Cardiac pathology in neuronal ceroid lipofuscinoses--a clinicopathologic correlation in three patients

Cardiac magnetic resonance findings in neuronal ceroid lipofuscinosis: A case report

Cardiac magnetic resonance imaging (MRI) is an essential tool for the study of hypertrophic cardiomyopathies (HCM) and for differentiating HCM from conditions with increased ventricular wall thickness, such as cardiac storage diseases. Although cardiac MRI is already used for the diagnosis and characterization of some forms of storage diseases involving the myocardium, it has not yet been used to study myocardial involvement in neuronal ceroid lipofuscinosis (NCL). Here, we describe comprehensive cardiac MRI findings in a patient with the CLN3 form of NCL showing basal inferior interventricular septal hypertrophy with maintained indexed LV mass within reference values and low T1-native values. MRI findings support a finding of abnormal storage material within the myocardium in CLN3 disease. We recommend the possible routine use of cardiac MRI for early diagnosis of cardiac involvement in CLN3 disease (also termed juvenile NCL) and to monitor the effects of emerging CLN3 therapies on the myocardium as well.

Neuronal Ceroid Lipofuscinosis: The Multifaceted Approach to the Clinical Issues, an Overview

The main aim of this review is to summarize the current state-of-art in the field of childhood Neuronal Ceroid Lipofuscinosis (NCL), a group of rare neurodegenerative disorders. These are genetic diseases associated with the formation of toxic endo-lysosomal storage. Following a brief historical review of the evolution of NCL definition, a clinically-oriented approach is used describing how the early symptoms and signs affecting motor, visual, cognitive domains, and including seizures, may lead clinicians to a rapid molecular diagnosis, avoiding the long diagnostic odyssey commonly observed. We go on to focus on recent advances in NCL research and summarize contributions to knowledge of the pathogenic mechanisms underlying NCL. We describe the large variety of experimental models which have aided this research, as well as the most recent technological developments which have shed light on the main mechanisms involved in the cellular pathology, such as apoptosis and autophagy. The search for innovative therapies is described. Translation of experimental data into therapeutic approaches is being established for several of the NCLs, and one drug is now commercially available. Lastly, we show the importance of palliative care and symptomatic treatments which are still the main therapeutic interventions.

Pacemaker Implantation in Juvenile Neuronal Ceroid Lipofuscinosis (CLN3)–A Long-Term Follow-Up Study

It is well documented that deteriorating heart function due to deposition of ceroid lipopigment is a significant co-morbidity in Juvenile Neuronal Ceroid Lipofuscinosis (CLN3 disease) although the exact disease mechanisms remain unknown in any NCL form. An increasing frequency of cardiac conduction disorders including severe bradycardia and sinus arrest is seen in the late teens, as is a left ventricular hypertrophy in the early 20s. Only a few case reports of pacemaker implantation have been published, and so far, no long-term follow-up study exists. As new treatment options emerge, more patients will live longer and the need for pacemaker will likely increase, why knowledge of long-term outcome is needed. In the present study, we present the course of six patients from the original Danish CLN3-heart population study (n = 29) published in 2011 in whom pacemaker implantation was indicated from a cardiac point of view. In two cases, the families deselected pacemaker implantation. In four males, aged 19-29 years, all having a good general condition, a dual-chamber pacemaker (St. Jude Medical™ Accent/Assurity MRI™) was implanted in general anesthesia without any complications. At follow-up 9 years later, three were still alive. According to the parents' opinion they still have a good quality of life, now 26, 30, and 36 years old. Pacemaker treatment is safe and may have great impact on quality of life. However, the medical indication for pacemaker treatment is relative and it is important that various aspects, including the patient's general condition and family preferences, are thoroughly discussed before making the final decision.

Tripeptidyl Peptidase 1 (TPP1) Deficiency in a 36-Year-Old Patient with Cerebellar-Extrapyramidal Syndrome and Dilated Cardiomyopathy

