Huntington’s disease (HD) is a late onset neurodegenerative disease with no known cure. It is an autosomal dominant disorder caused by mutation of a single gene resulting in an expanded polyglutamine stretch in the huntingtin protein causing altered function and neuronal toxicity.
One of the earliest stages of neurodegeneration is synaptic atrophy, which is caused by a failure of neurons to efficiently and accurately communicate at synapses. Therefore by determining the early molecular mechanisms that govern synaptic failure, we may be able correct this key function to prevent or slow the progression of synaptic atrophy.
We have identified two signatures of presynaptic dysfunction in a mouse model of HD (Q140 knock-in). These defects are caused by a loss of wt huntingtin function and can be rescued by introduction of the wt protein. We have also identified a number of novel target proteins that may be instrumental in the defective phenotypes and thus the first aim of this PhD project is to investigate the molecular mechanisms mediating the dysfunction. This will be achieved by monitoring presynaptic function in primary neuronal cultures from both wild type and Q140 mice. These cultures will be challenged with either targeted gene silencing or over-expression constructs to identify the molecular partners mediating these defects.
A key question is whether these signatures of presynaptic dysfunction (and the molecular players) are recapitulated in human HD neurons. Therefore, the second aim is to examine presynaptic function in a human model of HD – induced pluripotent stem cells (iPSCs) isolated from patients with HD and unaffected control individuals differentiated into neurons.
The integration of functional assays of presynaptic performance in both mouse and human HD model systems will provide important insights into the molecular cause of neuronal degeneration in this devastating condition. A conservation of presynaptic dysfunction from mouse to man and the molecular mechanism underpinning it, will provide key new avenues for therapeutic intervention.
Training in all techniques will be provided and include: live-cell real-time fluorescent imaging (genetically encoded reporter constructs and cargo uptake assays), primary neuronal and iPSC culture, molecular biology and biochemical techniques, electron microscopy.
Dr Karen Smillie
Prof Mike Cousin