Disruption of the autism-associated gene SCN2A alters synaptic development and neuronal signaling in patient iPSC-glutamatergic neurons

SCN2A is an autism spectrum disorder (ASD) risk gene and encodes a voltage-gated sodium channel. However, the impact of autism-associated SCN2A de novo variants on human neuron development is unknown. We studied SCN2A using isogenic SCN2A-/- induced pluripotent stem cells (iPSCs), and patient-derived iPSCs harboring a p.R607* or a C-terminal p.G1744* de novo truncating variant. We used Neurogenin2 to generate excitatory glutamatergic neurons and found that SCN2A+/p.R607* and SCN2A-/- neurons displayed a reduction in synapse formation and excitatory synaptic activity using multielectrode arrays and electrophysiology. However, the p.G1744* variant, which leads to early-onset seizures in addition to ASD, altered action-potential dynamics but not synaptic activity. Proteomic and functional analysis of SCN2A+/p.R607* neurons revealed defects in neuronal morphology and bioenergetic pathways, which were not present in SCN2A+/p.G1744* neurons. Our study reveals that SCN2A de novo variants can have differential impact on human neuron function and signaling.

An Introspective Approach: A Lifetime of Parkinson’s Disease Research and Not Much to Show for it Yet?

I feel part of a massive effort to understand what is wrong with motor systems in the brain relating to Parkinson’s disease. Today, the symptoms of the disease can be modified slightly, but dopamine neurons still die; the disease progression continues inexorably. Maybe the next research phase will bring the power of modern genetics to bear on halting, or better, preventing cell death. The arrival of accessible human neuron assemblies in organoids perhaps will provide a better access to the processes underlying neuronal demise.

Transcranial Magnetic stimulation (TMS) modulates functional activity of SH-SY5Y cells: An in vitro model provides support for assumed excitability changes

Repetitive Transcranial Magnetic Stimulation (rTMS) is an established neuromodulation technique, using electromagnetic pulses that, depending on the precise parameters, are assumed to lead to lasting neural excitability changes. rTMS has widespread applications in both research and therapy, where it has been FDA approved and is considered a first-line treatment for depression, according to recent North American and European guidelines. However, these assumed excitability effects are often difficult to replicate, and highly unreliable on the single subject/patient level. Given the increasing application of rTMS, especially in clinical practice, the absence of a method to unequivocally determine effects of rTMS on human neuronal excitability is problematic. We have taken a first step in addressing this bottleneck, by administering excitatory and inhibitory rTMS protocols, iTBS and cTBS, to a human in vitro neuron model; differentiated SH-SY5Y cells. We use live calcium imaging to assess changes in neural activity following stimulation, through quantifying fluorescence response to chemical depolarization. We found that iTBS and cTBS have opposite effects on fluorescence response; with iTBS increasing and cTBS decreasing response to chemical depolarization. Our results are promising, as they provide a clear demonstration of rTMS after-effects in a living human neuron model. We here present an in-vitro live calcium imaging setup that can be further applied to more complex human neuron models, for developing and evaluating subject/patient-specific brain stimulation protocols.

Human in vitro systems for examining synaptic function and plasticity in the brain

The human brain shows remarkable complexity in its cellular makeup and function, which are distinct from nonhuman species, signifying the need for human-based research platforms for the study of human cellular neurophysiology and neuropathology. However, the use of adult human brain tissue for research purposes is hampered by technical, methodological, and accessibility challenges. One of the major problems is the limited number of in vitro systems that, in contrast, are readily available from rodent brain tissue. With recent advances in the optimization of protocols for adult human brain preparations, there is a significant opportunity for neuroscientists to validate their findings in human-based systems. This review addresses the methodological aspects, advantages, and disadvantages of human neuron in vitro systems, focusing on the unique properties of human neurons and synapses in neocortical microcircuits. These in vitro models provide the incomparable advantage of being a direct representation of the neurons that have formed part of the human brain until the point of recording, which cannot be replicated by animal models nor human stem-cell systems. Important distinct cellular mechanisms are observed in human neurons that may underlie the higher order cognitive abilities of the human brain. The use of human brain tissue in neuroscience research also raises important ethical, diversity, and control tissue limitations that need to be considered. Undoubtedly however, these human neuron systems provide critical information to increase the potential of translation of treatments from the laboratory to the clinic in a way animal models are failing to provide.

Neuroprotective action of amidic neurolipins in models of neurotoxicity on the culture of human neural-like cells SH-SY5Y

It was established that in neurodegeneration models in the human neuron-like cell line SH-SY5Y, amide derivatives of arachidonic and docosahexaenoic acids were inactive in experiments with MPP+ and CoCl2 but protected from H2O2. The protective activity of neurolipins decreased in the series DHA-DA > AA-SER >= AA-GLY > AA-GABA >= AA-EA and was manifested starting from a concentration of 0.5 nM.