Juvenile neuronal ceroid lipofuscinosis (Batten disease): current insights

Mechanisms of Action of the US Food and Drug Administration-Approved Antisense Oligonucleotide Drugs

Antisense oligonucleotides (ASOs) are single stranded nucleic acids that target RNA. The US Food and Drug Administration has approved ASOs for several diseases. ASOs utilize three principal modes of action (MOA). The first MOA is initiated by base-pairing between the ASO and its target mRNA, followed by RNase H-dependent mRNA degradation. The second MOA is triggered by ASOs that occlude splice acceptor sites in pre-mRNAs leading to skipping of a mutation-bearing exon. The third MOA involves ASOs that sterically hinder mRNA function, often inhibiting translation. ASOs contain a variety of modifications to the sugar-phosphate backbone and bases that stabilize the ASO or render them resistant to RNase activity. RNase H-dependent ASOs include inotersen and eplontersen (for hereditary transthyretin amyloidosis), fomiversen (for opportunistic cytomegalovirus infection), mipomersen (for familial hypercholesterolemia), and tofersen [for amyotrophic lateral sclerosis (ALS)]. Splice modulating ASOs include nursinersen (for spinal muscular atrophy) and eteplirsen, golodirsen, viltolarsen, and casimersen (all for the treatment of Duchenne muscular dystrophy). In addition, a designer ASO, milasen, was used to treat a single individual afflicted with Batten disease. Since ASO design relies principally upon knowledge of mRNA sequence, the bench to bedside pipeline for ASOs is expedient compared with protein-directed drugs. [Graphical abstract available.].

DYT-THAP1: exploring gene expression in fibroblasts for potential biomarker discovery

Dystonia due to pathogenic variants in the THAP1 gene (DYT-THAP1) shows variable expressivity and reduced penetrance of ~ 50%. Since THAP1 encodes a transcription factor, modifiers influencing this variability likely operate at the gene expression level. This study aimed to assess the transferability of differentially expressed genes (DEGs) in neuronal cells related to pathogenic variants in the THAP1 gene, which were previously identified by transcriptome analyses. For this, we performed quantitative (qPCR) and Digital PCR (dPCR) in cultured fibroblasts. RNA was extracted from THAP1 manifesting (MMCs) and non-manifesting mutation carriers (NMCs) as well as from healthy controls. The expression profiles of ten of 14 known neuronal DEGs demonstrated differences in fibroblasts between these three groups. This included transcription factors and targets (ATF4, CLN3, EIF2A, RRM1, YY1), genes involved in G protein-coupled receptor signaling (BDKRB2, LPAR1), and a gene linked to apoptosis and DNA replication/repair (CRADD), which all showed higher expression levels in MMCs and NMCs than in controls. Moreover, the analysis of genes linked to neurological disorders (STXBP1, TOR1A) unveiled differences in expression patterns between MMCs and controls. Notably, the genes CUEDC2, DRD4, ECH1, and SIX2 were not statistically significantly differentially expressed in fibroblast cultures. With > 70% of the tested genes being DEGs also in fibroblasts, fibroblasts seem to be a suitable model for DYT-THAP1 research despite some restrictions. Furthermore, at least some of these DEGs may potentially also serve as biomarkers of DYT-THAP1 and influence its penetrance and expressivity.

The parent and family impact of CLN3 disease: an observational survey-based study

BACKGROUND

CLN3 disease (also known as CLN3 Batten disease or Juvenile Neuronal Ceroid Lipofuscinosis) is a rare pediatric neurodegenerative disorder caused by biallelic mutations in CLN3. While extensive efforts have been undertaken to understand CLN3 disease etiology, pathology, and clinical progression, little is known about the impact of CLN3 disease on parents and caregivers. Here, we investigated CLN3 disease progression, clinical care, and family experiences using semi-structured interviews with 39 parents of individuals with CLN3 disease. Analysis included response categorization by independent observers and quantitative methods.

RESULTS

Parents reported patterns of disease progression that aligned with previous reports. Insomnia and thought- and mood-related concerns were reported frequently. "Decline in visual acuity" was the first sign/symptom noticed by n = 28 parents (70%). A minority of parents reported "behavioral issues" (n = 5, 12.5%), "communication issues" (n = 3, 7.5%), "cognitive decline" (n = 1, 2.5%), or "seizures" (n = 1, 2.5%) as the first sign/symptom. The mean time from the first signs or symptoms to a diagnosis of CLN3 disease was 2.8 years (SD = 4.1). Misdiagnosis was common, being reported by n = 24 participants (55.8%). Diagnostic tests and treatments were closely aligned with observed symptoms. Desires for improved or stabilized vision (top therapeutic treatment concern for n = 14, 32.6%), cognition (n = 8, 18.6%), and mobility (n = 3, 7%) dominated parental concerns and wishes for therapeutic correction. Family impacts were common, with n = 34 (81%) of respondents reporting a financial impact on the family and n = 20 (46.5%) reporting marital strain related to the disease.

CONCLUSIONS

Collectively, responses demonstrated clear patterns of disease progression, a strong desire for therapies to treat symptoms related to vision and cognition, and a powerful family impact driven by the unrelenting nature of disease progression.

