UnTangle

Background

One of the most active areas of research into Alzheimer’s disease centres on the tau protein that forms the classic neurofibrillary tangles. Aberrant intracellular inclusions composed of hyperphosphorylated filamentous tau are not only a neuropathological hallmark of Alzheimer’s disease, but are also the key pathological species in progressive supranuclear palsy and other sporadic neurodegenerative disorders, which have been collectively termed tauopathies.

The discovery that pathogenic mutations in the tau gene microtubule associated protein tau (MAPT) can cause a familial neurodegenerative tauopathy has provided compelling evidence that tau dysfunction is sufficient to cause neurodegeneration. Many recent in vivo studies have shown that tau aggregates have ‘prion-like’ properties which not only allow them to transmit or seed further tau aggregation, but also spread to neighbouring cells or functionally connected brain regions. This process is referred to as ‘tau propagation’ and might explain the stereotypic progression of tau pathology in the brains of Alzheimer’s disease patients.

Study of the development and spread of tau pathology in animal models requires large numbers, is time consuming and expensive. Often, the mechanisms and/or potential drug targets that are identified do not translate into humans.

3Rs benefits

Thousands of transgenic mice are used per year in large pharmaceutical companies with additional breeding animals to obtain the required genotype. There are specific challenges associated with tau transgenics:

1. Phenotypic variability. Mice often undergo chronic treatment with a candidate drug to test for disease modifying actions. Large numbers of animals are required per treatment arm to ensure clear results. For example, Lilly have noted wide phenotypic variability in mice expressing mutant human tau (JNPL3) leading to n=25 animals per treatment arm being required for drug studies.
2. Variability in levels of tau expression. Some transgenic lines express varying levels of tau and/or only a certain portion of mice are suitable for drug testing (e.g. only 25% of tg4510 mice are bigenic).

Therefore, large breeding programmes are needed to generate sufficient numbers of mice for each study. A human cell-based assay would reduce the number of transgenic animals used to investigate tau pathology and also improve the research and development of new treatments in this area.

Phase 1 winners

Project teams led by:

• Dr Eric Hill, University of Aston, £95,453.
• Professor Maria Grazia Spillantini, University of Cambridge, £66,898. 
• Dr Selina Wray, University College London, £99,956.
• Dr Christopher Ward, University of Manchester, £81,956.

Phase 2 winner

Project team led by:

• Dr Selina Wray, University College London, £898,416.

Full Challenge information

A multidisciplinary team led by Dr Selina Wray (University College London) has generated human induced pluripotent stem cell-derived neurons (hiPSC-neurons) carrying mutations in the tau gene and isogenic controls, cultured in microfluidic devices, to study neuronal connectively and the spread of tau pathologies between synaptically connected chambers. This provides a human-relevant model of tauopathy, reducing the number of animals used to study tau pathology and for drug screening in the development of novel therapeutics.

HiPSC-neurons are seeded into environmentally isolated chambers in microfluidic devices. HiPSC-neurons cultured in the microfluidic devices form active synaptically connected networks, and the uptake and spread of tau between connected chambers can be detected using exogenous tau fibril seeds.

The team demonstrated that after long term culture (365 days), control neurons express all six tau isoforms seen in the adult human central nervous system, and that neurons with mutations in tau show dysregulated tau splicing (Sposito et al., 2015).

The team has developed methods to cryopreserve human hiPSC-dervied neuronal precursors directly within the microfluidic devices, with limited impact on cell viability or neuronal function. This offers the opportunity for product development to enable potential customers to purchase microfluidics kits with neurons ready plated within a device, which can be revived, cultured until maturity and used to study synaptic connectively and the spread of protein pathologies. The team are currently exploring options to support further development of this model prior to commercialisation.

For further information about the model please contact Dr Selina Wray

European Bank of induced Stem Cells (EBiSC)

Quality assured human induced pluripotent stem cell (hiPSC) lines carrying mutations in the tau gene (MAPT) are available for use by the research community, pharmaceutical industry and other organisations via a central repository – the European Bank of induced Stem cells (EBiSC).

Neurons produced by these cell lines provide a human-relevant model to study tau pathology and for drug screening of novel therapeutics, reducing reliance on animal models.

A total of 13 lines have been deposited with cell line names SIGi001-A-1 to SIGi001-A-13.

You can find out more on the EBiSC website.