Infantile Neuronal Ceroid Lipofuscinosis Research Articles

A survival analysis of ventricular access devices for delivery of cerliponase alfa.

Late infantile neuronal ceroid lipofuscinosis type 2 (CLN2) is a rare autosomal recessive disease caused by tripeptidyl peptidase 1 enzyme deficiency. At the authors' center, the medication cerliponase alfa is administered every 2 weeks via the intracerebroventricular (ICV) route. This requires the placement of a ventricular access device (VAD) or reservoir and frequent percutaneous punctures of this device over the child's lifetime. In this study, the authors audited the longevity and survival of these VADs and examined the causes of device failure. A single-center survival analysis of VAD insertions and revisions (January 2014 through June 2020) was conducted. All children received cerliponase alfa infusions through a VAD. Patient characteristics and complications were determined from a prospectively maintained surgical database and patient records. For the VAD survival analysis, the defined endpoint was when the device was removed or changed. Reservoir survival was assessed using Kaplan-Meier curves and the log-rank (Cox-Mantel) test. A total of 17 patients had VADs inserted for drug delivery; median (range) age at first surgery was 4 years 4 months (1 year 8 months to 15 years). Twenty-six VAD operations (17 primary insertions and 9 revisions) were required among these 17 patients. Twelve VAD operations had an associated complication, including CSF infection (n = 6) with Propionibacterium and Staphylococcus species being the most prevalent organisms, significant surgical site swelling preventing infusion (n = 3), leakage/wound breakdown (n = 2), and catheter obstruction (n = 1). There were no complications or deaths associated with VAD insertion. The median (interquartile range) number of punctures was 59.5 (7.5-82.0) for unrevised VADs (n = 17) versus 2 (6-87.5) for revised VADs (n = 9) (p = 0.70). The median survival was 301 days for revisional reservoirs (n = 9) versus 2317 days for primary inserted reservoirs (n = 17) (p = 0.019). In the context of the current interest in intrathecal drug delivery for rare metabolic disorders, the need for VADs is likely to increase. Auditing the medium- to long-term outcomes associated with these devices will hopefully result in their wider application and may have potential implications on the development of new VAD technologies. These results could also be used to counsel parents prior to commencement of therapy and VAD implantation.

Brain transcriptome analysis of a CLN2 mouse model as a function of disease progression

BackgroundNeuronal ceroid lipofuscinoses, (NCLs or Batten disease) are a group of inherited, early onset, fatal neurodegenerative diseases associated with mutations in 13 genes. All forms of the disease are characterized by lysosomal accumulation of fluorescent storage material, as well as profound neurodegeneration, but the relationship of the various genes’ function to a single biological process is not obvious. In this study, we used a well-characterized mouse model of classical late infantile NCL (cLINCL) in which the tripeptidyl peptidase 1 (Tpp1) gene is disrupted by gene targeting, resulting in loss of detectable TPP1 activity and leading to progressive neurological phenotypes including ataxia, increased motor deficiency, and early death.MethodsIn order to identify genes and pathways that may contribute to progression of the neurodegenerative process, we analyzed forebrain/midbrain and cerebellar transcriptional differences at 1, 2, 3 and 4 months of age in control and TPP1-deficient mice by global RNA-sequencing.ResultsProgressive neurodegenerative inflammatory responses involving microglia, astrocytes and endothelial cells were observed, accompanied by activation of leukocyte extravasation signals and upregulation of nitric oxide production and reactive oxygen species. Several astrocytic (i.e., Gfap, C4b, Osmr, Serpina3n) and microglial (i.e., Ctss, Itgb2, Itgax, Lyz2) genes were identified as strong markers for assessing disease progression as they showed increased levels of expression in vivo over time. Furthermore, transient increased expression of choroid plexus genes was observed at 2 months in the lateral and fourth ventricle, highlighting an early role for the choroid plexus and cerebrospinal fluid in the disease pathology. Based on these gene expression changes, we concluded that neuroinflammation starts, for the most part, after 2 months in the Tpp1−/− brain and that activation of microglia and astrocytes occur more rapidly in cerebellum than in the rest of the brain; confirming increased severity of inflammation in this region.ConclusionsThese findings have led to a better understanding of cLINCL pathological onset and progression, which may aid in development of future therapeutic treatments for this disease.

