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.     

Cathepsin D deficiency and NCL/Batten disease: there's more to death than apoptosis

Animal models of cathepsin D (CD) deficiency are characterized by a progressive and relentless neurodegenerative phenotype similar to that observed in Neuronal Ceroid Lipofuscinoses (NCL), a group of pediatric neurodegenerative diseases known collectively as Batten Disease. We have shown recently that the targeted deletion of the pro-apoptotic molecule Bax prevents apoptotic markers but not neuron death and neurodegeneration induced by CD deficiency, which suggests that alterations in the macroautophagy-lysosomal degradation pathway can mediate neuron death in NCL/Batten Disease in the absence of apoptosis. Herein, we review CD deficiency in the broader context of NCL and offer potential mechanisms for neuron death and neurodegeneration induced by CD deficiency.     

Funding resources for rare disease research

Research is an expensive venture requiring multiple sources of funding for small projects that test new theories, large projects to make major advancements, training the next generation of researchers and facilitating meetings to share findings and support collaboration. For rare conditions, such as Batten disease, research funds can be difficult to find.To see how investigators supported their work in the past, we did a key word search of the Acknowledgement Section of peer-reviewed literature published in Batten disease in the last 6.5 years. Interestingly, we discovered 193 separate funding sources. The authors hope that, by showing where funds are available, we will enable Batten disease researchers to continue their pursuits and expand their studies; moving key findings from discovery to application phases. This article is part of a Special Issue entitled: The Neuronal Ceroid Lipofuscinoses or Batten Disease.     

Pathogenesis and therapies for infantile neuronal ceroid lipofuscinosis (infantile CLN1 disease)

The neuronal ceroid lipofuscinoses (NCL, Batten disease) are a group of inherited neurodegenerative diseases. Infantile neuronal ceroid lipofuscinosis (INCL, infantile Batten disease, or infantile CLN1 disease) is caused by a deficiency in the soluble lysosomal enzyme palmitoyl protein thioesterase-1 (PPT1) and has the earliest onset and fastest progression of all the NCLs. Several therapeutic strategies including enzyme replacement, gene therapy, stem cell-mediated therapy, and small molecule drugs have resulted in minimal to modest improvements in the murine model of PPT1-deficiency. However, more recent studies using various combinations of these approaches have shown more promising results; in some instances more than doubling the lifespan of PPT1-deficient mice. These combination therapies that target different pathogenic mechanisms may offer the hope of treating this profoundly neurodegenerative disorder. Similar approaches may be useful when treating other forms of NCL caused by deficiencies in soluble lysosomal proteins. Different therapeutic targets will need to be identified and novel strategies developed in order to effectively treat forms of NCL caused by deficiencies in integral membrane proteins such as juvenile neuronal ceroid lipofuscinosis. Finally, the challenge with all of the NCLs will lie in early diagnosis, improving the efficacy of the treatments, and effectively translating them into the clinic. This article is part of a Special Issue entitled: The Neuronal Ceroid Lipofuscinoses or Batten Disease.     

Characterization of lipid-linked oligosaccharide accumulation in mouse models of Batten disease

The neuronal ceroid lipofuscinoses (NCLs, also known collectively as Batten disease) are a group of lysosomal storage disorders characterized by the accumulation of autofluorescent storage material in the brain and other tissues. A number of genes underlying various forms of NCL have been cloned, but the basis for the neurodegeneration in any of these is unknown. High levels of dolichol pyrophosphoryl oligosaccharides have previously been demonstrated in brain tissue from several NCL patients, but the specificity of the effect for the NCLs has been unclear. In the present study, we examine eight mouse models of lysosomal storage disorders by modern FACE and found striking lipid-linked oligosaccharide (LLO) accumulation in NCL mouse models (especially CLN1, CLN6, and CLN8 knockout or mutant mice) but not in several other lysosomal storage disorders affecting the brain. Using a mouse model of the most severe form of NCL (the PPT1 knockout mouse), we show that accumulated LLOs are not the result of a defect in LLO synthesis, extension, or transfer but rather are catabolic intermediates derived from LLO degradation. LLOs are enriched about 60-fold in the autofluorescent storage material purified from PPT1 knockoutmouse brain but comprise only 0.3% of the autofluorescent storage material by mass. The accumulation of LLOs is postulated to result from inhibition of late stages of lysosomal degradation of autophagosomes, which may be enriched in these metabolic precursors.     

