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Treatment of the neuronal ceroid lipofuscinoses, also known as Batten disease, is at the start of a new era because of diagnostic and therapeutic advances relevant to this group of inherited neurodegenerative and life-limiting disorders that affect children. Diagnosis has improved with the use of comprehensive DNA-based tests that simultaneously screen for many genes. The identification of disease-causing mutations in 13 genes provides a basis for understanding the molecular mechanisms underlying neuronal ceroid lipofuscinoses, and for the development of targeted therapies. These targeted therapies include enzyme replacement therapies, gene therapies targeting the brain and the eye, cell therapies, and pharmacological drugs that could modulate defective molecular pathways. Such therapeutic developments have the potential to enable earlier diagnosis and better targeted therapeutic management. The first approved treatment is an intracerebroventricularly administered enzyme for neuronal ceroid lipofuscinosis type 2 disease that delays symptom progression. Efforts are underway to make similar progress for other forms of the disorder.

Background CLN2 disease (Neuronal Ceroid Lipofuscinosis Type 2) is an ultra-rare, neurodegenerative lysosomal storage disease, caused by an enzyme deficiency of tripeptidyl peptidase 1 (TPP1). Lack of disease awareness and the non-specificity of presenting symptoms often leads to delayed diagnosis. These guidelines provide robust evidence-based, expert-agreed recommendations on the risks/benefits of disease-modifying treatments and the medical interventions used to manage this condition. Methods An expert mapping tool process was developed ranking multidisciplinary professionals, with knowledge of CLN2 disease, diagnostic or management experience of CLN2 disease, or family support professionals. Individuals were sequentially approached to identify two chairs, ensuring that the process was transparent and unbiased. A systematic literature review of published evidence using Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidance was independently and simultaneously conducted to develop key statements based upon the strength of the publications. Clinical care statements formed the basis of an international modified Delphi consensus determination process using the virtual meeting (Within3) online platform which requested experts to agree or disagree with any changes. Statements reaching the consensus mark became the guiding statements within this manuscript, which were subsequently assessed against the Appraisal of Guidelines for Research and Evaluation (AGREEII) criteria. Results Twenty-one international experts from 7 different specialities, including a patient advocate, were identified. Fifty-three guideline statements were developed covering 13 domains: General Description and Statements, Diagnostics, Clinical Recommendations and Management, Assessments, Interventions and Treatment, Additional Care Considerations, Social Care Considerations, Pain Management, Epilepsy / Seizures, Nutritional Care Interventions, Respiratory Health, Sleep and Rest, and End of Life Care. Consensus was reached after a single round of voting, with one exception which was revised, and agreed by 100% of the SC and achieved 80% consensus in the second voting round. The overall AGREE II assessment score obtained for the development of the guidelines was 5.7 (where 1 represents the lowest quality, and 7 represents the highest quality). Conclusion This program provides robust evidence- and consensus-driven guidelines that can be used by all healthcare professionals involved in the management of patients with CLN2 disease and other neurodegenerative disorders. This addresses the clinical need to complement other information available.

Batten diseases (BDs) are a group of lysosomal storage disorders characterized by seizure, visual loss, and cognitive and motor deterioration. We discovered increased levels of globotriaosylceramide (Gb3) in cellular and murine models of CLN3 and CLN7 diseases and used fluorescent‐conjugated bacterial toxins to label Gb3 to develop a cell‐based high content imaging (HCI) screening assay for the repurposing of FDA‐approved compounds able to reduce this accumulation within BD cells. We found that tamoxifen reduced the lysosomal accumulation of Gb3 in CLN3 and CLN7 cell models, including neuronal progenitor cells (NPCs) from CLN7 patient‐derived induced pluripotent stem cells (iPSC). Here, tamoxifen exerts its action through a mechanism that involves activation of the transcription factor EB (TFEB), a master gene of lysosomal function and autophagy. In vivo administration of tamoxifen to the CLN7 Δex2 mouse model reduced the accumulation of Gb3 and SCMAS, decreased neuroinflammation, and improved motor coordination. These data strongly suggest that tamoxifen may be a suitable drug to treat some types of Batten disease. SYNOPSIS The neuronal ceroid lipofuscinoses (NCL), commonly known as Batten disease (BD), are a group of recessively inherited fatal diseases of the nervous system that typically arise in childhood. There is neither cure nor drugs to revert the course of these diseases. Neural accumulation of lysosomal Gb3 is a novel hallmark of CLN3 and CLN7 batten diseases. The FDA‐approved drug tamoxifen reverts pathological phenotype of CLN3 and CLN7 diseases in vitro and in vivo . Tamoxifen effects are independent of the modulation of estrogen receptors but require the activation of TFEB. Graphical Abstract The neuronal ceroid lipofuscinoses (NCL), commonly known as Batten disease (BD), are a group of recessively inherited fatal diseases of the nervous system that typically arise in childhood. There is neither cure nor drugs to revert the course of these diseases.

