1
|
Pradeepan KS, McCready FP, Wei W, Khaki M, Zhang W, Salter MW, Ellis J, Martinez-Trujillo J. Calcium-Dependent Hyperexcitability in Human Stem Cell-Derived Rett Syndrome Neuronal Networks. BIOLOGICAL PSYCHIATRY GLOBAL OPEN SCIENCE 2024; 4:100290. [PMID: 38420187 PMCID: PMC10899066 DOI: 10.1016/j.bpsgos.2024.100290] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2023] [Revised: 12/20/2023] [Accepted: 01/14/2024] [Indexed: 03/02/2024] Open
Abstract
Background Mutations in MECP2 predominantly cause Rett syndrome and can be modeled in vitro using human stem cell-derived neurons. Patients with Rett syndrome have signs of cortical hyperexcitability, such as seizures. Human stem cell-derived MECP2 null excitatory neurons have smaller soma size and reduced synaptic connectivity but are also hyperexcitable due to higher input resistance. Paradoxically, networks of MECP2 null neurons show a decrease in the frequency of network bursts consistent with a hypoconnectivity phenotype. Here, we examine this issue. Methods We reanalyzed multielectrode array data from 3 isogenic MECP2 cell line pairs recorded over 6 weeks (n = 144). We used a custom burst detection algorithm to analyze network events and isolated a phenomenon that we termed reverberating super bursts (RSBs). To probe potential mechanisms of RSBs, we conducted pharmacological manipulations using bicuculline, EGTA-AM, and DMSO on 1 cell line (n = 34). Results RSBs, often misidentified as single long-duration bursts, consisted of a large-amplitude initial burst followed by several high-frequency, low-amplitude minibursts. Our analysis revealed that MECP2 null networks exhibited increased frequency of RSBs, which produced increased bursts compared with isogenic controls. Bicuculline or DMSO treatment did not affect RSBs. EGTA-AM selectively eliminated RSBs and rescued network burst dynamics. Conclusions During early development, MECP2 null neurons are hyperexcitable and produce hyperexcitable networks. This may predispose them to the emergence of hypersynchronic states that potentially translate into seizures. Network hyperexcitability depends on asynchronous neurotransmitter release that is likely driven by presynaptic Ca2+ and can be rescued by EGTA-AM to restore typical network dynamics.
Collapse
Affiliation(s)
- Kartik S. Pradeepan
- Graduate Program in Neuroscience, Schulich School of Medicine & Dentistry, Western University, London, Ontario, Canada
- Robarts Research Institute, Western University, London, Ontario, Canada
| | - Fraser P. McCready
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
- Developmental & Stem Cell Biology, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Wei Wei
- Developmental & Stem Cell Biology, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Milad Khaki
- Robarts Research Institute, Western University, London, Ontario, Canada
| | - Wenbo Zhang
- Neuroscience & Mental Health, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Michael W. Salter
- Neuroscience & Mental Health, The Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada
| | - James Ellis
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
- Developmental & Stem Cell Biology, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Julio Martinez-Trujillo
- Graduate Program in Neuroscience, Schulich School of Medicine & Dentistry, Western University, London, Ontario, Canada
- Robarts Research Institute, Western University, London, Ontario, Canada
- Western Institute for Neuroscience, Western University, London, Ontario, Canada
- Department of Physiology and Pharmacology, and Psychiatry, Schulich School of Medicine & Dentistry, Western University, London, Ontario, Canada
- Department of Psychiatry, Schulich School of Medicine & Dentistry, Western University, London, Ontario, Canada
| |
Collapse
|
2
|
Kumar R, Huang YT, Chen CC, Tzeng SF, Chan CK. Astrocytic Regulation of Synchronous Bursting in Cortical Cultures: From Local to Global. Cereb Cortex Commun 2020; 1:tgaa053. [PMID: 34296118 PMCID: PMC8153059 DOI: 10.1093/texcom/tgaa053] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Revised: 07/14/2020] [Accepted: 08/12/2020] [Indexed: 11/12/2022] Open
Abstract
Synchronous bursting (SB) is ubiquitous in neuronal networks and independent of network structure. Although it is known to be driven by glutamatergic neurotransmissions, its underlying mechanism remains unclear. Recent studies show that local glutamate recycle by astrocytes affects nearby neuronal activities, which indicate that the local dynamics might also be the origin of SBs in networks. We investigated the effects of local glutamate dynamics on SBs in both cultures developed on multielectrode array (MEA) systems and a tripartite synapse simulation. Local glutamate uptake by astrocytes was altered by pharmacological targeting of GLT-1 glutamate transporters, whereas neuronal firing activities and synaptic glutamate level was simultaneously monitored with MEA and astrocyte-specific glutamate sensors (intensity-based glutamate-sensing fluorescent reporter), respectively. Global SB properties were significantly altered on targeting GLT-1. Detailed simulation of a network with astrocytic glutamate uptake and recycle mechanisms, conforming with the experimental observations, shows that astrocytes function as a slow negative feedback to neuronal activities in the network. SB in the network can be realized as an alternation between positive and negative feedback in the neurons and astrocytes, respectively. An understanding of glutamate trafficking dynamics is of general application to explain how astrocyte malfunction can result in pathological seizure-like phenomena in neuronal systems.
Collapse
Affiliation(s)
- Ravi Kumar
- Taiwan International Graduate Program in Interdisciplinary Neuroscience, National Cheng Kung University and Academia Sinica, Taipei 115, Taiwan, R.O.C
- Institute of Physics, Academia Sinica, Taipei 115, Taiwan, R.O.C
| | - Yu-Ting Huang
- Institute of Physics, Academia Sinica, Taipei 115, Taiwan, R.O.C
| | - Chun-Chung Chen
- Institute of Physics, Academia Sinica, Taipei 115, Taiwan, R.O.C
| | - Shun-Fen Tzeng
- Department of Life Sciences, National Cheng Kung University, Tainan 70101, Taiwan, R.O.C
| | - Chi-Keung Chan
- Institute of Physics, Academia Sinica, Taipei 115, Taiwan, R.O.C
| |
Collapse
|