A novel pathogenic variant in the KCTD7 gene in a patient with neuronal ceroid lipofuscinosis (CLN14): a case report and review of the literature.

BACKGROUND: Neuronal ceroid lipofuscinosis (NCL) is a heterogeneous group of 13 rare, progressive neurodegenerative diseases of the brain and retina. CLN14 is a very rare subtype of NCL caused by pathogenic variants in the KCTD7 gene. Only four cases of this subtype have been reported in the literature. CASE PRESENTATION: A nine-month-old, previously healthy male who was firstborn to first-cousin parents presented with progressive psychomotor regression, dysmorphic facial features, myoclonus, and vision loss. Neurological examination showed generalized hypotonia and brisk reflexes. He continued to deteriorate until age 18 months, when he developed his first generalized tonic-clonic seizure. An ophthalmological examination showed a hypopigmented fundus and slight temporal disc pallor. Brain MRI showed mild generalized brain atrophy and white matter disease. EEG revealed a severely abnormal trace marked by generalized, high amplitude, sharply contoured, polymorphic delta slowing intermixed with theta slowing and some alpha activity, with disorganized and scattered spikes and sharp waves. The patient continued to have uncontrolled seizures and further psychomotor regression until he died of status epilepticus and pneumonia at the age of 44 months. WES identified a novel homozygous variant c.413T > C, p.(Leu138Pro) in the KCTD7 gene, causing an amino acid transition from leucine to proline at position 138. Both parents were carriers of the same variant. CONCLUSIONS: We present the fifth known case of CLN14 in the literature and report the clinical course and a novel underlying likely causative variant in the KCTD7 gene. The improving accessibility and affordability of genetic testing will likely uncover more NCL cases and further expand the disease's genotypic and phenotypic spectrum.

Upregulation of peroxisome proliferator-activated receptor γ with resorcinol alleviates reactive oxygen species generation and lipid accumulation in neuropathic lysosomal storage diseases.

Neuropathic lysosomal storage diseases (NLSDs), including ceroid lipofuscinosis neuronal 3 (CLN3) disease and Gaucher disease type 2 (GD2), are typically present in adolescents; however, there are no approved therapies. CLN3 disease is the most common of the 13 types of neuronal ceroid lipofuscinosis, and Gaucher disease is the most common type of lysosomal storage disease. These NLSDs share oxidative stress and lysosomal dysfunction with Parkinson's disease. In this study, we used patient-derived cells (PDCs) and resorcinol to develop a therapeutic agent based on peroxisome proliferator-activated receptor γ (PPARγ) activation. PPARγ is a major regulator of autophagy and reactive oxygen species (ROS). Resorcinol, a polyphenolic compound, has been reported to exhibit PPARγ agonistic potential. Protein levels were analyzed by immunoblotting and immunofluorescence microscopy. Changes in cellular metabolism, including ROS levels, lipid droplet content, and lysosomal activity, were measured by flow cytometry. Resorcinol reduced ROS levels by suppressing hypoxia-inducible factor 1α levels in CLN3-PDCs. Resorcinol upregulated autophagy and reduced lipid accumulation in CLN3-PDCs; however, these effects were abolished by autophagy inhibitors. Resorcinol increased nuclear PPARγ levels in CLN3-PDCs, and PPARγ antagonists abolished the therapeutic effects of resorcinol. Moreover, Resorcinol upregulated nuclear PPARγ levels and lysosomal activity in GD2-PDCs, and reduced lipid accumulation and ROS levels. In summary, resorcinol alleviated the shared pathogenesis of CLN3 disease and GD2 through PPARγ upregulation. These findings suggest that resorcinol is a potential therapeutic candidate for alleviating NLSD progression.

Evolution of Movement Disorders in Patients With CLN2-Batten Disease Treated With Enzyme Replacement Therapy.

