Distinct patterns of serum immunoreactivity as evidence for multiple brain-directed autoantibodies in juvenile neuronal ceroid lipofuscinosis

Brain proton MR spectroscopy measurements in CLN3 disease

BACKGROUND

CLN3 is an autosomal recessive lysosomal disorder with intracellular accumulation of ceroid-lipofuscins. CLN3 classically has onset around 4-6 years of age involving vision loss, followed by developmental regression and seizures. Symptoms are progressive and result in premature death. Because treatments are under development, here we explore magnetic resonance spectroscopy (MRS) measurements of metabolite levels in the brain as a potential objective outcome measures.

METHODS

Individuals with genetically confirmed CLN3 were enrolled from October 2017-November 2021 in a prospective natural history study (NCT033007304). Baseline concentrations of brain metabolites measured by MRS were compared to concurrently collected dimensional assessment measures: Vineland-3 Adaptive Behavior Composite (ABC) score, verbal intelligence quotient (VIQ), and the Physical, Capability with actual vision, and Clinical global impression of change sub-domains of the Unified Batten Disease Rating Scale (UBDRS).

RESULTS

27 participants with typical CLN3 presentation (15F:12M; ages 6.0-20.7 years) completed MRS, ABC, and UBDRS; 20 (12F:8M; ages 6.5-20.7 years) also completed the VIQ assessment. N-acetyl aspartate [B(95% CI) = -0.61(-0.78;-0.45)] and glutamine/glutamate/GABA [B(95% CI) = -0.82(-1.04;-0.6)] in the parietal gray matter (PGM) decreased across the ages. The strongest correlations between MRS metabolite measurements and the clinical severity assessments were found with N-acetyl aspartate [VIQ (ρ = 0.58), Vineland-3 ABC (ρ = 0.59), UBDRS |ρ| range = (0.57;0.7)] and glutamine/glutamate/GABA [VIQ (ρ = 0.57), Vineland-3 ABC (ρ = 0.60), UBDRS |ρ| range = (0.59;0.77)] measured in the midline PGM. These correlations were accounted for when age was considered.

CONCLUSIONS

Based on their correlations to established assessments, NAA and glutamine/glutamate/GABA measured in the midline parietal gray matter may be useful indicators of CLN3 disease state. In a clinical trial, divergence of the MRS measurements and clinical severity markers from age may be useful as surrogate measures for treatment responses.

[Neuroinflammation in neuronal ceroid lipofuscinosis]

BACKGROUND

Retinal degeneration and neuroinflammation are often early hallmarks of different subtypes of neuronal ceroid lipofuscinosis (NCL) in patients and genetic animal models.

OBJECTIVE

This article gives a summary of recently published research articles and novel concepts in the field of NCL-related neuroinflammation.

MATERIAL AND METHODS

A search was carried out in PubMed for relevant publications and the results as well as own NCL-related research are discussed.

RESULTS

Microglia and other glial cells are chronically activated and show various dysfunctions in the central nervous system (CNS) and retina of NCL patients and animal models. This is accompanied by significant changes in the transcriptome and proteome. In NCL there is also involvement of the adaptive immune response, as demonstrated by the influx of autoantibodies and activated T cells.

CONCLUSION

A deeper understanding of the molecular processes that contribute to neuroinflammation and ultimately lead to neuronal cell death is an important basis for the discovery of possible biomarkers and the development of immunotherapies in NCL.

Inherited disorders of lysosomal membrane transporters

Disorders caused by defects in lysosomal membrane transporters form a distinct subgroup of lysosomal storage disorders (LSDs). To date, defects in only 10 lysosomal membrane transporters have been associated with inherited disorders. The clinical presentations of these diseases resemble the phenotypes of other LSDs; they are heterogeneous and often present in children with neurodegenerative manifestations. However, for pathomechanistic and therapeutic studies, lysosomal membrane transport defects should be distinguished from LSDs caused by defective hydrolytic enzymes. The involved proteins differ in function, localization, and lysosomal targeting, and the diseases themselves differ in their stored material and therapeutic approaches. We provide an overview of the small group of disorders of lysosomal membrane transporters, emphasizing discovery, pathomechanism, clinical features, diagnostic methods and therapeutic aspects. We discuss common aspects of lysosomal membrane transporter defects that can provide the basis for preclinical research into these disorders.

Cellular models of Batten disease

The Neuronal Ceroid Lipofuscinoses (NCL), otherwise known as Batten disease, are a group of neurodegenerative diseases caused by mutations in 13 known genes. All except one NCL is autosomal recessive in inheritance, with similar aetiology and characterised by the accumulation of autofluorescent storage material in the lysosomes of cells. Age of onset and the rate of progression vary between the NCLs. They are collectively one of the most common lysosomal storage diseases, but the enigma remains of how genetically distinct diseases result in such remarkably similar pathogenesis. Much has been learnt from cellular studies about the function of the proteins encoded by the affected genes. Such research has utilised primitive unicellular models such as yeast and amoeba containing gene orthologues, cells derived from naturally occurring (sheep) and genetically engineered (mouse) animal models or patient-derived cells. Most recently, patient-derived induced pluripotent stem cell (iPSC) lines have been differentiated into neural cell-types to study molecular pathogenesis in the cells most profoundly affected by disease. Here, we review how cell models have informed much of the biochemical understanding of the NCLs and how more complex models are being used to further this understanding and potentially act as platforms for therapeutic efficacy studies in the future.

