLN1), classical late infantile (LINCL;CLN2) and juvenile NCL (JNCL;CLN3), distinguished on the basis of age of onset, clinical course and ultrastructural morphology, and recently genetic analysis. In addition several variant forms of the disease complex have been described as well as a rare adult onset form. Advances in both genetics and biochemistry have led to the identification of the genes for the three main subtypes of childhood NCL and their corresponding protein products and to mapping of two additional genes for two variant forms. The disease causing genes in both INCL and classical LINCL have been shown to encode lysosomal enzymes whilst the JNCL gene codes for a protein whose function is as yet unknown.

The development and characterisation of complex ovine neuron cultures from fresh and frozen foetal neurons

Cultures of ovine cerebral and cerebellar neurons from mid-term sheep foetal brains, 9-15 weeks old, have been established for the first time. These foetal brains are relatively mature, being at similar stages of development as peri and post-natal rodent brains. Cultures were routinely maintained for 3-4 weeks, and longer. Nearly all the cells from the younger foetuses adhered as neurons. The proportion of glial cells increased with age, as did the risk of cultures being overtaken by glial cells. Cultured neurons were bipolar, tripolar and multipolar, similar to the morphologies of neurons in vivo. Older foetuses also yield more complex neurons, notably giant cells. Other properties of the cultured neurons also mimic in vivo observations, including neurite beading, complexity in neurotransmitter class (GABAergic and glutamatergic) and calcium binding protein (calbindin and calretinin) content. Single cell divisions of neurons were observed in younger cultures by time-lapse photography and the occurrence of telophase nuclei. The advantage of the high yield of genetically identical cells obtained from a single sheep foetus, 150 million, was extended by cryopreservation of neurons after snap freezing, and later culture. These cultures showed the same characteristics as cultures from the freshly plated cells.

Assessment of retinal function and characterization of lysosomal storage body accumulation in the retinas and brains of Tibetan Terriers with ceroid-lipofuscinosis

OBJECTIVE

To characterize lysosomal storage body accumulation in the retina and brain of Tibetan Terriers with ceroid-lipofuscinosis and determine whether the disease in these dogs is accompanied by impaired retinal function and retinal degeneration.

ANIMALS

Three 7- to 10-year-old Tibetan Terriers with ceroid-lipofuscinosis and 1 healthy 5-year-old Tibetan Terrier.

PROCEDURE

Owners completed a questionnaire to identify behavioral and physical signs indicative of ceroid-lipofuscinosis. Neurologic, behavioral, and ophthalmologic evaluations, including full-field electroretinograms, were performed on each dog. Fluorescence, light, and electron microscopy were performed on specimens of retina, cerebral cortex, and cerebellum of all dogs postmortem.

RESULTS

Behavioral assessments of the affected dogs revealed moderate visual impairment in low-light conditions but good vision in bright light. On funduscopic evaluation of these dogs, abnormalities detected ranged from none to signs of moderately advanced retinal degeneration. Compared with findings in the control dog, electroretinography revealed depressed rod cell function with some impairment of cone cell function in the affected dogs. Morphologically, disease-specific storage bodies were detected in retinal Müller cells and neurons, particularly in ganglion cells, and in cells of the cerebral cortex and cerebellum in affected dogs. Substantial photoreceptor cell loss and disruption of photoreceptor outer segment morphology appeared to develop late in the disease. IMPLICATIONS FOR HUMAN MEDICINE: The similarities between ceroid-lipofuscinosis in Tibetan Terriers and some forms of ceroid-lipofuscinosis in humans suggest that the canine disease may have a genetic and biochemical basis similar to that of one of the ceroid-lipofuscinosis disorders in humans.