OBJECTIVES: Neuronal ceroid lipofuscinosis type 2 (CLN2-disease) is an inherited childhood-onset neurodegenerative condition, with classical early features of speech delay, epilepsy, myoclonus, ataxia, and motor regression. This study aimed to better characterize the spectrum of movement disorders in CLN2-disease in a cohort of children receiving enzyme replacement therapy (ERT). METHODS: A cohort of 18 children attending a single center for treatment with cerliponase alfa ERT was systematically assessed using a standardized structured history and a double-scored, video-recorded examination using the Unified Batten Disease Rating Scale (UBDRS) and Abnormal Involuntary Movement Scale. RESULTS: Noncanonical movement disorders are common: while ataxia (89%) and myoclonus (83%) were near-universal, spasticity and dystonia were experienced by over half (61% each), with children having a median of 4 distinct movement disorder phenotypes. This progression was stereotyped with initial ataxia/myoclonus, then hyperkinesia/spasticity, and later hypokinesia. ERT slows progression of movement disorders, as measured by the UBDRS physical subscale, with 1.45 points-per-month progression before diagnosis and 0.44 points-per-month while on treatment (p = 0.019). DISCUSSION: Movement disorders are a core feature of CLN2-disease and follow a typical pattern of progression which is slowed by ERT. Identifying and treating movement disorders should become standard, especially given increased patient survival.

TRPML1 activation ameliorates lysosomal phenotypes in CLN3 deficient retinal pigment epithelial cells.

Mutations in the lysosomal membrane protein CLN3 cause Juvenile Neuronal Ceroid Lipofuscinosis (JNCL). Activation of the lysosomal ion channel TRPML1 has previously been shown to be beneficial in several neurodegenerative disease models. Here, we tested whether TRPML1 activation rescues disease-associated phenotypes in CLN3-deficient retinal pigment epithelial (ARPE-19 CLN3-KO) cells. ARPE-19 CLN3-KO cells accumulate LAMP1 positive organelles and show lysosomal storage of mitochondrial ATPase subunit C (SubC), globotriaosylceramide (Gb3), and glycerophosphodiesters (GPDs), whereas lysosomal bis(monoacylglycero)phosphate (BMP/LBPA) lipid levels were significantly decreased. Activation of TRPML1 reduced lysosomal storage of Gb3 and SubC but failed to restore BMP levels in CLN3-KO cells. TRPML1-mediated decrease of storage was TFEB-independent, and we identified TRPML1-mediated enhanced lysosomal exocytosis as a likely mechanism for clearing storage including GPDs. Therefore, ARPE-19 CLN3-KO cells represent a human cell model for CLN3 disease showing many of the described core lysosomal deficits, some of which can be improved using TRPML1 agonists.

Mutations in CLCN6 as a Novel Genetic Cause of Neuronal Ceroid Lipofuscinosis in a Murine Model.

OBJECTIVE: The aim of this study was to explore the pathogenesis of CLCN6-related disease and to assess whether its Cl-/H+-exchange activity is crucial for the biological role of ClC-6. METHODS: We performed whole-exome sequencing on a girl with development delay, intractable epilepsy, behavioral abnormities, retinal dysfunction, progressive brain atrophy, suggestive of neuronal ceroid lipofuscinoses (NCLs). We generated and analyzed the first knock-in mouse model of a patient variant (p.E200A) and compared it with a Clcn6-/- mouse model. Additional functional tests were performed with heterologous expression of mutant ClC-6. RESULTS: We identified a de novo heterozygous p.E200A variant in the proband. Expression of disease-causing ClC-6E200A or ClC-6Y553C mutants blocked autophagic flux and activated transcription factors EB (TFEB) and E3 (TFE3), leading to autophagic vesicle and cholesterol accumulation. Such alterations were absent with a transport-deficient ClC-6E267A mutant. Clcn6E200A/+ mice developed severe neurodegeneration with typical features of NCLs. Mutant ClC-6E200A, but not loss of ClC-6 in Clcn6-/- mice, increased lysosomal biogenesis by suppressing mTORC1-TFEB signaling, blocked autophagic flux through impairing lysosomal function, and increased apoptosis. Carbohydrate and lipid deposits accumulated in Clcn6E200A/+ brain, while only lipid storage was found in Clcn6-/- brain. Lysosome dysfunction, autophagy defects, and gliosis were early pathogenic events preceding neuron loss. INTERPRETATION: CLCN6 is a novel genetic cause of NCLs, highlighting the importance of considering CLCN6 mutations in the diagnostic workup for molecularly undefined forms of NCLs. Uncoupling of Cl- transport from H+ countertransport in the E200A mutant has a dominant effect on the autophagic/lysosomal pathway. ANN NEUROL 2024;96:608-624.

