CLN5 disease, caused by mutations in the CLN5 gene, is a form of neuronal ceroid lipofuscinoses (Batten disease). Patients suffer progressive motor dysfunction, vision loss, seizures, and dementia, leading to premature death. Here, we report a preclinical study of AAV9-mediated gene therapy in a Cln5-/- mouse model. Single-dose AAV9 carrying human CLN5 driven by the CAG or human synapsin 1 promoter (hSYN) was administered via intracerebroventricular injection into neonatal and juvenile Cln5-/- mice. Treatment efficacy was evaluated by assessment of neurodegeneration, neuroinflammation, locomotor function, and survival. AAV9 expressing CLN5 driven by the hSYN promoter significantly alleviated neurodegeneration, improved biochemical and glycosphingolipid profiles, neuropathological and locomotor function, and extended lifespan of the Cln5-/- mice. However, gene transfer employing the CAG promoter demonstrated limited therapeutic efficacy. Furthermore, delayed intervention in juveniles provided superior therapeutic response compared with early neonatal intervention and normalized lifespan. Finally, blood plasma neurofilament light that is significantly elevated in the Cln5-/- mice is restored to normal wildtype levels following treatment. These results indicate that brain-directed adeno-associated virus (AAV) gene therapy could be a promising treatment strategy for CLN5 disease and efficacy might be monitored using a noninvasive blood plasma biomarker.

Neuronal ceroid lipofuscinoses (NCL) belong to a group of inherited neurodegenerative diseases characterized by psychomotor regression, seizures, and visual impairment, resulting from intracellular accumulation of lipofuscin. CLN5, a subtype typically manifesting between ages 4 to 17, is particularly rare in non-Finnish populations. Here, we report the first Japanese case of CLN5 in a 12-year-old girl with progressive myoclonic epilepsy and psychomotor regression. Initial assessments for common metabolic disorders, including GM2 gangliosidosis, were inconclusive. Trio-based genome sequencing (GS) identified a novel homozygous pathogenic variant in CLN5, confirming the diagnosis at 10 years and 6 months of age. Subsequent evaluations revealed progressive cerebral and cerebellar atrophy and vision loss. This case underscores the importance of GS in diagnosing rare neurodegenerative diseases and highlights the clinical spectrum of CLN5, which presents with rapid neurological decline. Expanding diagnostic frameworks with genetic testing is critical for early diagnosis and potential therapeutic interventions in CLN5 and related NCL disorders.

Neuronal ceroid lipofuscinoses (NCL; Batten disease) are a group of rare inherited neurodegenerative disorders caused by mutations in one of 13 ceroid lipofuscinosis neuronal (CLN) genes. The diseases share a common set of symptoms, including motor and cognitive dysfunction, progressive loss of vision, and seizure activity. A naturally occurring model of CLN5 NCL exists in New Zealand Borderdale sheep, which exhibit similar clinical disease and post-mortem pathology to the human disease. Recent trials of concurrent intracerebroventricular and intravitreal gene therapy in sheep with CLN5 disease confirmed the therapeutic efficacy of this approach. Given the documented natural history of brain volume changes, detected by MRI, in sheep with CLN5 disease, the current study sought to utilize MRI as both a longitudinal readout and cross-sectional measure of therapeutic efficacy in treated sheep. Sheep treated at a pre-symptomatic timepoint underwent five T1-weighted structural MRI scans between 5 and 18 months of age. Sheep treated at early and advanced symptomatic disease stages underwent a single MRI at 18 months of age. All scans from treated sheep were compared to historical healthy control and affected untreated sheep at each age. Pre-symptomatic treated sheep showed growth in intracranial volume at a comparable rate to healthy control sheep over the course of the study. Whilst grey matter volume decreased and cerebrospinal fluid volume increased in treated sheep, this was to a much smaller degree than in untreated affected sheep. The majority of the cortical regions assessed showed stable volumes over the course of the study, with the notable exception of the cerebellum. Both early and advanced symptomatic treated sheep showed intracranial volumes comparable to untreated affected sheep at 18 months of age. However, when individual tissue types were assessed, grey and white matter were significantly larger, and cerebrospinal fluid was significantly smaller in early symptomatic sheep compared to untreated affected sheep, while the same volumes in advanced symptomatic treated sheep were comparable to untreated affected sheep. Cortical regions assessed showed an age-at-treatment and dose effect. This study has demonstrated that MRI, a clinically relevant outcome measure, can be successfully utilized to assess therapeutic efficacy in a large animal model of CLN5 NCL, both in a longitudinal study and a cross-sectional study when robust natural history data is available for comparison.

CLN5 disease, a form of juvenile dementia within the neuronal ceroid lipofuscinosis (NCL), is associated with mutations in the CLN5 gene encoding the lysosomal bis(monoacylglycero)phosphate (BMP) synthase, essential for BMP production and lysosomal function. Limited knowledge of cellular mechanisms and unclear drug targets hinder translating this to children's treatment, which remains symptomatic. We developed and characterized a new cln5 knock-out zebrafish model that replicates key features and molecular signatures of the human disease. Loss of Cln5 function in vivo altered axonal growth of retinal ON-bipolar cells and disrupted calcium homeostasis in the cerebellum, revealing new disease features. Additionally, multi-omic analyses at different developmental stages revealed an impaired glucose metabolism as an original finding in NCL. A novel biomarker, PHGDH, was validated in zebrafish and human skin fibroblasts harboring pathogenic variants in CLN5, and in CLN7. We also tested metformin which improved the expression of PHGDH in patient-derived cells, and rescued zebrafish behavior. This work demonstrates the profound metabolic impact of CLN5 dysfunction, offering a promising avenue toward targeted therapies for juvenile dementia.

The neuronal ceroid lipofuscinoses (NCLs) are a group of common inherited neurodegenerative disorders of childhood. All forms of NCLs are life-limiting with no curative treatments. Most of the 13 NCL genes encode proteins residing in endolysosomal pathways, such as CLN5, a potential lysosomal enzyme. Two induced pluripotent stem cell lines (hiPSCs) were generated from skin fibroblasts of CLN5 disease patients via non-integrating Sendai virus reprogramming. They demonstrate typical stem cell morphology, express pluripotency markers, exhibit trilineage differentiation potential and also successfully differentiate into neurons. These hiPSCs represent a potential resource to model CLN5 disease in a human context and investigate potential therapies.