CLN3 deficiency leads to neurological and metabolic perturbations during early development

Juvenile neuronal ceroid lipofuscinosis (or Batten disease) is an autosomal recessive, rare neurodegenerative disorder that affects mainly children above the age of 5 yr and is most commonly caused by mutations in the highly conserved CLN3 gene. Here, we generated cln3 morphants and stable mutant lines in zebrafish. Although neither morphant nor mutant cln3 larvae showed any obvious developmental or morphological defects, behavioral phenotyping of the mutant larvae revealed hyposensitivity to abrupt light changes and hypersensitivity to pro-convulsive drugs. Importantly, in-depth metabolomics and lipidomics analyses revealed significant accumulation of several glycerophosphodiesters (GPDs) and cholesteryl esters, and a global decrease in bis(monoacylglycero)phosphate species, two of which (GPDs and bis(monoacylglycero)phosphates) were previously proposed as potential biomarkers for CLN3 disease based on independent studies in other organisms. We could also demonstrate GPD accumulation in human-induced pluripotent stem cell-derived cerebral organoids carrying a pathogenic variant for CLN3 Our models revealed that GPDs accumulate at very early stages of life in the absence of functional CLN3 and highlight glycerophosphoinositol and BMP as promising biomarker candidates for pre-symptomatic CLN3 disease.

Mechanistic Insights into S-Depalmitolyse Activity of Cln5 Protein Linked to Neurodegeneration and Batten Disease: A QM/MM Study

Ceroid lipofuscinosis neuronal protein 5 (Cln5) is encoded by the CLN5 gene. The genetic variants of this gene are associated with the CLN5 form of Batten disease. Recently, the first crystal structure of Cln5 was reported. Cln5 shows cysteine palmitoyl thioesterase S-depalmitoylation activity, which was explored via fluorescent emission spectroscopy utilizing the fluorescent probe DDP-5. In this work, the mechanism of the reaction between Cln5 and DDP-5 was studied computationally by applying a QM/MM methodology at the ωB97X-D/6-31G(d,p):AMBER level. The results of our study clearly demonstrate the critical role of the catalytic triad Cys280-His166-Glu183 in S-depalmitoylation activity. This is evidenced through a comparison of the pathways catalyzed by the Cys280-His166-Glu183 triad and those with only Cys280 involved. The computed reaction barriers are in agreement with the catalytic efficiency. The calculated Gibb's free-energy profile suggests that S-depalmitoylation is a rate-limiting step compared to the preceding S-palmitoylation, with barriers of 26.1 and 25.3 kcal/mol, respectively. The energetics were complemented by monitoring the fluctuations in the electron density distribution through NBO charges and bond strength alterations via local mode stretching force constants during the catalytic pathways. This comprehensive protocol led to a more holistic picture of the reaction mechanism at the atomic level. It forms the foundation for future studies on the effects of gene mutations on both the S-palmitoylation and S-depalmitoylation steps, providing valuable data for the further development of enzyme replacement therapy, which is currently the only FDA-approved therapy for childhood neurodegenerative diseases, including Batten disease.

Treatment of non-epileptic episodes of anxious, fearful behavior in adolescent juvenile neuronal ceroid lipofuscinosis (CLN3 disease)

Background

Recurrent non-epileptic episodes of frightened facial and body expression occur in more than half of post-adolescent patients with juvenile neuronal ceroid lipofuscinosis (JNCL, CLN3 disease). Clinically, the episodes look similar to the attacks of paroxysmal sympathetic hyperactivity (PSH) commonly seen following traumatic brain injury (TBI). The episodes occur when the patients are exposed to separation, hear loud sounds or are otherwise bothered by discomfort and as in PSH following TBI, the attacks are difficult to prevent and/or treat.

Aim and methods

Based on present knowledge of triggering factors, the neural anxiety/fear circuit, its afferent and efferent pathways and documented CLN3 disease-impact on these tracks, the current study discusses a rational approach how to prevent and/or treat the attacks.

Results

Patients with JNCL have a disturbed somatosensory modulation leading to a reduced threshold of pain; a degeneration within the neural anxiety/fear circuit leading to an imbalance of central network inhibition and excitation pathways; and finally, an, with advancing age, increasing autonomic imbalance leading to a significant dominance of the sympathetic neural system.

Discussion

Theoretically, there are three points of attack how to prevent or treat the episodes: (1) increase in threshold of discomfort impact; (2) modulation of imbalance of central network inhibition and excitation, and (3) restoring the balance between the sympathetic and parasympathetic neural systems prompted by a parasympathetic withdrawal. As to (1) and (2), prevention should have the greatest priority. As regards (3), research of transcutaneous vagal stimulation treatment in JNCL is warranted.

Cerebrospinal Fluid Protein Biomarker Discovery in CLN3

Syndromic CLN3-Batten is a fatal, pediatric, neurodegenerative disease caused by variants in CLN3, which encodes the endolysosomal transmembrane CLN3 protein. No approved treatment for CLN3 is currently available. The protracted and asynchronous disease presentation complicates the evaluation of potential therapies using clinical disease progression parameters. Biomarkers as surrogates to measure the progression and effect of potential therapeutics are needed. We performed proteomic discovery studies using cerebrospinal fluid (CSF) samples from 28 CLN3-affected and 32 age-similar non-CLN3 individuals. Proximal extension assay (PEA) of 1467 proteins and untargeted data-dependent mass spectrometry [MS; MassIVE FTP server (ftp://MSV000090147@massive.ucsd.edu)] were used to generate orthogonal lists of protein marker candidates. At an adjusted p-value of <0.1 and threshold CLN3/non-CLN3 fold-change ratio of 1.5, PEA identified 54 and MS identified 233 candidate biomarkers. Some of these (NEFL, CHIT1) have been previously linked with other neurologic conditions. Others (CLPS, FAM217B, QRICH2, KRT16, ZNF333) appear to be novel. Both methods identified 25 candidate biomarkers, including CHIT1, NELL1, and ISLR2 which had absolute fold-change ratios >2. NELL1 and ISLR2 regulate axonal development in neurons and are intriguing new candidates for further investigation in CLN3. In addition to identifying candidate proteins for CLN3 research, this study provides a comparison of two large-scale proteomic discovery methods in CSF.

