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Title: Gene therapy to improve vision in neuronal ceroid lipofuscinoses
Author: Kleine Holthaus, S. M.
ISNI:       0000 0004 7229 8168
Awarding Body: UCL (University College London)
Current Institution: University College London (University of London)
Date of Award: 2016
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The neuronal ceroid lipofuscinoses (NCLs) are inherited lysosomal storage disorders that present with severe neurodegeneration and loss of vision. A major obstacle to developing gene therapies for the NCLs is the challenge to efficiently deliver agents throughout the brain; particularly for NCL forms arising from membrane bound protein defects. Adeno-associated virus (AAV) mediated gene therapies have been used for several monogenic retinal degenerations to restore the expression of proteins and improve retinal morphology and function. As vision loss is a key feature in NCL, this thesis sought to explore the therapeutic potential of an ocular AAV-mediated gene therapy in the Cln6nclf mouse, a model deficient in the transmembrane protein Cln6. The ultimate goal of this work is to improve quality of life for patients by developing a therapy to preserve vision. In addition, this study may also help to overcome challenges associated with brain-directed treatments for NCL. To identify the cell population that needs to be therapeutically targeted, we performed an analysis of CLN6 expression in the eye. These data revealed that CLN6 is expressed in photoreceptor and bipolar cells of the retina and that the expression level of CLN6 is higher in bipolar cells than in photoreceptors. We also investigated the retinal phenotype in Cln6nclf mice to determine the time window for treatment and established measures assessing the effects of the treatment on the disease progression. Loss of photoreceptor cells and photoreceptor function occurred as early as 2 and 3 weeks of age ultimately resulting in dramatic thinning of the outer nuclear layer. To test whether we can slow degeneration by gene therapy, we performed subretinal injections targeting photoreceptors in Cln6-deficient mice using AAV2/8.CLN6 vectors. This work demonstrated that despite widespread transgene expression the treatment does not have a beneficial effect on retinal function or morphology. We concluded that photoreceptor treatment was not sufficient and hypothesised that bipolar cells need to be treated additionally to prevent vision loss in Cln6nclf mice. Finally, we investigated strategies to enhance the transduction efficiency of bipolar cells that are poorly transduced by commonly used AAVs. Injections of a recently engineered AAV vector showed widespread transduction of bipolar cells. Currently, we are assessing whether a gene supplementation therapy targeting bipolar cells and photoreceptors is therapeutic in Cln6-deficient mice.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available