We report on a 36-year-old man with cerebellar-extrapyramidal syndrome and severe heart failure because of dilated cardiomyopathy of unknown origin. Dysarthria and cardiac arrhythmia began at early childhood (4 years of age). Brain MRI (28 years of age) demonstrated severe cerebellar atrophy. At the age 32, he presented with dysarthria, ataxia, dystonia, and tremor of the right hand, bilateral slowed neural conduction in the visual pathways, and decreased mental acuity. At the age of 33 years, the patient underwent cardiac transplantation because of severe dilated cardiomyopathy. In the TPP1 gene, biallelic variants were identified: previously reported p.(Leu13Pro) and novel p.(Tyr508Cys) variant. Additionally, hemizygous novel missense variant in the ABCD1 gene was inherited from the mother p.(Arg17His). Normal very-long-chain fatty acids (VLCFA) levels both in patient and his mother excluded ABCD1 mutation as the pathogenic one. Tripeptidyl peptidase 1 (TPP1) activity was reduced (8,8 U/mg protein/h; reference range: 47.4 ± 10.7). In light microscopy the biopsy specimens obtained from explanted heart showed severe myocyte hypertrophy with perinuclear vacuolization with inclusions. Electron microscopy revealed absence of lipofuscin accumulation, no ultrastructural curvilinear profiles, fingerprint bodies, or granular osmiophilic deposits (GRODs) in lysosomes. As described here, the patient presents clinical symptoms observed in benign forms of ceroid lipofuscinosis type 2 (CLN2) and simultaneously some features of autosomal recessive spinocerebellar ataxia type 7 (SCAR7), which is also caused by mutations in the TPP1 gene.

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.

Cardiac pathology in neuronal ceroid lipofuscinoses (NCL): More than a mere co-morbidity

The neuronal ceroid lipofuscinoses (NCLs) are mostly seen as diseases affecting the central nervous system, but there is accumulating evidence that they have co-morbidities outside the brain. One of these co-morbidities is a decline in cardiac function. This is becoming increasingly recognised in teenagers and adolescents with juvenile CLN3, but it may also occur in individuals with other NCLs. The purpose of this review is to summarise the current knowledge of the structural and functional changes found in the hearts of animal models and people diagnosed with NCL. In addition, we present evidence of structural changes that were observed in a systematic comparison of the cardiomyocytes from CLN3^Δex7/8 mice.

Epileptological aspects of juvenile neuronal ceroid lipofuscinosis (CLN3 disease) through the lifespan

PURPOSE

Juvenile neuronal ceroid lipofuscinosis (CLN3 disease) is the most common neurodegenerative disorder in childhood with survival until young adult age. Visual loss is followed by epilepsy, cognitive, neuropsychiatric, and motor symptoms. We have studied the evolution of electroencephalographic (EEG) and seizure characteristics.

METHODS

Twenty-four patients were recruited via the Norwegian CLN3 disease parent association. Parents were interviewed. Medical records and EEG reports/recordings were collected. Electroencephalographic elements were classified according to Standardized computer-based organized reporting of EEG (SCORE). The evolution of EEG features along with seizure types was assessed by testing the difference in proportions with standardized normal deviate comparing findings below and above 15 years of age.

RESULTS

Mean age at study or death (n = 12) was 21.2 (10-39) years. Twenty-two patients had experienced seizures; the first was usually bilateral tonic-clonic (TC). Later, focal motor seizures frequently occurred, often with increasing multifocal and polymorphic features. Paroxysmal nonepileptic motor and autonomous symptoms were also suspected in several patients. Distinct myoclonic seizures were uncommon. In four patients, we identified episodes of bradycardia/sinus arrest. Electroencephalography showed progressive slowing of the background activity (p = 0.029). Focal epileptiform discharges were rare and mainly seen at age <10. Combined multifocal and bilateral epileptiform discharges increased in adolescence (p = 0.002).

CONCLUSION

Seizure and EEG characteristics change with time in CLN3 disease. Tonic-clonic seizures are common at onset, and multifocal motor seizures increase with age. In contrast, focal epileptiform abnormalities are more common in childhood, compared to later multifocal and bilateral discharges. This seizure disorder belongs to the combined generalized and focal epilepsies. Paucity of myoclonic seizures does not warrant classification as a classic progressive myoclonic epilepsy. When attacks with only behavior arrest occur, cardiac conduction abnormalities should be considered.

Emerging new roles of the lysosome and neuronal ceroid lipofuscinoses

Neuronal Ceroid Lipofuscinoses (NCLs), commonly known as Batten disease, constitute a group of the most prevalent neurodegenerative lysosomal storage disorders (LSDs). Mutations in at least 13 different genes (called CLNs) cause various forms of NCLs. Clinically, the NCLs manifest early impairment of vision, progressive decline in cognitive and motor functions, seizures and a shortened lifespan. At the cellular level, all NCLs show intracellular accumulation of autofluorescent material (called ceroid) and progressive neuron loss. Despite intense studies the normal physiological functions of each of the CLN genes remain poorly understood. Consequently, the development of mechanism-based therapeutic strategies remains challenging. Endolysosomal dysfunction contributes to pathogenesis of virtually all LSDs. Studies within the past decade have drastically changed the notion that the lysosomes are merely the terminal degradative organelles. The emerging new roles of the lysosome include its central role in nutrient-dependent signal transduction regulating metabolism and cellular proliferation or quiescence. In this review, we first provide a brief overview of the endolysosomal and autophagic pathways, lysosomal acidification and endosome-lysosome and autophagosome-lysosome fusions. We emphasize the importance of these processes as their dysregulation leads to pathogenesis of many LSDs including the NCLs. We also describe what is currently known about each of the 13 CLN genes and their products and how understanding the emerging new roles of the lysosome may clarify the underlying pathogenic mechanisms of the NCLs. Finally, we discuss the current and emerging therapeutic strategies for various NCLs.