Phenotypic/Genotypic Profile of Children with Neuronal Ceroid Lipofuscinosis in Southern Brazil.

INTRODUCTION: Neuronal ceroid lipofuscinoses (CLNs) are a group of lysosomal storage disorders of genetic origin, characterized by progressive neurodegeneration and intracellular accumulation of autofluorescent lipopigment. Thirteen genes related to CLNs are currently described, showing genetic and allelic heterogeneity, most of them with an autosomal recessive pattern. Due to the few descriptions of cases related to CLNs in Brazil, it is necessary to describe the phenotypic and genotypic characteristics of these patients. This study aims to evaluate the genotypic profile and correlate it with the phenotypic characteristics of patients with CLN in a children's hospital. METHODS: This study was performed as a descriptive cross-sectional study with analysis of medical records, imaging, and laboratory tests of patients who had a confirmed molecular diagnosis of CLN. RESULTS: The sample consisted of 11 patients from nine families with different subtypes of CLNs (CLN2, 5, 6, 7, and 8), with CLN2 being the most prevalent in the study. A total of 16 mutation variants were identified in genes associated with the five CLNs described in this study, with typical and atypical clinical phenotypes depending on the subtype and its variants. CONCLUSION: Novel mutations identified in the patients in this study showed phenotypes of rapid and severe progression in the CLN2 patient and similar characteristics in CLN6 and CLN7 patients, as previously described in the literature.

Neuronal ceroid lipofuscinosis in a Schapendoes dog is caused by a missense variant in CLN6.

Neuronal ceroid lipofuscinosis (NCL) is a group of neurodegenerative disorders that occur in humans, dogs, and several other species. NCL is characterised clinically by progressive deterioration of cognitive and motor function, epileptic seizures, and visual impairment. Most forms present early in life and eventually lead to premature death. Typical pathological changes include neuronal accumulation of autofluorescent, periodic acid-Schiff- and Sudan black B-positive lipopigments, as well as marked loss of neurons in the central nervous system. Here, we describe a 19-month-old Schapendoes dog, where clinical signs were indicative of lysosomal storage disease, which was corroborated by pathological findings consistent with NCL. Whole genome sequencing of the affected dog and both parents, followed by variant calling and visual inspection of known NCL genes, identified a missense variant in CLN6 (c.386T>C). The variant is located in a highly conserved region of the gene and predicted to be harmful, which supports a causal relationship. The identification of this novel CLN6 variant enables pre-breeding DNA-testing to prevent future cases of NCL6 in the Schapendoes breed, and presents a potential natural model for NCL6 in humans.

Neuronal Ceroid Lipofuscinosis in a Mixed-Breed Dog with a Splice Site Variant in CLN6.

A 23-month-old neutered male dog of unknown ancestry presented with a history of progressive neurological signs that included anxiety, cognitive impairment, tremors, seizure activity, ataxia, and pronounced visual impairment. The clinical signs were accompanied by global brain atrophy. Due to progression in the severity of disease signs, the dog was euthanized at 26 months of age. An examination of the tissues collected at necropsy revealed dramatic intracellular accumulations of autofluorescent inclusions in the brain, retina, and cardiac muscle. The inclusions were immunopositive for subunit c of mitochondrial ATP synthase, and their ultrastructural appearances were similar to those of lysosomal storage bodies that accumulate in some neuronal ceroid lipofuscinosis (NCL) diseases. The dog also exhibited widespread neuroinflammation. Based on these findings, the dog was deemed likely to have suffered from a form of NCL. A whole genome sequence analysis of the proband's DNA revealed a homozygous C to T substitution that altered the intron 3-exon 4 splice site of CLN6. Other mutations in CLN6 cause NCL diseases in humans and animals, including dogs. The CLN6 protein was undetectable with immunolabeling in the tissues of the proband. Based on the clinical history, fluorescence and electron-microscopy, immunohistochemistry, and molecular genetic findings, the disorder in this dog was classified as an NCL resulting from the absence of the CLN6 protein. Screening the dog's genome for a panel of breed-specific polymorphisms indicated that its ancestry included numerous breeds, with no single breed predominating. This suggests that the CLN6 disease variant is likely to be present in other mixed-breed dogs and at least some ancestral breeds, although it is likely to be rare since other cases have not been reported to date.

