Delivery of different genes into presynaptic and postsynaptic neocortical neurons connected by a BDNF-TrkB synapse

A high fat, sugar, and salt Western diet induces motor-muscular and sensory dysfunctions and neurodegeneration in mice during aging: Ameliorative action of metformin

Aims

To explore the novel linkage between a Western diet combining high saturated fat, sugar, and salt (HFSS) and neurological dysfunctions during aging as well as Metformin intervention, we assessed cerebral cortex abnormalities associated with sensory and motor dysfunctions and cellular and molecular insights in brains using HFSS‐fed mice during aging. We also explored the effect of Metformin treatment on these mice.

Methods

C57BL/6 mice were fed with HFSS and treated with metformin from 20 to 22 months of age, resembling human aging from 56 to 68 years of age (an entry phase of the aged portion of lifespan).

Results

The motor and sensory cortexes in mice during aging after HFSS diet showed: (A) decreased motor‐muscular and sensory functions; (B) reduced inflammation‐resolving Arg‐1⁺ microglia; (C) increased inflammatory iNOs⁺ microglia and TNFα levels; (D) enhanced abundance of amyloid‐β peptide and of phosphorylated Tau. Metformin attenuated these changes.

Conclusion

A HFSS‐combined diet caused motor‐muscular and sensory dysfunctions, neuroinflammation, and neurodegeneration, whereas metformin counteracted these effects. Our findings show neuroinflammatory consequences of a HFSS diet in aging. Metformin curbs the HFSS‐related neuroinflammation eliciting neuroprotection.

Connected neurons in multiple neocortical areas, comprising parallel circuits, encode essential information for visual shape learning

Neocortical areas comprised of multiple neuronal circuits which are encoded with innumerable advanced cognitive tasks. Studies focused on neuronal network and synaptic plasticity has hypothesized that every specific neuron and the circuit process the explicit essential information for the specific tasks. However, the structure of these circuits and the involved critical neurons remain to be elucidated. Considering our previous studies, showing the specificity of rat postrhinal cortex comprising specific neuronal circuit for encoding both the learning and recall of shape discrimination through a fast neurotransmitter release from the transduced neurons, here we have demonstrated that postsynaptic neurons in two distinct areas, perirhinal cortex and the ventral temporal association areas are required for the specific visual shape discriminations learning. The constitutively active PKC was delivered into neuronal cells in postrhinal cortex, and the animals were allowed to learn the new shape discriminations, and then the silencing siRNA was delivered into postsynaptic neurons in either perirhinal cortex or ventral temporal association areas, using a novel technology for gene transfer into connected neurons. We observed that expression of the siRNA caused the deficits in visual performance, via blocking the activity in the neurons, as displayed by activity-dependent gene imaging, and also subsequently obstructed the activation of specific signaling pathways required for further learning, and dendritic protein synthesis and CREB. Thus, ratifying the conclusion that the two parallel circuits are both required for the visual shape discrimination learning.

Efficient gene transfers into neocortical neurons connected by NMDA NR1-containing synapses

BACKGROUND

Within a circuit, specific neurons and synapses are hypothesized to have essential roles in circuit physiology and learning, and dysfunction in these neurons and synapses causes specific disorders. These critical neurons and synapses are embedded in complex circuits containing many neuron and synapse types.

NEW METHOD

We established technology that can deliver different genes into pre- and post-synaptic neurons connected by a specific synapse type. The first, presynaptic gene transfer employs standard gene transfer technology to express a synthetic peptide neurotransmitter which has three domains, a dense core vesicle sorting domain for processing the protein as a peptide neurotransmitter, a receptor-binding domain, here a small peptide that binds to NMDA NR1 subunits, and the His tag. Upon release, this peptide neurotransmitter binds to its cognate receptor on postsynaptic neurons. Gene transfer selectively into these postsynaptic neurons employs antibody-mediated, targeted gene transfer and anti-His tag antibodies, which recognize the His tag domain in the synthetic peptide neurotransmitter.

