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Background information The endo-lysosomal system (ELS) comprises a set of membranous organelles responsible for transporting intracellular and extracellular components within cells. Defects in lysosomal proteins usually affect a large variety of processes and underlie many diseases, most of them with a strong neuronal impact. Mutations in the endoplasmic reticulum-resident CLN8 protein cause CLN8 disease. This condition is one of the 14 known Neuronal Ceroid Lipofuscinoses (NCL), a group of inherited diseases characterized by accumulation of lipofuscin-like pigments within lysosomes. Besides mediating the transport of soluble lysosomal proteins, recent research suggested a role for CLN8 in the transport of vesicles and lipids, and autophagy. However, the consequences of CLN8 deficiency on ELS structure and activity, as well as the potential impact on neuronal development, remain poorly characterized. Therefore, we performed CLN8 knockdown in neuronal and non-neuronal cell models to analyze structural, dynamic, and functional changes in the ELS and to assess the impact of CLN8 deficiency on axodendritic development. Results CLN8 knockdown increased the size of the Golgi apparatus, the number of mobile vesicles, and the speed of endo-lysosomes. Using the fluorescent fusion protein mApple-LAMP1-pHluorin, we detected significant lysosomal alkalization in CLN8-deficient cells. In turn, experiments in primary rat hippocampal neurons showed that CLN8 deficiency decreased the complexity and size of the somatodendritic compartment. Conclusions Our results suggest the participation of CLN8 in vesicular distribution, lysosomal pH, and normal development of the dendritic tree. We speculate that the defects triggered by CLN8 deficiency on ELS structure and dynamics underlie morphological alterations in neurons, which ultimately lead to the characteristic neurodegeneration observed in this NCL. Significance This is, to our knowledge, the first characterization of the effects of CLN8 dysfunction on the structure and dynamics of the ELS. Moreover, our findings suggest a novel role for CLN8 in somatodendritic development, which may account at least in part for the neuropathological manifestations associated with CLN8 disease. This article is protected by copyright. All rights reserved.

The neuronal ceroid lipofuscinoses (NCLs) are a heterogeneous group of inherited neurodegenerative disorders. Their unifying clinical hallmarks are seizures, visual loss, myoclonus, ataxia, cognitive and motor regression which lead to early death. Based on the clinical onset of symptoms NCL-affected individuals have been classified into six categories. Fourteen genetic forms of NCL (CLN1 to CLN14) have been identified so far. The variant late-infantile form of the disease has been linked to CLN5, CLN6, CLN7 (MFSD8) and CLN8 mutations.We report a patient of 9 years from a consanguineous family who presented with progressive visual loss and seizures. Clinical Exome sequencing reveals a homozygous missense mutation in exon 11 of the MFSD8 gene (c.1235C>T, p.Pro412Leu). To our knowledge, this is the first report of MFSD8 gene mutation in a Bangladeshi patient with variant late-infantile NCL. This study also provides information regarding the phenotypic and molecular spectrum of CLN7 disease.

Batten disease is unique among lysosomal storage disorders for the early and profound manifestation in the central nervous system, but little is known regarding potential neuron-specific roles for the disease-associated proteins. We demonstrate substantial overlap in the protein interactomes of three transmembrane Batten proteins (CLN3, CLN6, and CLN8), and that their absence leads to synaptic depletion of key partners (i.e. SNAREs and tethers) and aberrant synaptic SNARE dynamics in vivo, demonstrating a novel shared etiology.