A novel homozygous CLN6 Tyr142Cys variant in a nonconsanguineous family with Kufs disease.

BACKGROUND: Neuronal ceroid lipofuscinoses are a genetically heterogeneous group of inherited lysosomal storage disorders. Kufs disease is the predominant form of neuronal ceroid lipofuscinosis in adults, but it's rare and challenging to diagnose. CASE DESCRIPTION: The proband initially presented with cognitive deterioration and parkinsonian traits. At 35, he was admitted to hospital following a tonic-clonic seizure. Brain magnetic resonance imaging showed atrophy of the cerebral cortex and cerebellum, enlarged ventricles, and thinned corpus callosum. The proband's younger brother and sister were also affected, and the clinical phenotype within the family was consistent. Whole-exome Sequencing of the proband revealed a novel homozygous mutation in CLN6 (NM_017882: c.425A > G, p. Tyr142Cys). Co-segregation analysis revealed that two other affected individuals carried a homozygous mutation at the same locus, with both parents exhibiting heterozygous mutations of c.425A > G. CONCLUSION: Our study not only provides insights into the clinical presentation and development of the disease within the affected family but also expanded the mutational and phenotypical spectrum of the CLN6 gene.

A needle in a haystack? The impact of a targeted epilepsy gene panel in the identification of a treatable but rapidly progressive metabolic epilepsy: CLN2 disease.

BACKGROUND: Neuronal ceroid lipofuscinoses (NCL) are a group of autosomal recessive, inherited, lysosomal, and neurodegenerative diseases that causes progressive dementia, seizures, movement disorders, language delay/regression, progressive visual failure, and early death. Neuronal ceroid lipofuscinosis type 2 (CLN2), caused by biallelic pathogenic variants of the TPP1 gene, is the only NCL with an approved targeted therapy. The laboratory diagnosis of CLN2 is established through highly specific tests, leading to diagnostic delays and eventually hampering the provision of specific treatment for patients with CLN2. Epilepsy is a common and clinically-identifiable feature among NCLs, and seizure onset is the main driver for families to seek medical care. OBJECTIVE: To evaluate the results of the Latin America Epilepsy and Genetics Program, an epilepsy gene panel, as a comprehensive tool for the investigation of CLN2 among other genetic causes of epilepsy. METHODS: A total of 1,284 patients with epilepsy without a specific cause who had at least 1 symptom associated with CLN2 were screened for variants in 160 genes associated with epilepsy or metabolic disorders presenting with epilepsy through an epilepsy gene panel. RESULTS: Variants of the TPP1 gene were identified in 25 individuals (1.9%), 21 of them with 2 variants. The 2 most frequently reported variants were p.Arg208* and p.Asp276Val, and 2 novel variants were detected in the present study: p.Leu308Pro and c.89 + 3G > C Intron 2. CONCLUSION: The results suggest that these genetic panels can be very useful tools to confirm or exclude CLN2 diagnosis and, if confirmed, provide disease-specific treatment for the patients.