Caspase 1 activity influences juvenile Batten disease (CLN3) pathogenesis

Juvenile Neuronal Ceroid Lipofuscinosis (JNCL) is an autosomal recessive lysosomal storage disease caused by loss-of-function mutations in CLN3. Symptoms appear between 5 and 10 years of age, beginning with blindness and seizures, followed by progressive cognitive and motor decline, and premature death. Glial activation and impaired neuronal activity are early signs of pathology in the Cln3^Δex7/8 mouse model of JNCL, whereas neuron death occurs much later in the disease process. We previously reported that Cln3^Δex7/8 microglia are primed toward a pro-inflammatory phenotype typified by exaggerated caspase 1 inflammasome activation and here we extend those findings to demonstrate heightened caspase activity in the Cln3^Δex7/8 mouse brain. Based on the ability of caspase 1 to cleave a large number of substrates that have been implicated in JNCL pathology, we examined the functional implications of caspase 1 inflammasome activity by crossing Cln3^Δex7/8 and caspase 1-deficient mice to create Cln3^Δex7/8 /Casp-1^-/- animals. Caspase 1 deletion influenced motor behavior deficits and astrocyte activation in the context of CLN3 mutation, since both were significantly reversed in Cln3^Δex7/8 /Casp-1^-/- mice, with phenotypes approaching that of wild-type animals. We also report a progressive age-dependent reduction in whisker length in Cln3^Δex7/8 mice that was partially caspase 1-dependent. However, not all CLN3 phenotypes were reversed following caspase 1 deletion, since no significant differences in lysosomal accumulation or microglial activation were observed between Cln3^Δex7/8 and Cln3^Δex7/8 /Casp-1^-/- mice. Although the molecular targets of aberrant caspase 1 activity in the context of CLN3 mutation remain to be identified, our studies suggest that caspase 1 may represent a potential therapeutic target to mitigate some attributes of CLN3 disease. This article is part of the Special Issue "Lysosomal Storage Disorders".

Extraneuronal pathology in a canine model of CLN2 neuronal ceroid lipofuscinosis after intracerebroventricular gene therapy that delays neurological disease progression

CLN2 neuronal ceroid lipofuscinosis is a hereditary lysosomal storage disease with primarily neurological signs that results from mutations in TPP1, which encodes the lysosomal enzyme tripeptidyl peptidase-1 (TPP1). Studies using a canine model for this disorder demonstrated that delivery of TPP1 enzyme to the cerebrospinal fluid (CSF) by intracerebroventricular administration of an AAV-TPP1 vector resulted in substantial delays in the onset and progression of neurological signs and prolongation of life span. We hypothesized that the treatment may not deliver therapeutic levels of this protein to tissues outside the central nervous system that also require TPP1 for normal lysosomal function. To test this hypothesis, dogs treated with CSF administration of AAV-TPP1 were evaluated for the development of non-neuronal pathology. Affected treated dogs exhibited progressive cardiac pathology reflected by elevated plasma cardiac troponin-1, impaired cardiac function and development of histopathological myocardial lesions. Progressive increases in the plasma activity levels of alanine aminotransferase and creatine kinase indicated development of pathology in the liver and muscles. The treatment also did not prevent disease-related accumulation of lysosomal storage bodies in the heart or liver. These studies indicate that optimal treatment outcomes for CLN2 disease may require delivery of TPP1 systemically as well as directly to the central nervous system.

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.