RESULTS

For the model system, we studied the connection from projection neurons in postrhinal cortex to specific neurons in perirhinal cortex. In our initial report, gene transfer to connected neurons was 20+1% specific. Here, we optimized the technology; we improved the transfection for packaging by using a modern using a modern lipid, Lipofectamine 3000, and used a modern confocal microscope to collect data. We now report 80+2% specific gene transfer to connected neurons.

COMPARISON WITH EXISTING METHODS

There is no existing method with this capability.

CONCLUSIONS

This technology may enable studies on the roles of specific neurons and synapses in circuit physiology and learning, and support gene therapy treatments for specific disorders.

Separate Gene Transfers into Pre- and Postsynaptic Neocortical Neurons Connected by mGluR5-Containing Synapses

mGluR5-containing synapses have essential roles in synaptic plasticity, circuit physiology, and learning, and dysfunction at these synapses is implicated in specific neurological disorders. As mGluR5-containing synapses are embedded in large and complex distributed circuits containing many neuron and synapse types, it is challenging to elucidate the roles of these synapses and to develop treatments for the associated disorders. Thus, it would be advantageous to deliver different genes into pre- and postsynaptic neurons connected by a mGluR5-containing synapse. Here, we develop this capability: The first gene transfer, into the presynaptic neurons, uses standard techniques to deliver a vector that expresses a synthetic peptide neurotransmitter. This peptide neurotransmitter has three domains: a dense core vesicle sorting domain, a mGluR5-binding domain composed of a single-chain variable fragment anti-mGluR5, and the His tag. Upon release, this peptide neurotransmitter binds to mGluR5, predominately located on the postsynaptic neurons. Selective gene transfer into these neurons uses antibody-mediated, targeted gene transfer and anti-His tag antibodies, as the synthetic peptide neurotransmitter contains the His tag. For the model system, we studied the connection between neurons in two neocortical areas: postrhinal and perirhinal cortices. Targeted gene transfer was over 80% specific for mGluR5-containing synapses, but untargeted gene transfer was only ~ 15% specific for these synapses. This technology may enable studies on the roles of mGluR5-containing neurons and synapses in circuit physiology and learning and support gene therapy treatments for specific disorders that involve dysfunction at these synapses.

Delivery of different genes into pre- and post-synaptic neocortical interneurons connected by GABAergic synapses

Local neocortical circuits play critical roles in information processing, including synaptic plasticity, circuit physiology, and learning, and GABAergic inhibitory interneurons have key roles in these circuits. Moreover, specific neurological disorders, including schizophrenia and autism, are associated with deficits in GABAergic transmission in these circuits. GABAergic synapses represent a small fraction of neocortical synapses, and are embedded in complex local circuits that contain many neuron and synapse types. Thus, it is challenging to study the physiological roles of GABAergic inhibitory interneurons and their synapses, and to develop treatments for the specific disorders caused by dysfunction at these GABAergic synapses. To these ends, we report a novel technology that can deliver different genes into pre- and post-synaptic neocortical interneurons connected by a GABAergic synapse: First, standard gene transfer into the presynaptic neurons delivers a synthetic peptide neurotransmitter, containing three domains, a dense core vesicle sorting domain, a GABAA receptor-binding domain, a single-chain variable fragment anti-GABAA ß2 or ß3, and the His tag. Second, upon release, this synthetic peptide neurotransmitter binds to GABAA receptors on the postsynaptic neurons. Third, as the synthetic peptide neurotransmitter contains the His tag, antibody-mediated, targeted gene transfer using anti-His tag antibodies is selective for these neurons. We established this technology by expressing the synthetic peptide neurotransmitter in GABAergic neurons in the middle layers of postrhinal cortex, and the delivering the postsynaptic vector into connected GABAergic neurons in the upper neocortical layers. Targeted gene transfer was 61% specific for the connected neurons, but untargeted gene transfer was only 21% specific for these neurons. This technology may support studies on the roles of GABAergic inhibitory interneurons in circuit physiology and learning, and support gene therapy treatments for specific disorders associated with deficits at GABAergic synapses.