Background Batten disease is a group of rare inherited neurodegenerative diseases. Juvenile CLN3 disease is the most prevalent type, and the most common pathogenic variant shared by most patients is the “1-kb” deletion which removes two internal coding exons (7 and 8) in CLN3 . Previously, we identified two transcripts in patient fibroblasts homozygous for the 1-kb deletion: the ‘major’ and ‘minor’ transcripts. To understand the full variety of disease transcripts and their role in disease pathogenesis, it is necessary to first investigate CLN3 transcription in “healthy” samples without juvenile CLN3 disease. Methods We leveraged PacBio long-read RNA sequencing datasets from ENCODE to investigate the full range of CLN3 transcripts across various tissues and cell types in human control samples. Then we sought to validate their existence using data from different sources. Results We found that a readthrough gene affects the quantification and annotation of CLN3. After taking this into account, we detected over 100 novel CLN3 transcripts, with no dominantly expressed CLN3 transcript. The most abundant transcript has median usage of 42.9%. Surprisingly, the known disease-associated ‘major’ transcripts are detected. Together, they have median usage of 1.5% across 22 samples. Furthermore, we identified 48 CLN3 ORFs, of which 26 are novel. The predominant ORF that encodes the canonical CLN3 protein isoform has median usage of 66.7%, meaning around one-third of CLN3 transcripts encode protein isoforms with different stretches of amino acids. The same ORFs could be found with alternative UTRs. Moreover, we were able to validate the translational potential of certain transcripts using public mass spectrometry data. Conclusion Overall, these findings provide valuable insights into the complexity of CLN3 transcription, highlighting the importance of studying both canonical and non-canonical CLN3 protein isoforms as well as the regulatory role of UTRs to fully comprehend the regulation and function(s) of CLN3 . This knowledge is essential for investigating the impact of the 1-kb deletion and rare pathogenic variants on CLN3 transcription and disease pathogenesis.

Background Neuronal Ceroid Lipofuscinoses (NCLs), also known as Batten disease, are a group of inherited neurodegenerative disorders that mostly arise in childhood. Each of the NCLs is a genetically distinct disease caused by variants in at least 13 different genes ( CLN1–CLN14 ). NCLs are neurodegenerative, and symptoms can include a combination of childhood dementia, epileptic seizures, motor decline and vision loss, and eventually lead to premature death. There is currently no cure for any subtype of NCL, however, enzyme replacement therapy is available for CLN2 disease, and several treatment strategies are being explored for other NCL subtypes. Early diagnosis and initiation of supportive services (e.g. health, education, social services) are essential to preserve quality of life. Only a few studies have investigated family experiences with NCL, many of which are international in scope. Methods A mixed-method research study was conducted in the UK to understand family experiences in CLN2 and CLN3 disease. It involved an initial literature review, followed by in-depth qualitative interviews. Interview data were analysed using a thematic analysis. Thirteen families ( n  = 13) participated in the interviews. This represented 16 parents (11 mothers and 5 fathers) of 18 children (10 diagnosed with CLN3 disease and 8 diagnosed with CLN2 disease). Findings were analysed jointly across CLN2 and CLN3 disease. Results Six overarching themes emerged from the analysis: difficulty in recognising early symptoms; the shock of a diagnosis; the demands of caring for complex and ever-changing needs; a constant battle to access appropriate and timely support services; the extensive impact on the unaffected sibling; and the all-encompassing impact on the family. Conclusions This study contributes novel UK specific data on family experiences and unmet needs in CLN2 and CLN3 disease. More needs to be done to ensure NCLs are diagnosed early, and timely local support services are made available to protect quality of life for both the affected children and their families.

Juvenile CLN3 disease is a recessively inherited paediatric neurodegenerative disorder, with most patients homozygous for a 1-kb intragenic deletion in CLN3 . The btn1 gene is the Schizosaccharomyces pombe orthologue of CLN3 . Here, we have extended the use of synthetic genetic array (SGA) analyses to delineate functional signatures for two different disease-causing mutations in addition to complete deletion of btn1 . We show that genetic-interaction signatures can differ for mutations in the same gene, which helps to dissect their distinct functional effects. The mutation equivalent to the minor transcript arising from the 1-kb deletion ( btn1 102–208del ) shows a distinct interaction pattern. Taken together, our results imply that the minor 1-kb deletion transcript has three consequences for CLN3: to both lose and retain some inherent functions and to acquire abnormal characteristics. This has particular implications for the therapeutic development of juvenile CLN3 disease. In addition, this proof of concept could be applied to conserved genes for other mendelian disorders or any gene of interest, aiding in the dissection of their functional domains, unpacking the global consequences of disease pathogenesis, and clarifying genotype–phenotype correlations. In doing so, this detail will enhance the goals of personalised medicine to improve treatment outcomes and reduce adverse events.