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Developments made in cellular models for neuronal ceroid lipofuscinosis (NCL) in basic biology and use as therapeutic platforms.

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Cellular models elucidating function of NCL proteins.

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NCL proteins implicated in the mTor signalling pathway.

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Patient-derived induced pluripotent stem cell (iPSC) lines have been differentiated into neural cell-types providing insights into the molecular pathogenesis of NCL.

Changes in motor behavior, neuropathology, and gut microbiota of a Batten disease mouse model following administration of acidified drinking water

CLN3 mutations cause the fatal neurodegenerative disorder, CLN3 Batten disease. The Cln3^−/− mouse model displays characteristic features of the human disease including motor deficits. When mice received acidified drinking water (pH 2.5–2.9) instead of normal tap water (pH 8.4) for several generations, the motor skills of Cln3^−/− mice normalized to control levels, indicating a disease-modifying effect of acidified water. Here we investigated if acidified water administered from postnatal day 21 has therapeutic benefits in Cln3^−/− mice. Indeed, acidified water temporarily attenuated the motor deficits, had beneficial effects on behavioral parameters and prevented microglial activation in the brain of Cln3^−/− mice. Interestingly, in control mice, acidified drinking water caused brain region-specific glial activation and significant changes in motor performance. Since the gut microbiota can influence neurological functions, we examined it in our disease model and found that the gut microbiota of Cln3^−/− mice was markedly different from control mice, and acidified water differentially changed the gut microbiota composition in these mice. These results indicate that acidified water may provide therapeutic benefit to CLN3 Batten disease patients, and that the pH of drinking water is a major environmental factor that strongly influences the results of murine behavioral and pathological studies.

Combined Anti-inflammatory and Neuroprotective Treatments Have the Potential to Impact Disease Phenotypes in Cln3 -/- Mice

Batten disease, or juvenile NCL, is a fatal neurodegenerative disorder that occurs due to mutations in the CLN3 gene. Because the function of CLN3 remains unclear, experimental therapies for JNCL have largely concentrated upon the targeting of downstream pathomechanisms. Neuron loss is preceded by localized glial activation, and in this proof-of-concept study we have investigated whether targeting this innate immune response with ibuprofen in combination with the neuroprotective agent lamotrigine improves the previously documented beneficial effects of immunosuppressants alone. Drugs were administered daily to symptomatic Cln3 -/- mice over a 3 month period, starting at 6 months of age, and their impact was assessed using both behavioral and neuropathological outcome measures. During the treatment period, the combination of ibuprofen and lamotrigine significantly improved the performance of Cln3 -/- mice on the vertical pole test, slowing the disease-associated decline, but had less of an impact upon their rotarod performance. There were also moderate and regionally dependent effects upon astrocyte activation that were most pronounced for ibuprofen alone, but there was no overt effect upon microglial activation. Administering such treatments for longer periods will enable testing for any impact upon the neuron loss that occurs later in disease progression. Given the partial efficacy of these treatments, it will be important to test further drugs of this type in order to find more effective combinations.

Clinical and molecular characterization of non-syndromic retinal dystrophy due to c.175G>A mutation in ceroid lipofuscinosis neuronal 3 (CLN3)

PURPOSE

Mutation of the CLN3 gene, associated with juvenile neuronal ceroid lipofuscinosis, has recently been associated with late-onset, non-syndromic retinal dystrophy. Herein we describe the multimodal imaging, immunological and systemic features of an adult with compound heterozygous CLN3 mutations.

METHODS

A 50-year-old female with non-syndromic retinal dystrophy from the age of 36 years underwent multimodal retinal imaging, electroretinography, neuroimaging, immunological studies and genetic testing. CLN3 transcripts were amplified from patient leukocytes by reverse transcriptase polymerase chain reaction and characterized by Sanger sequencing.

RESULTS

Visual acuity declined to 6/12 and 6/76 due to asymmetrical central scotoma. ERG responses became electronegative and patient's serum contained anti-retinal antibodies. Final visual acuity stabilized at 6/60 bilaterally 3 years after peri-ocular steroid and rituximab infusion. Genetic testing revealed compound heterozygous CLN3 mutations: the 1.02 kb deletion and a novel missense mutation (c.175G>A). In silico, analyses predicted the c.175G>A mutation disrupted an exonic splice enhancer site in exon 3. In patient leukocytes, CLN3 expression was reduced and novel CLN3 transcripts lacking exon 3 were detected.

CONCLUSIONS

Our case study shows that (1) non-syndromic CLN3 disease leads to rod and delayed primary cone degeneration resulting in constricting peripheral field and enlarging central scotoma and, (2) the c.175G>A CLN3 mutation, altered splicing of the CLN3 gene. Overall, we provide comprehensive clinical characterization of a patient with non-syndromic CLN3 disease.