The expression of tripeptidyl peptidase I in various tissues of rats and mice

To understand the precise distribution of tripeptidyl peptidase I (TPP-I), a defect of which has been shown to induce late infantile neuronal ceroid lipofuscinosis, various tissues from rats and mice were analyzed using biochemical and immunohistochemical techniques. Western blot analyses showed that a protein band immunoreactive to anti-TPP-I appeared in tissue extracts of both animals at a molecular weight of approximately 47 kD. Protein levels of TPP-I differed among tissues; they were high in the rat brain, liver, stomach, kidney, thyroid and adrenal glands and in the mouse brain, stomach, kidney, and testis. The proteolytic activity of TPP-I was detectable; it differed in the tissues examined and did not always reflect the expression levels of the protein in the tissues. In particular, the TPP-I activity was low in the brains of both animals and high in the rat testis, although its protein levels were high in the former tissue and low in the latter. Double immunostaining showed the immunoreactivity for TPP-I to be well localized in granular structures of epithelial cells in renal tubules and the cerebral choroid plexus, both of which were also stained with lamp2, a lysosomal membrane protein marker, indicating that TPP-I is a lysosomal enzyme. The immunoreactivity was intense in F4/80-immunopositive macrophages/microglial cells located in various tissues including the thymus, spleen, liver, alimentary tract, and central nervous system. Although the immunoreactivity differed depending on the tissues and even within the same tissues between the species, it was detected in all tissues examined, especially in nerve cells, some types of endocrine cells, and oxyntic cells such as gastric parietal cells and bone osteoclasts. However, the immunoreactivity was faint and week in rat thyroid gland, although its protein level was high in the tissue. These lines of evidence suggest that TPP-I, a lysosomal serine proteinase, is widely distributed in rat and mouse tissues, although its expression levels vary among them.

Assessment of plasma carnitine concentrations in relation to ceroid lipofuscinosis in Tibetan Terriers

OBJECTIVE

To determine whether the late onset form of inherited ceroid lipofuscinosis (CL) in Tibetan Terriers is accompanied by low plasma carnitine concentrations prior to the appearance of clinical signs.

ANIMALS

129 healthy Tibetan Terriers, 12 Tibetan Terriers with CL, and 95 healthy purebred dogs of other breeds.

PROCEDURE

After withholding food, blood samples were collected from all dogs into tubes containing EDTA. Blood samples were analyzed for plasma-free carnitine and acyl-carnitines concentrations.

RESULTS

Neither the mean plasma total carnitine concentration nor the mean fraction of carnitine in the free form differed significantly between Tibetan Terriers with CL and healthy Tibetan Terriers. Among Tibetan Terriers and the general dog population, plasma carnitine concentration increased with age. Castrated males had an overall increase in plasma carnitine concentrations and variability, compared with sexually intact males. By comparison, plasma carnitine concentrations were not significantly different between spayed and sexually intact females. The mean plasma carnitine concentration in the Tibetan Terriers was approximately 22% higher than in the general population of healthy dogs of other breeds.

CONCLUSIONS AND CLINICAL RELEVANCE

Contrary to what is seen in early onset CL in English Setters and in humans with some forms of CL, plasma carnitine concentrations are not decreased in the late-onset disorder in Tibetan Terriers. Our large-scale study establishes reference range values for plasma carnitine concentrations in dogs as functions of age and sex that will be useful in evaluating potential carnitine deficiencies in other disorders in dogs.

Neuronal ceroid lipofuscinosis in Merino sheep

OBJECTIVE

To characterise neuronal ceroid lipofuscinosis (NCL) in Merino sheep.

DESIGN

A prospective clinical, pathological, biochemical and genetic study.

PROCEDURE

NCL cases were studied from a medium-wool Merino flock, the stud of origin of its replacement rams, and an experimental flock established at the University of Sydney.

RESULTS

Behavioural changes and visual impairment were first detected at 7 to 12 months of age and progressed, with associated motor disturbances and at later stages seizures, to premature death by 27 months of age. At necropsy there was severe cerebrocortical atrophy associated with neuronal loss, astrocytosis and the presence in neurons of eosinophilic intracytoplasmic storage bodies with the characteristics of a lipopigment. In the retina there was progressive loss of photoreceptor cells. Storage bodies isolated from fresh brain, liver and pancreas formed electron-dense aggregates and coarse multilamellar and fine fingerprint profiles ultrastructurally, and consisted mainly of the hydrophobic protein, subunit c of mitochondrial ATP synthase. A homozygosity mapping approach localised the gene causing the disease in Merino sheep to the chromosomal region (OAR7q13-15) associated with NCL in South Hampshire sheep.