What’s not in the news headlines or titles of Alzheimer disease articles? #InMice

There is increasing scrutiny around how science is communicated to the public. For instance, a Twitter account @justsaysinmice (with 70.4K followers in January 2021) was created to call attention to news headlines that omit that mice, not humans, are the ones for whom the study findings apply. This is the case of many headlines reporting on Alzheimer disease (AD) research. AD is characterized by a degeneration of the human brain, loss of cognition, and behavioral changes, for which no treatment is available. Around 200 rodent models have been developed to study AD, even though AD is an exclusively human condition that does not occur naturally in other species and appears impervious to reproduction in artificial animal models, an information not always disclosed. It is not known what prompts writers of news stories to either omit or acknowledge, in the story’s headlines, that the study was done in mice and not in humans. Here, we raised the hypothesis that how science is reported by scientists plays a role on the news reporting. To test this hypothesis, we investigated whether an association exists between articles’ titles and news’ headlines regarding the omission, or not, of mice. To this end, we analyzed a sample of 623 open-access scientific papers indexed in PubMed in 2018 and 2019 that used mice either as models or as the biological source for experimental studies in AD research. We found a significant association (p < 0.01) between articles’ titles and news stories’ headlines, revealing that when authors omit the species in the paper’s title, writers of news stories tend to follow suit. We also found that papers not mentioning mice in their titles are more newsworthy and significantly more tweeted than papers that do. Our study shows that science reporting may affect media reporting and asks for changes in the way we report about findings obtained with animal models used to study human diseases.

This study reveals that when scientists omit from the papers’ title that research findings were obtained using mice, as opposed to humans, the media tend to replicate the trend by omitting the use of mice from the news stories headlines that report on these papers, thereby perpetuating the misleading omission.     

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.     

Genetic heterogeneity in neuronal ceroid lipofuscinosis (NCL): Evidence that the late-infantile subtype (Jansky-Bielschowsky disease; CLN2) is not an allelic form of the juvenile or infantile subtypes

The neuronal ceroid lipofuscinoses (NCLs) are a group of inherited neurodegenerative disorders characterized by the accumulation of autofluorescent lipopigment in neurons and other cell types. Inheritance is autosomal recessive. Three main childhood subtypes are recognized: infantile (Haltia-Santavuori disease; MIM 256743), late infantile (Jansky-Bielschowsky disease; MIM 204500), and juvenile (Spielmeyer-Sjögren-Vogt, or Batten, disease; MIM 204200). The gene loci for the juvenile (CLN3) and infantile (CLN1) types have been mapped to human chromosomes 16p and 1p, respectively, by linkage analysis. Linkage analysis of 25 families segregating for late-infantile NCL has excluded these regions as the site of this disease locus (CLN2). The three childhood subtypes of NCL therefore arise from mutations at distinct loci.     

The neuronal ceroid lipofuscinoses: the same, but different?

The NCLs (neuronal ceroid lipofuscinoses) (also known as Batten disease) are a group of at least ten fatal inherited storage disorders. Despite the identification of many of the disease-causing genes, very little is known about the underlying disease mechanisms. However, now that we have mouse or large-animal models for most forms of NCL, we can investigate pathogenesis and compare what happens in the brain in different types of the disease. Broadly similar neuropathological themes have emerged, including the highly selective nature of neuron loss, early effects upon the presynaptic compartment, together with an early and localized glial activation. These events are especially pronounced within the thalamocortical system, but it is clear that where and when they occur varies markedly between different forms of NCL. It is now becoming apparent that, despite having pathological endpoints that resemble one another, these are reached by a sequence of events that is specific to each subtype of NCL.     