Towards a new understanding of NCL pathogenesis

The Neuronal Ceroid Lipofuscinoses (NCLs, Batten disease) are a group of inherited neurodegenerative disorders that have been traditionally grouped together on the basis of certain shared clinical and pathological features. However, as the number of genes that appear to cause new forms of NCL continues to grow, it is timely to reassess our understanding of the pathogenesis of these disorders and what groups them together. The various NCL subtypes do indeed share features of a build-up of autofluorescent storage material, progressive neuron loss and activation of the innate immune system. The characterisation of animal models has highlighted the selective nature of neuron loss and its intimate relationship with glial activation, rather than the generalised build-up of storage material. More recent data provide evidence for the pathway-dependent nature of pathology, the contribution of glial dysfunction, and the involvement of new brain regions previously thought to be unaffected, and it is becoming apparent that pathology extends beyond the brain. These data have important implications, not just for therapy, but also for our understanding of these disorders. However, looking beneath these broadly similar pathological themes evidence emerges for marked differences in the nature and extent of these events in different forms of NCL. Indeed, given the widely different nature of the mutated gene products it is perhaps more surprising that these disorders resemble each other as much as they do. Such data raise the question whether we should rethink the collective grouping of these gene deficiencies together, or whether it would be better to consider them as separate entities. This article is part of a Special Issue entitled: Current Research on the Neuronal Ceroid Lipofuscinoses (Batten Disease).

Cell biology of the NCL proteins: What they do and don't do

The fatal, primarily childhood neurodegenerative disorders, neuronal ceroid lipofuscinoses (NCLs), are currently associated with mutations in 13 genes. The protein products of these genes (CLN1 to CLN14) differ in their function and their intracellular localization. NCL-associated proteins have been localized mostly in lysosomes (CLN1, CLN2, CLN3, CLN5, CLN7, CLN10, CLN12 and CLN13) but also in the Endoplasmic Reticulum (CLN6 and CLN8), or in the cytosol associated to vesicular membranes (CLN4 and CLN14). Some of them such as CLN1 (palmitoyl protein thioesterase 1), CLN2 (tripeptidyl-peptidase 1), CLN5, CLN10 (cathepsin D), and CLN13 (cathepsin F), are lysosomal soluble proteins; others like CLN3, CLN7, and CLN12, have been proposed to be lysosomal transmembrane proteins. In this review, we give our views and attempt to summarize the proposed and confirmed functions of each NCL protein and describe and discuss research results published since the last review on NCL proteins. This article is part of a Special Issue entitled: "Current Research on the Neuronal Ceroid Lipofuscinoses (Batten Disease)".

Loss of Cln3 function in the social amoeba Dictyostelium discoideum causes pleiotropic effects that are rescued by human CLN3

The neuronal ceroid lipofuscinoses (NCL) are a group of inherited, severe neurodegenerative disorders also known as Batten disease. Juvenile NCL (JNCL) is caused by recessive loss-of-function mutations in CLN3, which encodes a transmembrane protein that regulates endocytic pathway trafficking, though its primary function is not yet known. The social amoeba Dictyostelium discoideum is increasingly utilized for neurological disease research and is particularly suited for investigation of protein function in trafficking. Therefore, here we establish new overexpression and knockout Dictyostelium cell lines for JNCL research. Dictyostelium Cln3 fused to GFP localized to the contractile vacuole system and to compartments of the endocytic pathway. cln3⁻ cells displayed increased rates of proliferation and an associated reduction in the extracellular levels and cleavage of the autocrine proliferation repressor, AprA. Mid- and late development of cln3⁻ cells was precocious and cln3⁻ slugs displayed increased migration. Expression of either Dictyostelium Cln3 or human CLN3 in cln3⁻ cells suppressed the precocious development and aberrant slug migration, which were also suppressed by calcium chelation. Taken together, our results show that Cln3 is a pleiotropic protein that negatively regulates proliferation and development in Dictyostelium. This new model system, which allows for the study of Cln3 function in both single cells and a multicellular organism, together with the observation that expression of human CLN3 restores abnormalities in Dictyostelium cln3⁻ cells, strongly supports the use of this new model for JNCL research.

[Juvenile neuronal ceroid-lipofuscinosis with hypertrophic cardiomyopathy and left ventricular noncompaction: a case report]