Early recognition of CLN3 disease facilitated by visual electrophysiology and multimodal imaging

BACKGROUND

Neuronal ceroid lipofuscinosis is a group of neurodegenerative disorders with varying visual dysfunction. CLN3 is a subtype which commonly presents with visual decline. Visual symptomatology can be indistinct making early diagnosis difficult. This study reports ocular biomarkers of CLN3 patients to assist clinicians in early diagnosis, disease monitoring, and future therapy.

METHODS

Retrospective review of 5 confirmed CLN3 patients in our eye clinic. Best corrected visual acuity (BCVA), electroretinogram (ERG), ultra-widefield (UWF) fundus photography and fundus autofluorescence (FAF), and optical coherence tomography (OCT) studies were undertaken.

RESULTS

Five unrelated children, 4 females and 1 male, with median age of 6.2 years (4.6-11.7) at first assessment were investigated at the clinic from 2016 to 2021. Four homozygous and one heterozygous pathogenic CLN3 variants were found. Best corrected visual acuities (BCVAs) ranged from 0.18 to 0.88 logMAR at first presentation. Electronegative ERGs were identified in all patients. Bull's eye maculopathies found in all patients. Hyper-autofluorescence ring surrounding hypo-autofluorescence fovea on FAF was found. Foveal ellipsoid zone (EZ) disruptions were found in all patients with additional inner and outer retinal microcystic changes in one patient. Neurological problems noted included autism, anxiety, motor dyspraxia, behavioural issue, and psychomotor regression.

CONCLUSIONS

CLN3 patients presented at median age 6.2 years with visual decline. Early onset maculopathy with an electronegative ERG and variable cognitive and motor decline should prompt further investigations including neuropaediatric evaluation and genetic assessment for CLN3 disease. The structural parameters such as EZ and FAF will facilitate ocular monitoring.

Early postnatal administration of an AAV9 gene therapy is safe and efficacious in CLN3 disease

CLN3 disease, caused by biallelic mutations in the CLN3 gene, is a rare pediatric neurodegenerative disease that has no cure or disease modifying treatment. The development of effective treatments has been hindered by a lack of etiological knowledge, but gene replacement has emerged as a promising therapeutic platform for such disorders. Here, we utilize a mouse model of CLN3 disease to test the safety and efficacy of a cerebrospinal fluid-delivered AAV9 gene therapy with a study design optimized for translatability. In this model, postnatal day one administration of the gene therapy virus resulted in robust expression of human CLN3 throughout the CNS over the 24-month duration of the study. A range of histopathological and behavioral parameters were assayed, with the therapy consistently and persistently rescuing a number of hallmarks of disease while being safe and well-tolerated. Together, the results show great promise for translation of the therapy into the clinic, prompting the launch of a first-in-human clinical trial (NCT03770572).

Deterioration of visual quality and acuity as the first sign of ceroid lipofuscinosis type 3 (CLN3), a rare neurometabolic disease

Ceroid lipofuscinosis type 3 (CLN3) is an autosomal recessive, neurodegenerative metabolic disease. Typical clinical symptoms include progressive visual loss, epilepsy of unknown etiology and dementia. Presence of lipofuscin deposits with typical pattern of 'fingerprints' and vacuolized lymphocytes suggest the diagnosis of CLN3. Cause of CLN3 are mutations in the CLN3 gene, among which the most frequently found is the large deletion 1.02 kb spreading on exons 7 and 8. We present 4 patients from 2 families, in whom the deterioration of visual quality and acuity was observed as first clinical sign, when they were a few years old and it was successively accompanied by symptoms of neurologic deterioration (like generalized convulsions with consciousness impairment). In all patients the 1.02 kb deletion in the CLN3 gene was detected in homo- or heterozygosity with other CLN3 pathogenic variant. Ultrastructural studies revealed abnormal structures corresponding to 'fingerprint' profiles (FPPs) in conjunctival endothelial cells. It should be emphasized that in patients with blindness of unknown cause the diagnosis of ceroid lipofuscinosis should be considered and in older children-especially CLN3. The facility of the analysis for the presence of 1.02 kb deletion and economic costs are a solid argument for intensive use of this test in the diagnostic procedure of CLN3.

Etiology of anxious and fearful behavior in juvenile neuronal ceroid lipofuscinosis (CLN3 disease)

Background

Juvenile neuronal ceroid lipofuscinosis (JNCL, CLN3) is a childhood-onset neurodegenerative disease with prominent symptoms comprising a pediatric dementia syndrome. As in adult dementia, behavioral symptoms like mood disturbances and anxiety are common. In contrast to in adult dementia, however, the anxious behavioral symptoms increase during the terminal phase of JNCL disease. In the present study, the current understanding of the neurobiological mechanisms of anxiety and anxious behavior in general is addressed as will a discussion of the mechanism of the anxious behavior seen in young JNCL patients. Based on developmental behavioral points of view, known neurobiological mechanisms, and the clinical presentation of the anxious behavior, a theory of its etiology is described.

