Over-expression of CLN3P, the Batten disease protein, inhibits PANDER-induced apoptosis in neuroblastoma cells: further evidence that CLN3P has anti-apoptotic properties

Batten disease through different in vivo and in vitro models: A review

Batten disease consists of a family of primarily autosomal recessive, progressive neuropediatric disorders, also known as neuronal ceroid lipofuscinoses (NCLs). These pathologies are characterized by seizures and visual, cognitive and motor decline, and premature death. The pathophysiology of this rare disease is still unclear despite the years of trials and financial aids. This paper has reviewed advantages and limits of in vivo and in vitro models of Batten disease from murine and larger animal models to primitive unicellular models, until the most recently developed patient-derived induced pluripotent stem cells. For each model advantages, limits and applications were analyzed. The first prototypes investigated were murine models that due to their limits were replaced by larger animals. In vitro models gradually replaced animal models for practical, cost, and ethical reasons. Using induced pluripotent stem cells to study neurodegeneration is a new way of studying the disease, since they can be distinguished into differentiating elements like neurons, which are susceptible to neurodegeneration. In vivo and in vitro models have contributed to clarifying to some extent the pathophysiology of the disease. The collection and sharing of suitable human bio samples likely through biobanks can contribute to a better understanding, prevention, and to identify possible treatment strategies of Batten disease.

Loss of CLN3, the gene mutated in juvenile neuronal ceroid lipofuscinosis, leads to metabolic impairment and autophagy induction in retinal pigment epithelium

Juvenile neuronal ceroid lipofuscinosis (JNCL, aka. juvenile Batten disease or CLN3 disease) is a lysosomal storage disease characterized by progressive blindness, seizures, cognitive and motor failures, and premature death. JNCL is caused by mutations in the Ceroid Lipofuscinosis, Neuronal 3 (CLN3) gene, whose function is unclear. Although traditionally considered a neurodegenerative disease, CLN3 disease displays eye-specific effects: Vision loss not only is often one of the earliest symptoms of JNCL, but also has been reported in non-syndromic CLN3 disease. Here we described the roles of CLN3 protein in maintaining healthy retinal pigment epithelium (RPE) and normal vision. Using electroretinogram, fundoscopy and microscopy, we showed impaired visual function, retinal autofluorescent lesions, and RPE disintegration and metaplasia/hyperplasia in a Cln3 ~ 1 kb-deletion mouse model [1] on C57BL/6J background. Utilizing a combination of biochemical analyses, RNA-Seq, Seahorse XF bioenergetic analysis, and Stable Isotope Resolved Metabolomics (SIRM), we further demonstrated that loss of CLN3 increased autophagic flux, suppressed mTORC1 and Akt activities, enhanced AMPK activity, and up-regulated gene expression of the autophagy-lysosomal system in RPE-1 cells, suggesting autophagy induction. This CLN3 deficiency induced autophagy induction coincided with decreased mitochondrial oxygen consumption, glycolysis, the tricarboxylic acid (TCA) cycle, and ATP production. We also reported for the first time that loss of CLN3 led to glycogen accumulation despite of impaired glycogen synthesis. Our comprehensive analyses shed light on how loss of CLN3 affect autophagy and metabolism. This work suggests possible links among metabolic impairment, autophagy induction and lysosomal storage, as well as between RPE atrophy/degeneration and vision loss in JNCL.

The CLN3 gene and protein: What we know

Background

One of the most important steps taken by Beyond Batten Disease Foundation in our quest to cure juvenile Batten (CLN3) disease is to understand the State of the Science. We believe that a strong understanding of where we are in our experimental understanding of the CLN3 gene, its regulation, gene product, protein structure, tissue distribution, biomarker use, and pathological responses to its deficiency, lays the groundwork for determining therapeutic action plans.

Objectives

To present an unbiased comprehensive reference tool of the experimental understanding of the CLN3 gene and gene product of the same name.

Methods

BBDF compiled all of the available CLN3 gene and protein data from biological databases, repositories of federally and privately funded projects, patent and trademark offices, science and technology journals, industrial drug and pipeline reports as well as clinical trial reports and with painstaking precision, validated the information together with experts in Batten disease, lysosomal storage disease, lysosome/endosome biology.

Results

The finished product is an indexed review of the CLN3 gene and protein which is not limited in page size or number of references, references all available primary experiments, and does not draw conclusions for the reader.