CONCLUSION

NCL in Merino sheep is a subunit c-storing disease, clinically and pathologically similar to NCL in South Hampshire sheep. We propose that the disease in both breeds represents mutation at the same gene locus in chromosomal region OAR7q13-15.

Neuronal ceroid lipofuscinosis in Australian Merino sheep: a new animal model

In 1997, neuronal ceroid lipofuscinosis (NCL) was identified for the first time in Merino sheep in Australia. A homozygosity mapping approach localized the disease gene in Merino sheep to the same region on chromosome 7 in which NCL was recently mapped in South Hampshire sheep. This region shows conserved synteny with the region on human chromosome 15 in which the human late infantile NCL variant CLN6 was mapped. NCL in Merino and South Hampshire sheep are therefore potential animal models for the human late infantile variant CLN6.

Changes in GABAergic neuron distribution in situ and in neuron cultures in ovine (OCL6) Batten disease

The neuronal ceroid lipofuscinoses (NCLs) are a group of inherited human and animal diseases characterized by progressive brain atrophy. A form in sheep is syntenic to the human CLN6 disease. Cell type specific neurodegeneration in these sheep was indicated by the distribution of GABAergic interneurons in coronal sections of normal and CLN6 affected sheep brains. A reduction of parvalbumin immunoreactive neurons in NCL cerebral cortex was the most striking feature. This was most pronounced in parietal cortex where very few positive cells remained. Calretinin immunoreactive somata in infragranular layers of the neocortex were also reduced while the number of calbindin positive cells was similar in affected and normal brains. There were fewer GAD immunoreactive neurons in the deeper layers of all NCL cortical areas examined. The parietal lobe was relatively more affected than frontal or temporal lobes while the cerebellum and the basal ganglia showed no signs of selective neuron loss. Since horizontally extending basket cells are mainly labelled by parvalbumin, the loss of these interneurons in the neocortex may render pyramidal neurons more excitable and compromise their co-ordinated output. In vitro, cultures of control and affected neurons from 60 to 70-day-old fetal brain hemispheres were examined for the presence of GABAergic and glutamatergic neurons. Different neurons developed distinct immunoreactivity to glutamate or GABA but the overall distribution was similar in normal and affected cultures. This culture system may provide a useful model to compare GABAergic cell function of normal and NCL affected neurons.

Ovine ceroid lipofuscinosis (OCL6): postulated mechanism of neurodegeneration

It is proposed that ceroid lipofuscinosis in Southhampshire sheep (OCLSouthhampshire) be also known as OCL6 as it is syntenic with CLN6 of humans. Histopathological studies show a severe and progressive neurodegeneration of the cerebral cortex which sometimes appears to have a laminar pattern and which is accompanied by a severe midcortical astrocytosis. Other studies have shown that fibroblasts maintained in tissue culture have abnormal regulation of ATP synthase. If this was reflected in neurons, then selective neuron death is likely to be the result of energy-linked excitotoxicity of neurons receiving abundant glutamate input. Increased sensitivity of the NMDA receptor due to inefficient repolarization of the neuron membrane would allow increased cellular uptake of calcium, increased formation of free radicals, and neuron death. The general hypothesis, as developed for other chronic neurodegenerative diseases, is partly based on application of various drugs that block or mediate parts of the pathway involved. The same approach could be used to help test the hypothesis in OCL6 lambs and if successful some of the drugs might have therapeutic potential. As patterns of neurodegeneration are similar in various other forms of ceroid lipofuscinosis accumulating subunit c of mitochondrial ATP synthase, the model may have more general application than merely to CLN6.

