Tsuneya Ikezu, United States of America
Mayo Clinic Florida NeuroscienceAuthor Of 3 Presentations
ENTORHINAL CORTEX WOLFRAMIN-1-EXPRESSING NEURONS PROPAGATE TAU TO CA1 NEURONS AND IMPAIR HIPPOCAMPAL MEMORY
Abstract
Aims
In early stages of Alzheimer’s Disease (AD), phosphorylated tau propagates from layer II of the entorhinal cortex (ECII) to the CA1 in the hippocampus. Wolframin-1-expressing (Wfs1+) pyramidal neurons in ECII connect to the CA1 region via temporo-ammonic pathway. We hypothesized that Wfs1+neurons in ECII mediate tau propagation to the CA1 and mimic early stages of tau pathology in AD.
Methods
Wfs1-Cre mice at 4-6 months of age were injected with Cre-inducible AAV2/6-Flex-P301Ltau expressing human P301L tau mutant or AAV2/6-Flex-TdTomato in ECII to specifically express mutant tau in Wfs1+ neurons. At 4 weeks post-injection, the mice were euthanized for immunohistochemistry, electrophysiology and electron microscopy or underwent behavioral test. The functional effect of tau propagation was assessed by multielectrode array to evaluate light-evoked CA1 neuronal firing responses after optogenetic stimulation of Wfs1+ECII axons.
Results
Wfs1-Cre mice injected in ECII with AAV2/6-Flex-P301Ltau displayed significant human tau positivity in CA1 pyramidal neurons but not in DG at 4-weeks post-injection. Electron microscopy revealed a synaptic connection between ECII Wfs1+ axons and CA1 dendrites, and the presence of human tau in pre- and post-synaptic elements. Field recordings of CA1 pyramidal neurons showed reduced measures of excitability. Multielectrode array recordings of optogenetically stimulated Wfs1+ axons resulted in a reduced CA1 neuronal firing after AAV2/6-Flex-P301Ltau injection. Trace fear conditioning revealed deficits in trace and contextual memory in the AAV2/6-Flex-P301Ltau injected mice.
Conclusions
Expression of P301Ltau in Wfs1+ neurons in ECII spreads tau specifically to CA1 pyramidal neurons, and is accompanied by several measures of neurophysiological impairment, including reduced neuronal excitability and deficits in contextual memory.
LIVE DISCUSSION
ALZHEIMER’S DISEASE BRAIN-DERIVED EXTRACELLULAR VESICLES SPREAD TAU PATHOLOGY IN INTERNEURONS
Abstract
Aims
We hypothesize that tau-containing exosomes derived from Alzheimer’s affected human brains can serve as a seed for the spread of tauopathy in recipient animal brains.
Methods
Exosome-enriched fractions were isolated from unfixed frozen human brain samples from Alzheimer’s disease (AD) and control (CTRL) cases, as well as from tau knockout (TKO) mouse brains. Tau oligomer epitopes were determined by dot blot using multiple oligomeric antibodies. EVs were further examinedthe atomic force microscopy (AFM), and the efficiency for the neuronal uptake in vitro. Moreover, aged C57BL/6 mice were inoculated with human brain exosomes containing tau, comparing with the fibril or oligomeric tau, into the right dorsal hippocampus. After injection, the brains were incubated for 18 weeks. The brains were then subjected to immunohistochemistry for phosphorylated-tau (p-tau) epitopes.
Results
The inoculation of AD or prodromal AD extracellular vesicles (EVs) containing only 300 pg of tau into the OML of the DG resulted in the accumulation of abnormally phosphorylated tau by 4.5 months, whereas inoculation of an equal amount of tau from control EVs, isolated tau oligomers, or fibrils showed little tau pathology. Unexpectedly, phosphorylated tau was primarily accumulated in GABAergic interneurons and, to a lesser extent, GluR 2/3-positive excitatory mossy cells, showing preferential EV-mediated GABAergic interneuronal tau propagation. Whole-cell patch clamp recordings of CA1 pyramidal cells showed significant reduction in the amplitude of spontaneous inhibitory post-synaptic currents.
Conclusions
This is the first time comprehensively characterized the physicochemical structure and pathogenic function of human brain-derived EVs isolated from AD, prodromal AD, and non-demented control cases.
Presenter of 2 Presentations
LIVE DISCUSSION
ENTORHINAL CORTEX WOLFRAMIN-1-EXPRESSING NEURONS PROPAGATE TAU TO CA1 NEURONS AND IMPAIR HIPPOCAMPAL MEMORY
Abstract
Aims
In early stages of Alzheimer’s Disease (AD), phosphorylated tau propagates from layer II of the entorhinal cortex (ECII) to the CA1 in the hippocampus. Wolframin-1-expressing (Wfs1+) pyramidal neurons in ECII connect to the CA1 region via temporo-ammonic pathway. We hypothesized that Wfs1+neurons in ECII mediate tau propagation to the CA1 and mimic early stages of tau pathology in AD.
Methods
Wfs1-Cre mice at 4-6 months of age were injected with Cre-inducible AAV2/6-Flex-P301Ltau expressing human P301L tau mutant or AAV2/6-Flex-TdTomato in ECII to specifically express mutant tau in Wfs1+ neurons. At 4 weeks post-injection, the mice were euthanized for immunohistochemistry, electrophysiology and electron microscopy or underwent behavioral test. The functional effect of tau propagation was assessed by multielectrode array to evaluate light-evoked CA1 neuronal firing responses after optogenetic stimulation of Wfs1+ECII axons.
Results
Wfs1-Cre mice injected in ECII with AAV2/6-Flex-P301Ltau displayed significant human tau positivity in CA1 pyramidal neurons but not in DG at 4-weeks post-injection. Electron microscopy revealed a synaptic connection between ECII Wfs1+ axons and CA1 dendrites, and the presence of human tau in pre- and post-synaptic elements. Field recordings of CA1 pyramidal neurons showed reduced measures of excitability. Multielectrode array recordings of optogenetically stimulated Wfs1+ axons resulted in a reduced CA1 neuronal firing after AAV2/6-Flex-P301Ltau injection. Trace fear conditioning revealed deficits in trace and contextual memory in the AAV2/6-Flex-P301Ltau injected mice.
Conclusions
Expression of P301Ltau in Wfs1+ neurons in ECII spreads tau specifically to CA1 pyramidal neurons, and is accompanied by several measures of neurophysiological impairment, including reduced neuronal excitability and deficits in contextual memory.