Result and discussion

During the terminal phase, the cognitive developmental age of JNCL patients is below 2 years. At this stage of mental development individuals act primarily from a concrete world of consciousness and do not have the cognitive ability to encounter a normal anxiety response. Instead, they experience the evolutionary basic emotion of fear, and as the episodes typically are provoked when the adolescent JNCL patient is exposed to either loud sounds, is lifted from the ground, or separated from the mother/known caregiver, the fear can best be perceived as the developmental natural fear-response that appears in children 0-2 years of age. The efferent pathways of the neural fear circuits are mediated through autonomic, neuroendocrine, and skeletal-motor responses. The autonomic activation occurs early, is mediated through the sympathetic and parasympathetic neural systems, and as JNCL patients beyond puberty have an autonomic imbalance with a significant sympathetic hyperactivity, the activation of the autonomic nervous system results in a disproportionate high sympathetic activity resulting in tachycardia, tachypnea, excessive sweating, hyperthermia, and an increased atypical muscle activity. The episodes are thus phenotypically similar to what is seen as Paroxysmal Sympathetic Hyperactivity (PSH) following an acute traumatic brain injury. As in PSH, treatment is difficult and so far, no consensus of a treatment algorithm exists. Use of sedative and analgesic medication and minimizing or avoiding provocative stimuli may partly reduce the frequency and intensity of the attacks. Transcutaneous vagal nerve stimulation might be an option worth to investigate rebalancing the sympathetic-parasympathetic disproportion.

Parental experiences of having a child with CLN3 disease (juvenile Batten disease) and how these experiences relate to family resilience

BACKGROUND

CLN3 disease is a neurodegenerative condition presenting in the first decade of life typically leading to death in the third decade. The earliest symptom is rapidly progressive visual impairment followed by intellectual and motor impairments, epilepsy and behavioural disturbances. There are limited data on how the condition affects the family system or the role of family resilience in paediatric neurodegenerative diseases.

METHODS

Semi-structured interviews were conducted with eight parents (five mothers and three fathers) of five children with CLN3. Interview questions focused on the experience of having a child with CLN3, its impact on the family system as well as the concept of family resilience. Data were analysed via thematic analysis.

RESULTS

The thematic analysis resulted in four main themes. The theme 'recurring losses' included the feeling of losing a healthy child, the child's loss of abilities and loss of relationships. The theme 'disruption to the family system' included that siblings could be 'side-lined', the potential negative impact on romantic relationships and difficulties finding time to oneself. The theme 'Society is not developed for a progressive disease' highlighted the difficulties parents faced with respect to contacts with the health and/or social insurance system. The paediatric health care system was seen as supportive, but the adult health care system was not seen as fit for the purpose. Regarding family resilience, parents felt that the disease forced them to reconsider what was important in life. Several parents described that they learned to value small moments of joy and create deep connections through involvement in family routines and rituals.

CONCLUSIONS

CLN3 places a very significant burden on the family system including parental feelings of loss, impact on family relationships and lack of understanding within the health/social insurance systems. The concept of family resilience may be useful in understanding the experiences of families affected by paediatric neurodegenerative conditions.

Towards Understanding Behaviour and Emotions of Children with CLN3 Disease (Batten Disease): Patterns, Problems and Support for Child and Family

The juvenile variant of Neuronal Ceroid Lipofuscinosis (CLN3 disease/Batten disease) is a rare progressive brain disease in children and young adults, characterized by vision loss, decline in cognitive and motor capacities and epilepsy. Children with CLN3 disease often show disturbed behaviour and emotions. The aim of this study is to gain a better understanding of the behaviour and emotions of children with CLN3 disease and to examine the support that the children and their parents are receiving. A combination of qualitative and quantitative analysis was used to analyse patient files and parent interviews. Using a framework analysis approach a codebook was developed, the sources were coded and the data were analysed. The analysis resulted in overviews of (1) typical behaviour and emotions of children as a consequence of CLN3 disease, (2) the support children with CLN3 disease receive, (3) the support parents of these children receive, and (4) the problems these parents face. For a few children their visual, physical or cognitive deterioration was found to lead to specific emotions and behaviour. The quantitative analysis showed that anxiety was reported for all children. The presented overviews on support contain tacit knowledge of health care professionals that has been made explicit by this study. The overviews may provide a lead to adaptable support-modules for children with CLN3 disease and their parents.

Metabolism and Vascular Retinopathies: Current Perspectives and Future Directions

The retina is one of the most metabolically active organs in the body. Although it is an extension of the brain, the metabolic needs of the retina and metabolic exchanges between the different cell types in the retina are not the same as that of the brain. Retinal photoreceptors convert most of the glucose into lactate via aerobic glycolysis which takes place in their cytosol, yet there are immense numbers of mitochondria in photoreceptors. The present article is a focused review of the metabolic dysregulation seen in retinopathies with underlying vascular abnormalities with aberrant mitochondrial metabolism and Hypoxia-inducible factor (HIF) dependent pathogenesis. Special emphasis has been paid to metabolic exchanges between different cell types in retinopathy of prematurity (ROP), age-related macular degeneration (AMD), and diabetic retinopathy (DR). Metabolic similarities between these proliferative retinopathies have been discussed.

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.

Differential gene expression analysis following olfactory learning in honeybee (Apis mellifera L.)