Disease-specific pathology in neurons cultured from sheep affected with ceroid lipofuscinosis

The neuronal ceroid lipofuscinoses (NCL, Batten disease) are a group of inherited neurodegenerative storage diseases in children. Mutations in different genes underlie different forms. Subunit c of mitochondrial ATP synthase is specifically stored in autofluorescent bodies in most of them, including a form in sheep. Mature bodies are lysosomal but the initial site of storage is not known, nor is it known how this leads to the characteristic neurodegeneration. Neurons were cultured in serum-free medium from control and affected sheep fetuses at 90 days gestation. They showed positive microtubule-associated protein staining, developed neurites, and had typical neuron morphology. Time-dependent accumulation of subunit c and of fluorescent storage bodies was observed in affected cells by immunocytochemistry and confocal microscopy. A small number of autofluorescent bodies were apparent after 4 days in culture. After 10 days these bodies were more numerous, more intensely autofluorescent, and often larger in size. By 14 and 21 days many neurons were packed with autofluorescent material. These bodies were not seen in control cultures. Immunocytochemistry revealed subunit c-positive storage material only in affected neurons and not in affected glial cells. Confocal microscope analysis, using organelle-specific dyes, demonstrated colocalization of autofluorescent bodies with lysosomes, not with mitochondria. Survival rates of the affected cells were unaffected by the storage body accumulation over a 3-month period. These cultures can now be used to study the mechanism of subunit c accumulation and of neurodegeneration and to test therapeutic possibilities.

Pathological study on sibling autopsy cases of the late infantile form of neuronal ceroid lipofuscinosis

We report autopsy cases of two brothers with the late infantile form of neuronal ceroid lipofuscinosis (LINCL) and examine apoptotic cell death in autopsied brains. Both patients showed psychomotor developmental delay, cerebellar ataxia, convulsions, visual disturbance and myoclonus, and they became bedridden around the age of 6-7 years. Macular changes, mimicking cherry-red spots, were observed on funduscopy, but conjunctival biopsy failed to disclose storage materials. In these cases, the autopsies demonstrated severe atrophy with neuronal loss and gliosis throughout the brain and spinal cord, except the hypothalamic neurons and motor neurons in the brain-stem and spinal cord, and autofluorescent lipofuscin-like materials of two types, fine granular deposits and coarse round bodies, were stored in the remaining neurons and glial cells, and in the epithelial cells of various visceral organs. Immunostaining for mitochondrial subunit C visualized the fine granular deposits but not the coarse round bodies. The nuclei of neurons and glia cells were stained by in situ nick end labeling, which was more pronounced in the younger case, although the expression of both bcl-2 and bcl-x was not significantly altered in these cases. It is suggested that immunohistochemistry for subunit C may be useful for diagnosis of NCL, and further investigations are necessary to clarify the relationship between LINCL and apoptosis, especially in severely affected cases.

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.

Accumulation of sphingolipid activator proteins (SAPs) A and D in granular osmiophilic deposits in miniature Schnauzer dogs with ceroid-lipofuscinosis

The neuronal ceroid-lipofuscinoses (NCL, Batten disease) are fatal inherited neurodegenerative diseases of children characterized by retinal and brain atrophy and the accumulation of electron-dense storage bodies in cells. Mutations in different genes underlie different major forms. The infantile disease (CLN-1, McKusick 256730) is distinguished by the storage of the sphingolipid activator proteins (SAPs) A and D in distinctive granular osmiophilic deposits (GRODs). This contrasts with the other major forms, where subunit c of mitochondrial ATP synthase is stored in various multilamellar profiles. Ceroid-lipofuscinoses also occur in dogs, including a form in miniature Schnauzers with distinctive granular osmiophilic deposit-like storage bodies. Antisera to SAPs A and D reacted to these storage bodies in situ. The presence of SAP D was confirmed by Western blotting and of SAP A by protein sequencing. Neither subunit c of mitochondrial ATP synthase nor of vacuolar ATPase is stored. This suggests that there are two families of ceroid-lipofuscinoses, the subunit c-storing forms, and those in which SAPs A and D, and perhaps other proteins, accumulate. Further work is required to determine whether other forms with granular osmiophilic deposits belong to the latter class and the genetic relationships between them and the human infantile disease.