Cathepsin D Deficiency and NCL/Batten Disease: There’s More to Death than Apoptosis

Animal models of cathepsin D (CD) deficiency are characterized by a progressive and relentless neurodegenerative phenotype similar to that observed in Neuronal Ceroid Lipofuscinoses (NCL), a group of pediatric neurodegenerative diseases known collectively as Batten Disease. We have shown recently that the targeted deletion of the pro-apoptotic molecule Bax prevents apoptotic markers but not neuron death and neurodegeneration induced by CD deficiency, which suggests that alterations in the macroautophagy-lysosomal degradation pathway can mediate neuron death in NCL/Batten Disease in the absence of apoptosis. Herein, we review CD deficiency in the broader context of NCL and offer potential mechanisms for neuron death and neurodegeneration induced by CD deficiency.

Addendum to:

Cathepsin D Deficiency Induces Persistent Neurodegeneration in the Absence of Bax-Dependent Apoptosis

J.J. Shacka, B.J. Klocke, C. Young, M. Shibata, J.W. Olney, Y. Uchiyama, P. Saftig and K.A. Roth

J Neurosci 2007; 27:2081-90     

Loss of the Batten disease gene CLN3 prevents exit from the TGN of the mannose 6-phosphate receptor

The neuronal ceroid lipofuscinoses (NCLs, Batten disease) are a group of inherited childhood-onset neurodegenerative disorders characterized by the lysosomal accumulation of undigested material within cells. To understand this dysfunction, we analysed trafficking of the cation-independent mannose 6-phosphate receptor (CI-MPR), which delivers the digestive enzymes to lysosomes. A common form of NCL is caused by mutations in CLN3, a multipass transmembrane protein of unknown function. We report that ablation of CLN3 causes accumulation of CI-MPR in the trans Golgi network, reflecting a 50% reduction in exit. This CI-MPR trafficking defect is accompanied by a fall in maturation and cellular activity of lysosomal cathepsins. CLN3 is therefore essential for trafficking along the route needed for delivery of lysosomal enzymes, and its loss thereby contributes to and may explain the lysosomal dysfunction underlying Batten disease.     

A Murine Model of Variant Late Infantile Ceroid Lipofuscinosis Recapitulates Behavioral and Pathological Phenotypes of Human Disease

Neuronal ceroid lipofuscinoses (NCLs; also known collectively as Batten Disease) are a family of autosomal recessive lysosomal storage disorders. Mutations in as many as 13 genes give rise to ∼10 variants of NCL, all with overlapping clinical symptomatology including visual impairment, motor and cognitive dysfunction, seizures, and premature death. Mutations in CLN6 result in both a variant late infantile onset neuronal ceroid lipofuscinosis (vLINCL) as well as an adult-onset form of the disease called Type A Kufs. CLN6 is a non-glycosylated membrane protein of unknown function localized to the endoplasmic reticulum (ER). In this study, we perform a detailed characterization of a naturally occurring Cln6 mutant (Cln6^nclf) mouse line to validate its utility for translational research. We demonstrate that this Cln6^nclf mutation leads to deficits in motor coordination, vision, memory, and learning. Pathologically, we demonstrate loss of neurons within specific subregions and lamina of the cortex that correlate to behavioral phenotypes. As in other NCL models, this model displays selective loss of GABAergic interneuron sub-populations in the cortex and the hippocampus with profound, early-onset glial activation. Finally, we demonstrate a novel deficit in memory and learning, including a dramatic reduction in dendritic spine density in the cerebral cortex, which suggests a reduction in synaptic strength following disruption in CLN6. Together, these findings highlight the behavioral and pathological similarities between the Cln6^nclf mouse model and human NCL patients, validating this model as a reliable format for screening potential therapeutics.     

Molecular genetics of the NCLs — status and perspectives

The neuronal ceroid lipofuscinoses (NCLs) are a group of inherited neurodegenerative disorders characterized by the accumulation of autofluorescent storage material in many cell types, including neurons. Most NCL subtypes are inherited in an autosomal recessive manner and characterized clinically by epileptic seizures, progressive psychomotor decline, visual failure, variable age of onset, and premature death. To date, seven genes underlying human NCLs have been identified. Most of the mutations in these genes are associated with specific disease subtypes, while some result in variable disease onset, severity and progression. In addition to these, there are still disease subgroups with unknown molecular genetic backgrounds. Although apparent clinical homogeneity exists within some of these subgroups, actual genetic heterogeneity may complicate gene identification. Additional clues to the identification of these unknown genes may come from animal models of NCL and from functional studies of already known genes which may suggest further candidates.     