Neuronal Ceroid Lipofuscinosis (NCL) refers to a group of inherited lysosomal storage disorders characterized by the intracellular accumulation of ceroid-lipofuscin compounds and neurodegeneration. Fourteen genes are currently recognized with disease-causing DNA variants: PPT1/CLN1, TPP1/CLN2, CLN3, DNAJC5/CLN4, CLN5, CLN6, MFSD8/CLN7, CLN8, CTSD/CN10, GRN/CLN11, ATP13A2/CLN12, CTSF/CLN13, KCTD7/CLN14, TBCK/CLN15. In the frame of the Cordoba cohort, we studied N=51 cases. The aim of this paper is the observational and retrospective analysis of the “atypical” phenotypes. PCR-Sanger sequencing and/or massive exome sequencing were used as a screening methodology. One CLN1 subject showed an atypical prolonged (P) phenotype with null PPT1 activity and a heterozygous compound genotype: E5 c.451C>T, p.Arg151*/g.6302T>G (I3 c.363-3T>G). Other 11 CLN2 individuals (except one girl) showed TPP1 activity decreased to around 10% of the minimum value of the reference interval in leukocytes and saliva. The DNA variants E7 c.827A>T, p.Asp276Val and I7 c.887-10A>G were the most prevalent. One CLN8 individual showed an atypical congenital phenotype with a heterozygous combination of DNA variants: E2 c.1A>G, p.?/E3 c.792C>G, p.Asn264Lys. Massive sequencing was installed as a screening methodology for the precision diagnosis of atypical CLN1, CLN2, and CLN8 phenotypes. A genetic/phenotypic local registry is under construction. publishedVersion Fil: Pesaola, Favio. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigación en Ciencias de la Salud; Argentina. Fil: Pesaola, Favio. Universidad Nacional de Córdoba. Facultad de Ciencias Médicas; Argentina. Fil: Pesaola, Favio. Hospital de Niños de la Provincia de Córdoba. Programa de Investigación Traslacional de Lipofuscinosis Ceroideas Neuronales; Argentina. Fil: Guelbert, Guillermo. Universidad Nacional de Córdoba. Facultad de Ciencias Médicas; Argentina. Fil: Guelbert, Guillermo. Hospital de Niños de la Provincia de Córdoba. Programa de Investigación Traslacional de Lipofuscinosis Ceroideas Neuronales; Argentina. Fil: Guelbert, Guillermo. Hospital de Niños de la Provincia de Córdoba. Sección de Enfermedades Metabólicas Hereditarias; Argentina. Fil: Venier, Ana Clara. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina. Fil: Venier, Ana Clara. Hospital de Niños de la Provincia de Córdoba. Programa de Investigación Traslacional de Lipofuscinosis Ceroideas Neuronales; Argentina. Fil: Venier, Ana Clara. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigación en Ciencias de la Salud; Argentina. Fil: Cismondi, Inés Adriana. Universidad Nacional de Córdoba. Facultad de Odontología; Argentina. Fil: Cismondi, Inés Adriana. Hospital de Niños de la Provincia de Córdoba. Programa de Investigación Traslacional de Lipofuscinosis Ceroideas Neuronales; Argentina. Fil: Becerra, Adriana. Universidad Nacional de Córdoba. Facultad de Ciencias Médicas; Argentina. Fil: Beccera, Adriana. Hospital de Niños de la Provincia de Córdoba. Programa de Investigación Traslacional de Lipofuscinosis Ceroideas Neuronales; Argentina. Fil: Becerra, Adriana. Hospital de Niños de la Provincia de Córdoba. Sección de Enfermedades Metabólicas Hereditarias; Argentina. Fil: Vazquez, Juan Carlos G. Universidad Católica de Córdoba; Argentina. Fil: Vazquez, Juan Carlos G. Consejo Nacional de Investigaciones Científicas y Técnicas, Centro de Investigación y Desarrollo en Inmunología y Enfermedades Infecciosas; Argentina. Fil: Fernández, Elmer. Universidad Católica de Córdoba; Argentina. Fil: Fernández, Elmer. Consejo Nacional de Investigaciones Científicas y Técnicas, Centro de Investigación y Desarrollo en Inmunología y Enfermedades Infecciosas; Argentina. Fil: De Paul, Ana Lucia. Universidad Nacional de Córdoba. Facultad de Ciencias Médicas. Centro de Microscopía Electrónica; Argentina. Fil: De Paul, Ana Lucia. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigación en Ciencias de la Salud; Argentina. Fil: Guelbert, Norberto. Universidad Nacional de Córdoba. Facultad de Ciencias Médicas; Argentina. Fil: Guelbert, Norberto. Hospital de Niños de la Provincia de Córdoba. Programa de Investigación Traslacional de Lipofuscinosis Ceroideas Neuronales; Argentina. Fil: Guelbert, Norberto. Clínica Universitaria Reina Fabiola; Argentina. Fil: Noher, Inés. Fil: Venier, Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina. Fil: Noher, Inés. Hospital de Niños de la Provincia de Córdoba. Programa de Investigación Traslacional de Lipofuscinosis Ceroideas Neuronales; Argentina.

