Cell-Type Specific Patterned Stimulus-Independent Neuronal Activity in the Drosophila Visual System During Synapse Formation

SummaryStereotyped synaptic connections define the neural circuits of the brain. In vertebrates, stimulus-independent activity contributes to neural circuit formation. It is unknown whether this type of activity is a general feature of nervous system development. Here, we report patterned, stimulus-independent neural activity in the Drosophila visual system during synaptogenesis. Using in vivo calcium, voltage, and glutamate imaging, we found that all neurons participate in this spontaneous activity, which is characterized by brain-wide periodic active and silent phases. Glia are active in a complementary pattern. Each of the 15 examined of the over 100 specific neuron types in the fly visual system exhibited a unique activity signature. The activity of neurons that are synaptic partners in the adult was highly correlated during development. We propose that this cell type-specific activity coordinates the development of the functional circuitry of the adult brain.

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Neuronal activity disrupts myelinated axon integrity in the absence of NKCC1b

The Journal of Cell Biology ◽

10.1083/jcb.201909022 ◽

2020 ◽

Vol 219 (7) ◽

Cited By ~ 2

Author(s):

Katy L.H. Marshall-Phelps ◽

Linde Kegel ◽

Marion Baraban ◽

Torben Ruhwedel ◽

Rafael G. Almeida ◽

...

Keyword(s):

Neuronal Activity ◽

Ion Homeostasis ◽

Myelinated Axon ◽

Cell Type ◽

Myelinated Axons ◽

Specific Loss ◽

Uncharacterized Gene ◽

Interface Cell ◽

Cell Type Specific ◽

Periaxonal Space

Through a genetic screen in zebrafish, we identified a mutant with disruption to myelin in both the CNS and PNS caused by a mutation in a previously uncharacterized gene, slc12a2b, predicted to encode a Na+, K+, and Cl− (NKCC) cotransporter, NKCC1b. slc12a2b/NKCC1b mutants exhibited a severe and progressive pathology in the PNS, characterized by dysmyelination and swelling of the periaxonal space at the axon–myelin interface. Cell-type–specific loss of slc12a2b/NKCC1b in either neurons or myelinating Schwann cells recapitulated these pathologies. Given that NKCC1 is critical for ion homeostasis, we asked whether the disruption to myelinated axons in slc12a2b/NKCC1b mutants is affected by neuronal activity. Strikingly, we found that blocking neuronal activity completely prevented and could even rescue the pathology in slc12a2b/NKCC1b mutants. Together, our data indicate that NKCC1b is required to maintain neuronal activity–related solute homeostasis at the axon–myelin interface, and the integrity of myelinated axons.

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Molecular and cellular adaptations in hippocampal parvalbumin neurons mediate behavioral responses to chronic social stress

10.1101/2021.09.14.459024 ◽

2021 ◽

Author(s):

Dionnet L Bhatti ◽

Lucian Medrihan ◽

Michelle X Chen ◽

Junghee Jin ◽

Kathryn McCabe ◽

...

Keyword(s):

Neuronal Activity ◽

Affinity Purification ◽

Behavioral Outcomes ◽

Behavioral Responses ◽

Specific Gene ◽

Mrna Levels ◽

Cell Type ◽

Stress Resilience ◽

Cell Type Specific ◽

Stress Susceptibility

BACKGROUND: Behavioral responses to stress are, in part, mediated by the hippocampus and Parvalbumin (PV)-expressing neurons. However, whether chronic stress induces molecular and cellular adaptations in hippocampal PV neurons contribute to stress-induced behavioral outcomes remains elusive. METHOD: Using chronic social defeat stress (CSDS), we investigated the role of neuronal activity and gene expression in hippocampal PV neurons in mediating stress-resilience and -susceptibility. We first used in vivo high-density silicon probe recordings and chemogenetics to test whether the activity of PV neurons in ventral dentate gyrus (PVvDG) is associated with particular behavioral outcomes. To find critical molecular pathways associated with stress-resilience and -susceptibility, we used PV-neuron-selective translating ribosome affinity purification and RNAseq. We used immunoblotting, RNAscope, and region- or cell type-specific gene deletion to determine whether Ahnak, a molecule regulating depression-like behavior, was necessary for behavioral divergence after CSDS. RESULTS: We find CSDS modulates neuronal activity in vDG. Notably, stress-susceptibility is associated with an increase of PVvDG firing, which we find is necessary and sufficient for susceptibility. Additionally, genes involved in mitochondrial function, protein synthesis and synaptogenesis are differentially expressed in hippocampal PV neurons of stress-resilient and -susceptible mice. Interestingly, protein and mRNA levels of Ahnak, an endogenous regulator of L-type calcium channels are associated with susceptibility after CSDS. vDG- and PV cell type-specific deletions reveal that Ahnak is required for stress-susceptibility to CSDS. CONCLUSIONS: These findings indicate that CSDS-induced molecular and cellular adaptations in hippocampal PV neurons mediate behavioral consequences, proposing a mechanism underlying individual differences in stress vulnerability.