Towards Splicing Therapy for Lysosomal Storage Disorders: Methylxanthines and Luteolin Ameliorate Splicing Defects in Aspartylglucosaminuria and Classic Late Infantile Neuronal Ceroid Lipofuscinosis.

Splicing defects caused by mutations in the consensus sequences at the borders of introns and exons are common in human diseases. Such defects frequently result in a complete loss of function of the protein in question. Therapy approaches based on antisense oligonucleotides for specific gene mutations have been developed in the past, but they are very expensive and require invasive, life-long administration. Thus, modulation of splicing by means of small molecules is of great interest for the therapy of genetic diseases resulting from splice-site mutations. Using minigene approaches and patient cells, we here show that methylxanthine derivatives and the food-derived flavonoid luteolin are able to enhance the correct splicing of the AGA mRNA with a splice-site mutation c.128-2A>G in aspartylglucosaminuria, and result in increased AGA enzyme activity in patient cells. Furthermore, we also show that one of the most common disease causing TPP1 gene variants in classic late infantile neuronal ceroid lipofuscinosis may also be amenable to splicing modulation using similar substances. Therefore, our data suggest that splice-modulation with small molecules may be a valid therapy option for lysosomal storage disorders.

CLN6 deficiency causes selective changes in the lysosomal protein composition.

Neuronal ceroid lipofuscinoses (NCLs) collectively account for the highest prevalence of inherited neurodegenerative diseases in childhood. This disease group is classified by the deposition of similar autofluorescence storage material in lysosomes that is accompanied by seizures, blindness and premature mortality in later disease stages. Defects in several genes affecting various proteins lead to NCL, one of them being CLN6, a transmembrane protein resident in the endoplasmic reticulum. Dysfunctionality of CLN6 causes variant late infantile NCL (vLINCL). The function of CLN6 and how its deficiency affects lysosomal integrity remains unknown. In this work, we performed a comparative proteomic analysis of isolated lysosomal fractions from liver tissue of nclf mice, a natural mouse model displaying a similar disease course than its human counterpart. We could identify a drastic reduction in the protein amounts of selected lysosomal proteins, amongst them several members of the NCL protein family. Most of these proteins were N-glycosylated, soluble hydrolases and their reduction in protein levels was verified by western blotting and enzymatic assays. Hereby we could directly link Cln6 dysfunction to changes in the lysosomal compartment and to other NCL forms.

A RARE CASE OF KCTD7 MUTATION

Progressive myoclonus epilepsy (PME) is a rare condition caused by numerous genetic diseases. Pathogenic variants in KCTD7 have been reported in association with rare form of infantile neuronal ceroid-lipofuscinosis, autosomal recessive progressive myoclonic epilepsy-3 with or without intracellular inclusions. We report about a 4 years old girl with focal epilepsy, mild intellectual disability, developmental delay, muscle weakness, walking difficulties, dysphagia, nystagmus, episodic ataxia, dystonia, and hypotonia. The first symptoms began at 18 months with focal epileptic seizure. Genetic testing reveals homozygous KCTD7 c.295C>T, p.(Arg99*) mutation.

Ablation of microRNA-155 and neuroinflammation in a mouse model of CLN1-disease

Infantile neuronal ceroid lipofuscinosis (INCL), also known as CLN1-disease, is a devastating neurodegenerative lysosomal storage disorder (LSD), caused by inactivating mutations in the CLN1 gene. The Cln1−/− mice, which mimic INCL, manifest progressive neuroinflammation contributing to neurodegeneration. However, the underlying mechanism of neuroinflammation in INCL and in Cln1−/− mice has remained elusive. Previously, it has been reported that microRNA-155 (miR-155) regulates inflammation and miR profiling in Cln1−/− mouse brain showed that the level of miR-155 was upregulated. Thus, we sought to determine whether ablation of miR-155 in Cln1−/− mice may suppress neuroinflammation in these mice. Towards this goal, we generated Cln1−/−/miR-155−/− double-knockout mice and evaluated the inflammatory signatures in the brain. We found that the brains of double-KO mice manifest progressive neuroinflammatory changes virtually identical to those found in Cln1−/− mice. We conclude that ablation of miR-155 in Cln1−/− mice does not alter the neuroinflammatory trajectory in INCL mouse model.