To date only five patients with 8p23.2-pter microdeletions manifesting a mild-to-moderate cognitive impairment and/or developmental delay, dysmorphisms and neurobehavioral issues were reported. The smallest microdeletion described by Wu in 2010 suggested a critical region (CR) of 2.1 Mb including several genes, out of which FBXO25, DLGAP2, CLN8, ARHGEF10 and MYOM2 are the main candidates. Here we present seven additional patients with 8p23.2-pter microdeletions, ranging from 71.79 kb to 4.55 Mb. The review of five previously reported and nine Decipher patients confirmed the association of the CR with a variable clinical phenotype characterized by intellectual disability/developmental delay, including language and speech delay and/or motor impairment, behavioral anomalies, autism spectrum disorder, dysmorphisms, microcephaly, fingers/toes anomalies and epilepsy. Genotype analysis allowed to narrow down the 8p23.3 candidate region which includes only DLGAP2, CLN8 and ARHGEF10 genes, accounting for the main signs of the broad clinical phenotype associated to 8p23.2-pter microdeletions. This region is more restricted compared to the previously proposed CR. Overall, our data favor the hypothesis that DLGAP2 is the actual strongest candidate for neurodevelopmental/behavioral phenotypes. Additional patients will be necessary to validate the pathogenic role of DLGAP2 and better define how the two contiguous genes, ARHGEF10 and CLN8, might contribute to the clinical phenotype.

Background: The neuronal ceroid lipofuscinoses (NCL) constitute a group of gray matter neurodegenerative disorders characterized by the accumulation of ceroid lipopigment in lysosomes in neurons and other cell types. There are very few published studies on NCL from India, especially in children. Methods: A retrospective study of confirmed patients of NCL diagnosed over a period of 10 years from January 2019 to December 2019. Results: Fifty children had a definitive diagnosis of NCL based on enzymatic studies or genetic testing using next-generation sequencing. Around 15 children were diagnosed to have CLN-1 (ceroid lipofuscinoses, neuronal-1) based on palmitoyl protein thioesterase-1 deficiency; 24 children were diagnosed with CLN2 (ceroid lipofuscinoses, neuronal-2) based on deficient tripeptidyl-peptidase-1 activity; three patients were diagnosed as CLN6, five patients as CLN7, one case each of CLN8, CLN11, and CLN14 based on genetic testing. Clinical presentation was quite varied and included refractory seizures, developmental delay/regression, and abnormal movements. Visual failure was not common in the present case series. Neuroimaging patterns in different types of NCL were different. All children had a progressive downhill course resulting in death in many over a period of 5–10 years of disease onset. Conclusion: NCL is not uncommon and diagnosis can be suspected based on clinical investigations and neuroimaging findings. Diagnosis can be confirmed by enzymatic assays or genetic testing.

CLN8 disease is a rare form of neuronal ceroid lipofuscinosis caused by biallelic mutations in the CLN8 gene, which encodes a transmembrane endoplasmic reticulum protein involved in trafficking of lysosomal enzymes. CLN8 disease patients present with myoclonus, tonic-clonic seizures, and progressive declines in cognitive and motor function, with many cases resulting in premature death early in life. There are currently no treatments that can cure the disease or substantially slow disease progression. Using a mouse model of CLN8 disease, we tested the safety and efficacy of an intracerebroventricularly (ICV)-delivered self-complementary AAV9 (scAAV9) gene therapy vector driving expression of human CLN8. A single neonatal injection was safe and well-tolerated, resulting in robust transgene expression throughout the brain and spinal cord from 4 to 24 months, reducing histopathological and behavioral hallmarks of the disease and completely restoring lifespan from 10 months in untreated animals to beyond 24 months of age in treated animals. These results demonstrate, by far, the most successful rescue reported in an animal model of CLN8 disease, and supports gene therapy as a promising therapeutic strategy for this disorder.

CLN8 disease is a rare form of neuronal ceroid lipofuscinosis caused by biallelic mutations in the CLN8 gene, which encodes a transmembrane endoplasmic reticulum protein involved in trafficking of lysosomal enzymes. CLN8 disease patients present with myoclonus, tonic-clonic seizures, and progressive declines in cognitive and motor function, with many cases resulting in premature death early in life. There are currently no treatments that can cure the disease or substantially slow disease progression. Using a mouse model of CLN8 disease, we tested the safety and efficacy of an intracerebroventricularly (i.c.v.) delivered self-complementary adeno-associated virus serotype 9 (scAAV9) gene therapy vector driving expression of human CLN8. A single neonatal injection was safe and well tolerated, resulting in robust transgene expression throughout the CNS from 4 to 24 months, reducing histopathological and behavioral hallmarks of the disease and restoring lifespan from 10 months in untreated animals to beyond 24 months of age in treated animals. While it is unclear whether some of these behavioral improvements relate to preserved visual function, improvements in learning/memory, or other central or peripheral benefits, these results demonstrate, by far, the most successful degree of rescue reported in an animal model of CLN8 disease, and they support further development of gene therapy for this disorder.