Conclusions

Revisiting the experimental history of a target gene and its product ensures that inaccuracies and contradictions come to light, long‐held beliefs and assumptions continue to be challenged, and information that was previously deemed inconsequential gets a second look. Compiling the information into one manuscript with all appropriate primary references provides quick clues to which studies have been completed under which conditions and what information has been reported. This compendium does not seek to replace original articles or subtopic reviews but provides an historical roadmap to completed works.

Exogenous Galactosylceramide as Potential Treatment for CLN3 Disease

OBJECTIVE

CLN3 disease is the commonest of the neuronal ceroid lipofuscinoses, a group of pediatric neurodegenerative disorders. Functions of the CLN3 protein include antiapoptotic properties and facilitating anterograde transport of galactosylceramide from Golgi to lipid rafts. This study confirms the beneficial effects of long-term exogenous galactosylceramide supplementation on longevity, neurobehavioral parameters, neuronal cell counts, astrogliosis, and diminution in brain and serum ceramide levels in Cln3 ^Δex7/8 knock-in mice. Additionally, the impact of galactosylceramide on ceramide synthesis enzymes is documented.

METHODS

A group of 72 mice received galactosylceramide or vehicle for 40 weeks. The effect of galactosylceramide supplementation on Cln3 ^Δex7/8 mice was determined by performing behavioral tests, measuring ceramide in brains and serum, and assessing impact on longevity, subunit C storage, astrogliosis, and neuronal cell counts.

RESULTS

Galactosylceramide resulted in enhanced grip strength of forelimbs in male and female mice, better balance on the accelerating rotarod in females, and improved motor coordination during pole climbing in male mice. Brain and serum ceramide levels as well as apoptosis rates were lower in galactosylceramide-treated Cln3 ^Δex7/8 mice. Galactosylceramide also increased neuronal cell counts significantly in male and female mice and tended to decrease subunit C storage in specific brain regions. Astrogliosis dropped in females compared to a slight increase in males after galactosylceramide. Galactosylceramide increased the lifespan of affected mice.

INTERPRETATION

Galactosylceramide improved behavioral, neuropathological, and biochemical parameters in Cln3 ^Δex7/8 mice, paving the way for effective therapy for CLN3 disease and use of serum ceramide as a potential biomarker to track impact of therapies. ANN NEUROL 2019;86:729-742.

Overexpression of CLN3 contributes to tumour progression and predicts poor prognosis in hepatocellular carcinoma

The aberrant expression of ceroid-lipofuscinosis 3 (CLN3) has been reported in a variety of human malignancies. However, the role of CLN3 in the progression and prognosis of hepatocellular carcinoma (HCC) remains unknown. In this study, we found that CLN3 was frequently upregulated in HCC clinical samples and HCC-derived cell lines and was significantly correlated with an APF serum level ≥20 μg/L, a tumour size ≥5 cm, multiple tumours, and the absence of encapsulation. Kaplan-Meier showed that CLN3 upregulation predicted shorter recurrence-free survival (RFS) and overall survival (OS) time in HCC patients. Cox regression analysis revealed that CLN3 upregulation was an independent risk factor for RFS and OS. A functional study demonstrated that the knockdown of CLN3 expression profoundly suppressed the growth and metastasis of HCC cells both in vitro and in vivo. Mechanistic investigation revealed that the EGFR/PI3K/AKT pathway was essential for mediating CLN3 function. In conclusion, our results provide the first evidence that CLN3 contributes to tumour progression and metastasis and offer a potential prognostic predictor and therapeutic target for HCC.

Effects of circulating member B of the family with sequence similarity 3 on the risk of developing metabolic syndrome and its components: A 5-year prospective study

AIMS/INTRODUCTION

Member B of the family with sequence similarity 3 (FAM3B), also known as pancreatic-derived factor, is mainly synthesized and secreted by islet β-cells, and plays a role in abnormal metabolism of glucose and lipids. However, the prospective association of FAM3B with metabolic disorders remains unclear. The present study aimed to reveal the predictive relationship between pancreas-specific cytokine and metabolic syndrome (MetS).

MATERIALS AND METHODS

A total of 210 adults (88 men and 122 women) without MetS, aged between 40 and 65 years, were recruited and received a comprehensive health examination. Baseline serum FAM3B levels were determined by sandwich enzyme-linked immunosorbent assay. Subsequently, all participants underwent a follow-up examination after 5 years. MetS was identified in accordance with the International Diabetes Federation criteria.