The mannosidoses and ceroid-lipofuscinoses: experimental studies on two types of storage disease

alpha-Mannosidosis of Angus calves was studied both for its veterinary importance and as a model of analogous human lysosomal storage diseases. This study facilitated a similar study in Australia on Swainsona spp. intoxication of livestock in which the toxic principle was shown to be an indolizidine alkaloid, Swainsonine. These genetic and acquired alpha-mannosidoses are compared with beta-mannosidosis. Collectively the study has helped the understanding of the processes of glycosylation and catabolism of glycoproteins. An experiment of nature involving an alpha-mannosidosis chimeric calf born co-twin to a normal calf helped to define the expectations and limitations of bone marrow transplants in this type of storage disease in humans. The inherited ceroid-lipofuscinoses (Batten disease) were studied in an ovine model. Isolation and analyses of the fluorescent accumulated lipopigment denied the dogma of lipid peroxidation current in the 1970s and 1980s. It was shown that in this, and analogous diseases in humans, the dominantly accumulated species was the very hydrophobic protein, subunit c of mitochondrial ATP synthase. Contrary to the adage that this should reflect a disorder of lysosomal proteolysis, there is accumulating evidence that the primary defect resides in mitochondria. Because of its hydrophobic nature, subunit c forms paracrystaline complexes which appear resistant to proteolysis within the lysosomal apparatus.

Alzheimer's disease, Kuf's disease, tellurium and selenium

The possible role of the abnormal trace element tellurium in the pathogenesis of Alzheimer's disease is examined. Tellurium has been reported to produce cognitive impairment and cerebral lipofuscinosis in rats-changes akin to those seen in Kuf's disease, a condition which shares certain clinical and neuropathological features with Alzheimer's disease. Tellurium can damage mitochondria; defects in mitochondrial energy metabolism may be relevant to the pathogenesis of neurodegenerative disease. The deficiency of selenium, which may act physiologically as an antagonist of tellurium, in the Alzheimer's disease brain would also be in keeping with the hypothesis of tellurium toxicity as a factor in the pathogenesis of Alzheimer's disease.

Batten disease (ceroid-lipofuscinosis): the enigma of subunit c of mitochondrial ATP synthase accumulation

Ceroid-lipofuscinosis is an inherited neurodegenerative disease of human beings and domestic animals characterized by the accumulation in neurons and other cells of a fluorescent lipopigment. In the ovine form of disease, subunit c of mitochondrial ATP synthase is the dominant accumulated metabolite ( > 50%). It also accumulates significantly in the late infantile and juvenile forms of the human disease and several other animal forms. Evidence is accumulating that the underlying biochemical defect may be associated with mitochondria. The extreme hydrophobicity of subunit c and its propensity to aggregate with lipids into regular multilamellar arrays that cannot be catabolised may reflect an initial defect not necessarily associated with faulty proteolysis. This hypothesis extends an earlier one that subunit c accumulated due to a defect in its catabolic pathway.

Neuronal ceroid lipofuscinosis in the Polish Owczarek Nizinny (PON) dog. A retinal study

Visual dysfunction and neurological symptoms were found in Polish Owczarek Nizinny (PON) dogs. Two dogs were examined, one at 2 years of age and the other one at 4 years. The oldest dog was totally blind. The 2-year-old dog developed mental disturbances and the 4-year-old dog became severely ataxic. Ophthalmoscopical findings were retinal hyper-reflectivity, attenuation of the retinal vessels and the presence of greyish to brown spots in the fundus. Electrophysiological and ultrastructural studies were performed in the 2-year-old dog. Scotopic ERG responses were absent, whereas 30 Hz cone flicker responses were recordable, although with an amplitude reduced to about 30% of the normal level. A slow negative potential replaced the c-wave, indicating a dysfunction of the RPE. Intracellular inclusions with a granular appearance or containing membranous fingerprint-like or curvilinear profiles, resembling ceroid, were found in different retinal cells. The RPE cells in the central areas were charged with autofluorescent material having similar structure, Photoreceptor degeneration was most severe in the central areas, corresponding to the RPE changes. It appears than the PON dog may provide a new animal model for neuronal ceroid lipofuscinosis.