Neuronal ceroid lipofuscinoses (NCLs) are a group of autosomal recessive inherited neurodegenerative disorders mainly affecting children, and at least 13 causative genes (CLN1 to CLN8 and CLN10 to CLN14) have been identified. Here, we reported a novel homozygous missense mutation (c.434G > C, p.Arg145Pro) identified in CLN5 gene via whole exome sequencing in a 5-year-old girl. The patient first presented paroxysmal epilepsy associated with vomiting, followed by progressive regression in walking, vision, intelligence and speaking. Combining the molecular and clinical analysis, the diagnosis of NCL could be made, although the missense mutation (c.434G > C, p.Arg145Pro) in CLN5 was evaluated to be a variant of uncertain significance according to American College of Medical Genetics and Genomics (ACMG) standard. We further performed expression and localization studies and our results provide evidence of impaired cellular trafficking of CLN5 to lysosome, indicating that this mutation might be deleterious to the function of CLN5 for its mislocalization. Our study demonstrated the efficacy of next generation sequencing in molecular diagnosis, and a deleterious effect of the variant discovered in our patient on CLN5, triggering the NCL disease.

Neuronal ceroid lipofuscinoses (NCLs) are the most common group of neurodegenerative diseases that presents in childhood and are characterized by seizures and progressive neurological deterioration, which results in dementia, ataxia, visual failure, and various forms of abnormal movement. The most common form of neuronal ceroid lipofuscinoses is late infantile (LI-NCL), in association with the genes CLN2, CLN5, CLN6, and CLN8. We report the cases of neuronal ceroid lipofuscinoses type 8 in 3 patients from 2 unrelated families, which was confirmed by molecular testing in 2 of them. Multiple spontaneous abortions, early death, and early onset of motor disability were observed in our cases, reflecting a possible association of NCL 8 with other unrecognized neurodegenerative diseases. Our results expand the genotypic/phenotypic background of variant late Infantile-NCL in Arabic ethnicity.

Two littermate German Shorthaired Pointers, a male and a female, were adopted as puppies from an animal shelter. Both puppies developed normally until approximately 11 months of age when the male began to exhibit neurological signs including ataxia, vision loss, and behavioral changes indicative of cognitive decline. These signs increased in severity over time. The female remained neurologically normal and healthy. The affected dog was euthanized at approximately 21 months of age. Autofluorescent cytoplasmic storage bodies were detected in neurons in unstained tissue sections from the cerebellum, the cerebrum, and the retina. Electron micrographs of these storage bodies showed that they were membrane bound and that most contained tightly packed aggregates of membranous whorls along with a variety of other ultrastructural features. This ultrastructure, along with the autofluorescence and the clinical signs supported a diagnosis of neuronal ceroid lipofuscinosis (NCL). Unlike earlier investigated forms of canine NCL with causal alleles in ATP13A2, TPP1, MFSD8 and CLN5 that had autofluorescent cytoplasmic storage bodies in cardiac muscle, no autofluorescence was detected in cardiac muscle from the affected German Shorthaired Pointer. A 39-fold average coverage whole genome sequence indicated that the affected German Shorthaired Pointer was homozygous for the A allele of a G > A transversion at position 30,895,648 chromosome 37. This 37:30895648G > A mutation created a CLN8 termination codon that had been previously reported to cause NCL in a mixed breed dog with Australian Shepherd and Australian Cattle Dog ancestry. This nonsense allele was heterozygous in the clinically normal female sibling, while archived DNA samples from 512 other German Shorthaired Pointers were all homozygous for the reference allele. The affected German Shorthaired Pointer and the previously diagnosed mixed breed dog with the same nonsense mutation shaired an identical homozygous haplotype that extended for 4.41 Mb at the telomeric end of chromosome 37, indicating the both dogs inherited the nonsense mutation from a common ancestor. Keywords: Lysosomal storage disease, Dog, Neurodegeneration, Whole genome sequence