We report a 17-year-old female with juvenile neuronal ceroid-lipofuscinosis (NCL) accompanied by hypertrophic cardiomyopathy (HCM) and left ventricular noncompaction (LVNC). Within our knowledge, this is the first reported case of juvenile NCL with LVNC, and the youngest case of HCM diagnosed by ultrasound. Juvenile NCL is a progressive hereditary disease involving multi-organ accumulation of ceroid-lipofuscin; its resulting complications require prompt attention. Due to its relative rarity, its cardiac involvement is not well known. Based on findings from this patient and related juvenile NCL cases, the risk of cardiac involvement tends to increase with age; a high frequency of ventricular hypertrophy has been reported in patients aged older than 20 years of age. Medical progress and comprehensive care have led to longer survival in patients with juvenile NCL, which likely increases the incidence of cardiac involvement. In relation to HCM in other metabolic disorders, attention should be paid to arrhythmias, including repolarization disturbances, sinus node dysfunction and ventricular tachycardia. LVNC is a cardiomyopathy characterized by prominent left ventricular trabeculae and deep intratrabecular recesses, which are associated with diastolic or systolic dysfunction, thromboembolic complications and arrhythmias. From ours and other case reports, we recommend regular follow-up of NCL patients as follows: echocardiography to estimate cardiomyopathy, Holter monitoring to identify arrhythmias, and computed tomography to detect thrombosis from both ventricles. The mechanism of the HCM and LVNC associated with juvenile NCL remains unclear. Our case requires careful follow-up. Prospective studies of the cardiac involvement in juvenile NCL are necessary to further elucidate its pathomechanism.

Combination small molecule PPT1 mimetic and CNS-directed gene therapy as a treatment for infantile neuronal ceroid lipofuscinosis

Infantile neuronal ceroid lipofuscinosis (INCL) is a profoundly neurodegenerative disease of children caused by a deficiency in the lysosomal enzyme palmitoyl protein thioesterase-1 (PPT1). There is currently no effective therapy for this invariably fatal disease. To date, preclinical experiments using single treatments have resulted in incremental clinical improvements. Therefore, we determined the efficacy of CNS-directed AAV2/5-mediated gene therapy alone and in combination with the systemic delivery of the lysosomotropic PPT1 mimetic phosphocysteamine. Since CNS-directed gene therapy provides relatively high levels of PPT1 activity to specific regions of the brain, we hypothesized that phosphocysteamine would complement that activity in regions expressing subtherapeutic levels of the enzyme. Results indicate that CNS-directed gene therapy alone provided the greatest improvements in biochemical and histological measures as well as motor function and life span. Phosphocysteamine alone resulted in only minor improvements in motor function and no increase in lifespan. Interestingly, phosphocysteamine did not increase the biochemical and histological response when combined with AAV2/5-mediated gene therapy, but it did result in an additional improvement in motor function. These data suggest that a CNS-directed gene therapy approach provides significant clinical benefit, and the addition of the small molecule PPT1 mimetic can further increase that response.

Intravenous high-dose enzyme replacement therapy with recombinant palmitoyl-protein thioesterase reduces visceral lysosomal storage and modestly prolongs survival in a preclinical mouse model of infantile neuronal ceroid lipofuscinosis

PPT1-related neuronal ceroid lipofuscinosis (NCL) is a lysosomal storage disorder caused by deficiency in a soluble lysosomal enzyme, palmitoyl-protein thioesterase-1 (PPT1). Enzyme replacement therapy (ERT) has not been previously examined in a preclinical animal model. Homozygous PPT1 knockout mice reproduce the known features of the disease, developing signs of motor dysfunction at 5 months of age and death by around 8 months. In the current study, PPT1 knockout mice were treated with purified recombinant PPT1 (0.3 mg, corresponding to 12 mg/kg or 180 U/kg for a 25 g mouse) administered intravenously weekly either 1) from birth; or 2) beginning at 8 weeks of age. The treatment was surprisingly well tolerated and neither anaphylaxis nor antibody formation was observed. In mice treated from birth, survival increased from 236 to 271 days (p<0.001) and the onset of motor deterioration was similarly delayed. In mice treated beginning at 8 weeks, no increases in survival or motor performance were seen. An improvement in neuropathology in the thalamus was seen at 3 months in mice treated from birth, and although this improvement persisted it was attenuated by 7 months. Outside the central nervous system, substantial clearance of autofluorescent storage material in many tissues was observed. Macrophages in spleen, liver and intestine were especially markedly improved, as were acinar cells of the pancreas and tubular cells of the kidney. These findings suggest that ERT may be an option for addressing visceral storage as part of a comprehensive approach to PPT1-related NCL, but more effective delivery methods to target the brain are needed.

Progressive conduction defects and cardiac death in late infantile neuronal ceroid lipofuscinosis

This article reports the case of a female with late infantile neuronal ceroid lipofuscinosis who developed right and left anterior bundle branch blocks and episodic bradycardia at 23 years of age. Several episodes of supraventricular tachycardia manifested at 23 and 27 years of age. In addition, a transient second-degree atrioventricular conduction block also emerged at 27 years of age. Atrial fibrillation and aggravation of the atrioventricular conduction block resulted in progressive bradycardia and cardiac death at the age of 28 years. Cardiac involvement and accumulation of lipopigments in the myocardium and cardiac conduction system have been recognized in juvenile neuronal ceroid lipofuscinosis, but this is the first report to describe progressive conduction defects in a case of late infantile neuronal ceroid lipofuscinosis.

