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Case Study

Model recapitulating key features of human tauopathies.

‍Bondulich MK, et al. Tauopathy induced by low level expression of a human brain-derived tau fragment in mice is rescued by phenylbutyrate. Brain. 2016.

Tauopathies are characterized by progressive cognitive and/or motor dysfunction, together with highly phosphorylated aggregates of the microtubule-associated protein tau in brain and peripheral nerve.

Most existing mouse models of tauopathy overexpress mutant tau at levels that do not occur in human neurodegenerative disease.

Model: New highly disease-relevant mouse model of tauopathy expressing Hprt locus-targeted Tau35, highly phosphorylated C-terminal human tau fragment.

Aim: Evaluate a new model of tauopathy for developing novel treatments for human tauopathies.

Results: Tau35 mice represent a pathophysiologically relevant mouse model in which to test new, potentially disease-modifying therapies.

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Figure 1. Tau expression in Tau35 mouse brains

Excessive accumulation of cGMP and subsequent rod photoreceptor death, followed by a mutation-independent, secondary death of cone photoreceptors.

A) RT-PCR confirms Tau35 expression.

B) Sagittal sections show widespread hemagglutinin labeling in Tau35 mouse brain (upper panels, scale bar = 2 mm). Higher magnifications of the hippocampal CA1 region show strongly hemagglutinin-positive pyramidal neurons in Tau35 mice (lower panels, scale bar = 200 mm). Western blots of frontal region and hippocampus/associated cortex (HC) show hemagglutinin protein expression only in Tau35 mice.

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Figure 2. Progressive neuromuscular impairment

A) Limb clasping is apparent in Tau35 mice from 2 months of age (image shows 8 months), with all Tau35 animals affected by 18 months. Clasping is not observed in wildtype (wt) mice at any age examined.

B) Spine curvature is apparent in Tau35, but not wildtype mice, at 14 months of age. A progressive reduction in the kyphotic index in Tau35 mice after 4 months of age indicates increasing spine curvature.

C) Visible platform (VP) training in the Morris water maze was followed by 4 days of hidden platform training. At 10 months of age, Tau35 mice exhibit longer escape latency on the fourth day of testing compared to wildtype mice.

D) The grip strength of Tau35 mice declines steadily with age.

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Figure 3. Phenylbutyrate rescues disease-related changes in Tau35 mice.

A) Morris water maze (10 months) testing of 4-phenylbutyrate (PBA, dotted lines) and vehicle-treated (solid lines) Tau35 (circles) and wildtype (wt, squares) mice. PBA-treated Tau35 mice show improved learning after 3 days, resulting in decreased escape latency.

B) Grip strength of Tau35 (10 months) is restored by PBA treatment.