Insects change their stimulus-response through the perception of associating these stimuli with important survival events such as rewards, threats, and mates. Insects develop strong associations and relate them to their experiences through several behavioral procedures. Among the insects, Apis species, Apis mellifera ligustica are known for their outstanding ability to learn with tremendous economic importance. Apis mellifera ligustica has a strong cognitive ability and promising model species for investigating the neurobiological basis of remarkable olfactory learning abilities. Here we evaluated the olfactory learning ability of A. mellifera by using the proboscis extension reflex (PER) protocol. The brains of the learner and failed-learner bees were examined for comparative transcriptome analysis by RNA-Seq to explain the difference in the learning capacity. In this study, we used an appetitive olfactory learning paradigm in the same age of A. mellifera bees to examine the differential gene expression in the brain of the learner and failed-learner. Bees that respond in 2nd and 3rd trials or only responded to 3rd trials were defined as learned bees, failed-learner individuals were those bees that did not respond in all learning trials The results indicate that the learning ability of learner bees was significantly higher than failed-learner bees for 12 days. We obtained approximately 46.7 and 46.4 million clean reads from the learner bees failed-learner bees, respectively. Gene expression profile between learners' bees and failed-learners bees identified 74 differentially expressed genes, 57 genes up-regulated in the brains of learners and 17 genes were down-regulated in the brains of the bees that fail to learn. The qRT-PCR validated the differently expressed genes. Transcriptome analyses revealed that specific genes in learner and failed-learner bees either down-regulated or up-regulated play a crucial role in brain development and learning behavior. Our finding suggests that down-regulated genes of the brain involved in the integumentary system, storage proteins, brain development, sensory processing, and neurodegenerative disorder may result in reduced olfactory discrimination and olfactory sensitivity in failed-learner bees. This study aims to contribute to a better understanding of the olfactory learning behavior and gene expression information, which opens the door for understanding of the molecular mechanism of olfactory learning behavior in honeybees.

Neuronal Ceroid Lipofuscinosis Type 6 (CLN6) clinical findings and molecular diagnosis: Costa Rica's experience

Background

Commonly known as Batten disease, the neuronal ceroid lipofuscinoses (NCLs) are a genetically heterogeneous group of rare pediatric lysosomal storage disorders characterized by the intracellular accumulation of autofluorescent material (known as lipofuscin), progressive neurodegeneration, and neurological symptoms. In 2002, a disease-causing NCL mutation in the CLN6 gene was identified (c.214G > T) in the Costa Rican population, but the frequency of this mutation among local Batten disease patients remains incompletely characterized, as do clinical and demographic attributes for this rare patient population.

Objective

To describe the main sociodemographic and clinical characteristics of patients with a clinical diagnosis for Batten Disease treated at the National Children's Hospital in Costa Rica and to characterize via molecular testing their causative mutations.

Methods

DNA extracted from buccal swabs was used for CLN6 gene sequencing. Participants’ sociodemographic and clinical characteristics were also obtained from their medical records.

Results

Nine patients with a clinical diagnosis of Batten disease were identified. Genetic sequencing determined the presence of the previously described Costa Rican homozygous mutation in 8 of 9 cases. One patient did not have mutations in the CLN6 gene. In all cases where the Costa Rican CLN6 mutation was present, it was accompanied by a substitution in intron 2. Patients were born in 4 of the 7 Costa Rican provinces, with an average onset of symptoms close to 4 years of age. No parental consanguinity was present in pedigrees. Initial clinical manifestations varied between patients but generally included: gait disturbances, language problems, visual impairment, seizures and psychomotor regression. Cortical and cerebellar atrophy was a constant finding when neuroimaging was performed. Seizure medication was a common element of treatment regimens.

Conclusions

This investigation supports that the previously characterized c.214G > T mutation is the most common causative NCL mutation in the Costa Rican population. This mutation is geographically widespread among Costa Rican NCL patients and yields a clinical presentation similar to that observed for CLN6 NCL patients in other geographies.

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.

Seizure phenotype in CLN3 disease and its relation to other neurologic outcome measures

CLN3 disease is a pediatric neurodegenerative condition wherein seizures are common. The most common disease-causing variant is an ~1-kb deletion in CLN3. We investigated seizure phenotype in relation to genotype and to adaptive behavior, MR spectroscopy and CSF biochemical markers in a CLN3 cohort. We performed seizure phenotyping using clinical history, EEG, and the Unified Batten Disease Rating Scale (UBDRS) seizure score. We assessed correlations of seizure severity with disease severity (UBDRS capability), adaptive behavior composite score (ABC; Vineland-3), glutamate+glutamine+GABA and N-acetylaspartate+N-acetylaspartyl glutamate (MR spectroscopy), and CSF neurofilament light chain (NEFL) levels. In 20 participants, median age was 10.7 years (IQR = 7.8). Eighteen completed baseline EEG; 12 had a 1-year follow-up. Seizures were reported in 14 (8 1-kb deletion homozygotes), with median age at onset of 10.0 (IQR = 6.8). Epileptiform discharges were noted in 15 (9 homozygotes). Bilateral tonic clonic (n = 11) and nonmotor seizures (n = 7) were most common. UBDRS seizure score correlated with age (rp = 0.50; [0.08,0.77]; P = .02), UBDRS capability (rp = -0.57; [-0.81,-0.17]; P = .009) and ABC (rp = -0.66; [-0.85,-0.31]; P = .001) scores, glutamate+glutamine+GABA (rp = -0.54; [-0.80,-0.11]; P = .02) and N-acetylaspartate+N-acetylaspartyl glutamate (rp = -0.54; [-0.80,-0.11]; P = .02), and CSF NEFL (rp = 0.65; [0.29,0.85]; P = .002) levels. After controlling for age, correlations with ABC and CSF NEFL remained significant. In our CLN3 cohort, seizures and epileptiform discharges were frequent and often started by age 10 years without significant difference between genotypes. ABC and CSF NEFL correlate with UBDRS seizure score, reflecting the role of seizures in the neurodegenerative process. Longitudinal evaluations in a larger cohort are needed to confirm these findings.