RESULTS

During follow up, 35.7% participants developed MetS. In comparison with the non-MetS group, participants with MetS had an increased serum FAM3B at baseline (21.85 ng/mL [19.38, 24.17 ng/mL] vs 28.56 ng/mL [25.32, 38.10 ng/mL], P < 0.001). Moreover, serum FAM3B was significantly associated with variations in fasting plasma insulin (r = -0.306, P < 0.001), homeostasis model assessment of β-cell function (r = -0.328, P < 0.001) and homeostasis model assessment of insulin resistance (r = -0.191, P = 0.006). Furthermore, a positive correlation between baseline FAM3B and the incidence of MetS was observed, even after multivariable adjustment (relative risk 1.23 [1.15, 1.31], P < 0.001). Furthermore, the optimal cut-off values of FAM3B was 23.98 ng/mL for predicting MetS based on the Youden Index.

CONCLUSIONS

Elevated circulating FAM3B might be considered as a predictor of newly-onset MetS and its progression.

The Parkinson's disease-associated protein DJ-1 plays a positive nonmitochondrial role in endocytosis in Dictyostelium cells

The loss of function of DJ-1 caused by mutations in DJ1 causes a form of familial Parkinson's disease (PD). However, the role of DJ-1 in healthy and in PD cells is poorly understood. Even its subcellular localization in mammalian cells is uncertain, with both cytosolic and mitochondrial locations having been reported. We show here that DJ-1 is normally located in the cytoplasm in healthy Dictyostelium discoideum cells. With its unique life cycle, straightforward genotype-phenotype relationships, experimental accessibility and genetic tractability, D.discoideum offers an attractive model to investigate the roles of PD-associated genes. Furthermore, the study of mitochondrial biology, mitochondrial genome transcription and AMP-activated protein kinase-mediated cytopathologies in mitochondrial dysfunction have been well developed in this organism. Unlike mammalian systems, Dictyostelium mitochondrial dysfunction causes a reproducible and readily assayed array of aberrant phenotypes: defective phototaxis, impaired growth, normal rates of endocytosis and characteristic defects in multicellular morphogenesis. This makes it possible to study whether the underlying cytopathological mechanisms of familial PD involve mitochondrial dysfunction. DJ-1 has a single homologue in the Dictyostelium genome. By regulating the expression level of DJ-1 in D. discoideum, we show here that in unstressed cells, DJ-1 is required for normal rates of endocytic nutrient uptake (phagocytosis and, to a lesser extent, pinocytosis) and thus growth. Reduced expression of DJ-1 had no effect on phototaxis in the multicellular migratory ‘slug’ stage of the life cycle, but resulted in thickened stalks in the final fruiting bodies. This pattern of phenotypes is distinct from that observed in Dictyostelium to result from mitochondrial dyfunction. Direct measurement of mitochondrial respiratory function in intact cells revealed that DJ-1 knockdown stimulates whereas DJ-1 overexpression inhibits mitochondrial activity. Together, our results suggest positive roles for DJ-1 in endocytic pathways and loss-of-function cytopathologies that are not associated with impaired mitochondrial function.

Editor's choice: The Dictyostelium homologue of the Parkinson's disease-associated protein DJ-1 is located in the cytosol, and its loss causes cytopathological defects in endocytic and autophagic cell death pathways, but stimulates respiration by functionally normal mitochondrial respiratory complexes.

Flunarizine rescues reduced lifespan in CLN3 triple knock-out Caenorhabditis elegans model of batten disease