Background Neuronal ceroid lipofuscinoses are neurodegenerative disorders. To investigate the diagnostic yield of direct Sanger sequencing of the CLN genes, we reviewed Molecular Genetics Laboratory Database for molecular genetic test results of the CLN genes from a single clinical molecular diagnostic laboratory. Methods We reviewed electronic patient charts. We used consent forms and Research Electronic Data Capture questionnaires for the patients from outside of our Institution. We reclassified all variants in the CLN genes. Results Six hundred and ninety three individuals underwent the direct Sanger sequencing of the CLN genes for the diagnosis of neuronal ceroid lipofuscinoses. There were 343 symptomatic patients and 350 family members. Ninety‐one symptomatic patients had molecular genetic diagnosis of neuronal ceroid lipofuscinoses including CLN1 (PPT1) (n = 10), CLN2 (TPP1) (n = 33), CLN3 (n = 17), CLN5 (n = 7), CLN6 (n = 10), CLN7 (MFSD8) (n = 10), and CLN8 (n = 4) diseases. The diagnostic yield of direct Sanger sequencing of CLN genes was 27% in symptomatic patients. We report detailed clinical and investigation results of 33 NCL patients. Juvenile onset CLN1 (PPT1) and adult onset CLN6 diseases were nonclassical phenotypes. Conclusion In our study, the diagnostic yield of direct Sanger sequencing was close to diagnostic yield of whole exome sequencing. Developmental regression, cognitive decline, visual impairment and cerebral and/or cerebellar atrophy in brain MRI are significant clinical and neuroimaging denominators to include NCL in the differential diagnosis.

Lysosomal enzymes are synthesized in the endoplasmic reticulum (ER) and transferred to the Golgi complex by interaction with the Batten disease protein CLN8. Here we investigated the relationship of this pathway with CLN6, an ER-associated protein of unknown function that is defective in a different Batten disease subtype. Experiments focused on protein interaction and trafficking identified CLN6 as an obligate component of a CLN6-CLN8 complex (herein referred to as EGRESS:ER-to-Golgi relaying ofenzymes of the lysosomalsystem) which recruits lysosomal enzymes at the ER to promote their Golgi transfer. Simultaneous deficiency of CLN6 and CLN8 did not aggravate mouse pathology compared to the single deficiencies, indicating that the EGRESS complex works as a functional unit. Mutagenesis experiments showed that the second luminal loop of CLN6 is required for the interaction of CLN6 with the enzymes but dispensable for interaction with CLN8, and in vitro and in vivo studies showed that CLN6 deficiency results in inefficient ER export of lysosomal enzymes and diminished levels of the enzymes at the lysosome. These results identify CLN6 and the EGRESS complex as key players in lysosome biogenesis and shed light on the molecular etiology of Batten disease caused by defects in CLN6.

Lysosomal enzymes are synthesized in the endoplasmic reticulum (ER) and transferred to the Golgi complex by interaction with the Batten disease protein CLN8 (ceroid lipofuscinosis, neuronal, 8). Here we investigated the relationship of this pathway with CLN6, an ER-associated protein of unknown function that is defective in a different Batten disease subtype. Experiments focused on protein interaction and trafficking identified CLN6 as an obligate component of a CLN6-CLN8 complex (herein referred to as EGRESS: ER-to-Golgi relaying of enzymes of the lysosomal system), which recruits lysosomal enzymes at the ER to promote their Golgi transfer. Mutagenesis experiments showed that the second luminal loop of CLN6 is required for the interaction of CLN6 with the enzymes but dispensable for interaction with CLN8. In vitro and in vivo studies showed that CLN6 deficiency results in inefficient ER export of lysosomal enzymes and diminished levels of the enzymes at the lysosome. Mice lacking both CLN6 and CLN8 did not display aggravated pathology compared with the single deficiencies, indicating that the EGRESS complex works as a functional unit. These results identify CLN6 and the EGRESS complex as key players in lysosome biogenesis and shed light on the molecular etiology of Batten disease caused by defects in CLN6.