A novel deletion variant in CLN3 with highly variable expressivity is responsible for juvenile neuronal ceroid lipofuscinoses

Mutations in CLN3 (OMIM: 607042) are associated with juvenile neuronal ceroid lipofuscinoses (JNCL)-a rare neurodegenerative disease with early retinal degeneration and progressive neurologic deterioration. The study aimed to determine the underlying genetic factors justifying the NCL phenotype in a large Iraqi consanguineous family. Four affected individuals with an initial diagnosis of NCL were recruited. By doing neuroimaging and also pertinent clinical examinations, e.g. fundus examination, due to heterogeneity of neurodevelopmental disorders, the proband was subjected to the paired-end whole-exome sequencing to identify underlying genetic factors. The candidate variant was also confirmed by Sanger sequencing. Various in silico predictions were used to show the pathogenicity of the variant. This study revealed a novel homozygous frameshift variant-NM_000086.2: c.1127del; p.(Leu376Argfs*15)-in the exon 14 of the CLN3 gene as the most likely disease-causing variant. Three out of 4 patients showed bilateral vision loss (< 7 years) and retinal degeneration with macular changes in both eyes. Electroencephalography demonstrated the loss of normal posterior alpha rhythm and also low amplitude multifocal slow waves. Brain magnetic resonance imaging of the patients with a high degree of deterioration showed mild cerebral and cerebellar cortical atrophy, mild ventriculomegaly, thinning of the corpus callosum and vermis, and non-specific periventricular white matter signal changes in the occipital area. The novel biallelic deletion variant of CLN3 was identified that most probably led to JNCL with variable expressivity of the phenotype. This study also expanded our understanding of the clinical and genetic spectrum of JNCL.

Characterizing upper limb function in the context of activities of daily living in CLN3 disease

In CLN3 disease, impairments in motor function are frequently reported to have later onset compared to visual and cognitive decline, but upper limb motor function has yet to be explored in this population. In a cohort of 22 individuals with CLN3, we used a novel application of multiple measures to (1) characterize motor function, particularly of the upper limbs, in activities of daily living (ADLs), and (2) explore associations between motor function and age as well as visual ability, disease severity, and cognitive function, as evaluated by the Unified Batten Disease Rating Scale (UBDRS), a validated CLN3 disease measure. ADLs that required coordination, speed, and fine motor control were particularly challenging for children with CLN3 based on item-level performance across direct assessments (Jebsen-Taylor Hand Function Test [JTHFT] and MyoSet Tools) and caregiver reports (Pediatric Evaluation of Disability Inventory-Computer Adaptive Testing [PEDI-CAT] and Patient-Reported Outcomes Measurement Information System [PROMIS] Pediatric Upper Extremity). Poorer visual ability, disease severity, and cognitive function were associated with worse performance on these measures, whereas age had limited impact. These findings support the need for children with CLN3 to receive skilled clinical evaluation and treatment tailored to their individual needs, particularly in the context of ADLs, as their symptom profile progresses.

A human model of Batten disease shows role of CLN3 in phagocytosis at the photoreceptor-RPE interface

Mutations in CLN3 lead to photoreceptor cell loss in CLN3 disease, a lysosomal storage disorder characterized by childhood-onset vision loss, neurological impairment, and premature death. However, how CLN3 mutations cause photoreceptor cell death is not known. Here, we show that CLN3 is required for phagocytosis of photoreceptor outer segment (POS) by retinal pigment epithelium (RPE) cells, a cellular process essential for photoreceptor survival. Specifically, a proportion of CLN3 in human, mouse, and iPSC-RPE cells localized to RPE microvilli, the site of POS phagocytosis. Furthermore, patient-derived CLN3 disease iPSC-RPE cells showed decreased RPE microvilli density and reduced POS binding and ingestion. Notably, POS phagocytosis defect in CLN3 disease iPSC-RPE cells could be rescued by wild-type CLN3 gene supplementation. Altogether, these results illustrate a novel role of CLN3 in regulating POS phagocytosis and suggest a contribution of primary RPE dysfunction for photoreceptor cell loss in CLN3 disease that can be targeted by gene therapy.

Low Incidence of Postdural Puncture Headache Further Reduced With Atraumatic Spinal Needle: A Retrospective Cohort Study

BACKGROUND

The purpose of the study was to evaluate the incidence of postdural puncture headache in a predominantly pediatric sample before and after a transition from conventional to atraumatic spinal needles.

METHODS

In this retrospective cohort study, we analyzed data from 1059 lumbar puncture procedures in 181 individuals enrolled in NIH Clinical Center research protocols. Multivariate logistic regression was used to evaluate the association between postdural puncture headache and spinal needle type after adjusting for patient age, sex, and body mass index. A random effect of participant was used to accommodate repeated observations.

RESULTS

The median age at time of procedure was 15.3 years. The overall rate of postdural puncture headache was 5.1% (54 of 1059). With conventional needles and atraumatic needles, respectively, the rate of postdural puncture headache was 7.7% (43 of 588) and 2.3% (11 of 471); (odds ratio 0.32, 95% confidence interval 0.15 to 0.68).