Progress in gene and cell therapies for the neuronal ceroid lipofuscinoses

INTRODUCTION

The neuronal ceroid lipofuscinoses (NCLs) are a subset of lysosomal storage diseases (LSDs) that cause myoclonic epilepsy, loss of cognitive and motor function, degeneration of the retina leading to blindness, and early death. Most are caused by loss-of-function mutations in either lysosomal proteins or transmembrane proteins. Current therapies are supportive in nature. NCLs involving lysosomal enzymes are amenable to therapies that provide an exogenous source of protein, as has been used for other LSDs. Those that involve transmembrane proteins, however, require new approaches.

AREAS COVERED

This review will discuss potential gene and cell therapy approaches that have been, are, or may be in development for these disorders and those that have entered clinical trials.

EXPERT OPINION

In animal models, gene therapy approaches have produced remarkable improvements in neurological function and lifespan. However, a complete cure has not been reached for any NCL, and a better understanding of the limits of the current crop of vectors is needed to more fully address these diseases. The prospects for gene therapy, particularly those that can be delivered systemically and treat both the brain and peripheral tissue, are high. The future is beginning to look bright for NCL patients and their families.

Short-Term Administration of Mycophenolate Is Well-Tolerated in CLN3 Disease (Juvenile Neuronal Ceroid Lipofuscinosis)

Mycophenolate, an immunosuppressant, is commonly used off-label for autoimmune neurological conditions. In CLN3 disease, a neurodegenerative disorder of childhood, preclinical and clinical data suggest secondary autoimmunity and inflammation throughout the central nervous system are key components of pathogenesis. We tested the short-term tolerability of mycophenolate in individuals with CLN3 disease, in preparation for possible long-term efficacy trials of this drug. We conducted a randomized, double-blind, placebo-controlled, crossover study of mycophenolate in 19 ambulatory individuals with CLN3 disease to determine the safety and tolerability of short-term administration (NCT01399047). The study included two 8-week treatment periods with a 4-week intervening washout. Mycophenolate was well tolerated. 89.5% of participants completed the mycophenolate arm, on the assigned study dose (95% CI: 66.9-98.7%), and there were no significant differences in tolerability rates between mycophenolate and placebo arms (10.5%; 95% CI: -3.3-24.3%, p = 0.21). All reported adverse events were mild in severity; the most common adverse events on mycophenolate were vomiting (31.6%; 95% CI: 12.6-56.6%), diarrhea (15.8%; 95% CI: 3.4-39.6%), and cough (15.8%; 95% CI: 3.4-39.6%). These did not occur at a significantly increased frequency above placebo. There were no definite effects on measured autoimmunity or clinical outcomes in the setting of short-term administration. Study of long-term exposure is needed to test the impact of mycophenolate on key clinical features and CLN3 disease trajectory.

Altered Expression of Ganglioside Metabolizing Enzymes Results in GM3 Ganglioside Accumulation in Cerebellar Cells of a Mouse Model of Juvenile Neuronal Ceroid Lipofuscinosis

Juvenile neuronal ceroid lipofuscinosis (JNCL) is caused by mutations in the CLN3 gene. Most JNCL patients exhibit a 1.02 kb genomic deletion removing exons 7 and 8 of this gene, which results in a truncated CLN3 protein carrying an aberrant C-terminus. A genetically accurate mouse model (Cln3^Δex7/8 mice) for this deletion has been generated. Using cerebellar precursor cell lines generated from wildtype and Cln3^Δex7/8 mice, we have here analyzed the consequences of the CLN3 deletion on levels of cellular gangliosides, particularly GM3, GM2, GM1a and GD1a. The levels of GM1a and GD1a were found to be significantly reduced by both biochemical and cytochemical methods. However, quantitative high-performance liquid chromatography analysis revealed a highly significant increase in GM3, suggesting a metabolic blockade in the conversion of GM3 to more complex gangliosides. Quantitative real-time PCR analysis revealed a significant reduction in the transcripts of the interconverting enzymes, especially of β-1,4-N-acetyl-galactosaminyl transferase 1 (GM2 synthase), which is the enzyme converting GM3 to GM2. Thus, our data suggest that the complex a-series gangliosides are reduced in Cln3^Δex7/8 mouse cerebellar precursor cells due to impaired transcription of the genes responsible for their synthesis.

