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.     

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.     

Use of model organisms for the study of neuronal ceroid lipofuscinosis

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

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.     

Sex bias and omission exists in Batten disease research: Systematic review of the use of animal disease models

Batten disease, also known as the neuronal ceroid lipofuscinoses (NCL), is a group of inherited neurodegenerative disorders mainly affecting children. NCL are characterised by seizures, loss of vision, and progressive motor and cognitive decline, and are the most common form of childhood dementia. At least one type of Batten disease and three types of mouse disease models show sex differences in their severity and progression. Scientific research has a recognised prevalent omission of female animals when using model organisms for basic and preclinical research. Sex bias and omission in research using animal models of Batten disease may affect understanding and treatment development. We conducted a systematic review of research publications since the first identification of NCL genes in 1995, identifying those using animal models. We found that <10 % of these papers considered sex as a biological variable. There was consistent omission of female model organisms in studies. This varied over the period but is improving; one third of papers considered sex as a biological variable in the last decade, and there is a noticeable increase in the last 5 years. The wide-ranging reasons for this published sex bias are discussed, including misunderstanding regarding oestrogen, impact on sample size, and the underrepresentation of female scientists. Their implications for Batten disease and future research are considered. Recommendations going forward support requirements by funders for consideration of sex in all stages of experimental design and implementation, and a role for publishers, families and others with a particular interest in Batten disease.     

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.     

Genetic basis and phenotypic correlations of the neuronal ceroid lipofusinoses

The neuronal ceroid lipofuscinoses (NCLs) are a group of inherited neurodegenerative disorders that mainly affect children and are grouped together by similar clinical features and the accumulation of autofluorescent storage material. More than a dozen genes containing nearly 400 mutations underlying human NCLs have been identified. Most of the mutations in these genes are associated with a typical disease phenotype, but some result in variable disease onset, severity and progression. There are still disease subgroups with unknown molecular genetic backgrounds. This article is part of a Special Issue entitled: The Neuronal Ceroid Lipofuscinoses or Batten Disease.     

Batten disease gene, CLN3: linkage disequilibrium mapping in the Finnish population, and analysis of European haplotypes.

The gene for Batten disease (juvenile-onset neuronal ceroid lipofuscinosis, or Spielmeyer-Sjögren disease), CLN3, maps to 16p11.2-12.1. Four microsatellite markers--D16S288, D16S299, D16S298, and SPN--are in strong linkage disequilibrium with CLN3 in 142 families from 16 different countries. These markers span a candidate region of approximately 2.1 cM. CLN3 is most prevalent in northern European populations and is especially enriched in the isolated Finnish population, with an incidence of 1:21,000. Linkage disequilibrium mapping was applied to further refine the localization of CLN3 in 27 Finnish families by using linkage disequilibrium data and information about the population history of Finland to estimate the distance of the closest markers from CLN3. CLN3 is predicted to lie 8.8 kb (range 6.3-13.8 kb) from D16S298 and 165.4 kb (132.4-218.1 kb) from D16S299. Enrichment of allele "6" at D16S298 (on 96% of Finnish and 92% of European CLN3 chromosomes) provides strong evidence that the same major mutation is responsible for Batten disease in Finland as in most other European countries and that it is therefore not a Finnish mutation. Genealogical studies show that Batten disease is widespread throughout the densely populated regions of Finland. The ancestors of two Finnish patients carrying rare alleles "3" and "5" at D16S298 in heterozygous form originate from the southwestern coast of Finland, and these probably represent other foreign mutations. Analysis of the number and distribution of CLN3 haplotypes from 12 European countries provides evidence that more than one mutation has arisen in Europe.     

Molecular basis of gestational trophoblastic diseases

Gestational trophoblastic disease (GTD) encompasses a diverse group of lesions with specific pathogenesis, morphological characteristics and clinical features. The modified World Health Organization-classification of GTD includes complete and partial hydatidiform mole, invasive mole, choriocarcinoma, placental site trophoblastic tumor, epithelioid trophoblastic tumor, exaggerated placental site, and placental site nodule. The various forms of gestational trophoblastic disease can be defined and related to discrete pathologic aberrations occurring at different stages of trophoblastic differentiation. Some of these lesions are true neoplasms, whereas others represent abnormally formed placentas with a predisposition for neoplastic transformation of the trophoblast. Except hydatidiform moles in which the cytogenetic studies have been extensively reported, the pathogenesis of other trophoblastic lesions is poorly understood. Recent studies have shed light on the molecular mechanisms of trophoblastic function, especially as it relates to trophoblastic disease. This review will focus on these advances with special emphasis on the pathogenesis of each specific form of GTD. In addition, the morphology and clinical behavior of each of these entities will be briefly discussed.     

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.     