CONCLUSIONS

Lumbar puncture for cerebrospinal fluid collection is an essential and common procedure in pediatric clinical care and research. Postdural puncture headache is the most common adverse event of the lumbar puncture procedure. Our data indicate that lumbar puncture is safe in pediatrics and that use of an atraumatic spinal needle further reduces the risk of postdural puncture headache.

Neurofilament light chain levels correlate with clinical measures in CLN3 disease

PURPOSE

CLN3 disease is a neurodegenerative disorder with onset in childhood. It affects multiple functions at different developmental stages. Incomplete understanding of the pathophysiology hampers identification of cell and tissue biochemical compounds reflective of the disease process. As treatment approaches are being explored, more sensitive, objective, quantifiable, and clinically relevant biomarkers are needed.

METHODS

We collected prospective biosamples from 21 phenotyped individuals with CLN3. We measured neurofilament light chain (NEFL) levels, a marker of neuronal damage, in cross-sectional CSF and serum samples from individuals with CLN3 and in pediatric non-CLN3 controls using two different assays.

RESULTS

Cerebrospinal fluid (CSF) and serum NEFL levels are significantly higher in CLN3 (CSF: 2096 ± 1202; serum: 29.0 ± 18.0 pg/mL) versus similarly aged non-CLN3 (CSF: 345 ± 610; serum: 6.7 ± 3.2 pg/mL) samples. NEFL levels correlate with Unified Batten Disease Rating Scale and adaptive behavior composite scores, and magnetic resonance (MR) spectroscopy markers. NEFL levels from CSF and serum are strongly correlated (r_p = 0.83; p < 0.0001).

CONCLUSION

CSF and serum NEFL levels increase in multiple neurologic conditions. Here, we show that CSF and serum NEFL levels also increase in CLN3 (versus non-CLN3) and correlate with other disease-relevant measures. These findings suggest NEFL as a relevant and feasible biomarker for applications in CLN3 clinical trials and management.

Neuronal Ceroid Lipofuscinosis: Potential for Targeted Therapy

Neuronal ceroid lipofuscinosis (NCLs) is a group of inherited neurodegenerative lysosomal storage diseases that together represent the most common cause of dementia in children. Phenotypically, patients have visual impairment, cognitive and motor decline, epilepsy, and premature death. A primary challenge is to halt and/or reverse these diseases, towards which developments in potential effective therapies are encouraging. Many treatments, including enzyme replacement therapy (for CLN1 and CLN2 diseases), stem-cell therapy (for CLN1, CLN2, and CLN8 diseases), gene therapy vector (for CLN1, CLN2, CLN3, CLN5, CLN6, CLN7, CLN10, and CLN11 diseases), and pharmacological drugs (for CLN1, CLN2, CLN3, and CLN6 diseases) have been evaluated for safety and efficacy in pre-clinical and clinical studies. Currently, cerliponase alpha for CLN2 disease is the only approved therapy for NCL. Lacking is any study of potential treatments for CLN4, CLN9, CLN12, CLN13 or CLN14 diseases. This review provides an overview of genetics for each CLN disease, and we discuss the current understanding from pre-clinical and clinical study of potential therapeutics. Various therapeutic interventions have been studied in many experimental animal models. Combination of treatments may be useful to slow or even halt disease progression; however, few therapies are unlikely to even partially reverse the disease and a complete reversal is currently improbable. Early diagnosis to allow initiation of therapy, when indicated, during asymptomatic stages is more important than ever.

Current Insights in Elucidation of Possible Molecular Mechanisms of the Juvenile Form of Batten Disease

The neuronal ceroid lipofuscinoses (NCLs) collectively constitute one of the most common forms of inherited childhood-onset neurodegenerative disorders. They form a heterogeneous group of incurable lysosomal storage diseases that lead to blindness, motor deterioration, epilepsy, and dementia. Traditionally the NCL diseases were classified according to the age of disease onset (infantile, late-infantile, juvenile, and adult forms), with at least 13 different NCL varieties having been described at present. The current review focuses on classic juvenile NCL (JNCL) or the so-called Batten (Batten-Spielmeyer-Vogt; Spielmeyer-Sjogren) disease, which represents the most common and the most studied form of NCL, and is caused by mutations in the CLN3 gene located on human chromosome 16. Most JNCL patients carry the same 1.02-kb deletion in this gene, encoding an unusual transmembrane protein, CLN3, or battenin. Accordingly, the names CLN3-related neuronal ceroid lipofuscinosis or CLN3-disease sometimes have been used for this malady. Despite excessive in vitro and in vivo studies, the precise functions of the CLN3 protein and the JNCL disease mechanisms remain elusive and are the main subject of this review. Although the CLN3 gene is highly conserved in evolution of all mammalian species, detailed analysis of recent genomic and transcriptomic data indicates the presence of human-specific features of its expression, which are also under discussion. The main recorded to date changes in cell metabolism, to some extent contributing to the emergence and progression of JNCL disease, and human-specific molecular features of CLN3 gene expression are summarized and critically discussed with an emphasis on the possible molecular mechanisms of the malady appearance and progression.

