ORCID
0000-0003-2183-068X
Date of Award
5-6-2024
Degree Name
Doctor of Philosophy (PhD)
Degree Type
Dissertation
Abstract
The neuronal ceroid lipofuscinoses (NCLs) are a group of neurodegenerative lysosomal storage disorders affecting children and young adults. CLN2 disease, or classic late infantile neuronal ceroid lipofuscinosis, is one of the most common forms of NCL and is caused by a deficiency of tripeptidyl peptidase 1 (TPP1). Although an FDA-approved enzyme replacement therapy for CLN2 disease now exists, a poor understanding of pathophysiology has hampered the development of more effective and persistent therapy. While Cln2R207X/R207X knock-in mice which carry one of the most common pathogenic mutations in human patients were developed in 2017, this genetically accurate mouse model for CLN2 disease is yet to be fully characterized. First, we investigated the nature and progression of neurological and underlying neuropathological changes in Cln2R207X/R207X mice. Long-term electroencephalography (EEG) recordings revealed progressive epileptiform abnormalities, including spontaneous seizures, providing robust, quantifiable, and clinically relevant phenotypes. Histopathological analyses revealed that these seizures were accompanied by the loss of multiple cortical neuron populations, including those stained for GABAergic interneuron markers. These results led us to hypothesize that epileptogenesis and interneuron loss in CLN2 disease might be causally related. Secondly, to investigate the mechanistic contribution of interneuron deficits to epileptogenesis in CLN2 disease, we generated novel transgenic mice expressing LoxP-flanked membrane-tethered TPP1 (TPP1LAMP1) to study the cell-autonomous effects of cell-type-specific TPP1 deficiency. Crossing TPP1LAMP1 mice with Vgat-Cre mice introduced interneuron-specific TPP1 deficiency, resulting in storage material accumulation in several interneuron populations both in the cortex and striatum, and increased susceptibility to die after PTZ-induced seizures. Additionally, we selectively activated interneuron activities in Vgat-Cre: Cln2R207X/R207X mice by expressing Cre-dependent hM3Dq, one of the Designer Receptors Exclusively Activated by Designer Drugs (DREADDs). DREADD-mediated activation of interneurons accelerated the onset of spontaneous seizures and seizure-associated death in Vgat-Cre: Cln2R207X/R207X mice compared to the control mice, suggesting that modulating interneuron activity can exert influence over epileptiform abnormalities in CLN2 disease. Lastly, we used those clinically relevant phenotypes in Cln2R207X/R207X mice as outcome measures to study the therapeutic efficacy of a novel gene therapy approach. Neonatal administration of adeno-associated virus serotype 9 (AAV9)–mediated gene therapy ameliorated their seizure and gait phenotypes, significantly prolonged life span, and attenuated most pathological changes in Cln2R207X/R207X mice. Our results not only show that AAV9-mediate gene therapy has a promising pre-clinical efficacy, but they also emphasize the significance of clinically relevant outcome measures in assessing the preclinical effectiveness of therapeutic approaches for CLN2 disease.
Language
English (en)
Chair and Committee
Jonathan Cooper
Recommended Citation
Takahashi, Keigo, "Investigating the Involvement of GABAergic Interneurons and a Gene Therapy Strategy for Epilepsy in CLN2 Disease" (2024). Arts & Sciences Electronic Theses and Dissertations. 3063.
https://openscholarship.wustl.edu/art_sci_etds/3063