Large-scale phenotyping of an accurate genetic mouse model of JNCL identifies novel early pathology outside the central nervous system

Cln3^Δex7/8 mice harbor the most common genetic defect causing juvenile neuronal ceroid lipofuscinosis (JNCL), an autosomal recessive disease involving seizures, visual, motor and cognitive decline, and premature death. Here, to more thoroughly investigate the manifestations of the common JNCL mutation, we performed a broad phenotyping study of Cln3^Δex7/8 mice. Homozygous Cln3^Δex7/8 mice, congenic on a C57BL/6N background, displayed subtle deficits in sensory and motor tasks at 10–14 weeks of age. Homozygous Cln3^Δex7/8 mice also displayed electroretinographic changes reflecting cone function deficits past 5 months of age and a progressive decline of retinal post-receptoral function. Metabolic analysis revealed increases in rectal body temperature and minimum oxygen consumption in 12–13 week old homozygous Cln3^Δex7/8mice, which were also seen to a lesser extent in heterozygous Cln3^Δex7/8 mice. Heart weight was slightly increased at 20 weeks of age, but no significant differences were observed in cardiac function in young adults. In a comprehensive blood analysis at 15–16 weeks of age, serum ferritin concentrations, mean corpuscular volume of red blood cells (MCV), and reticulocyte counts were reproducibly increased in homozygous Cln3^Δex7/8 mice, and male homozygotes had a relative T-cell deficiency, suggesting alterations in hematopoiesis. Finally, consistent with findings in JNCL patients, vacuolated peripheral blood lymphocytes were observed in homozygous Cln3^Δex7/8 neonates, and to a greater extent in older animals. Early onset, severe vacuolation in clear cells of the epididymis of male homozygous Cln3^Δex7/8 mice was also observed. These data highlight additional organ systems in which to study CLN3 function, and early phenotypes have been established in homozygous Cln3^Δex7/8 mice that merit further study for JNCL biomarker development.

The juvenile Batten disease protein, CLN3, and its role in regulating anterograde and retrograde post-Golgi trafficking

Loss-of-function mutations in CLN3 are responsible for juvenile-onset neuronal ceroid lipofuscinosis (JNCL), or Batten disease, which is an incurable lysosomal disease that manifests with vision loss, followed by seizures and progressive neurodegeneration, robbing children of motor skills, speech and cognition, and eventually leading to death in the second or third decade of life. Emerging clinical evidence points to JNCL pathology outside of the CNS, including the cardiovascular system. The CLN3 gene encodes an unusual transmembrane protein, CLN3 or battenin, whose elusive function has been the subject of intense study for more than 10 years. Owing to the detailed characterization of a large number of disease models, our knowledge of CLN3 protein function is finally coming into focus. This review will describe the most current understanding of CLN3 structure, function and dysfunction in JNCL.

Analysis of potential biomarkers and modifier genes affecting the clinical course of CLN3 disease

Mutations in the CLN3 gene lead to juvenile neuronal ceroid lipofuscinosis, a pediatric neurodegenerative disorder characterized by visual loss, epilepsy and psychomotor deterioration. Although most CLN3 patients carry the same 1-kb deletion in the CLN3 gene, their disease phenotype can be variable. The aims of this study were to (i) study the clinical phenotype in CLN3 patients with identical genotype, (ii) identify genes that are dysregulated in CLN3 disease regardless of the clinical course that could be useful as biomarkers, and (iii) find modifier genes that affect the progression rate of the disease. A total of 25 CLN3 patients homozygous for the 1-kb deletion were classified into groups with rapid, average or slow disease progression using an established clinical scoring system. Genome-wide expression profiling was performed in eight CLN3 patients with different disease progression and matched controls. The study showed high phenotype variability in CLN3 patients. Five genes were dysregulated in all CLN3 patients and present candidate biomarkers of the disease. Of those, dual specificity phosphatase 2 (DUSP2) was also validated in acutely CLN3-depleted cell models and in CbCln3(Δex7/8) cerebellar precursor cells. A total of 13 genes were upregulated in patients with rapid disease progression and downregulated in patients with slow disease progression; one gene showed dysregulation in the opposite way. Among these potential modifier genes, guanine nucleotide exchange factor 1 for small GTPases of the Ras family (RAPGEF1) and transcription factor Spi-B (SPIB) were validated in an acutely CLN3-depleted cell model. These findings indicate that differential perturbations of distinct signaling pathways might alter disease progression and provide insight into the molecular alterations underlying neuronal dysfunction in CLN3 disease and neurodegeneration in general.