Mouse Models of Inherited Retinal Degeneration with Photoreceptor Cell Loss

Inherited retinal degeneration (RD) leads to the impairment or loss of vision in millions of individuals worldwide, most frequently due to the loss of photoreceptor (PR) cells. Animal models, particularly the laboratory mouse, have been used to understand the pathogenic mechanisms that underlie PR cell loss and to explore therapies that may prevent, delay, or reverse RD. Here, we reviewed entries in the Mouse Genome Informatics and PubMed databases to compile a comprehensive list of monogenic mouse models in which PR cell loss is demonstrated. The progression of PR cell loss with postnatal age was documented in mutant alleles of genes grouped by biological function. As anticipated, a wide range in the onset and rate of cell loss was observed among the reported models. The analysis underscored relationships between RD genes and ciliary function, transcription-coupled DNA damage repair, and cellular chloride homeostasis. Comparing the mouse gene list to human RD genes identified in the RetNet database revealed that mouse models are available for 40% of the known human diseases, suggesting opportunities for future research. This work may provide insight into the molecular players and pathways through which PR degenerative disease occurs and may be useful for planning translational studies.

Advances in the Treatment of Neuronal Ceroid Lipofuscinosis

Neuronal ceroid lipofuscinoses (NCL) represent a class of neurodegenerative disorders involving defective lysosomal processing enzymes or receptors, leading to lysosomal storage disorders, typically characterized by observation of cognitive and visual impairments, epileptic seizures, ataxia, and deterioration of motor skills. Recent success of a biologic (Brineura®) for the treatment of neurologic manifestations of the central nervous system (CNS) has led to renewed interest in therapeutics for NCL, with the goal of ablating or reversing the impact of these devastating disorders. Despite complex challenges associated with CNS therapy, many treatment modalities have been evaluated, including enzyme replacement therapy, gene therapy, stem cell therapy, and small molecule pharmacotherapy. Because the clinical endpoints for the evaluation of candidate therapies are complex and often reliant on subjective clinical scales, the development of quantitative biomarkers for NCLs has become an apparent necessity for the validation of potential treatments. We will discuss the latest findings in the search for relevant biomarkers for assessing disease progression. For this review, we will focus primarily on recent pre-clinical and clinical developments for treatments to halt or cure these NCL diseases. Continued development of current therapies and discovery of newer modalities will be essential for successful therapeutics for NCL.

AREAS COVERED

The reader will be introduced to the NCL subtypes, natural histories, experimental animal models, and biomarkers for NCL progression; challenges and different therapeutic approaches, and the latest pre-clinical and clinical research for therapeutic development for the various NCLs. This review corresponds to the literatures covering the years from 1968 to mid-2019, but primarily addresses pre-clinical and clinical developments for the treatment of NCL disease in the last decade and as a follow-up to our 2013 review of the same topic in this journal.

EXPERT OPINION

Much progress has been made in the treatment of neurologic diseases, such as the NCLs, including better animal models and improved therapeutics with better survival outcomes. Encouraging results are being reported at symposiums and in the literature, with multiple therapeutics reaching the clinical trial stage for the NCLs. The potential for a cure could be at hand after many years of trial and error in the preclinical studies. The clinical development of enzyme replacement therapy (Brineura® for CLN2), immunosuppression (CellCept® for CLN3), and gene therapy vectors (for CLN1, CLN2, CLN3, and CLN6) are providing encouragement to families that have a child afflicted with NCL. We believe that successful therapies in the future may involve the combination of two or more therapeutic modalities to provide therapeutic benefit especially as the patients grow older.

Juvenile Batten Disease (CLN3): Detailed Ocular Phenotype, Novel Observations, Delayed Diagnosis, Masquerades, and Prospects for Therapy

Purpose

To characterize the retinal phenotype of juvenile neuronal ceroid lipofuscinosis (JNCL), highlight delayed and mistaken diagnosis, and propose an algorithm for early identification.

Design

Retrospective case series.

Participants

Eight children (5 female) with JNCL.

Methods

Review of clinical notes, retinal imaging including fundus autofluorescence and OCT, electroretinography (ERG), and both microscopy and molecular genetic testing.

Main Outcome Measurements

Demographic data, signs and symptoms, visual acuity (VA), fundus autofluorescence and OCT findings, ERG phenotype, and microscopy/molecular genetics.

Results

Participants presented with rapid bilateral vision loss over 1 to 18 months, with mean VA deteriorating from 0.44 logarithm of the minimum angle of resolution (logMAR) (range, 0.20–1.78 logMAR) at baseline to 1.34 logMAR (0.30 logMAR - light perception) at last follow-up. Age of onset ranged from 3 to 7 years (mean, 5.3 years). The age at diagnosis of JNCL ranged from 7 to 10 years (mean, 8.3 years). Six children displayed eccentric fixation, and 6 children had cognitive or neurologic signs at the time of diagnosis (75%). Seven patients had bilateral bull’s-eye maculopathy at presentation. Coats-like exudative vasculopathy, not previously reported in JNCL, was observed in 1 patient. OCT imaging revealed near complete loss of outer retinal layers and marked atrophy of the nerve fiber and ganglion cell layers at the central macula. An electronegative ERG was present in 4 patients (50%), but with additional a-wave reduction, there was an undetectable ERG in the remaining 4 patients. Blood film microscopy revealed vacuolated lymphocytes, and electron microscopy showed lysosomal (fingerprint) inclusions in all 8 patients.

Conclusions

In a young child with bilateral rapidly progressive vision loss and macular disturbance, blood film microscopy to detect vacuolated lymphocytes is a rapid, readily accessible, and sensitive screening test for JNCL. Early suspicion of JNCL can be aided by detailed directed history and high-resolution retinal imaging, with subsequent targeted microscopy/genetic testing. Early diagnosis is critical to ensure appropriate management, counseling, support, and social care for children and their families. Furthermore, although potential therapies for this group of disorders are in early-phase clinical trial, realistic expectations are that successful intervention will be most effective when initiated at the earliest stage of disease.