Batten disease fibroblasts in culture accumulate mitochondrial ATP synthase subunit 9.

Batten Disease is a lysosomal storage disease in which the major component that accumulates is subunit 9 of mitochondrial ATP synthase. Whether or not fibroblasts in culture exhibit this phenotype is controversial. We show that fibroblasts from a human Batten Disease patient and from a mouse model of this disease exhibit autofluorescent inclusion bodies. We also demonstrate that levels of ATP synthase subunit 9 are elevated in these diseased fibroblasts when compared to control cells. However, the exact growth state of the human fibroblasts was critical, and this factor probably accounts for discrepencies in the literature.     

Molecular screening of Batten disease: identification of a missense mutation (E295K) in the CLN3 gene

Batten disease, the juvenile form of neuronal ceroid lipofuscinosis, is a prevalent neuron degenerative disorder of childhood. A 1.02-kb genomic deletion in the Batten disease gene CLN3 has been determined to be a common mutation. We developed a PCR method to screen for this deletion and tested 43 Batten disease probands. We found 36% (31/86) of Batten disease chromosomes did not carry the 1.02-kb deletion. Of the three heterozygotes for the 1.02-kb deletion, a novel G-to-A missense mutation at nucleotide 1020 of the CLN3 cDNA sequence was found on two of the non-1.02-kb deletion chromosomes. The missense mutation resulted in a substitution of glutamic acid (E) by lysine (K) at position 295 (E295 K). The E295 K mutation causes a change in predicted local protein conformation. This glutamic acid is a highly conserved acidic amino acid, being present in human, mouse, dog and yeast, which suggests it may play an important role in the function of the Batten disease protein. Received: 12 May 1997 / Accepted: 21 August 1997     

Epigenetic mechanisms in neurological disease

The exploration of brain epigenomes, which consist of various types of DNA methylation and covalent histone modifications, is providing new and unprecedented insights into the mechanisms of neural development, neurological disease and aging. Traditionally, chromatin defects in the brain were considered static lesions of early development that occurred in the context of rare genetic syndromes, but it is now clear that mutations and maladaptations of the epigenetic machinery cover a much wider continuum that includes adult-onset neurodegenerative disease. Here, we describe how recent advances in neuroepigenetics have contributed to an improved mechanistic understanding of developmental and degenerative brain disorders, and we discuss how they could influence the development of future therapies for these conditions.     

Is there a potential therapeutic role for vitamin E or other antioxidants in atherosclerosis?

In-vitro studies and animal model studies provide an ever-growing body of evidence, direct and indirect, that oxidation of low-density lipoprotein and/or related oxidative mechanisms play a role in atherogenesis. However, two recent, very large, carefully conducted clinical intervention trials using adequate doses of vitamin E demonstrated no effect on a composite end-point of non-fatal infarction, stroke or death from cardiovascular causes. Why the unexpected negative results? Possibly because the animal intervention evidence on which these trials were based deals primarily with very early lesions (fatty streaks). That evidence does not necessarily provide a basis for predicting what antioxidant intervention will do in patients with advanced lesions, particularly when the end-points used relate to unstable plaques and fatal thrombosis, events for which we have no adequate animal models. Nor does it necessarily follow that the same antioxidants used successfully in animals will be effective in humans. The strength of the evidence for the oxidative modification hypothesis is such that negative clinical trials with one particular antioxidant, in patients with very advanced coronary heart disease and lasting only 3-5 years, should not be taken as refutation of the hypothesis. Perhaps different kinds of human trials are needed, trials in which the development of new lesions is measured, in order to test whether antioxidants can decrease the rate of initiation and early progression of atherosclerosis as they do in animals. The answer to the title query is 'Probably, but it is too soon to say'.     

Dendritic cell migration and lymphocyte homing imprinting

For an effective adaptive immune response to occur, dendritic cells (DC), which are the most efficient antigen-presenting cells, must be able to sample the peripheral microenvironment and migrate towards secondary lymphoid organs (SLO) where they activate naive lymphocytes. Upon activation, lymphocytes proliferate and acquire the capacity to migrate to extralymphoid compartments. Although the molecular mechanisms controlling lymphocyte homing to lymphoid and to some extralymphoid tissues have been described in significant detail, it is much less clear how DC migration is controlled. Do DC obey similar adhesion cues that lymphocytes do, or do they have their own "zip codes"? This is relevant from a therapeutic standpoint because effective DC-based vaccines should be able to reach the appropriate tissues in order to generate protective immune responses. Here, we discuss some of the mechanisms used by DC to reach their target tissues. Once DC arrive at their destination, they are exposed to the tissue microenvironment, which likely modulates their functional properties in a tissue-specific fashion. This local DC "education" is probably responsible among other things; for the acquisition of tissue-specific homing imprinting capacity by which DC instruct lymphocytes to migrate to specific tissues. Finally, we discuss how dysregulation of these signals may play a key role in disease.     