CLN3 disease (Spielmeyer-Vogt-Sjogren-Batten disease, previously known as classic juvenile neuronal ceroid lipofuscinosis, NCL) is a pediatric-onset progressive neurodegenerative disease characterized by progressive vision loss, seizures, loss of cognitive and motor function, and early death. While no precise biochemical mechanism or therapies are known, the pathogenesis of CLN3 disease involves intracellular calcium accumulation that may trigger apoptosis. Our prior work in in vitro cell models of CLN3 deficiency suggested that FDA-approved calcium channel antagonists may have therapeutic value. To further evaluate the potential efficacy of this approach in an otherwise untreatable disorder, we sought to compare the therapeutic effects and underlying mechanisms in an animal model of CLN3 disease. Here, we used the well-characterized XT7 complete cln-3 knockout strain of C. elegans to evaluate the therapeutic efficacy of calcium channel antagonist therapy in a living animal model of Batten disease. Therapeutic effects of five calcium channel antagonists were evaluated on XT7 animal lifespan and in vivo mitochondrial physiology. Remarkably, maximal therapeutic efficacy in this model animal was observed with 1 μM flunarizine, the identical concentration previously identified in cell-based neuronal models of CLN3 disease. Specifically, flunarizine rescued the short lifespan of XT7 worms and prevented their pathophysiologic mitochondrial accumulation. These results confirm the treatment efficacy and dosing of flunarizine in cln-3 disease in a translational model organism. Clinical treatment trials in CLN3 human patients are now needed to test the dosing regimen and efficacy of flunarizine in individuals suffering with this otherwise untreatable and ultimately lethal neurologic disease.

Progress in the Development of Small Molecule Therapeutics for the Treatment of Neuronal Ceroid Lipofuscinoses (NCLs)

The neuronal ceroid lipofuscinoses (NCLs) are a group of inherited and incurable neurodegenerative disorders primarily afflicting the pediatric population. Current treatment regimens offer only symptomatic relief and do not target the underlying cause of the disease. Although the underlying pathophysiology that drives disease progression is unknown, several small molecules have been identified with diverse mechanisms of action that provide promise for the treatment of this devastating disease. This review aims to summarize the current cellular and animal models available for the identification of potential therapeutics and presents the current state of knowledge on small molecule compounds that demonstrate in vitro and/or in vivo efficacy across the NCLs with an emphasis on targets of action.

RNAi-mediated knockdown of the CLN3 gene inhibits proliferation and promotes apoptosis in drug-resistant ovarian cancer cells

CLN3 is a recently identified anti-apoptotic gene, which has been demonstrated to be highly expressed in a diverse range of cancer cell lines, including ovarian cancer. In the present study, RNA interference, mediated by a lentivirus expressing CLN3 short hairpin RNA (shRNA) was utilized to knockdown the expression of CLN3 in the A2780 human ovarian cancer cell line, and its cisplatin-resistant and carboplatin-resistant sublines, A2780/DDP and A2780/CBP cells. It was revealed that the mRNA and protein expression levels of CLN3 were significantly reduced in the CLN3-specific shRNA-transduced cells, compared with the untransduced and control shRNA-transduced cells. In addition, specific knockdown of CLN3 in these cells inhibited cell proliferation and led to cell cycle arrest at the G0/G1 phase, with eventual apoptosis. CLN3 knockdown caused increases in the levels of Bax, FAX, cleaved-caspase 3, cleaved-caspase 8 and cleaved-RARP, but decreased the level of Bcl-2. Finally, it was observed that CLN3 depletion markedly reduced the half maximum inhibitory concentration in the A2780/DDP and A2780/CBP cells. Taken together, these data suggested that CLN3 is involved in tumorigenesis and drug resistance in ovarian cancer, and may serve as a promising therapeutic target for its treatment.

The neuronal ceroid-lipofuscinoses

The neuronal ceroid-lipofuscinoses (NCL's, Batten disease) represent a group of severe neurodegenerative diseases, which mostly present in childhood. The phenotypes are similar and include visual loss, seizures, loss of motor and cognitive function, and early death. At autopsy, there is massive neuronal loss with characteristic storage in remaining neurons. Neurons appear to die because of increased rates of apoptosis and altered autophagy. Ten genes have been identified so far that result in an NCL (CLN1-10). The most common forms are CLN1, CLN2, and CLN3, which were previously known as Infantile, Late-Infantile, and Juvenile NCL's, respectively. CLN1 and CLN2 result from mutations in soluble lysosomal enzymes palmitoyl-protein thioesterase (PPT) and tripeptidyl peptidase 1 (TPP1), which can be measured in white blood cells for clinical diagnosis. Molecular diagnostic testing is routinely available for CLN1, CLN2, and CLN3. Sequencing of other NCL genes may be required to establish a diagnosis when the common forms are ruled out. The pathogenesis of NCL neuronal loss resulting from loss of function of any of the NCL gene products remains unknown and no treatment options are presently available.