Juvenile neuronal ceroid lipofuscinosis (Batten disease): current insights

The present review is focused on juvenile neuronal ceroid lipofuscinosis (JNCL; Batten disease) due to a mutation in CLN3. Functional vision impairment occurring around 5-6 years of age is the first symptom in more than 80% of patients. Approximately 2 years later (though sometimes simultaneously), obvious signs of cognitive impairment appear. Behavior problems can occur in advance, especially in boys. These include anxious and depressed mood, aggressive behavior, and hallucinations, and even psychotic symptoms. Following the teens, severe dementia is present, including loss of memory, attention, and general reasoning abilities, as well as loss of independent adaptive skills such as mobility, feeding, and communicating. Sleep abnormalities, such as settling problems, nocturnal awakenings, and nightmares, are reported in more than half of patients. The vast majority, if not all, patients develop seizures, starting at approximately 10 years of age. Generalized tonic-clonic seizure occurs as the only type of seizure in approximately half of patients, and in combination with partial seizures in a third of patients. There seems to be no difference in seizure severity according to sex or genotype, and there is great variation in seizure activity among patients. Soon after diagnosis, patients begin to have slight ataxic symptoms, and at adolescence extrapyramidal symptoms (rigidity, bradykinesia, slow steps with flexion in hips and knees) occur with increasing frequency. Chewing and swallowing difficulties emerge as well, and food intake is hampered in the late teens. Disabling periodically involuntary movements may occur as well. A progressive cardiac involvement with repolarization disturbances, ventricular hypertrophy, and sinus-node dysfunction, ultimately leading to severe bradycardia and/or other conduction abnormalities, starts in the mid-teens. Patients are usually bedridden at 20 years of age, and death usually occurs in the third decade of life.

Vision loss in juvenile neuronal ceroid lipofuscinosis (CLN3 disease)

Juvenile neuronal ceroid lipofuscinosis (JNCL; also known as CLN3 disease) is a devastating neurodegenerative lysosomal storage disorder and the most common form of Batten disease. Progressive visual and neurological symptoms lead to mortality in patients by the third decade. Although ceroid-lipofuscinosis, neuronal 3 (CLN3) has been identified as the sole disease gene, the biochemical and cellular bases of JNCL and the functions of CLN3 are yet to be fully understood. As severe ocular pathologies manifest early in disease progression, the retina is an ideal tissue to study in the efforts to unravel disease etiology and design therapeutics. There are significant discrepancies in the ocular phenotypes between human JNCL and existing murine models, impeding investigations on the sequence of events occurring during the progression of vision impairment. This review focuses on current understanding of vision loss in JNCL and discusses future research directions toward molecular dissection of the pathogenesis of the disease and associated vision problems in order to ultimately improve the quality of patient life and cure the disease.

Neuroinflammatory paradigms in lysosomal storage diseases

Lysosomal storage diseases (LSDs) include approximately 70 distinct disorders that collectively account for 14% of all inherited metabolic diseases. LSDs are caused by mutations in various enzymes/proteins that disrupt lysosomal function, which impairs macromolecule degradation following endosome-lysosome and phagosome-lysosome fusion and autophagy, ultimately disrupting cellular homeostasis. LSDs are pathologically typified by lysosomal inclusions composed of a heterogeneous mixture of various proteins and lipids that can be found throughout the body. However, in many cases the CNS is dramatically affected, which may result from heightened neuronal vulnerability based on their post-mitotic state. Besides intrinsic neuronal defects, another emerging factor common to many LSDs is neuroinflammation, which may negatively impact neuronal survival and contribute to neurodegeneration. Microglial and astrocyte activation is a hallmark of many LSDs that affect the CNS, which often precedes and predicts regions where eventual neuron loss will occur. However, the timing, intensity, and duration of neuroinflammation may ultimately dictate the impact on CNS homeostasis. For example, a transient inflammatory response following CNS insult/injury can be neuroprotective, as glial cells attempt to remove the insult and provide trophic support to neurons. However, chronic inflammation, as seen in several LSDs, can promote neurodegeneration by creating a neurotoxic environment due to elevated levels of cytokines, chemokines, and pro-apoptotic molecules. Although neuroinflammation has been reported in several LSDs, the cellular basis and mechanisms responsible for eliciting neuroinflammatory pathways are just beginning to be defined. This review highlights the role of neuroinflammation in select LSDs and its potential contribution to neuron loss.

Abnormally increased surface expression of AMPA receptors in the cerebellum, cortex and striatum of Cln3(-/-) mice

Mutations in the CLN3 gene cause a fatal neurodegenerative disorder, juvenile CLN3 disease. Exploring the cause of the motor coordination deficit in the Cln3(-/-) mouse model of the disease we have previously found that attenuation of AMPA receptor activity in 1-month-old Cln3(-/-) mice significantly improves their motor coordination [20]. To elucidate the mechanism of the abnormally increased AMPA receptor function in Cln3(-/-) mice, we examined the surface expression of AMPA receptors using surface cross-linking in brain slices from 1-month-old wild type (WT) and Cln3(-/-) mice. In surface cross-linked brain samples, Western blotting for AMPA receptor subunits revealed significantly increased surface levels of GluA1 and GluA2 in the cerebellum, and of GluA2 in the cortex and striatum of Cln3(-/-) mice as compared to WT mice. Expression levels of the GluA4 subunit were similar in the cerebellum of WT and Cln3(-/-) mice. While intracellular GluA1 levels in the WT and Cln3(-/-) cerebellum or cortex were similar, the intracellular expression of GluA1 in the Cln3(-/-) striatum was decreased to 56% of the WT level. Our results show a prominent increase in AMPA receptor surface expression in the brain of Cln3(-/-) mice and suggest that CLN3 is involved in the regulation of AMPA receptor surface expression.