Neuronal Ceroid Lipofuscinoses (NCLs) are progressive degenerative diseases mainly affect brain and retina. They are characterized by accumulation of autofluorescent storage material, mitochondrial ATPase subunit C, or sphingolipid activator proteins A and D in lysosomes of most cells. Heterogenous storage material in NCLs is not completely disease-specific. Most of CLN proteins and their natural substrates are not well-characterized. Studies have suggested variants of Late-Infantile NCLs (LINCLs) include the major type CLN2 and minor types CLN5, CLN6, CLN7, and CLN8. Therefore, combination of clinical and molecular analysis has become a more effective diagnosis method. We studied 4 late-infantile NCL siblings characterized by seizures, ataxia as early symptoms, followed by progressive regression in intelligence and behavior, but mutations are located in different genes. Symptoms and progression of 4 types of LINCLs are compared. Pathology of LINCLs is also discussed. We performed Nest-Generation Sequencing on these phenotypically similar families. Three novel variants c.1551+1insTGAT in TPP1, c.244G>T in CLN6, c.554-5A>G in MFSD8 were identified. Potential outcome of the mutations in structure and function of proteins are studied. In addition, we observed some common and unique clinical features of Chinese LINCL patient as compared with those of Western patients, which greatly improved our understanding of the LINCLs.

Introduction Neuronal ceroid lipofuscinoses (NCLs; CLN) are mainly autosomal recessive neurodegenerative disorders characterized by the accumulation of autofluorescent lipopigments in neuronal and other cells. Symptoms include visual disabilities, motor decline, and epilepsy. Causative genes are CLN1, CLN2, CLN3, CLN5, CLN6, CLN7, CLN8, CLN10, CLN11, CLN12, CLN13, and CLN14. We present the fourth Japanese case with a CLN6 mutation. Case presentation At 3 years of age, our patient became clumsy and fell down easily. He developed focal seizures with impaired consciousness and was started on carbamazepine. He showed ataxic walking and dysarthria with increased deep tendon reflexes. Interictal electroencephalogram revealed slow waves in the left temporal and occipital areas. Brain magnetic resonance imaging showed cerebellar atrophy and ventriculomegaly. In optical coherence tomography (OCT), the inner layer of the retina was thick and highly reflective. Exome sequencing revealed a known homozygous mutation, C.794_976del, p. (Ser265del) in CLN6. Discussion A total of 130 cases of NCL with CLN6 mutations have been reported globally, of which only four were from Japan including the current patient. The deletion of serine at position 265 has been reported in six cases. Ser265 is located in a region of short repeated sequences that is susceptible to mutation. Clinical trials of gene therapy using adeno-associated virus serotype 9 have started for NCL6, making early diagnosis crucial. OCT examination might be helpful in achieving a diagnosis.

Riunione Annuale CLNet sullo stato dell'arte delle patologie ceroidolipofuscinosi neuronali (NCLs) e sui geni (CLN) coinvolti. Discussione sulla terapia enzimatica sostitutiva con alfa-Cerliponasi per la forma NCL associata al gene CLN2 approvata dall'AIFA: quali effetti nel medio-termine. Discussione sugli altri geni CLN e strategie di studio. Discussione sul gene CLN8 e le ultime conoscenze acquisite sulla funzione della proteina e sui meccanismi disfunzionali associati a mutazioni CLN8. Strategie di possibili approcci di terapia.