Amlodipine prevents apoptotic cell death by correction of elevated intracellular calcium in a primary neuronal model of Batten disease (CLN3 disease)

CLN3 disease (Spielmeyer-Vogt-Sjogren-Batten disease) is a severe pediatric neurodegenerative disorder for which there is currently no effective treatment. The disease is characterized by progressive neuronal death, which may be triggered by abnormal intracellular calcium levels leading to neuronal apoptosis. Previously, we demonstrated reversal of the calcium effect in a neuroblastoma cell line using amlodipine and other calcium channel antagonists. In the present studies, we developed a CLN3 siRNA-inhibited primary rat neuron model to further study etoposide-induced calcium changes and apoptosis in CLN3 disease followed by recovery experiments with amlodipine. Our results show that intracellular calcium is significantly elevated in siRNA-inhibited cortical neurons after potassium chloride-induced depolarization. We were also able to show that amlodipine, a predominantly L-type dihydropyrimidine calcium channel antagonist can reverse the aberrant calcium elevations in this model of the disease. We performed an in situ TUNEL assay following etoposide-exposure to siRNA inhibited primary neurons, and apoptotic nuclei were detected providing additional evidence that increased neuronal apoptosis is associated with increased calcium levels. Amlodipine also reduced the absolute number of apoptotic cells in this experimental model.

Drafting the CLN3 protein interactome in SH-SY5Y human neuroblastoma cells: a label-free quantitative proteomics approach

Neuronal ceroid lipofuscinoses (NCL) are the most common inherited progressive encephalopathies of childhood. One of the most prevalent forms of NCL, Juvenile neuronal ceroid lipofuscinosis (JNCL) or CLN3 disease (OMIM: 204200), is caused by mutations in the CLN3 gene on chromosome 16p12.1. Despite progress in the NCL field, the primary function of ceroid-lipofuscinosis neuronal protein 3 (CLN3) remains elusive. In this study, we aimed to clarify the role of human CLN3 in the brain by identifying CLN3-associated proteins using a Tandem Affinity Purification coupled to Mass Spectrometry (TAP-MS) strategy combined with Significance Analysis of Interactome (SAINT). Human SH-SY5Y-NTAP-CLN3 stable cells were used to isolate native protein complexes for subsequent TAP-MS. Bioinformatic analyses of isolated complexes yielded 58 CLN3 interacting partners (IP) including 42 novel CLN3 IP, as well as 16 CLN3 high confidence interacting partners (HCIP) previously identified in another high-throughput study by Behrends et al., 2010. Moreover, 31 IP of ceroid-lipofuscinosis neuronal protein 5 (CLN5) were identified (18 of which were in common with the CLN3 bait). Our findings support previously suggested involvement of CLN3 in transmembrane transport, lipid homeostasis and neuronal excitability, as well as link it to G-protein signaling and protein folding/sorting in the ER.

Diagnosis of neuronal ceroid lipofuscinosis: mutation detection strategies

The neuronal ceroid lipofuscinoses (NCL) are a group of rare genetically inherited neurodegenerative disorders in children. These diseases are classified by age of onset (congenital, infantile, late-infantile, juvenile and adult-onset) and by the gene bearing mutations (CLN10/CTSD, CLN1/PPT1, CLN2/TPP1, CLN3, CLN5, CLN6, CLN7/MFSD8 and CLN8). Enzyme activity assays are helpful in identifying several of these disorders; however confirmation of the mutation in the gene causing these diseases is vital for definitive diagnosis. There exists considerable heterogeneity in the NCLs as a whole and within each type of NCL both in phenotype (disease manifestation and progression) and genotype (type of mutation), which complicates NCL diagnosis. In order to streamline the diagnostic process, the age of symptom onset, geography and/or ethnicity, and enzyme activity may be considered together. However, these ultimately serve to guide targeting the correct route to genetic confirmation of an NCL through mutational analysis. Herein, an effective protocol to diagnose NCLs using these criteria is presented.

