Human iPSC-Derived Neurons with Reliable Synapses and Large Presynaptic Action Potentials

Area of Science:

• Neuroscience
• Cell Biology
• Molecular Biology

Background:

• Understanding human brain function necessitates characterizing synaptic transmission in human neurons.
• Presynaptic action potential properties, crucial for neurotransmitter release, remain controversial in human neurons.
• Previous measurements lacked high temporal resolution in human neurons.

Purpose of the Study:

• To determine the properties of presynaptic action potentials in human neurons.
• To establish a model system for studying human glutamatergic synaptic transmission.
• To investigate mechanisms of synchronous high-frequency glutamate release.

Main Methods:

• Generated human glutamatergic neurons from pluripotent stem cells via Neurogenin 2 (Ngn2) expression.
• Utilized super-resolution microscopy to visualize pre- and postsynaptic protein alignment.
• Performed direct presynaptic patch-clamp recordings from mature human neurons.

Main Results:

• Ngn2-induced human neurons showed decreased multiple axon initial segments and increased axonal tau and excitability with maturation.
• Synaptic transmission was reliable at high frequencies (20-100 Hz) with increasing synchronicity over 9 weeks.
• Direct recordings revealed human presynaptic action potentials with large overshoots (~25 mV) and short durations (~0.5 ms).

Conclusions:

• Ngn2-induced neurons provide an effective model for high spatiotemporal resolution analysis of human glutamatergic synaptic transmission.
• The findings predict that human brain glutamatergic transmission involves large, rapid presynaptic action potentials.
• This study offers crucial insights into fundamental mechanisms of neurotransmission in the human brain.