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.

Human recombinant palmitoyl-protein thioesterase-1 (PPT1) for preclinical evaluation of enzyme replacement therapy for infantile neuronal ceroid lipofuscinosis

Infantile neuronal ceroid lipofuscinosis (INCL, also known as Haltia-Santavuori disease) is a lysosomal storage disorder of infants and children characterized by blindness, seizures and a progressive neurodegenerative course. Recent clinical trials have involved neural stem cells and gene therapy directed to the central nervous system; however, enzyme replacement therapy has never been addressed. In the current paper, we describe the production of human recombinant PPT1 (the defective enzyme in INCL) by standard methods in Chinese Hamster Ovary (CHO) cells. The enzyme is largely mannose 6-phosphorylated as assessed by mannose 6-phosphate receptor binding (80% bound) and taken up rapidly by immortalized patient lymphoblasts, where clearance of PPT substrates was demonstrated (EC(50) of 0.25 nM after overnight incubation). When injected intravenously into PPT1-deficient mice, the clearance of recombinant human PPT1 from plasma was rapid, with a half-life of 10 min. Most of the injected dose was distributed to the kidney and liver and potentially corrective levels were also observed in heart, lung and spleen. Brain uptake was minimal, as expected based on experience with other intravenously administered lysosomal enzymes. The enzyme may be useful as an adjunct to central nervous system-directed therapies and could be used as a starting point for modifications designed to improve brain delivery.

Children with infantile neuronal ceroid lipofuscinosis have an increased risk of hypothermia and bradycardia during anesthesia

BACKGROUND

Neuronal ceroid lipofuscinoses (NCLs) are a group of autosomal recessive neurodegenerative diseases characterized by lysosomal accumulation of autofluorescent material in neurons and other cell types. The infantile NCL (INCL) subtype is rare (1 in >100,000 births), the most devastating of childhood subtypes, and is caused by mutations in the gene CLN1, which encodes palmitoyl-protein thioesterase-1.

METHODS

To investigate the incidence of hypothermia and bradycardia during general anesthesia in patients with INCL, we conducted a case-control study to examine the perianesthetic course of patients with INCL and of controls receiving anesthesia for diagnostic studies.

RESULTS

Eight children with INCL (mean age 25 mo [range, 10-32] at first anesthetic) and 25 controls (mean age 44 mo [range, 18-92]) underwent 62 anesthetics for nonsurgical procedures. Patients with INCL had neurologic deficits including developmental delay, myoclonus, and visual impairment. Patients with INCL had lower baseline temperature (36.4 +/- 0.1 vs 36.8 +/- 0.1, INCL versus controls, P < 0.007), and during anesthesia, despite active warming techniques, had significantly more hypothermia (18 vs 0 episodes, P < 0.001) and sinus bradycardia (10 vs 1, P < 0.001) compared with controls. INCL diagnosis was significantly associated with temperature decreases during anesthesia (P < 0.001), whereas age, sex, and duration of anesthesia were not (P = NS).

CONCLUSIONS

We report that patients with INCL have lower baseline body temperature and during general anesthesia, despite rewarming interventions, are at increased risk for hypothermia and bradycardia. This suggests a previously unknown INCL phenotype, impaired thermoregulation. Therefore, when anesthetizing these children, careful monitoring and routine use of warming interventions are warranted.

A murine model of infantile neuronal ceroid lipofuscinosis-ultrastructural evaluation of storage in the central nervous system and viscera

Infantile neuronal ceroid lipofuscinosis (INCL), also known as Santavuori-Haltia disease, is an inherited neurodegenerative disorder caused by a mutation in the gene encoding the lysosomal enzyme palmitoyl-protein-thioesterase-1 (PPT1). Fatty acid-modified proteins are not degraded and accumulate as granular osmiophilic deposits in cells in the central nervous system; patients have blindness, seizures, progressive psychomotor deterioration, and die in early childhood. Although the disease manifests clinically primarily with neurological symptoms, visceral storage also accumulates. A murine model of INCL due to PPT1 deficiency exhibits clinical findings and pathology similar to those seen in patients with INCL. Homozygous PPT1-deficient mice have a shortened life span and neurological abnormalities including seizures, blindness, and mental and motor deficits. Widespread granular osmiophilic deposits (GRODs) accumulate in lysosomes in neurons and glia in the brain, retinal cells, kidney glomerular cells, aortic smooth muscle cells, and, in lesser amounts, in the fixed-tissue macrophage system. Accumulation of GRODs in aortic smooth muscle cells is accompanied by abnormalities in cardiac function and aortic root dilatation. This PPT1-deficient murine model is a well-defined genetic system that can be used to test potential therapies for lysosomal storage disease and to study the pathophysiology of INCL.