Mouse models of neuronal ceroid lipofuscinoses: useful pre-clinical tools to delineate disease pathophysiology and validate therapeutics

The neuronal ceroid lipofuscinoses (NCL, also known as Batten disease) is a devastating neurodegenerative diseases caused by mutations in either soluble enzymes or membrane-associated structural proteins that result in lysosome dysfunction. Different forms of NCL were defined initially by age of onset, affected population and/or type of storage material but collectively represent the most prevalent pediatric hereditary neurovisceral storage disorder. Specific gene mutations are now known for each subclass of NCL in humans that now largely define the disease: cathepsin D (CTSD) for congenital (CLN10 form); palmitoyl protein thioesterase 1 (PPT1) for infantile (CLN1 form); tripeptidyl peptidase 1 (TPP1) for classic late infantile (CLN2 form); variant late infantile-CLN5, CLN6 or CLN8 for variant late infantile forms; and CLN3 for juvenile (CLN3 form). Several mouse models of NCL have been developed, or in some cases exist sporadically, that exhibit mutations producing a progressive neurodegenerative phenotype similar to that observed in human NCL. The study of these mouse models of NCL has dramatically advanced our knowledge of NCL pathophysiology and in some cases has helped delineate the function of proteins mutated in human NCL. In addition, NCL mutant mice have been tested for several different therapeutic approaches and as such they have become important pre-clinical models for validating treatment options. In this review we will assess the current state of mouse models of NCL with regards to their unique pathophysiology and how these mice have helped investigators achieve a better understanding of human NCL disease and therapy.

Role of pancreatic-derived factor in type 2 diabetes: evidence from pancreatic β cells and liver

Pancreatic-derived factor (PANDER) is a cytokine-like protein that is highly expressed in pancreatic islets. In vitro, PANDER pretreatment or viral-mediated overexpression promotes apoptosis of islet β cells. Under conditions of insulin resistance, chronic hyperglycemia potently activates PANDER expression and stimulates the cosecretion of insulin and PANDER in β cells. PANDER binds to the liver cell membrane and induces insulin resistance, resulting in increased gluconeogenesis. Recently, PANDER was found to be expressed in rodent and human liver, and its expression is increased in the liver of diabetic mice and rats. Hepatic overexpression of PANDER promotes lipogenesis in the liver and induces insulin resistance in C57BL/6 mice, whereas the inactivation of hepatic PANDER markedly reduces steatosis, insulin resistance, and hyperglycemia in db/db mice. PANDER deficiency protects mice from high-fat-diet-induced hyperglycemia by decreasing gluconeogenesis in the liver. In summary, PANDER plays an important role in the progression of type 2 diabetes by negatively regulating islet β-cell function and insulin sensitivity in the liver.

Flow injection tandem mass spectrometric measurement of ceramides of multiple chain lengths in biological samples

A method is presented for the measurement of ceramide species in biological fluids using flow injection tandem mass spectrometry. Ceramides are important signaling compounds in a number of cell:cell interactions including apoptosis and neurodegeneration. Because of the large number of potential fatty acid constituent moieties on ceramide molecules, a method which accurately distinguishes different chain-length species was required. The present method does not require HPLC separation and is designed to be applicable to high throughput analysis required for clinical studies. We provide a reference range for all measurable ceramide species in normal human plasma and an example of the utility of the assay in providing biomarkers in an in vitro apoptotic cell death study using murine hematopoietic cells treated with daunorubicin.

Screening for calcium channel modulators in CLN3 siRNA knock down SH-SY5Y neuroblastoma cells reveals a significant decrease of intracellular calcium levels by selected L-type calcium channel blockers

BACKGROUND

Defects of the CLN3 gene on chromosome 16p12.1 lead to the juvenile form of neuronal ceroid-lipofuscinosis (JNCL, Batten Disease), the most common recessive inherited neurodegenerative disorder in children. Dysregulation of intracellular calcium homeostasis in the absence of a functional CLN3 protein (CLN3P, Battenin) has been linked to synaptic dysfunction and accelerated apoptosis in vulnerable neuronal cells. Prolonged increase of intracellular calcium concentration is considered to be a significant trigger for neuronal apoptosis and cellular loss in JNCL.

METHODS

We examined the potential effect of 41 different calcium channel modulators on intracellular calcium concentration in CLN3 siRNA knock down SH-SY5Y neuroblastoma cells.

RESULTS

Six drugs belonging to the group of voltage dependent L-type channel blockers show significant lowering of the increased intracellular calcium levels in CLN3 siRNA knock down cells.

CONCLUSIONS

Our studies provide important new data suggesting possible beneficial effects of the tested drugs on calcium flux regulated pathways in neuronal cell death. Therapeutic intervention in this untreatable disease will likely require drugs that cross the blood-brain barrier as did all of the positively screened drugs in this study.