Molecular genetics of the NCLs -- status and perspectives

The neuronal ceroid lipofuscinoses (NCLs) are a group of inherited neurodegenerative disorders characterized by the accumulation of autofluorescent storage material in many cell types, including neurons. Most NCL subtypes are inherited in an autosomal recessive manner and characterized clinically by epileptic seizures, progressive psychomotor decline, visual failure, variable age of onset, and premature death. To date, seven genes underlying human NCLs have been identified. Most of the mutations in these genes are associated with specific disease subtypes, while some result in variable disease onset, severity and progression. In addition to these, there are still disease subgroups with unknown molecular genetic backgrounds. Although apparent clinical homogeneity exists within some of these subgroups, actual genetic heterogeneity may complicate gene identification. Additional clues to the identification of these unknown genes may come from animal models of NCL and from functional studies of already known genes which may suggest further candidates.     

The neuronal ceroid-lipofuscinoses: A historical introduction

The neuronal ceroid-lipofuscinoses (Batten disease) collectively constitute one of the most common groups of inherited childhood onset neurodegenerative disorders, and have also been identified in many domestic and laboratory animals. The group of human neuronal ceroid-lipofuscinoses currently comprises 14 genetically distinct disorders, mostly characterised by progressive mental, motor and visual deterioration with onset in childhood or adolescence. Abnormal autofluorescent, electron-dense granules accumulate in the cytoplasm of nerve cells, and this storage process is associated with selective destruction and loss of neurons in the brain and retina. The present paper outlines nearly 200 years of clinical, neuropathological, biochemical and molecular genetic research, gradually leading, since 1995, to the identification of 13 different genes and over 360 mutations that underlie these devastating brain disorders and form the basis of a new classification system. These genes are evidently of vital importance for the normal development and maintenance of cerebral neurons. Elucidation of their functions and interactions in health and disease is a prerequisite for the identification of possible therapeutic targets, but may also further our understanding of the basic mechanisms of neurodegeneration and ageing. An account is also given of the development of international cooperation and free access electronic resources facilitating NCL research. This article is part of a Special Issue entitled: The Neuronal Ceroid Lipofuscinoses or Batten Disease.     

Gender and human chronic renal disease

Background: Gender affects the incidence, prevalence, and progression of renal disease. In animal models of the disease, female sex appears to modify the course of progression. Hormonal manipulation by male or female castration also changes the course of renal disease progression, suggesting direct effects of sex hormones in influencing the course of these maladies.Objective: This review examines the pertinent animal and human studies assessing the role of gender, and strives to shed light on the possible physiologic mechanisms underlying the effect of gender, on renal disease progression.Methods: A summary and evaluation of past and recent studies describing the rate of renal disease progression in animal models and humans as it pertains to gender is provided. In addition, studies elucidating the factors involved in the more modest renal progression rate in females are reviewed and conclusions drawn. Relevant English-language publications were identified by searching the PubMed database from January 1990 until November 2007 using the search terms gender, sex, renal disease, and kidney.Results: In polycystic kidney disease, membranous nephropathy, immunoglobulin A nephropathy, and “chronic renal disease of unknown etiology,” men progress at a faster rate to end-stage renal failure than do women. In type 1 diabetes mellitus, there is evidence that males are more likely to manifest signs of renal disease, such as proteinuria. The factors involved in this gender disparity may include diet, kidney and glomerular size, differences in glomerular hemodynamics, and the direct effects of sex hormones. In many, but not all, animal models of renal disease, estrogens slow progression rate. Several studies have recently evaluated the effect of selective estrogen receptor modulators on renal function in humans.Conclusion: Further studies assessing the factors involved in the gender disparity in renal disease progression and the effects of hormonal treatments are warranted.     