An ERG and OCT study of neuronal ceroid lipofuscinosis CLN2 Battens retinopathy

BackgroundLate infantile neuronal ceroid lipofuscinosis (CLN2 Batten disease) is a rare, progressive neurodegenerative disease of childhood. The natural history of motor and language regression is used to monitor the efficacy of CNS treatments. Less is known about CLN2 retinopathy. Our aim is to elaborate the nature, age of onset, and symmetry of CLN2 retinopathy using visual electrophysiology and ophthalmic imaging.Subjects and methodsWe reviewed 22 patients with genetically confirmed CLN2 disease; seventeen showing classical and five atypical disease. Flash electroretinograms (ERGs), flash and pattern reversal visual evoked potentials (VEPs), recorded from awake children were collated. Available fundus images were graded, optical coherence tomography (OCT) central subfoveal thickness (CST) measured, and genotype, age, clinical vision assessment and motor language grades assembled.ResultsERGs show cone/rod system dysfunction preceded by localised macular ellipsoid zone disruption on OCT from 4.8 years. Electroencephalogram (EEG) time-locked spikes confounded both pattern 6/17 (35%) and flash VEPs 12/16 (75%). Paired right eye (RE) and left eye (LE) ERG amplitudes did not differ significantly for each flash stimulus at the p 0.001 level, Wilcoxon ranked signed test. Cone ERGs show a functional deficit before CST thinning in classical disease. Optomap hyper fundus autofluorescence (FAF) at the fovea was noted in three patients with normal ERGs. The oldest patient showed an ovoid aggregate above the external limiting membrane at the fovea, which did not affect the PERG.ConclusionERG findings in CLN2 retinopathy show symmetrical cone-rod dysfunction, from 4y10m in this series, but a broad range of ages when ERG function is preserved.

Effect of small molecule eRF3 degraders on premature termination codon readthrough.

Premature termination codon (PTC) readthrough is considered a potential treatment for genetic diseases caused by nonsense mutations. High concentrations of aminoglycosides induce low levels of PTC readthrough but also elicit severe toxicity. Identifying compounds that enhance PTC readthrough by aminoglycosides or reduce their toxicity is a continuing challenge. In humans, a binary complex of eukaryotic release factors 1 (eRF1) and 3 (eRF3a or eRF3b) mediates translation termination. They also participate in the SURF (SMG1-UPF1-eRF1-eRF3) complex assembly involved in nonsense-mediated mRNA decay (NMD). We show that PTC readthrough by aminoglycoside G418 is considerably enhanced by eRF3a and eRF3b siRNAs and cereblon E3 ligase modulators CC-885 and CC-90009, which induce proteasomal degradation of eRF3a and eRF3b. eRF3 degradation also reduces eRF1 levels and upregulates UPF1 and selectively stabilizes TP53 transcripts bearing a nonsense mutation over WT, indicating NMD suppression. CC-90009 is considerably less toxic than CC-885 and it enhances PTC readthrough in combination with aminoglycosides in mucopolysaccharidosis type I-Hurler, late infantile neuronal ceroid lipofuscinosis, Duchenne muscular dystrophy and junctional epidermolysis bullosa patient-derived cells with nonsense mutations in the IDUA, TPP1, DMD and COL17A1 genes, respectively. Combination of CC-90009 with aminoglycosides such as gentamicin or ELX-02 may have potential for PTC readthrough therapy.

GFAP hyperpalmitoylation exacerbates astrogliosis and neurodegenerative pathology in PPT1-deficient mice