The neuronal ceroid lipofuscinoses (NCLs) are autosomal recessive diseases with progressive dementia, motor disturbance, epilepsy, visual loss and early death, affecting mainly children but also adults. Mutations in 13 distinct genes cause NCLs with marked phenotypic heterogeneity and undefined pathomechanism. CLN8 gene shows wide complexity with 31 different mutations leading to late-infantile NCL variants (vLINCL) and progressive epilepsy with mental retardation (EPMR) (www.ucl.ac.uk/ncl/mutation.shtml). CLN8 encodes an ER-resident transmembrane protein with an ER-ERGIC retrieval signal, a TLC domain normally related to lipid sensing/trafficking, and possible multiple roles (1, 2). We proposed to study the functional meaning of CLN8-VAPA interaction previously characterized (Passantino et al., 2013), being VAPA an ER-docking-site for cytosolic lipid-binding-proteins responsible of ceramide transport, sphingolipid (SL), phospholipid and cholesterol synthesis/trafficking. We expect to define CLN8 implication in SL, and pinpoint the molecular bases of the phenotypic heterogeneity. In the frame of the current project, using recombinant proteins and mammalian expression vectors (mono/bicistronic) encoding flCLN8, its subregions and flVAPA, and in vitro and in vivo assays, we identified a putative CLN8 region interacting with VAPA, that is highly conserved in vertebrates and bears some vLINCL mutations. In vitro SphingoStrips and TLC overlay assay revealed no direct binding of flCLN8 and subregions to ceramides;whereas, metabolic labeling studies showed kinetic changes in the ceramide pathway of HeLa cells overexpressing CLN8 and VAPA. Interestingly, CLN8 (presumably the N-terminus) was able to bind sulfatide, which regulates myelination; considering the myelin defects in NCLs (3), further studies are ongoing. Throughout site-directed-mutagenesis, we created a model of EPMR-type mutation. In cells expressing both EPMR and VAPA, we found a strong EPMR-VAPA interaction and higher sphingomyelin and cholesterol levels. We also generated CRISPR/Cas9 CLN8 KO clones that show to maintain survival and migration capacities similar to native HeLa cell line but grow as autophagy predisposed cells. In CLN8-KO clones, even though the high VAPA levels, the only difference observed in sphingolipid was a marked change in the ganglioside patterns, with a shift toward more complex species. The overall results indicate a multifaceted and at least in part novel role of CLN8 alone and with VAPA toward SL trafficking, also supported by the finding that flCLN8 and subregions were able to bind different phosphoinositides in vitro. We are underway using the newly created CRISPR-CERT KO clones to analyze this ceramide transporter as part of CLN8-VAPA complex and possible target of CLN8 dysfunction. Fibroblast cells of patients with CLN8-vLINCL and EPMR are being used to correlate phenotype/genotype divergences to the CLN8-VAPA complex.

CLN8 is a ubiquitously expressed membrane-spanning protein that localizes primarily in the ER, with partial localization in the ER-Golgi intermediate compartment. Mutations in CLN8 cause late-infantile neuronal ceroid lipofuscinosis (LINCL). We describe a female pediatric patient with LINCL. She exhibited a typical phenotype associated with LINCL, except she did not present spontaneous myoclonus, her symptoms occurrence was slower and developed focal sensory visual seizures. In addition, whole-exome sequencing identified a novel homozygous variant in CLN8, c.531G&gt, T, resulting in p.Trp177Cys. Ultrastructural examination featured abundant lipofuscin deposits within mucosal cells, macrophages, and monocytes. We report a novel CLN8 mutation as a cause for NCL8 in a girl with developmental delay and epilepsy, cerebellar syndrome, visual loss, and progressive cognitive and motor regression. This case, together with an analysis of the available literature, emphasizes the existence of a continuous spectrum of CLN8-associated phenotypes rather than a sharp distinction between them.

Background The presence of deletions can complicate genetic diagnosis of autosomal recessive disease. Method The DNA of patients was analyzed in a diagnostic setting. Results We present three unrelated patients each carrying deletions that encompass the 37 kb CLN8 gene and discuss their phenotype. Two of the cases were hemizygous for a mutant allele – their deletions unmasked a mutation in CLN8 on the other chromosome. Conclusion Microarray analysis is recommended in any patient suspected of NCL who is apparently homozygous for a mutation that is not present in one of the parents or when the family has no known consanguinity.

The neuronal ceroid lipofuscinoses (NCL) are neurodegenerative conditions that associate cognitive decline, progressive cerebellar atrophy, retinopathy, and myoclonic epilepsy. NCL result from the excessive accumulation of neuronal and extraneuronal lipopigments, despite having diverse underlying biochemical aetiologies. Here we review the clinical presentation, pathophysiology and genetics of these conditions as well as the approach to diagnosis and management.

Purpose To report atypical presentation of neuronal ceroid lipofuscinoses type 8 (CLN8) to the eye clinic and review clinical features of CLN8. Observations Detailed eye exam by slit lamp exam, indirect ophthalmoscopy, fundus photography, optical coherence tomography, visual fields and electroretinogram (ERG). Molecular genetic testing using Next Generation Sequencing panel (NGS) and array Comparative Genomic Hybridization (aCGH). The siblings in this study presented to the eye clinic with retinitis pigmentosa and cystoid macular edema, and a history of seizures but no severe neurocognitive deficits or regression. Genetic testing identified a c.200C > T (p.A67V) variant in the CLN8 gene and a deletion encompassing the entire gene. Electron microscopy of lymphocytes revealed fingerprint inclusions in both siblings. Conclusions and Importance: Pathogenic variants in CLN8 account for the retinitis pigmentosa and seizures in our patients however, currently, they do not have regression or neurocognitive decline. The presentation of NCL can be very diverse and it is important for ophthalmologists to consider this in the differential diagnosis of retinal disorders with seizures or other neurological features. Molecular genetic testing of multiple genes causing isolated and syndromic eye disorders using NGS panels and aCGH along with additional complementary testing may often be required to arrive at a definitive diagnosis.