Experimental therapies in the neuronal ceroid lipofuscinoses

The neuronal ceroid lipofuscinoses represent a group of severe childhood lysosomal storage diseases. With at least 13 identified variants they are the most common cause of inherited neurodegeneration in children. These diseases share common pathological characteristics including motor problems, vision loss, seizures, and cognitive decline, culminating in premature death. Currently, no form of the disease can be treated or cured, with only palliative care to minimise discomfort. This review focuses on current and potentially ground-breaking clinical trials, including small molecule, enzyme replacement, stem cell, and gene therapies, in the development of effective treatments for the various disease subtypes. This article is part of a Special Issue entitled: "Current Research on the Neuronal Ceroid Lipofuscinoses (Batten Disease)".

CLN3 deficient cells display defects in the ARF1-Cdc42 pathway and actin-dependent events

Juvenile Batten disease (juvenile neuronal ceroid lipofuscinosis, JNCL) is a devastating neurodegenerative disease caused by mutations in CLN3, a protein of undefined function. Cell lines derived from patients or mice with CLN3 deficiency have impairments in actin-regulated processes such as endocytosis, autophagy, vesicular trafficking, and cell migration. Here we demonstrate the small GTPase Cdc42 is misregulated in the absence of CLN3, and thus may be a common link to multiple cellular defects. We discover that active Cdc42 (Cdc42-GTP) is elevated in endothelial cells from CLN3 deficient mouse brain, and correlates with enhanced PAK-1 phosphorylation, LIMK membrane recruitment, and altered actin-driven events. We also demonstrate dramatically reduced plasma membrane recruitment of the Cdc42 GTPase activating protein, ARHGAP21. In line with this, GTP-loaded ARF1, an effector of ARHGAP21 recruitment, is depressed. Together these data implicate misregulated ARF1-Cdc42 signaling as a central defect in JNCL cells, which in-turn impairs various cell functions. Furthermore our findings support concerted action of ARF1, ARHGAP21, and Cdc42 to regulate fluid phase endocytosis in mammalian cells. The ARF1-Cdc42 pathway presents a promising new avenue for JNCL therapeutic development.

CLN3 loss disturbs membrane microdomain properties and protein transport in brain endothelial cells

Juvenile neuronal ceroid lipofuscinosis (JNCL) is a fatal childhood-onset neurodegenerative disorder caused by mutations in ceroid lipofuscinosis neuronal-3 (CLN3), a hydrophobic transmembrane protein of unresolved function. Previous studies indicate blood-brain barrier (BBB) defects in JNCL, and our earlier report showed prominent Cln3 expression in mouse brain endothelium. Here we find that CLN3 is necessary for normal trafficking of the microdomain-associated proteins caveolin-1, syntaxin-6, and multidrug resistance protein 1 (MDR1) in brain endothelial cells. Correspondingly, CLN3-null cells have reduced caveolae, and impaired caveolae- and MDR1-related functions including endocytosis, drug efflux, and cell volume regulation. We also detected an abnormal blood-brain barrier response to osmotic stress in vivo. Evaluation of the plasma membrane with fluorescent sphingolipid probes suggests microdomain destabilization and enhanced fluidity in CLN3-null cells. In further work we found that application of the glycosphingolipid lactosylceramide to CLN3-deficient cells rescues protein transport and caveolar endocytosis. Last, we show that CLN3 localizes to the trans-Golgi network (TGN) and partitions with buoyant microdomain fractions. We propose that CLN3 facilitates TGN-to-plasma membrane transport of microdomain-associated proteins. Insult to this pathway may underlie BBB dysfunction and contribute to JNCL pathogenesis.

Neuronal surface and glutamic acid decarboxylase autoantibodies in Nonparaneoplastic stiff person syndrome

IMPORTANCE

High titers of autoantibodies to glutamic acid decarboxylase (GAD) are well documented in association with stiff person syndrome (SPS). Glutamic acid decarboxylase is the rate-limiting enzyme in the synthesis of γ-aminobutyric acid (GABA), and impaired function of GABAergic neurons has been implicated in the pathogenesis of SPS. Autoantibodies to GAD might be the causative agent or a disease marker.

OBJECTIVE

To investigate the characteristics and potential pathogenicity of GAD autoantibodies in patients with SPS and related disorders.

DESIGN

Retrospective cohort study and laboratory investigation.

SETTING

Weatherall Institute of Molecular Medicine, University of Oxford.

PARTICIPANTS

Twenty-five patients with SPS and related conditions identified from the Neuroimmunology Service.

EXPOSURES

Neurological examination, serological characterization and experimental studies.

MAIN OUTCOMES AND MEASURES

Characterization of serum GAD antibodies from patients with SPS and evidence for potential pathogenicity.