The homeostasis of protein palmitoylation and depalmitoylation is essential for proper physiological functions in various tissues, in particular the central nervous system (CNS). The dysfunction of PPT1 (PPT1-KI, infantile neuronal ceroid lipofuscinosis [INCL] mouse model), which catalyze the depalmitoylation process, results in serious neurodegeneration accompanied by severe astrogliosis in the brain. Endeavoring to determine critical factors that might account for the pathogenesis in CNS by palm-proteomics, glial fibrillary acidic protein (GFAP) was spotted, indicating that GFAP is probably palmitoylated. Questions concerning if GFAP is indeed palmitoylated in vivo and how palmitoylation of GFAP might participate in neural pathology remain unexplored and are waiting to be investigated. Here we show that GFAP is readily palmitoylated in vitro and in vivo; specifically, cysteine-291 is the unique palmitoylated residue in GFAP. Interestingly, it was found that palmitoylated GFAP promotes astrocyte proliferation in vitro. Furthermore, we showed that PPT1 depalmitoylates GFAP, and the level of palmitoylated GFAP is overwhelmingly up-regulated in PPT1-knockin mice, which lead us to speculate that the elevated level of palmitoylated GFAP might accelerate astrocyte proliferation in vivo and ultimately led to astrogliosis in INCL. Indeed, blocking palmitoylation by mutating cysteine-291 into alanine in GFAP attenuate astrogliosis, and remarkably, the concurrent neurodegenerative pathology in PPT1-knockin mice. Together, these findings demonstrate that hyperpalmitoylated GFAP plays critical roles in regulating the pathogenesis of astrogliosis and neurodegeneration in the CNS, and most importantly, pinpointing that cysteine-291 in GFAP might be a valuable pharmaceutical target for treating INCL and other potential neurodegenerative diseases.

Immune modulation attenuates infantile neuronal ceroid lipofuscinosis in mice before and after disease onset.

Targeting neuroinflammation in models for infantile and juvenile forms of neuronal ceroid lipofuscinosis (NCL, CLN disease) with the clinically established immunomodulators fingolimod and teriflunomide significantly attenuates the neurodegenerative phenotype when applied preventively, i.e. before the development of substantial neural damage and clinical symptoms. Here, we show that in a mouse model for the early onset and rapidly progressing CLN1 form, more complex clinical phenotypes like disturbed motor coordination and impaired visual acuity are also ameliorated by immunomodulation. Moreover, we show that the disease outcome can be attenuated even when fingolimod and teriflunomide treatment starts after disease onset, i.e. when neurodegeneration is ongoing and clinical symptoms are detectable. In detail, treatment with either drug led to a reduction in T-cell numbers and microgliosis in the CNS, although not to the same extent as upon preventive treatment. Pharmacological immunomodulation was accompanied by a reduction of axonal damage, neuron loss and astrogliosis in the retinotectal system and by reduced brain atrophy. Accordingly, the frequency of myoclonic jerks and disturbed motor coordination were attenuated. Overall, disease alleviation was remarkably substantial upon therapeutic treatment with both drugs, although less robust than upon preventive treatment. To test the relevance of putative immune-independent mechanisms of action in this model, we treated CLN1 mice lacking mature T- and B-lymphocytes. Immunodeficient CLN1 mice showed, as previously reported, an improved neurological phenotype in comparison with genuine CLN1 mice which could not be further alleviated by either of the drugs, reflecting a predominantly immune-related therapeutic mechanism of action. The present study supports and strengthens our previous view that repurposing clinically approved immunomodulators may alleviate the course of CLN1 disease in human patients, even though diagnosis usually occurs when symptoms have already emerged.

Human INCL fibroblasts display abnormal mitochondrial and lysosomal networks and heightened susceptibility to ROS-induced cell death.

Infantile Neuronal Ceroid Lipofuscinosis (INCL) is a pediatric neurodegenerative disorder characterized by progressive retinal and central nervous system deterioration during infancy. This lysosomal storage disorder results from a deficiency in the Palmitoyl Protein Thioesterase 1 (PPT1) enzyme—a lysosomal hydrolase which cleaves fatty acid chains such as palmitate from lipid-modified proteins. In the absence of PPT1 activity, these proteins fail to be degraded, leading to the accumulation of autofluorescence storage material in the lysosome. The underlying molecular mechanisms leading to INCL pathology remain poorly understood. A role for oxidative stress has been postulated, yet little evidence has been reported to support this possibility. Here we present a comprehensive cellular characterization of human PPT1-deficient fibroblast cells harboring Met1Ile and Tyr247His compound heterozygous mutations. We detected autofluorescence storage material and observed distinct organellar abnormalities of the lysosomal and mitochondrial structures, which supported previous postulations about the role of ER, mitochondria and oxidative stress in INCL. An increase in the number of lysosomal structures was found in INCL patient fibroblasts, which suggested an upregulation of lysosomal biogenesis, and an association with endoplasmic reticulum stress response. The mitochondrial network also displayed abnormal spherical punctate morphology instead of normal elongated tubules with extensive branching, supporting the involvement of mitochondrial and oxidative stress in INCL cell death. Autofluorescence accumulation and lysosomal pathologies can be mitigated in the presence of conditioned wild type media suggesting that a partial restoration via passive introduction of the enzyme into the cellular environment may be possible. We also demonstrated, for the first time, that human INCL fibroblasts have a heightened susceptibility to exogenous reactive oxygen species (ROS)-induced cell death, which suggested an elevated basal level of endogenous ROS in the mutant cell. Collectively, these findings support the role of intracellular organellar networks in INCL pathology, possibly due to oxidative stress.