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Secreted reporter assay enables quantitative and longitudinal monitoring of neuronal activity

10.1101/2021.01.22.427811 ◽

2021 ◽

Author(s):

Ana C. Santos ◽

Sungjin Park

Keyword(s):

Neuronal Activity ◽

Specific Activity ◽

Repeated Measurements ◽

Reporter Assay ◽

Cell Type ◽

Conditional Expression ◽

Specific Manner ◽

A Cell ◽

Cell Type Specific ◽

And Function

AbstractThe ability to measure changes in neuronal activity in a quantifiable and precise manner is of fundamental importance to understand neuron development and function. Repeated monitoring of neuronal activity of the same population of neurons over several days is challenging and, typically, low-throughput. Here, we describe a new biochemical reporter assay that allows for repeated measurements of neuronal activity in a cell type-specific manner. We coupled activity-dependent elements from the Arc/Arg3.1 gene with a secreted reporter, Gaussia luciferase, to quantify neuronal activity without sacrificing the neurons. The reporter predominantly senses calcium and NMDA receptor-dependent activity. By repeatedly measuring the accumulation of the reporter in cell media, we can profile the developmental dynamics of neuronal activity in cultured neurons from male and female mice. The assay also allows for longitudinal analysis of pharmacological treatments, thus distinguishing acute from delayed responses. Moreover, conditional expression of the reporter allows for monitoring cell type-specific changes. This simple, quantitative, cost-effective, automatable, and cell type-specific activity reporter is a valuable tool to study the development of neuronal activity in normal and disease-model conditions, and to identify small molecules or protein factors that selectively modulate the activity of a specific population of neurons.SignificanceNeurological and neurodevelopmental disorders are prevalent worldwide. Despite significant advances in our understanding of synapse formation and function, developing effective therapeutics remains challenging, in part due to the lack of simple and robust high-throughput screening assays of neuronal activity. Here, we describe a simple biochemical assay that allows for repeated measurements of neuronal activity in a cell type-specific manner. Thus filling the need for assays amenable to longitudinal studies, such as those related to neural development. Other advantages include its simple and quantitative nature, logitudinal profiling, cell type-specificity, and being multiplexed with other invasive techniques.

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Layer- and Cell Type-Specific Modulation of Excitatory Neuronal Activity in the Neocortex

Frontiers in Neuroanatomy ◽

10.3389/fnana.2018.00001 ◽

2018 ◽

Vol 12 ◽

Cited By ~ 22

Author(s):

Gabriele Radnikow ◽

Dirk Feldmeyer

Keyword(s):

Neuronal Activity ◽

Cell Type ◽

Cell Type Specific

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Sonic hedgehog signaling in astrocytes mediates cell type-specific synaptic organization

eLife ◽

10.7554/elife.45545 ◽

2019 ◽

Vol 8 ◽

Cited By ~ 10

Author(s):

Steven A Hill ◽

Andrew S Blaeser ◽

Austin A Coley ◽

Yajun Xie ◽

Katherine A Shepard ◽

...

Keyword(s):

Sonic Hedgehog ◽

Hedgehog Signaling ◽

Neuronal Excitability ◽

Synapse Formation ◽

Critical Role ◽

K Channel ◽

Synaptic Organization ◽

Cell Type ◽

Shh Signaling ◽

Cell Type Specific

Astrocytes have emerged as integral partners with neurons in regulating synapse formation and function, but the mechanisms that mediate these interactions are not well understood. Here, we show that Sonic hedgehog (Shh) signaling in mature astrocytes is required for establishing structural organization and remodeling of cortical synapses in a cell type-specific manner. In the postnatal cortex, Shh signaling is active in a subpopulation of mature astrocytes localized primarily in deep cortical layers. Selective disruption of Shh signaling in astrocytes produces a dramatic increase in synapse number specifically on layer V apical dendrites that emerges during adolescence and persists into adulthood. Dynamic turnover of dendritic spines is impaired in mutant mice and is accompanied by an increase in neuronal excitability and a reduction of the glial-specific, inward-rectifying K+ channel Kir4.1. These data identify a critical role for Shh signaling in astrocyte-mediated modulation of neuronal activity required for sculpting synapses.

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