RESULTS

We detected GAD autoantibodies at a very high titer (median, 7500 U/mL) in 19 patients (76%), including all 12 patients with classic SPS. The GAD autoantibodies were high affinity (antibody dissociation constant, 0.06-0.78 nmol) and predominantly IgG1 subclass. The patients’ autoantibodies co-localized with GAD on immunohistochemistry and in permeabilized cultured cerebellar GABAergic neurons, as expected, but they also bound to the cell surface of unpermeabilized GABAergic neurons. Adsorption of the highest titer (700 000 U/mL) serum with recombinant GAD indicated that these neuronal surface antibodies were not directed against GAD itself. Although intraperitoneal injection of IgG purified from the 2 available GAD autoantibody–ositive purified IgG preparations did not produce clinical or pathological evidence of disease, SPS and control IgG were detected in specific regions of the mouse central nervous system, particularly around the lateral and fourth ventricles.

CONCLUSIONS AND RELEVANCE

Autoantibodies to GAD are associated with antibodies that bind to the surface of GABAergic neurons and that could be pathogenic. Moreover, in mice, human IgG from the periphery gained access to relevant areas in the hippocampus and brainstem. Identification of the target of the non-GAD antibodies and peripheral and intrathecal transfer protocols, combined with adsorption studies, should be used to demonstrate the role of the non-GAD IgG in SPS.

Do females with juvenile ceroid lipofuscinosis (Batten disease) have a more severe disease course? The Danish experience

BACKGROUND

Juvenile neuronal ceroid lipofuscinosis (JNCL; Batten disease) is characterized by progressive visual failure starting at 4-7 years of age, followed by seizures, dementia as well as a progressive decline in motor function. The patients are typically bedridden in the late teens and death usually occurs in the third decade of life. It has been suggested, that females may have a more precipitous decline than do males.

OBJECTIVE

To compare sex differences in loss of skills and age at death in an unselected population of Danish Adolescents with Batten disease.

METHOD

Review of hospital records of all 35 Danish patients with JNCL born in the period 1971-2003. The records contain a continuously maintained history of the clinical course and first moments for different events, thus eliminating recall bias.

RESULTS

We found that females with JNCL experienced a later age at diagnosis, but showed an earlier loss of independent functions, and died at an earlier age.

CONCLUSION

Females with JNCL have a more precipitous decline than males, and die at an earlier age. Further studies are needed in order to provide possible explanations for this difference.

Retinal ganglion cell loss is accompanied by antibody depositions and increased levels of microglia after immunization with retinal antigens

Background

Antibodies against retinal and optic nerve antigens are detectable in glaucoma patients. Recent studies using a model of experimental autoimmune glaucoma demonstrated that immunization with certain ocular antigens causes an immun-mediated retinal ganglion cell loss in rats.

Methodology/Principal Findings

Rats immunized with a retinal ganglion cell layer homogenate (RGA) had a reduced retinal ganglion cell density on retinal flatmounts (p = 0.007) and a lower number of Brn3⁺retinal ganglion cells (p = 0.0001) after six weeks. The autoreactive antibody development against retina and optic nerve was examined throughout the study. The levels of autoreactive antibodies continuously increased up to 6 weeks (retina: p = 0.004; optic nerve: p = 0.000003). Additionally, antibody deposits were detected in the retina (p = 0.02). After 6 weeks a reactive gliosis (GFAP density: RGA: 174.7±41.9; CO: 137.6±36.8, p = 0.0006; %GFAP⁺ area: RGA: 8.5±3.4; CO: 5.9±3.6, p = 0.006) as well as elevated level of Iba1⁺ microglia cells (p = 0.003) was observed in retinas of RGA animals.

Conclusions/Significance

Our findings suggest that these antibodies play a substantial role in mechanisms leading to retinal ganglion cell death. This seems to lead to glia cell activation as well as the invasion of microglia, which might be associated with debris clearance.

Females experience a more severe disease course in Batten disease

Juvenile neuronal ceroid lipofuscinosis (JNCL; CLN3 disease; Batten disease) is an autosomal recessive neurodegenerative disease of childhood. Symptoms typically present at school age with vision loss followed by progressive cognitive decline, motor dysfunction, seizures, and behavior problems. Studies on sex differences in JNCL have yielded mixed results, but parent anecdotes suggest that females experience a more precipitous disease course. Therefore, we sought to determine if sex-based differences exist in JNCL. We used data from the Unified Batten Disease Rating Scale (UBDRS), the Batten Disease Support and Research Association (BDSRA) database, and the PedsQL quality of life (QoL) survey to evaluate sex-based differences in functional independence and time from symptom onset to death. On average, females had JNCL symptom onset one year later and death one year earlier than did males. Despite a later age at onset, females had lower functional capability, earlier loss of independent function, and lower physical QoL. Future research in sex differences in JNCL may help to further understand the biological mechanisms underpinning the disease course and may point to targeted therapies.