“Real world effectiveness of cerliponase alfa in classical and atypical patients. A case series”

IntroductionLate infantile neuronal ceroid lipofuscinosis is an autosomal recessive disease caused by mutations in the CLN2/TPP1 gene, with secondary enzyme deficiency. In classical phenotypes, initial symptoms include seizures and delayed language development between 2 and 4 years of age. This article describes the presentation of CLN2 disease in a cohort of Colombian patients, as well as the impact of treatment on the course and progression of the disease. MethodsCase series report of 8 patients with a confirmed diagnosis of neuronal ceroid lipofuscinosis treated with cerliponase alfa who remained on clinical and paraclinical follow-up for up to 24 months before and after treatment. ResultsAn atypical phenotype, associated with initial symptoms and late diagnosis, was present in 5/8 patients. The most frequent symptoms were seizures and developmental delay, with age of onset at 24 months (classical phenotype) and 48 months (atypical phenotype). A novel mutation (c.1438G > A) was found in two siblings. All of the patients received cerliponase alfa, and there were no serious adverse events. No decline in the clinical status greater than 2 points on Hamburg, Weill Cornell and CNL2 clinical assessment scale was observed during follow-up after treatment initiation. ConclusionThis is the first case series reported for neuronal ceroid lipofuscinosis patients in Colombia. In contrast with other reports, the majority of cases reported here displayed an atypical phenotype. Our study highlights the importance of early diagnosis and timely initiation of therapy, which is a feasible therapy, well tolerated by patients and accepted by caregivers in this country, generating a positive impact in the quality of life of CLN2 patients and on disease outcome.

Devising effective enzyme replacement therapy for infantile onset neuronal ceroid lipofuscinosis (CLN1 disease)

Devising effective enzyme replacement therapy for infantile onset neuronal ceroid lipofuscinosis (CLN1 disease)

Single-dose AAV9-CLN6 gene transfer slows the decline in motor and language function in variant late infantile neuronal ceroid lipofuscinosis 6: Interim results from phase 1/2 trial

Single-dose AAV9-CLN6 gene transfer slows the decline in motor and language function in variant late infantile neuronal ceroid lipofuscinosis 6: Interim results from phase 1/2 trial

Characterizing expressive language skills in children with late infantile neuronal ceroid lipofuscinosis type 2 (CLN2): The caregiver perspective

Characterizing expressive language skills in children with late infantile neuronal ceroid lipofuscinosis type 2 (CLN2): The caregiver perspective

Neuronal ceroid lipofuscinosis: genetic and phenotypic spectrum of 14 patients from Turkey.

