AAV9 Gene Therapy Increases Lifespan and Treats Pathological and Behavioral Abnormalities in a Mouse Model of CLN8-Batten Disease.

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.

Acidified drinking water attenuates motor deficits and brain pathology in a mouse model of a childhood neurodegenerative disorder.

We recently demonstrated that HCl-acidified drinking water, which is widely used in laboratory animal facilities, had some beneficial effects in the Cln3-/- mouse model of juvenile Batten disease, a neurodegenerative lysosomal storage disorder1. Here we tested if acidified drinking water has therapeutic effects in Cln1R151X nonsense mutant mice, a model of the infantile form of Batten disease. In Cln1R151X mice, acidified drinking water received from weaning prevented the impairment in pole climbing ability measured at 3 and 6 months of age. Histopathological analysis of the brain at 6 months showed that acidified drinking water decreased the amount of lysosomal storage material, reduced astrocytosis in the striatum and somatosensory barrelfield cortex, and attenuated microglial activation in the thalamus. Compared to wild-type mice, the gut microbiota of Cln1R151X mice was markedly different. Acidified drinking water significantly altered the gut microbiota composition of Cln1R151X mice, indicating a contribution of gut bacteria to the therapeutic effects of acidified water. Our results in Cln1R151X mice suggest that acidified drinking water may have beneficial effects for patients with infantile Batten disease. This study also verifies that acidified drinking water can modify disease phenotypes in mouse models, contributing to the inter-laboratory variations in neurological and pathological findings.

A tailored Cln3Q352X mouse model for testing therapeutic interventions in CLN3 Batten disease.

CLN3 Batten disease (CLN3 disease) is a pediatric lysosomal storage disorder that presents with progressive blindness, motor and cognitive decline, seizures, and premature death. CLN3 disease results from mutations in CLN3 with the most prevalent mutation, a 966 bp deletion spanning exons 7-8, affecting ~ 75% of patients. Mouse models with complete Cln3 deletion or Cln3Δex7/8 mutation have been invaluable for learning about both the basic biology of CLN3 and the underlying pathological changes associated with CLN3 disease. These models, however, vary in their disease presentation and are limited in their utility for studying the role of nonsense mediated decay, and as a consequence, in testing nonsense suppression therapies and read-through compounds. In order to develop a model containing a disease-causing nonsense point mutation, here we describe a first-of-its-kind Cln3Q352X mouse model containing a c.1054C > T (p.Gln352Ter) point mutation. Similar to previously characterized Cln3 mutant mouse lines, this novel model shows pathological deficits throughout the CNS including accumulation of lysosomal storage material and glial activation, and has limited perturbation in behavioral measures. Thus, at the molecular and cellular level, this mouse line provides a valuable tool for testing nonsense suppression therapies or read through compounds in CLN3 disease in the future.

Changes in motor behavior, neuropathology, and gut microbiota of a Batten disease mouse model following administration of acidified drinking water.

CLN3 mutations cause the fatal neurodegenerative disorder, CLN3 Batten disease. The Cln3-/- mouse model displays characteristic features of the human disease including motor deficits. When mice received acidified drinking water (pH 2.5-2.9) instead of normal tap water (pH 8.4) for several generations, the motor skills of Cln3-/- mice normalized to control levels, indicating a disease-modifying effect of acidified water. Here we investigated if acidified water administered from postnatal day 21 has therapeutic benefits in Cln3-/- mice. Indeed, acidified water temporarily attenuated the motor deficits, had beneficial effects on behavioral parameters and prevented microglial activation in the brain of Cln3-/- mice. Interestingly, in control mice, acidified drinking water caused brain region-specific glial activation and significant changes in motor performance. Since the gut microbiota can influence neurological functions, we examined it in our disease model and found that the gut microbiota of Cln3-/- mice was markedly different from control mice, and acidified water differentially changed the gut microbiota composition in these mice. These results indicate that acidified water may provide therapeutic benefit to CLN3 Batten disease patients, and that the pH of drinking water is a major environmental factor that strongly influences the results of murine behavioral and pathological studies.

A tailored mouse model of CLN2 disease: A nonsense mutant for testing personalized therapies.

The Neuronal Ceroid Lipofuscinoses (NCLs), also known as Batten disease, result from mutations in over a dozen genes. Although, adults are susceptible, the NCLs are frequently classified as pediatric neurodegenerative diseases due to their greater pediatric prevalence. Initial clinical presentation usually consists of either seizures or retinopathy but develops to encompass both in conjunction with declining motor and cognitive function. The NCLs result in premature death due to the absence of curative therapies. Nevertheless, preclinical and clinical trials exist for various therapies. However, the genotypes of NCL animal models determine which therapeutic approaches can be assessed. Mutations of the CLN2 gene encoding a soluble lysosomal enzyme, tripeptidyl peptidase 1 (TPP1), cause late infantile NCL/CLN2 disease. The genotype of the original mouse model of CLN2 disease, Cln2-/-, excludes mutation guided therapies like antisense oligonucleotides and nonsense suppression. Therefore, the purpose of this study was to develop a model of CLN2 disease that allows for the assessment of all therapeutic approaches. Nonsense mutations in CLN2 disease are frequent, the most common being CLN2R208X. Thus, we created a mouse model that carries a mutation equivalent to the human p.R208X mutation. Molecular assessment of Cln2R207X/R207X tissues determined significant reduction in Cln2 transcript abundance and TPP1 enzyme activity. This reduction leads to the development of neurological impairment (e.g. tremors) and neuropathology (e.g. astrocytosis). Collectively, these assessments indicate that the Cln2R207X/R207X mouse is a valid CLN2 disease model which can be used for the preclinical evaluation of all therapeutic approaches including mutation guided therapies.