Fractionation for Resolution of Soluble and Insoluble Huntingtin Species.

The accumulation of misfolded proteins is central to pathology in Huntington's disease (HD) and many other neurodegenerative disorders. Specifically, a key pathological feature of HD is the aberrant accumulation of mutant HTT (mHTT) protein into high molecular weight complexes and intracellular inclusion bodies composed of fragments and other proteins. Conventional methods to measure and understand the contributions of various forms of mHTT-containing aggregates include fluorescence microscopy, western blot analysis, and filter trap assays. However, most of these methods are conformation specific, and therefore may not resolve the full state of mHTT protein flux due to the complex nature of aggregate solubility and resolution. For the identification of aggregated mHTT and various modified forms and complexes, separation and solubilization of the cellular aggregates and fragments is mandatory. Here we describe a method to isolate and visualize soluble mHTT, monomers, oligomers, fragments, and an insoluble high molecular weight (HMW) accumulated mHTT species. HMW mHTT tracks with disease progression, corresponds with mouse behavior readouts, and has been beneficially modulated by certain therapeutic interventions1. This approach can be used with mouse brain, peripheral tissues, and cell culture but may be adapted to other model systems or disease contexts.

Human Neural Stem Cell Transplantation Rescues Functional Deficits in R6/2 and Q140 Huntington's Disease Mice.

Huntington's disease (HD) is an inherited neurodegenerative disorder with no disease-modifying treatment. Expansion of the glutamine-encoding repeat in the Huntingtin (HTT) gene causes broad effects that are a challenge for single treatment strategies. Strategies based on human stem cells offer a promising option. We evaluated efficacy of transplanting a good manufacturing practice (GMP)-grade human embryonic stem cell-derived neural stem cell (hNSC) line into striatum of HD modeled mice. In HD fragment model R6/2 mice, transplants improve motor deficits, rescue synaptic alterations, and are contacted by nerve terminals from mouse cells. Furthermore, implanted hNSCs are electrophysiologically active. hNSCs also improved motor and late-stage cognitive impairment in a second HD model, Q140 knockin mice. Disease-modifying activity is suggested by the reduction of aberrant accumulation of mutant HTT protein and expression of brain-derived neurotrophic factor (BDNF) in both models. These findings hold promise for future development of stem cell-based therapies.

Human Neural Progenitor Transplantation Rescues Behavior and Reduces α-Synuclein in a Transgenic Model of Dementia with Lewy Bodies.

Synucleinopathies are a group of neurodegenerative disorders sharing the common feature of misfolding and accumulation of the presynaptic protein α-synuclein (α-syn) into insoluble aggregates. Within this diverse group, Dementia with Lewy Bodies (DLB) is characterized by the aberrant accumulation of α-syn in cortical, hippocampal, and brainstem neurons, resulting in multiple cellular stressors that particularly impair dopamine and glutamate neurotransmission and related motor and cognitive function. Recent studies show that murine neural stem cell (NSC) transplantation can improve cognitive or motor function in transgenic models of Alzheimer's and Huntington's disease, and DLB. However, examination of clinically relevant human NSCs in these models is hindered by the challenges of xenotransplantation and the confounding effects of immunosuppressant drugs on pathology and behavior. To address this challenge, we developed an immune-deficient transgenic model of DLB that lacks T-, B-, and NK-cells, yet exhibits progressive accumulation of human α-syn (h-α-syn)-laden inclusions and cognitive and motor impairments. We demonstrate that clinically relevant human neural progenitor cells (line CNS10-hNPCs) survive, migrate extensively and begin to differentiate preferentially into astrocytes following striatal transplantation into this DLB model. Critically, grafted CNS10-hNPCs rescue both cognitive and motor deficits after 1 and 3 months and, furthermore, restore striatal dopamine and glutamate systems. These behavioral and neurochemical benefits are likely achieved by reducing α-syn oligomers. Collectively, these results using a new model of DLB demonstrate that hNPC transplantation can impact a broad array of disease mechanisms and phenotypes and suggest a cellular therapeutic strategy that should be pursued. Stem Cells Translational Medicine 2017;6:1477-1490.