Neuronal ceroid lipofuscinosis in a 31-year-old woman presenting as biventricular heart failure with restrictive features

A 31-year-old woman presented with dyspnea and left-sided chest discomfort and was found to have biventricular heart failure with impaired ventricular filling. Clinically, she was thought to have restrictive cardiomyopathy or constrictive pericarditis. Transmission electron microscopy of myocardial tissue unexpectedly revealed crosshatched, curvilinear, and fingerprint depositions, which were characteristic for neuronal ceroid lipofuscinosis. Cardiac involvement by this inherited disorder is discussed in light of the findings in this patient and in 15 other reported cases.

Autophagy is disrupted in a knock-in mouse model of juvenile neuronal ceroid lipofuscinosis

Juvenile neuronal ceroid lipofuscinosis is caused by mutation of a novel, endosomal/lysosomal membrane protein encoded by CLN3. The observation that the mitochondrial ATPase subunit c protein accumulates in this disease suggests that autophagy, a pathway that regulates mitochondrial turnover, may be disrupted. To test this hypothesis, we examined the autophagic pathway in Cln3(Deltaex7/8) knock-in mice and CbCln3(Deltaex7/8) cerebellar cells, accurate genetic models of juvenile neuronal ceroid lipofuscinosis. In homozygous knock-in mice, we found that the autophagy marker LC3-II was increased, and mammalian target of rapamycin was down-regulated. Moreover, isolated autophagic vacuoles and lysosomes from homozygous knock-in mice were less mature in their ultrastructural morphology than the wild-type organelles, and subunit c accumulated in autophagic vacuoles. Intriguingly, we also observed subunit c accumulation in autophagic vacuoles in normal aging mice. Upon further investigation of the autophagic pathway in homozygous knock-in cerebellar cells, we found that LC3-positive vesicles were altered and overlap of endocytic and lysosomal dyes was reduced when autophagy was stimulated, compared with wildtype cells. Surprisingly, however, stimulation of autophagy did not significantly impact cell survival, but inhibition of autophagy led to cell death. Together these observations suggest that autophagy is disrupted in juvenile neuronal ceroid lipofuscinosis, likely at the level of autophagic vacuolar maturation, and that activation of autophagy may be a prosurvival feedback response in the disease process.

Sequelae of storage in Fabry disease--pathology and comparison with other lysosomal storage diseases

AIM

To evaluate the sequelae of the lysosomal storage of globotriaosylceramide (Gb3) in a series of patients with Fabry disease.

METHODS

Biopsy and post-mortem samples from 12 patients with Fabry disease were examined microscopically, including, in some cases, immunohistochemistry and electron microscopy. Where possible, comparisons were made with other lysosomal storage disorders.

RESULTS

Storage of Gb3 in cardiocytes leads commonly to progressive hypertrophy, which is a non-specific phenomenon also observed in other lysosomal storage disorders. Capillary endothelial storage was associated with a tendency for capillary basement membrane multiplication. In the single angiokeratoma studied, the basement membrane was rudimentary. Sinusoids in the adrenal cortex and liver displayed either a slight degree of storage or were unaffected. The glomeruli of the kidney exhibited focal hyalinization starting in the mesangial region. Proximal tubular cells were essentially free of lysosomal accumulation, including protein absorption droplets, despite the presence of proteinuria. In only one case, an autopsied Fabry heterozygote, were the proximal tubular cells loaded with protein absorption droplets. The arterial wall in large muscular arteries (coronary, renal and intrarenal) displayed arteriopathy with pronounced involvement of the smooth muscle cells in the media. Arteriopathy started with storage, followed by cell degeneration and breakdown, extracellular matrix deposition and, often, calcification (confined to the muscular layer). Smooth muscle cells occasionally exhibited shrinkage-type necrosis, with dispersion of the stored lipid into the dense cytoplasmic mass. Intimal and mitral valve fibroblasts exhibited variable storage, which was associated with cell loss and necrosis. Intensive storage was found in Leydig cells and in the epididymal epithelium.

CONCLUSION

These long-term sequelae of Gb3 storage are mostly irreversible. Some may interfere with enzyme replacement therapy. It is important, therefore, to consider starting enzyme replacement therapy as early as possible.