Zinc Finger based gene therapy in Huntington's disease

It is broadly understood that Huntington's Disease is a neurodegenerative disorder where there is the expression of a toxic expansion of the CAG sequence on the htt gene. This gene is involved in a wide range of cellular functions, such as the transport of material within the cell and the overall maintenance of cellular structural integrity.
This toxic expansion leads to abnormal aggregation of protein products of the gene within the cell. This process primarily occurs in a class of neurons involved in integrating and relaying information relating to motor function - Medium Spiny Neurons (MSN) (Schulte & Littleton, 2011).
However, recent studies have shown that other classes of neurons upstream of the MSNs, including Primary Motor Neurons and interneurons are also affected, and functional & structural impairments may be measured and quantified in these neurons well before the onset of motor symptoms (Burgold 2019; Deng 2014).
Motor symptoms, on average, are observed in the 5th decade of human life, but mouse models can be used to model the degenerative timeline and pathophysiology observed in humans in a much shorter timeframe.
For my PhD, I will be using several techniques to understand the effects of a zinc-finger based gene therapy in Huntington's disease on the structure & function of cells involved in the motor system. This zinc-finger based gene therapy is composed of protein scaffolds, stabilised by zinc ions, that bind to the CAG-repeat expansions within the gene.
This approach has been proven to improve motor function in a Huntington's Disease mouse model, and, in another case, has shown to reduce expression of the affected gene & protein levels for at least 6 months in a similar, less aggressive mouse model, where disease progression is slower (Augustin-Pavon 2016).
I will be conducting electrophysiological experiments such as whole cell patch-clamping, which aims to understand the how the MSNs function. This will allow us to measure functional differences in the MSNs at different timepoints of disease progression, whilst paying close attention to the inputs arriving onto MSNs from the Primary Motor Cortex (M1) and interneurons.
I will be using a less aggressive mouse model, R6/1, which is believed to better model the key stages of degeneration observed in humans. I will inject the zinc-finger based therapy intrathecally, within the spinal canal, which is a much safer approach than the classic approach of administering the therapy directly within the brain. This safer approach can also be used in humans in the future.
The therapy will be administered at different times of disease onset and I will then analyse the effects of this therapeutic intervention on the functional profiles of MSNs, M1 & Interneurons`.
In addition to the functional experiments, I will be carrying out automated serial 2-photon imaging to provide high, single-cell resolution across the whole mouse brain from the mouse model to accurately quantify the structural changes induced by the zinc-finger based therapy. This imaging will also be undertaken following intrathecal injections of different adeno-associated virus (AAV) serotypes, containing Green-fluorescent Protein, to quantify which virus serotypes are the most effective in infecting different cell subtypes and delivering the therapy.
Finally, we will be carrying out several behavioural tests that test both cognitive and motor functions across different timepoints. These tests include the 9-arm radial maze test, which tests aspects of cognitive function such as memory and decision-making skills. The motor tests include the rotarod and hang-time tests which tests motor function and force of both fore and hindlimbs of the mice.
By the end of this project, we hope to have better understood the mechanisms of action of the zinc-finger based therapy from a behavioural, functional and structural point of view. We also hope to have optimised safer delivery strategies for the zinc-finger bas