Therapeutic approaches to the challenge of neuronal ceroid lipofuscinoses

The Neuronal Ceroid Lipofuscinoses (NCLs) are lysosomal storage diseases (LSDs) affecting the central nervous system (CNS), with generally recessive inheritance. They are characterized by pathological lipofuscin-like material accumulating in cells. The clinical phenotypes at all onset ages show progressive loss of vision, decreasing cognitive and motor skills, epileptic seizures and premature death, with dementia without visual loss prominent in the rarer adult forms. Eight causal genes, CLN10/CTSD, CLN1/PPT1, CLN2/TPP1, CLN3, CLN5, CLN6, CLN7/MFSD8, CLN8, with more than 265 mutations and 38 polymorphisms (http://www.ucl.ac.uk/ncl) have been described. Other NCL genes are hypothesized, including CLN4 and CLN9; CLCN6, CLCN7 and possibly SGSH are under study. Some therapeutic strategies applied to other LSDs with significant systemic involvement would not be effective in NCLs due to the necessity of passing the blood brain barrier to prevent the neurodegeneration, repair or restore the CNS functionality. There are therapies for the NCLs currently at preclinical stages and under phase 1 trials to establish safety in affected children. These approaches involve enzyme replacement, gene therapy, neural stem cell replacement, immune therapy and other pharmacological approaches. In the next decade, progress in the understanding of the natural history and the biochemical and molecular cascade of events relevant to the pathogenesis of these diseases in humans and animal models will be required to achieve significant therapeutic advances.

Immune-mediated epilepsies

A pathogenic role of immunity in epilepsies has long been suggested based on observations of the efficacy of immune-modulating treatments and, more recently, by the finding of inflammation markers including autoantibodies in individuals with a number of epileptic disorders. Clinical and experimental data suggest that both innate and adaptive immunity may be involved in epilepsy. Innate immunity represents an immediate, nonspecific host response against pathogens via activation of resident brain immune cells and inflammatory mediators. These are hypothesized to contribute to seizures and epileptogenesis. Adaptive immunity employs activation of antigen-specific B and T lymphocytes or antibodies in the context of viral infections and autoimmune disorders. In this article we critically review the evidence for pathogenic roles of adaptive immune responses in several types of epilepsy, and discuss potential mechanisms and therapeutic targets. We highlight future directions for preclinical and clinical research that are required for improved diagnosis and treatment of immune-mediated epilepsies.

Immunosuppression alters disease severity in juvenile Batten disease mice

Autoantibodies to brain proteins are present in Juvenile Neuronal Ceroid Lipofuscinosis (Batten disease) patients and in the Cln3-/- mouse model of this disease, suggesting an autoimmune component to pathogenesis. Using genetic or pharmaceutical approaches to attenuate this immune response in Cln3-/- mice, we demonstrate decreased neuroinflammation, decreased deposition of immunoglobulin G in the brain and protection of vulnerable neuron populations. Moreover, immune suppression results in a significant improvement in motor performance providing for the first plausible therapeutic approach for juvenile Batten disease.

Common and uncommon pathogenic cascades in lysosomal storage diseases

Lysosomal storage diseases (LSDs), of which about 50 are known, are caused by the defective activity of lysosomal proteins, resulting in accumulation of unmetabolized substrates. As a result, a variety of pathogenic cascades are activated such as altered calcium homeostasis, oxidative stress, inflammation, altered lipid trafficking, autophagy, endoplasmic reticulum stress, and autoimmune responses. Some of these pathways are common to many LSDs, whereas others are only altered in a subset of LSDs. We now review how these cascades impact upon LSD pathology and suggest how intervention in the pathways may lead to novel therapeutic approaches.

Juvenile neuronal ceroid lipofuscinosis (JNCL) and the eye

Juvenile neuronal ceroid lipofuscinoses, or Batten disease, is the most common type of NCL in the United States and Europe. This devastating disorder presents with vision failure and progresses to include seizures, motor dysfunction, and dementia. Death usually occurs in the third decade, but some patients die before age twenty. Though the mechanism of visual failure remains poorly understood, recent advances in molecular genetics have improved diagnostic testing and suggested possible therapeutic strategies. The ophthalmologist plays a crucial role in both early diagnosis and documentation of progression of juvenile neuronal ceroid lipofuscinoses. We update Batten disease research, particularly as it relates to the eye, and present various theories on the pathophysiology of retinal degeneration.

Neuronal ceroid lipofuscinoses: many players, and more to come

The neuronal ceroid lipofuscinoses (NCL) are the most common group of progressive neurodegenerative diseases of childhood. The overall clinical features are highly similar regardless of the age at disease manifestation, the extent and shape of abnormally stored cytosomes and the severity of clinical course, and are generally characterized by failure and regression of psychomotor development, impaired vision, seizures and fatal outcome. The expanding array of genetic etiologies and disease-associated mutations in NCL provide the basis for the heterogeneity of these clinical conditions and are the focus of this review. Less understood are the pathogenic mechanisms, but common themes and molecular pathways are now emerging and new players are expected to come into the scene of NCL.