Mitochondrial dysfunction in the neuronal ceroid-lipofuscinoses (Batten disease)

There are at least eight genetic entities known as the ceroid-lipofuscinoses in humans which share clinical and pathological features that have caused them to be grouped together under the eponym of Batten disease. They present pathologically as lysosomal storage diseases but are also characterised by severe neurodegeneration. Although the biochemical defects appear primarily centred on lysosomes and defects in proteolysis, the link between this and pathogenesis of neuronal death is poorly understood.The pathogenesis of neurodegeneration has been studied particularly in two animal models these being the English setter dog and the New Zealand Southhampshire sheep (OCL6). In these, and some of the human entities, there is evidence of mitochondrial dysfunction. This includes the accumulation of subunit c of ATP synthase as a component of storage material in at least six of eight genetic forms of the disease; structural abnormalities of mitochondria and selective loss of neurons in areas of the brain that are particularly metabolically active. Direct evidence of dysfunction comes from mitochondrial function tests in fibroblasts and, in animal models, isolated liver mitochondria. Supporting evidence of mitochondrial dysfunction was shown by disturbances in proportions of energy-rich phosphates in fibroblasts in some of these diseases. If these various defects were reflected in neurons, then it would support the hypothesis that neuron death was associated with energy-linked excitotoxicity.     

Pharmacological approaches to tackle NCLs

Neuronal ceroid lipofuscinoses, also collectively known as Batten disease, are a group of rare monogenic disorders caused by mutations in at least 13 different genes. They are characterized by the accumulation of lysosomal storage material and progressive neurological deterioration with dementia, epilepsy, retinopathy, motor disturbances, and early death [1]. Although the identification of disease-causing genes provides an important step for understanding the molecular mechanisms underlying neuronal ceroid lipofuscinoses, compared to other diseases, obstacles to the development of therapies for these rare diseases include less extensive physiopathology knowledge, limited number of patients to test treatments, and poor commercial interest from the industry. Current therapeutic strategies include enzyme replacement therapies, gene therapies targeting the brain and the eye, cell therapies, and pharmacological drugs that could modulate defective molecular pathways. In this review, we will focus in the emerging therapies based in the identification of small-molecules. Recent advances in high- throughput and high-content screening (HTS and HCS) using relevant cell-based assays and applying automation and imaging analysis algorithms, will allow the screening of a large number of compounds in lesser time. These approaches are particularly useful for drug repurposing for Batten disease, that takes the advantage to search for compounds that have already been tested in humans, thereby reducing significantly the resources needed for translation to clinics.     

Naturally acquired MAGE-A10- and SSX-2-specific CD8+ T cell responses in patients with hepatocellular carcinoma

Immunotherapy is being proposed to treat patients with hepatocellular carcinoma (HCC). However, more detailed knowledge on tumor Ag expression and specific immune cells is required for the preparation of highly targeted vaccines. HCC express a variety of tumor-specific Ags, raising the question whether CTL specific for such Ags exist in HCC patients. Indeed, a recent study revealed CTLs specific for two cancer-testis (CT) Ags (MAGE-A1 and MAGE-A3) in tumor infiltrating lymphocytes of HCC patients. Here we assessed the presence of T cells specific for additional CT Ags: MAGE-A10, SSX-2, NY-ESO-1, and LAGE-1, which are naturally immunogenic as demonstrated in HLA-A2(+) melanoma patients. In two of six HLA-A2(+) HCC patients, we found that MAGE-A10- and/or SSX-2-specific CD8(+) T cells naturally responded to the disease, because they were enriched in tumor lesions but not in nontumoral liver. Isolated T cells specifically and strongly killed tumor cells in vitro, providing evidence that these CTL were selected in vivo for high avidity Ag recognition. Therefore, besides melanoma, HCC is the second solid human tumor with clear evidence for in vivo tumor recognition by T cells, providing the rational for specific immunotherapy, based on immunization with CT Ags such as MAGE-A10 and SSX-2.     

Does HLA type predispose some individuals to cancer?

Polymorphic human major histocompatibility complex (MHC) genes are pivotal to the functioning immune system, and strong autoimmune disease associations with human leukocyte antigens (HLAs) have been established, although the precise mechanisms of these associations are not fully defined. There is now clear evidence of immunosurveillance in cancer, thus it seems reasonable to hypothesize that HLA types might predispose some individuals to particular malignancies. In addition, HLAs could influence the susceptibility or progression of a malignancy, and this might be most apparent in virally associated cancers. This article discusses the results and problems of searching for such HLAs and cancer associations. To date, it appears that no strong associations between HLAs and cancer risk exist.