Inherited biallelic mutations in the CLN7 gene result in the variant late infantile onset neuronal ceroid lipofuscinosis, a subtype of Batten disease (BD), a severe and fatal childhood neurodegenerative disease. Intriguingly, CLN7 genetic variants have also been associated with retinopathies, amyotrophic lateral sclerosis, and frontotemporal dementia. CLN7 encodes a transmembrane protein localizing to endolysosomal membranes with outward-facing chloride channel activity. Loss of CLN7 function results in cortical neurons accumulating swollen lipofuscin-containing lysosomes, leading to neuroinflammation and neurodegeneration. The molecular mechanisms underlying CLN7 BD neuropathology are not completely understood. We have generated iPSC lines from two CLN7 BD patients and age-matched unaffected controls to interrogate intracellular molecular phenotypes in iPSC-derived neural progenitor cells (iNPC). Taking a multi-omics approach we have identified disease-modified activities in endolysosomal transport in iNPC BD that lead to lysosomal dysfunction and decreased mitophagy, resulting in the accumulation of metabolically defective mitochondria. We further observe a breakdown in nuclear functions that centre on RNA processing and nuclear export, linking to CLN7 protein interactions at the stress granule. We have identified dual and distinct functions for CLN7, promoting cell survival during the cellular stress response. CLN7 loss of function in BD results in neuronal apoptosis.

Background CLN3 disease, also called Juvenile Neuronal Ceroid Lipofuscinosis (JNCL), or Batten disease, is an ultra‑rare, neurodegenerative lysosomal storage disorder generally affecting individuals during the first decade of life. There can be a delay in diagnosis or misdiagnosis due to a lack of awareness, and when the most common presenting symptom of visual loss is attributed to more common conditions affecting vision. Methods We used a previously published Expert Mapping Tool (EMT) to identify multidisciplinary professionals with diagnostic or clinical management expertise, as well as patient advocates with experience of CLN3 disease. A systematic literature review of published evidence using the Preferred Reporting Items for Systematic Reviews and Meta‑Analyses (PRISMA) guidance was conducted independently and simultaneously to develop key clinical care statements. Each statement was based on the strength of the evidence. The statements formed the basis of an international modified-Delphi consensus process using a virtual meeting platform (Within3). Experts were asked to agree or disagree with each statement and suggest any changes. Statements that reached a consensus of 75% or over are the guiding statements within this manuscript. The processes and manuscript have been independently assessed using the Appraisal of Guidelines for Research and Evaluation (AGREE II) criteria. Results Thirty‑nine international experts from eight specialities were identified, including a patient advocate. Fifty‑three recommendation statements were developed covering eleven domains: General statements, Diagnostics, Clinical Recommendations and Management, Assessments, Social Considerations, Ocular Management, Epilepsy/Seizures, Nutrition, Respiratory Health, Sleep and Rest, and End-of-Life Care. Consensus was reached after one round of voting for all except three statements. The overall AGREE II score for developing these recommendations was 6.4, where 1 represents the lowest and 7 is the highest quality. Conclusion Currently, there are no comprehensive clinical recommendations for CLN3 disease. These recommendations provide a comprehensive, evidence- and consensus‑based tool that can be used by all healthcare professionals involved in the management of CLN3 disease and other similar neurodegenerative conditions. The goal is to address the unmet clinical need for CLN3 disease management and complement other information available.

Background Biallelic variants in the major facilitator superfamily domain containing 8 gene (MFSD8) are associated with distinct clinical presentations that range from typical late‐infantile neuronal ceroid lipofuscinosis type 7 (CLN7 disease) to isolated adult‐onset retinal dystrophy. Classic late‐infantile CLN7 disease is a severe, rare neurological disorder with an age of onset typically between 2 and 6 years, presenting with seizures and/or cognitive regression. Its clinical course is progressive, leading to premature death, and often includes visual loss due to severe retinal dystrophy. In rare cases, pathogenic variants in MFSD8 can be associated with isolated non‐syndromic macular dystrophy with variable age at onset, in which the disease process predominantly or exclusively affects the cones of the macula and where there are no neurological or neuropsychiatric manifestations. Methods Here we present longitudinal studies on four adult‐onset patients who were biallelic for four MFSD8 variants. Results Two unrelated patients who presented with adult‐onset ataxia and had macular dystrophy on examination were homozygous for a novel variant in MFSD8 NM_152778.4: c.935T>C p.(Ile312Thr). Two other patients presented in adulthood with visual symptoms, and one of these developed mild to moderate cerebellar ataxia years after the onset of visual symptoms. Conclusions Our observations expand the knowledge on biallelic pathogenic MFSD8 variants and confirm that these are associated with a spectrum of more heterogeneous clinical phenotypes. In MFSD8‐related disease, adult‐onset recessive ataxia can be the presenting manifestation or may occur in combination with retinal dystrophy. Biallelic pathogenic variants in major facilitator superfamily domain containing 8 gene (MFSD8) have classically been associated with late‐infantile neuronal ceroid lipofuscinosis type 7 and with isolated/nonsyndromic macular dystrophy with central cone involvement. Here, we present two patients with biallelic pathogenic MFSD8 variants from Sweden and India with ataxia starting in their 20s and 30s and two patients with retinal dystrophy, of whom one developed ataxia later in life.