Biology subjects

Bacskai, B. J.

Publications and source records attributed to Bacskai, B. J..

3 recordsLinked to original sources

bioRxiv2024

Recording gamma-secretase activity in living mouse brains

{gamma}-Secretase plays a pivotal role in the central nervous system. Our recent development of genetically encoded Forster resonance energy transfer (FRET)-based biosensors has enabled the spatiotemporal recording of {gamma}-secretase activity on a cell-by-cell basis in live neurons in culture. Nevertheless, how {gamma}-secretase activity is regulated in vivo remains unclear. Here we employ the near-infrared (NIR) C99 720-670 biosensor and NIR confocal microscopy to quantitatively record {gamma}-secretase activity in individual neurons in living mouse brains. Intriguingly, we uncovered that {gamma}-secretase activity may influence the activity of {gamma}-secretase in neighboring neurons, suggesting a potential "cell non-autonomous" regulation of {gamma}-secretase in mouse brains. Given that {gamma}-secretase plays critical roles in important biological events and various diseases, our new assay in vivo would become a new platform that enables dissecting the essential roles of {gamma}-secretase in normal health and diseases.

neuroscience↗

bioRxiv2024

Instability of excitatory synapses in experimental autoimmune encephalomyelitis and the outcome for excitatory circuit inputs to individual cortical neurons

Synapses are lost on a massive scale in the brain and spinal cord of people living with multiple sclerosis (PwMS), and this synaptic loss extends far beyond demyelinating lesions. Post-mortem studies show the long-term consequences of multiple sclerosis (MS) on synapses but do not inform on the early impacts of neuroinflammation on synapses that subsequently lead to synapse loss. How excitatory circuit inputs are altered across the dendritic tree of individual neurons under neuroinflammatory stress is not well understood. Here, we directly assessed the structural dynamics of labeled excitatory synapses in experimental autoimmune encephalomyelitis (EAE) as a model of immune-mediated cortical neuronal damage. We used in vivo two-photon imaging and a synthetic tissue-hydrogel super-resolution imaging technique to reveal the dynamics of excitatory synapses, map their location across the dendritic tree of individual neurons, and examine neurons at super-resolution for synaptic loss. We found that excitatory synapses are destabilized but not lost from dendritic spines in EAE, starting with the earliest imaging session before symptom onset. This led to dramatic changes in excitatory circuit inputs to individual cells. In EAE, stable synapses are replaced by synapses that appear or disappear across the imaging sessions or repeatedly change at the same location. These unstable excitatory inputs occur closer to one another in EAE than in healthy controls and are distributed across the dendritic tree. When imaged at super-resolution, we found that a small proportion of dendritic protrusions lost their presynapse and/or postsynapse. Our finding of diffuse destabilizing effects of neuroinflammation on excitatory synapses across cortical neurons may have significant functional consequences since normal dendritic spine dynamics and clustering are essential for learning and memory.

neuroscience↗

bioRxiv2022

Hyperactive somatostatin interneurons near amyloid plaque and cell-type-specific firing deficits in a mouse model of Alzheimer's disease

Alzheimers disease (AD) is characterized by synaptic loss and neuronal network dysfunction. These network deficits are mediated by early alterations in neuronal firing rates that coincide with amyloid plaque accumulation. Mounting evidence supports that inhibitory networks are impaired in AD, but the mechanisms driving these inhibitory deficits are poorly understood. Here we use in vivo multiphoton calcium imaging to determine the relationship between amyloid accumulation and the spontaneous activity of excitatory neurons and inhibitory interneurons in an APP/PS1 mouse model of Alzheimers disease. We show that somatostatin-expressing (SOM) interneurons are hyperactive, while parvalbumin-expressing interneurons are hypoactive in APP/PS1 mice. Only SOM interneuron hyperactivity correlated with proximity to amyloid plaque. These inhibitory deficits were accompanied by decreased excitatory neurons activity and decreased pairwise activity correlations in APP/PS1 mice. Our study identifies cell-specific interneuronal firing deficits driven by amyloid pathology in APP/PS1 mice and provides new insights for targeting inhibitory circuits in Alzheimers disease.

neuroscience↗