ANTECEDENTES: As lipofuscinoses ceroides neuronais (neuronal ceroid lipofuscinoses, NCLs, em inglês) são um grupo de doenças autossômicas recessivas, hereditárias, lisossomais e neurodegenerativas que causam demência progressiva, crises epiléticas, distúrbios de movimento, atraso/regressão da linguagem, deficiência visual progressiva e morte precoce. A lipofuscinose ceroide neuronal tipo 2 (neuronal ceroid lipofuscinosis type 2, CLN2, em inglês), causada por variantes patogênicas bialélicas do gene TPP1, é a única com terapia-alvo aprovada. O diagnóstico laboratorial é realizado por testes específicos, o que leva a atrasos diagnósticos e, consequentemente, prejudica a disponibilização de tratamento. A epilepsia é uma característica comum e clinicamente identificável entre as NCLs, e o início das convulsões é o principal motivo para as famílias buscarem atendimento médico. OBJETIVO: Avaliar os resultados do Programa de Epilepsia e Genética da América Latina, um painel genético, como uma ferramenta abrangente para a investigação de CLN2 entre outras causas genéticas de epilepsia. MéTODOS: Um total de 1.284 pacientes com epilepsia sem uma causa específica e que tinham pelo menos 1 sintoma associado à CLN2 foram rastreados em busca de variantes em 160 genes associados à epilepsia ou a distúrbios metabólicos que apresentam epilepsia, por meio de um painel genético. RESULTADOS: Variantes do gene TPP1 foram identificadas em 25 indivíduos (1,9%), sendo que ; 21 apresentavam duas variantes. As duas variantes mais frequentes foram p.Arg208* e p.Asp276Val, e duas variantes novas foram detectadas neste: p.Leu308Pro e c.89 + 3G > C Intron 2. CONCLUSãO: Os resultados sugerem que os painéis genéticos de epilepsia podem ser uma ferramenta útil para confirmar ou excluir o diagnóstico de CLN2 e, se confirmado, fornecer tratamento específico para os pacientes.

Targeting autophagy impairment improves the phenotype of a novel CLN8 zebrafish model.

CLN8 is an endoplasmic reticulum cargo receptor and a regulator of lysosome biogenesis whose loss of function leads to neuronal ceroid lipofuscinosis. CLN8 has been linked to autophagy and lipid metabolism, but much remains to be learned, and there are no therapies acting on the molecular signatures in this disorder. The present study aims to characterize the molecular pathways involved in CLN8 disease and, by pinpointing altered ones, to identify potential therapies. To bridge the gap between cell and mammalian models, we generated a new zebrafish model of CLN8 deficiency, which recapitulates the pathological features of the disease. We observed, for the first time, that CLN8 dysfunction impairs autophagy. Using autophagy modulators, we showed that trehalose and SG2 are able to attenuate the pathological phenotype in mutant larvae, confirming autophagy impairment as a secondary event in disease progression. Overall, our successful modeling of CLN8 defects in zebrafish highlights this novel in vivo model's strong potential as an instrument for exploring the role of CLN8 dysfunction in cellular pathways, with a view to identifying small molecules to treat this rare disease.

Ceroid lipofuscinosis type 2 disease: Effective presymptomatic therapy-Oldest case of a presymptomatic enzyme therapy.

Neuronal ceroid lipofuscinosis type 2 (CLN2) disease is a rare, lysosomal storage disorder that causes pediatric onset neurodegenerative disease. It is characterized by mutations in the TPP1 gene. Symptoms begin between 2 and 4 years of age with loss of previously acquired motor, cognitive, and language abilities. Cerliponase alfa, a recombinant human TPP1 enzyme, is the only approved therapy. We report the first presymptomatic cerliponase alfa intraventricular treatment in a familial case of CLN2 related to a classical TPP1 variant. Sister 1 presented with motor, cognitive, and language decline and progressive myoclonic epilepsy since the age of 3 years, evolved with severe diffuse encephalopathy, received no specific treatment, and died at 11 years. Sister 2 had a CLN2 presymptomatic diagnosis and has been treated with cerliponase since she was 12 months old. She is now 6 years 8 months and has no CLN2 symptom except one generalized seizure 1 year ago. No serious adverse event has occurred. Repeated Wechsler Preschool and Primary Scale of Intelligence, Fourth Edition standardized index scores are heterogeneous in the extremely low to low average ranges. Mean length of utterances, a global index of sentence complexity, showed a delay, but a gradual improvement. The reported case enhances the major contribution of presymptomatic diagnosis and significant middle-term treatment benefit for patients with CLN2.

Intragenic MFSD8 duplication and histopathological findings in a rabbit with neuronal ceroid lipofuscinosis.

