Identifying and treating the mechanisms leading to cellular dysfunction in a rare form of childhood epilepsy (late infantile neuronal ceroid lipofuscinosis, CLN5 disease)

Shipley, Katie Lynne 2019. Identifying and treating the mechanisms leading to cellular dysfunction in a rare form of childhood epilepsy (late infantile neuronal ceroid lipofuscinosis, CLN5 disease). PhD Thesis, Cardiff University. Item availability restricted.

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Abstract

CLN5 disease, also known as variant late-infantile neuronal ceroid lipofuscinosis (vLINCL), is one of a group of rare, childhood neurodegenerative diseases called the neuronal ceroid lipofuscinoses (NCLs). The NCLs are characterised by the lysosomal accumulation of lipofuscin throughout all bodily tissues and are clinically similar, presenting with progressive motor and cognitive decline, visual deterioration leading to blindness, sleep disturbances, and the onset of myoclonic epilepsy. Although the genetics of CLN5 disease have been well explored, much of the cell biology, including the function of the CLN5 protein, remains elusive, limiting the possibility for therapeutic intervention in this disease This thesis aimed to uncover key disease phenotypes of CLN5 patient cells. It was hoped that elucidating the cell biology of this disease may uncover new potential targets for therapeutic intervention. In this thesis we provide the first in-depth characterisation of cell biological changes in a range of human CLN5 patient fibroblasts and that endocytosis of exogenous recombinant CLN5 protein can rescue these phenotypes. In terms of cell biological changes, we demonstrate irregular ER and mitochondrial Ca2+ handling in CLN5 patient fibroblasts, as well as defective autophagy, lysosomal expansion and glycosphingolipid accumulation. We show that reducing glycosphingolipid accumulation with miglustat, an inhibitor of glycosphingolipid biosynthesis, successfully rescues these phenotypes. These data indicate that glycosphingolipid storage is a primary event in the CLN5 disease pathogenic cascade, and are therefore a suitable target for therapeutic intervention. This work has led to an off-label clinical safety study of miglustat in two CLN5 patients in the UK. Analysis of patient blood smears reveals that miglustat is able to correct lipid storage defects in CLN5 patient blood cells, indicating that miglustat is exhibiting its desired effect in patients and has the potential to be the first small molecule substrate reduction therapy for CLN5 disease. We also show decreased protein levels, and enzyme activity, of TPP1 (the protein deficient in CLN2 disease) in CLN5 patient fibroblasts. Utilising high throughput drug screening, we demonstrate the potential of TPP1 as a target for CLN5 disease, identifying 3 further 2 potential small molecule therapies for the treatment of CLN5 disease. Together, our data has increased the understanding of basic cell biology in CLN5 disease, and demonstrates the potential of glycosphingolipid storage as a therapeutic target for pharmacological intervention.

Item Type:	Thesis (PhD)
Date Type:	Completion
Status:	Unpublished
Schools:	Biosciences
Subjects:	Q Science > Q Science (General) R Medicine > R Medicine (General)
Date of First Compliant Deposit:	16 March 2020
Last Modified:	26 Oct 2021 01:28
URI:	https://orca.cardiff.ac.uk/id/eprint/130344

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