Neuronal ceroid lipofuscinoses (NCLs) is a group of congenital metabolic diseases where the neurodegenerative process with the accumulation of ceroid and lipofuscin autofluorescent storage materials is at the forefront. According to the age of presentation, NCLs are classified as congenital, infantile (INCL), late infantile (LINCL), juvenile (JNCL), and adult (ANCL) NCLs. In our study, it was aimed to discuss the clinical and molecular characteristics of our patients diagnosed with NCL. This is a descriptive cross-sectional study which was conducted in 14 patients from 10 unrelated families who were diagnosed with different types of NCL based on clinical presentation, neuroimaging, biochemical measurements, and molecular analyses, at the department of pediatric metabolism between June 2015 and June 2020. A total of 14 patients were diagnosed with different types of NCL. Of those, 4 patients were diagnosed with NCL7 (4/14; 30%), 3/14 (23%) with NCL1, 3/14 (23%) with NCL2, 2/14 (14.2%) with NCL13, and 1/14 (7.1%) with NCL10. Eleven pathogenic variants were detected, 5 of which are novel (c.721G>T [p.Gly241Ter] and c.301G>C [p.Ala146Pro] in MFDS8 gene; c.316C>T [p.Gln106Ter] in PPT1 gene; c.341C>T [p.Ala114Val] in TPP1 gene; c.686A>T [p.Glu229Val] in CTSD gene) CONCLUSION: This study is one of the pioneer comprehensive researches from Turkey that provides information about disease-causing variants and clinical presentation of different and rare types of NCLs. The identification of novel variants and phenotypic expansion is important for genetic counselling in Turkey and expected to improve understanding of NCLs.

A novel pathogenic frameshift variant unmasked by a large de novo deletion at 13q21.33-q31.1 in a Chinese patient with neuronal ceroid lipofuscinosis type 5

BackgroundNeuronal ceroid lipofuscinosis type 5 (CLN5) is a rare form of neuronal ceroid lipofuscinoses (NCLs) which are a group of inherited neurodegenerative diseases characterized by progressive intellectual and motor deterioration, visual failure, seizures, behavioral changes and premature death. CLN5 was initially named Finnish variant late infantile NCL, it is now known to be present in other ethnic populations and with variable age of onset. Few CLN5 patients had been reported in Chinese population.Case presentationIn this paper, we report the symptoms of a Chinese patient who suffer from developmental regression and grand mal epilepsy for several years. The DNA was extracted from peripheral blood of proband and both parents, and then whole exome sequencing was performed using genomic DNA. Both sequence variants and copy number variants (CNVs) were analyzed and classified according to guidelines. As the result, a novel frameshift mutation c.718_719delAT/p.Met240fs in CLN5 and a de novo large deletion at 13q21.33-q31.1 which unmasked the frameshift mutation were identified in the proband. Despite the large de novo deletion, which can be classified as a pathogenic copy number variant (CNV), the patient’s clinical presentation is mostly consistent with that of CLN5, except for early developmental delay which is believed due to the large deletion. Both variants were detected simultaneously by exome sequencing.ConclusionsThis is the first report of whole gene deletion in combination with a novel pathogenic sequence variant in a CLN5 patient. The two mutations detected with whole exome sequencing simultaneously proved the advantage of the sequencing technology for genetic diagnostics.

Cln1-mutations suppress Rab7-RILP interaction and impair autophagy contributing to neuropathology in a mouse model of infantile neuronal ceroid lipofuscinosis.

Infantile neuronal ceroid lipofuscinosis (INCL) is a devastating neurodegenerative lysosomal storage disease (LSD) caused by inactivating mutations in the CLN1 gene. CLN1 encodes palmitoyl-protein thioesterase-1 (PPT1), a lysosomal enzyme that catalyzes the deacylation of S-palmitoylated proteins to facilitate their degradation and clearance by lysosomal hydrolases. Despite the discovery more than two decades ago that CLN1 mutations causing PPT1-deficiency underlies INCL, the precise molecular mechanism(s) of pathogenesis has remained elusive. Here, we report that autophagy is dysregulated in Cln1-/- mice, which mimic INCL and in postmortem brain tissues as well as cultured fibroblasts from INCL patients. Moreover, Rab7, a small GTPase, critical for autophagosome-lysosome fusion, requires S-palmitoylation for trafficking to the late endosomal/lysosomal membrane where it interacts with Rab-interacting lysosomal protein (RILP), essential for autophagosome-lysosome fusion. Notably, PPT1-deficiency in Cln1-/- mice, dysregulated Rab7-RILP interaction and preventing autophagosome-lysosome fusion, which impaired degradative functions of the autolysosome leading to INCL pathogenesis. Importantly, treatment of Cln1-/- mice with a brain-penetrant, PPT1-mimetic, small molecule, N-tert (butyl)hydroxylamine (NtBuHA), ameliorated this defect. Our findings reveal a previously unrecognized role of CLN1/PPT1 in autophagy and suggest that small molecules functionally mimicking PPT1 may have therapeutic implications.