Neuronal ceroid lipofuscinoses (NCL) are among the most prevalent neurodegenerative disorders of early life in humans. Disease-causing variants have been described for 13 different NCL genes. In this study, a refined pathological characterization of a female rabbit with progressive neurological signs reminiscent of NCL was performed. Cytoplasmic pigment present in neurons was weakly positive with Sudan black B and autofluorescent. Immunohistology revealed astrogliosis, microgliosis and axonal degeneration. During the subsequent genetic investigation, the genome of the affected rabbit was sequenced and examined for private variants in NCL candidate genes. The analysis revealed a homozygous ~10.7 kb genomic duplication on chromosome 15 comprising parts of the MFSD8 gene, NC_013683.1:g.103,727,963_103,738,667dup. The duplication harbors two internal protein coding exons and is predicted to introduce a premature stop codon into the transcript, truncating ~50% of the wild-type MFSD8 open reading frame encoding the major facilitator superfamily domain containing protein 8, XP_002717309.2:p.(Glu235Leufs*23). Biallelic loss-of-function variants in MFSD8 have been described to cause NCL7 in human patients, dogs and a single cat. The available clinical and pathological data, together with current knowledge about MFSD8 variants and their functional impact in other species, point to the MFSD8 duplication as a likely causative defect for the observed phenotype in the affected rabbit.

A current view of mitochondria damage and the diversity of lipopigment inclusions in neuronal ceroid lipofuscinose type 2 from rectal biopsy.

Neuronal ceroid lipofuscinoses (NCLs) are a growing group of neurodegenerative storage diseases, in which specific features are sought to facilitate the creation of a universal diagnostic algorithm in the future. In our ultrastructural studies, the group of NCLs was represented by the CLN2 disease caused by a defect in the TPP1 gene encoding the enzyme tripeptidyl-peptidase 1. A 3.5-year-old girl was affected by this disease. Due to diagnostic difficulties, the spectrum of clinical, enzymatic, and genetic tests was extended to include analysis of the ultrastructure of cells from a rectal biopsy. The aim of our research was to search for pathognomonic features of CLN2 and to analyse the mitochondrial damage accompanying the disease. In the examined cells of the rectal mucosa, as expected, filamentous deposits of the curvilinear profile (CVP) type were found, which dominated quantitatively. Mixed deposits of the CVP/fingerprint profile (FPP) type were observed less frequently in the examined cells. A form of inclusions of unknown origin, not described so far in CLN2 disease, were wads of osmophilic material (WOMs). They occurred alone or co-formed mixed deposits. In addition, atypically damaged mitochondria were observed in muscularis mucosae. Their deformed cristae had contact with inclusions that looked like CVPs. Considering the confirmed role of the c subunit of the mitochondrial ATP synthase in the formation of filamentous lipopigment deposits in the group of NCLs, we suggest the possible significance of other mitochondrial proteins, such as mitochondrial contact site and cristae organizing system (MICOS), in the formation of these deposits. The presence of WOMs in the context of searching for ultrastructural pathognomonic features in CLN2 disease also requires further research.

Clinical and Molecular Characteristics of Neuronal Ceroid Lipofuscinosis in Saudi Arabia.

BACKGROUND: Neuronal ceroid lipofuscinoses (NCLs) represent a heterogeneous group of inherited metabolic lysosomal disorders characterized by neurodegeneration. This study sought to describe the clinical and molecular characteristics of NCLs in Saudi Arabia and determine the most common types in that population. METHODS: A retrospective review of electronic medical records was conducted for 63 patients with NCL (55 families) from six tertiary and referral centers in Saudi Arabia between 2008 and 2022. Clinical, radiological, and neurophysiological data as well as genetic diagnoses were reviewed. RESULTS: CLN6 was the predominant type, accounting for 45% of cases in 25 families. The most common initial symptoms were speech delay (53%), cognitive decline (50%) and/or gait abnormalities (48%), and seizure (40%). Behavioral symptomatology was observed in 20%, whereas visual impairment was less frequently (9.3%) encountered. Diffuse cerebral and cerebellar atrophy was the predominant finding on brain magnetic resonance imaging. Electroencephalography generally revealed background slowing in all patients with generalized epileptiform discharges in 60%. The most common genotype detected was the p.Ser265del variant found in 36% (20 of 55 families). The most rapidly progressive subtypes were CLN2 and CLN6. Two patients with each died at age five years. The earliest age at which a patient was nonambulatory was two years in a patient with CLN14. CONCLUSIONS: This is the largest molecularly confirmed NCL cohort study from Saudi Arabia. Characterizing the natural history of specific NLC types can increase understanding of the underlying pathophysiology and distinctive genotype-phenotype characteristics, facilitating early diagnosis and treatment initiation as well as genetic counseling for families.