Cerebellar defects in a mouse model of juvenile neuronal ceroid lipofuscinosis

Juvenile neuronal ceroid lipofuscinosis (JNCL), or Batten disease, is a neurodegenerative disease resulting from a mutation in CLN3, which presents clinically with visual deterioration, seizures, motor impairments, cognitive decline, hallucinations, loss of circadian rhythm, and premature death in the late-twenties to early-thirties. Using a Cln3 null (Cln3(-/-)) mouse, we report here several deficits in the cerebellum in the absence of Cln3, including cell loss and early onset motor deficits. Surprisingly, early onset glial activation and selective neuronal loss within the mature fastigial pathway of the deep cerebellar nuclei (DCN), a region critical for balance and coordination, are seen in many regions of the Cln3(-/-) cerebellum. Additionally, there is a loss of Purkinje cells (PC) in regions of robust Bergmann glia activation in Cln3(-/-) mice and human JNCL post-mortem cerebellum. Moreover, the Cln3(-/-) cerebellum had a mis-regulation in granule cell proliferation and maintenance of PC dendritic arborization and spine density. Overall, this study defines a novel multi-faceted, early-onset cerebellar disruption in the Cln3 null brain, including glial activation, cell loss, and aberrant cell proliferation and differentiation. These early alterations in the maturation of the cerebellum could underlie some of the motor deficits and pathological changes seen in JNCL patients.

Immune system irregularities in lysosomal storage disorders

Lysosomal storage disorders (LSDs) are genetically inherited diseases characterized by the accumulation of disease-specific biological materials such as proteolipids or metabolic intermediates within the lysosome. The lysosomal compartment's central importance to normal cellular function can be appreciated by examining the various pathologies that arise in LSDs. These disorders are invariably fatal, and many display profound neurological impairment that begins in childhood. However, recent studies have revealed that several LSDs also have irregularities in the function of the immune system. Gaucher disease, mucopolysaccharidosis VII, and alpha-mannosidosis are examples of a subset of LSD patients that are predisposed towards immune suppression. In contrast, GM2 gangliosidosis, globoid cell leukodystrophy, Niemann-Pick disease type C1 and juvenile neuronal ceroid lipofuscinosis are LSDs that are predisposed towards immune system hyperactivity. Antigen presentation and processing by dedicated antigen presenting cells (APCs), secretion of pore-forming perforins by cytotoxic-T lymphocytes, and release of pro-inflammatory mediators by mast cells are among the many crucial immune system functions in which the lysosome plays a central role. Although the relationship between the modification of the lysosomal compartment in LSDs and modulation of the immune system remains unknown, there is emerging evidence for early neuroimmune responses in a variety of LSDs. In this review we bridge biochemical studies on the lysosomal compartment's role in the immune system with clinical data on immune system irregularities in a subset of LSDs.

IgG entry and deposition are components of the neuroimmune response in Batten disease

Patients and a mouse model of Batten disease, the juvenile form of neuronal ceroid lipofuscinosis (JNCL), raise autoantibodies against GAD65 and other brain-directed antigens. Here we investigate the adaptive component of the neuroimmune response. Cln3(-/-) mice have autoantibodies to GAD65 in their cerebrospinal fluid and elevated levels of brain bound immunoglobulin G (IgG). IgG deposition was found within human JNCL autopsy material, a feature that became more evident with increased age in Cln3(-/-) mice. The lymphocyte infiltration present in human and murine JNCL occurred late in disease progression, and was not capable of central/intrathecal IgG production. In contrast, we found evidence for an early systemic immune dysregulation in Cln3(-/-) mice. In addition evidence for a size-selective breach in the blood-brain barrier integrity in these mice suggests that systemically produced autoantibodies can access the JNCL central nervous system and contribute to a progressive inflammatory response.

Progress towards understanding disease mechanisms in small vertebrate models of neuronal ceroid lipofuscinosis

Model systems provide an invaluable tool for investigating the molecular mechanisms underlying the NCLs, devastating neurodegenerative disorders that affect the relatively inaccessible tissues of the central nervous system. These models have enabled the assessment of behavioural, pathological, cellular, and molecular abnormalities, and also allow for development and evaluation of novel therapies. This review highlights the relative advantages of the two available small vertebrate species, the mouse and zebrafish, in modelling NCL disease, summarising how these have been useful in NCL research and their potential for the development and testing of prospective disease treatments. A panel of mouse mutants is available representing all the cloned NCL gene disorders (Cathepsin D, CLN1, CLN2, CLN3, CLN5, CLN6, CLN8). These NCL mice all have progressive neurodegenerative phenotypes that closely resemble the pathology of human NCL. The analysis of these models has highlighted several novel aspects underlying NCL pathogenesis including the selective nature of neurodegeneration, evidence for glial responses that precede neuronal loss and identification of the thalamus as an important pathological target early in disease progression. Studies in mice have also highlighted an unexpected heterogeneity underlying NCL phenotypes, and novel potential NCL-like mouse models have been described including mice with mutations in cathepsins, CLC chloride channels, and other lysosome-related genes. These new models are likely to provide significant new information on the spectrum of NCL disease. Information on NCL mice is available in the NCL Mouse Model Database (). There are homologs of most of the NCL genes in zebrafish, and NCL zebrafish models are currently in development. This model system provides additional advantages to those provided by NCL mouse models including high-throughput mutational, pharmacogenetic and therapeutic technique analyses. Mouse and zebrafish models are an important shared resource for NCL research, offering a unique possibility to dissect disease mechanisms and to develop therapeutic approaches.