Neuronal ceroid lipofuscinosis type 2: an Australian case series.

AimLate infantile neuronal ceroid lipofuscinosis type 2 (CLN2) disease is a rare neurodegenerative disorder presenting in children aged 2–4 years with seizures and loss of motor and language skills, followed by blindness and death in late childhood. Initial presenting features are similar to a range of common epilepsies. We aim to highlight typical clinical and radiological features that may prompt diagnosis of CLN2 disease in early disease stages.MethodsWe present a series of 13 Australian patients with CLN2 disease, describing clinical features, disease evolution, neuroimaging, electroencephalogram, biochemical and genetic results. Expert neuroradiological magnetic resonance imaging (MRI) analysis was retrospectively performed on 10 cases.ResultsTwelve patients presented with seizures, with initial seizures being focal (n = 4), generalised tonic–clonic (n = 3), absence (n = 3) and febrile (n = 2). Eleven patients (85%) had a language delay before the onset of seizures. Cerebellar or cerebral atrophy was noted in all patients on centralised MRI review, with abnormalities of the brain‐stem, ventricles, corpus callosum and hippocampi.ConclusionsEarly language delay with the onset of seizures at 2–4 years of age is the hallmark of CLN2 disease. MRI findings of early subtle atrophy in the cerebellum or posterior cortical regions should hasten testing for CLN2 disease to enable early initiation of enzyme replacement therapy.

Lysosomal PPT1‐insufficiency is a common pathogenic link between INCL and JNCL

Neuronal Ceroid Lipofuscinoses (NCLs), also known as Batten disease, constitute a group of the most common inherited childhood neurodegenerative lysosomal storage disorders (LSDs). Even though mutations in >13 different genes cause various NCLs, at the cellular level, all the NCLs characteristically accumulate autofluorescent material (ceroid) in lysosomes and clinically, develop seizures, visual failure and a progressive decline in cognitive and motor functions. These findings suggest shared pathogenic mechanism(s) in these diseases. While inactivating mutations in the CLN1 gene, encoding lysosomal PPT1, cause infantile NCL (INCL), mutations in the CLN3 gene encoding a lysosomal membrane protein of unknown function underlie juvenile NCL (JNCL). PPT1 catalyzes depalmitoylation of S‐acylated proteins, required for their degradation by lysosomal hydrolases. Thus, PPT1‐deficiency causes lysosomal accumulation of S‐acylated proteins (ceroid) leading to INCL. The Cln1−/− and Cln3−/− mice are reliable animal models of INCL and JNCL, respectively. Here we report for the first time that Cln3‐protein requires S‐palmitoylation for its endosomal transport to the lysosomal membrane. Moreover, we found that in the brain of Cln3−/− mice, lysosomal PPT1‐protein as well as Ppt1‐enzymatic activity are significantly lower compared with lysosomes derived from their age‐ and sex‐matched WT counterparts. Unexpectedly, we found that the lysosomes from Cln3−/− mice accumulate significantly higher levels of S‐palmitoylated proteins, characteristically found in those from Cln1−/− mice. Previously, it has been reported that CLN3 mutations suppress the exit of cation‐independent mannose 6‐phosphate receptor (CI‐M6PR) from trans‐Golgi network (TGN), essential for its endosomal trafficking to the late endosome/lysosome. Since CI‐M6PR transports soluble proteins including Ppt1 to the lysosome, we hypothesized that Cln3 mutations may adversely affect the transport of PPT1 to the lysosome causing Ppt1‐insufficiency. Biochemical and confocal microscopic analyses of brain tissues from Cln3−/− mice revealed significantly higher levels of Ppt1 and CI‐M6PR in the Golgi compared to those of their WT counterparts. Collectively, our results demonstrate that lysosomal Ppt1‐insufficiency is a common pathogenic link between INCL and JNCL and suggest that a recently identified Ppt1‐mimetic, neuroprotective small molecule, NtBuHA, may have therapeutic implications for both INCL and JNCL.Support or Funding InformationIntramural Research Program of the Eunice Kennedy Shriver NICHD, NIH