Cell Biology of Mutant Huntingtin

Disease relevant cell models for HD are lacking, in particular human cell models for neuronal populations most affected by the presence of mHtt. Use of neuronal cell lines alongside animal models of HD has been essential in identifying key cellular processes perturbed by the expression of mutant huntingtin. Our current research aims at fully characterising these effects and translating these finding to a physiologically relevant human cell model for high content drug compound screening. Using patient fibroblasts from affected and unaffected individuals from a single family, we have developed induced pluripotent stem cells (iPSCs) that can be differentiated to medium spiny neurons and cortical neurons, most affected in HD pathology.

We are using iPSCs to explore fundamental questions that remain unanswered in the pathomechanisms of mHTT:

Using live cell imaging and biochemical analyses we are examining the effects of mHtt on the viability and function of human neuronal populations and whether the HD brain microenvironment exacerbates mHtt pathomechanisms. For example, glutamate excitotoxicity has been identified as a key mechanism occurring in neurodegeneration and may be in part determined by the disrupted function of HD astrocytes in clearing glutamate from the extracellular milieu. Are neurons expressing mHtt more susceptible to excitotoxicity?

We are also interested in the CAG repeat dependence of the cellular effects of mHTT. CAG repeat length is linked to disease onset and progression, though the mechanisms are unknown. In particular, it remains unclear if increasing CAG expansion leads to differences in the HTT protein profile. Using iPSCs with the same genetic background but varying CAG repeats our current work is aimed at characterising the effect of CAG expansion on key elements of mHtt proteotoxicity such as splice variance, post-translational cleavage and aggregation.

Mitochondrial function and trafficking

Mitochondrial dysfunction is described as part of the neuronal dysfunction and degeneration that occurs in HD and is a key target for therapeutics. We are interested in characterising the interaction between mHtt and mitochondria identified previously in mouse models and peripheral cells and further exploring the dysfunction associated with impaired mitochondrial function that may trigger apoptosis, such as calcium homeostasis, respiratory chain ATP generation and reactive oxygen species generation.

High content screening and drug compound research endpoints

Ultimately, through investigation of the mechanisms of mHTT in human in vitro cell models, we have identifed novel targets for disease modifying therapies. In collaboration with Takeda we are performing primary drug screens aimed at manipulating cellular processes compromised in degenerating neurons, using the endpoints described above to assess therapeutic potential.

Details of all our published research results can be found on our Publications page.

Updated August 13, 2015