NCL diseases — clinical perspectives

The neuronal ceroid lipofuscinoses (NCLs) are lysosomal storage disorders and together are the most common degenerative brain diseases in childhood. They are a group of disorders linked by the characteristic accumulation of abnormal storage material in neurons and other cell types, and a degenerative disease course. All NCLs are characterized by a combination of dementia, epilepsy, and motor decline. For most childhood NCLs, a progressive visual failure is also a core feature. The characteristics of these symptoms can vary and the age at disease onset ranges from birth to young adulthood. Genetic heterogeneity, with fourteen identified NCL genes and wide phenotypic variability render diagnosis difficult. A new NCL classification system based on the affected gene and the age at disease onset allows a precise and practical delineation of an individual patient's NCL type. A diagnostic algorithm to identify each NCL form is presented here. Precise NCL diagnosis is essential not only for genetic counseling, but also for the optimal delivery of care and information sharing with the family and other caregivers. These aspects are challenging because there are also potential long term complications which are specific to NCL type. Therefore care supported by a specifically experienced team of clinicians is recommended. As the underlying pathophysiological mechanism is still unclear for all NCL forms, the development of curative therapies remains difficult. This article is part of a Special Issue entitled: The neuronal ceroid lipofuscinoses or Batten Disease.     

Increased Zinc and Manganese in Parallel with Neurodegeneration,Synaptic Protein Changes and Activation of Akt/GSK3 Signaling in Ovine CLN6 Neuronal Ceroid Lipofuscinosis

Mutations in the CLN6 gene cause a variant late infantile form of neuronal ceroid lipofuscinosis (NCL; Batten disease). CLN6 loss leads to disease clinically characterized by vision impairment, motor and cognitive dysfunction, and seizures. Accumulating evidence suggests that alterations in metal homeostasis and cellular signaling pathways are implicated in several neurodegenerative and developmental disorders, yet little is known about their role in the NCLs. To explore the disease mechanisms of CLN6 NCL, metal concentrations and expression of proteins implicated in cellular signaling pathways were assessed in brain tissue from South Hampshire and Merino CLN6 sheep. Analyses revealed increased zinc and manganese concentrations in affected sheep brain in those regions where neuroinflammation and neurodegeneration first occur. Synaptic proteins, the metal-binding protein metallothionein, and the Akt/GSK3 and ERK/MAPK cellular signaling pathways were also altered. These results demonstrate that altered metal concentrations, synaptic protein changes, and aberrant modulation of cellular signaling pathways are characteristic features in the CLN6 ovine form of NCL.     

N‐acetylcysteine normalizes the urea cycle and DNA repair in cells from patients with Batten disease

Batten disease is an inherited disorder characterized by early onset neurodegeneration due to the mutation of the CLN3 gene. The function of the CLN3 protein is not clear, but an association with oxidative stress has been proposed. Oxidative stress and DNA damage play critical roles in the pathogenesis of neurodegenerative diseases. Antioxidants are of interest because of their therapeutic potential for treating neurodegenerative diseases. We tested whether N‐acetylcysteine (NAC), a well‐known antioxidant, improves the pathology of cells from patients with Batten disease. At first, the expression levels of urea cycle components and DNA repair enzymes were compared between Batten disease cells and normal cells. We used both mRNA expression levels and Western blot analysis. We found that carbamoyl phosphate synthetase 1, an enzyme involved in the urea cycle, 8‐oxoguanine DNA glycosylase 1 and DNA polymerase beta, enzymes involved in DNA repair, were expressed at higher levels in Batten disease cells than in normal cells. The treatment of Batten disease cells with NAC for 48 h attenuated activities of the urea cycle and of DNA repair, as indicated by the substantially decreased expression levels of carbamoyl phosphate synthetase 1, 8‐oxoguanine DNA glycosylase 1 and DNA polymerase beta proteins compared with untreated Batten cells. NAC may serve in alleviating the burden of urea cycle and DNA repair processes in Batten disease cells. We propose that NAC may have beneficial effects in patients with Batten disease. Copyright © 2012 John Wiley & Sons, Ltd.