Neuronal ceroid lipofuscinoses (NCLs) are a group of neurodegenerative disorders caused by mutations in fourteen distinct ceroid lipofuscinoses, neuronal (CLN) genes described with various severe symptoms such as seizures, visual failure, motor decline, and progressive cognitive deterioration. The current research represents novel CLN5 (c.741G > A) and CLN8 (c.565delT) mutations in two different Iranian families with late-infantile NCL (LINCL) and their relatives by using whole-exome sequencing (WES). The first family had a 10-year-old male with consanguineous parents and severe NCL symptoms, including motor clumsiness, telangiectasia, and cerebellar atrophy. The second family with a child who suffered from nystagmus rotation, motor difficulties, and seizure was a 5-year-old male with consanguineous parent. WES of probands 1 and 2 revealed homozygotic mutations in exon 4 of CLN5 (c.741G > A, p.W247X) and deletion in exon 3 (c.565delT, p.F189fs) of CLN8, respectively. Both patients’ parents were heterozygous for these alterations. In concordance with previous studies, our results indicate that pathogenic mutations in CLN genes, especially CLN5 and 8, are a main cause of LINCL; these results also suggest that LINCL is not a regionally or nationally dependent disorder and can occur in any ethnic group despite the fact that some populations may be more at risk. Consequently, CLN gene screening for patients with typical signs of LINCL is recommended.

The neuronal ceroid lipofuscinoses (NCLs) are a group of inherited neurodegenerative lysosomal storage disorders. CLN8 deficiency causes a subtype of NCL, referred to as CLN8 disease. CLN8 is an ER resident protein with unknown function; however, a role in ceramide metabolism has been suggested. In this report, we identified PP2A and its biological inhibitor I2PP2A as interacting proteins of CLN8. PP2A is one of the major serine/threonine phosphatases in cells and governs a wide range of signaling pathways by dephosphorylating critical signaling molecules. We showed that the phosphorylation levels of several substrates of PP2A, namely Akt, S6 kinase, and GSK3β, were decreased in CLN8 disease patient fibroblasts. This reduction can be reversed by inhibiting PP2A phosphatase activity with cantharidin, suggesting a higher PP2A activity in CLN8-deficient cells. Since ceramides are known to bind and influence the activity of PP2A and I2PP2A, we further examined whether ceramide levels in the CLN8-deficient cells were changed. Interestingly, the ceramide levels were reduced by 60% in CLN8 disease patient cells compared to controls. Furthermore, we observed that the conversion of ER-localized NBD-C6-ceramide to glucosylceramide and sphingomyelin in the Golgi apparatus was not affected in CLN8-deficient cells, indicating transport of ceramides from ER to the Golgi apparatus was normal. A model of how CLN8 along with ceramides affects I2PP2A and PP2A binding and activities is proposed.

Background Neuronal ceroid lipofuscinoses (NCLs) are one of the most frequent childhood-onset neurodegenerative pathologies characterized by seizures, progressive cognitive decline, motor impairment and loss of vision. For the past two decades, more than 430 variants in 13 candidate genes have been identified in the affected patients. Most of the variants were almost exclusively reported in Western patients, and very little clinical and genetic information was available for Chinese patients. Case presentation We report a Chinese boy whose clinical phenotypes were suspected to be NCL, including intractable epilepsy, cognitive and motor decline and progressive vision loss. Using targeted next-generation sequencing, two novel null variants in CLN8 (c.298C > T, p.Gln100Ter; c.551G > A, p.Trp184Ter) were detected in this patient in trans model. These two variants were interpreted as pathogenic according to the variant guidelines of the American College of Medical Genetics and Genomics. Conclusions This is the first case report of NCL due to CLN8 variants in China. Our findings expand the variant diversity of CLN8 and demonstrate the tremendous diagnosis value of targeted next-generation sequencing for pediatric NCLs. Electronic supplementary material The online version of this article (10.1186/s12881-018-0535-7) contains supplementary material, which is available to authorized users.