A recessive CLN3 variant is responsible for delayed-onset retinal degeneration in Hereford cattle.

Thirteen American Hereford cattle were reported blind with presumed onset when ~12-mo-old. All blind cattle shared a common ancestor through both the maternal and paternal pedigrees, suggesting a recessive genetic origin. Given the pedigree relationships and novel phenotype, we characterized the ophthalmo-pathologic changes associated with blindness and identified the responsible gene variant. Ophthalmologic examinations of 5 blind cattle revealed retinal degeneration. Histologically, 2 blind cattle had loss of the retinal photoreceptor layer. Whole-genome sequencing (WGS) of 7 blind cattle and 9 unaffected relatives revealed a 1-bp frameshift deletion in ceroid lipofuscinosis neuronal 3 (CLN3; chr25 g.26043843del) for which the blind cattle were homozygous and their parents heterozygous. The identified variant in exon 16 of 17 is predicted to truncate the encoded protein (p. Pro369Argfs*8) battenin, which is involved in lysosomal function necessary for photoreceptor layer maintenance. Of 462 cattle genotyped, only blind cattle were homozygous for the deletion. A query of WGS data of > 5,800 animals further revealed that the variant was only observed in related Hereford cattle. Mutations in CLN3 are associated with human juvenile neuronal ceroid lipofuscinosis (JNCL), or Batten disease, which results in early-onset retinal degeneration and lesions similar to those observed in our cases. Our data support the frameshift variant of CLN3 as causative of blindness in these Hereford cattle, and provide additional evidence of the role of this gene in retinal lesions, possibly as a model for human non-syndromic JNCL.

Natural History of Neuronal Ceroid Lipofuscinosis Type 6, Late Infantile Disease.

BACKGROUND: Mutations in the CLN6 gene cause late infantile neuronal ceroid lipofuscinosis, a neurodegenerative lysosomal storage disease of childhood onset. Clinically, individuals present with progressive motor and cognitive regression, ataxia, and early death. The aim of this study is to establish natural history data of individuals with classic, late-infantile-onset (age less than five years) CLN6 disease. METHODS: We analyzed the natural history of 25 patients with late-infantile-onset CLN6, utilizing the Hamburg motor-language scale to measure disease progression. The key outcomes were CLN6 disease progression, assessed by rate of decline in motor and language clinical domain summary scores (0 to 6 total points); onset and type of first symptom; onset of first seizure; and time from first symptom to complete loss of function. RESULTS: Median age of total motor and language onset of decline was 42 months (interquartile range 36 to 48). The estimated rate of decline in total score was at a slope of -1.20 (S.D. 0.30) per year, after the start of decline. Complete loss of both motor and language function was found to be, on average, 88.1 months (S.D. 13.5). CONCLUSIONS: To our knowledge, this is the largest international study that monitors the longitudinal natural history and progression of CLN6 disease. These data may serve as a template for future interventional trials targeted to slow the progression of this devastating disease.

Glycerophosphodiesters inhibit lysosomal phospholipid catabolism in Batten disease.

Batten disease, the most prevalent form of neurodegeneration in children, is caused by mutations in the CLN3 gene, which encodes a lysosomal transmembrane protein. CLN3 loss leads to significant accumulation of glycerophosphodiesters (GPDs), the end products of glycerophospholipid catabolism in the lysosome. Despite GPD storage being robustly observed upon CLN3 loss, the role of GPDs in neuropathology remains unclear. Here, we demonstrate that GPDs act as potent inhibitors of glycerophospholipid catabolism in the lysosome using human cell lines and mouse models. Mechanistically, GPDs bind and competitively inhibit the lysosomal phospholipases PLA2G15 and PLBD2, which we establish to possess phospholipase B activity. GPDs effectively inhibit the rate-limiting lysophospholipase activity of these phospholipases. Consistently, lysosomes of CLN3-deficient cells and tissues accumulate toxic lysophospholipids. Our work establishes that the storage material in Batten disease directly disrupts lysosomal lipid homeostasis, suggesting GPD clearance as a potential therapeutic approach to this fatal disease.

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.