GENERAL SIGNIFICANCE

Better comprehension of the mechanism of neurodegeneration in rare recessive disorders, such as neuronal ceroid-lipofuscinoses, is likely to help to better understand mechanisms involved in more complex genetic neurodegenerative conditions, such as those associated with aging.

A knock-in reporter mouse model for Batten disease reveals predominant expression of Cln3 in visual, limbic and subcortical motor structures

Juvenile neuronal ceroid lipofuscinosis (JNCL) or Batten disease is an autosomal recessive neurodegenerative disorder of children caused by mutation in CLN3. JNCL is characterized by progressive visual impairment, cognitive and motor deficits, seizures and premature death. Information about the localization of CLN3 expressing neurons in the nervous system is limited, especially during development. The present study has systematically mapped the spatial and temporal localization of CLN3 reporter neurons in the entire nervous system including retina, using a knock-in reporter mouse model. CLN3 reporter is expressed predominantly in post-migratory neurons in visual and limbic cortices, anterior and intralaminar thalamic nuclei, amygdala, cerebellum, red nucleus, reticular formation, vestibular nuclei and retina. CLN3 reporter in the nervous system is mainly expressed during the first postnatal month except in the dentate gyrus, parasolitary nucleus and retina, where it is still strongly expressed in adulthood. The predominant distribution of CLN3 reporter neurons in visual, limbic and subcortical motor structures correlates well with the clinical symptoms of JNCL. These findings have also revealed potential target brain regions and time periods for future investigations of the disease mechanisms and therapeutic intervention.

Altered arginine metabolism in the central nervous system (CNS) of the Cln3-/- mouse model of juvenile Batten disease

BACKGROUND

Juvenile neuronal ceroid lipofuscinoses (JNCL) or juvenile Batten disease is a recessively inherited childhood neurodegenerative disorder resulting from a mutation in CLN3, which encodes a putative lysosomal protein of unknown function.

AIM

Recent evidence suggests that a disruption in CLN3 function results in altered regulation of arginine transport into lysosomes, and may influence intracellular arginine levels. We sought to investigate the possible consequences of arginine dysregulation in the brain of the Cln3(-/-) mouse model of JNCL.

METHODS

Using a combination of enzyme assays, metabolite profiling, quantitative reverse-transcription polymerase chain reaction and Western blotting, we analysed the activities and expression of enzymes involved in arginine metabolism in the cerebral cortex and cerebellum of Cln3(-/-) mice over several developmental time points.

RESULTS

We report subtle, but significant changes in the activities of enzymes involved in the citrulline-NO recycling pathway, and altered regulation of neuronal nitric oxide synthase in the cortex and cerebellum of Cln3(-/-) mice. In addition, a significant decrease in arginine transport into cerebellar granule cells was observed, despite an apparent upregulation of the cationic amino acid transporter-1 transporter at the cell surface. Our results provide further evidence that CLN3 function and arginine homeostasis are intricately related, and that cellular mechanisms may act to compensate for the loss of this protein.

CONCLUSIONS

This and other studies indicate that CLN3 dysfunction in JNCL may result in multiple disturbances in metabolism that together contribute to the pathophysiological processes underlying this disease.

CLN3P, the Batten's disease protein, is a novel palmitoyl-protein Delta-9 desaturase

OBJECTIVE

Batten's disease, one of the most common recessively inherited, untreatable, neurodegenerative diseases of humans, is characterized by progressive neuronal loss and intraneuronal proteolipid storage. Although the gene for the disorder was cloned more than a decade ago, the function of the encoded protein, CLN3P, has not been defined thus far.

METHODS

Sequence analysis using the Pfam server identified a low stringency match to a fatty acid desaturase domain in the N-terminal sequence of CLN3P. We developed a fatty acid desaturase assay based on measurement of desaturase products by gas chromatography/mass spectrometry.

RESULTS

We show that CLN3P is a novel palmitoyl-protein Delta-9 desaturase, which converts membrane-associated palmitoylated proteins to their respective palmitoleated derivatives. We have further demonstrated that this palmitoyl-protein Delta-9 desaturase activity is deficient in cln3(-/-) mouse pancreas and is completely ablated in neuroblastoma cells by RNA inhibition.

INTERPRETATION

We propose that palmitoyl-protein desaturation defines a new mechanism of proteolipid modification, and that deficiency of this process leads to the signs and symptoms of Batten's disease.