Key result
TRN-specific deletion of Plcβ1 in mice led to the development of spontaneous spike-and-wave discharges (153±8 per hour) and absence seizures by reducing the intrinsic excitability of TRN neurons.
Why the study?
The brain regions and circuit mechanisms related to the generation of absence seizures with Plc1 deficiency were unknown.
p-value: p=<0.001
Loss of Plcβ1 in the thalamic reticular nucleus decreases neuronal excitability and disrupts feedforward inhibition, leading to hypersynchrony and spontaneous absence seizures in mice.
Plcβ1 loss in mouse TRN induces absence seizures; human therapeutic relevance remains to be tested.
Absence seizures are caused by abnormal synchronized oscillations in the thalamocortical (TC) circuit, which result in widespread spike-and-wave discharges (SWDs) on electroencephalography (EEG) as well as impairment of consciousness. Thalamic reticular nucleus (TRN) and TC neurons are known to interact dynamically to generate TC circuitry oscillations during SWDs. Clinical studies have suggested the association of Plc1 with early-onset epilepsy, including absence seizures. However, the brain regions and circuit mechanisms related to the generation of absence seizures with Plc1 deficiency are unknown. In this study, we found that loss of Plc1 in mice caused spontaneous complex-type seizures, including convulsive and absence seizures. Importantly, TRN-specific deletion of Plc1 led to the development of only spontaneous SWDs, and no other types of seizures were observed. Ex vivo slice patch recording demonstrated that the number of spikes, an intrinsic TRN neuronal property, was significantly reduced in both tonic and burst firing modes in the absence of Plc1. We conclude that the loss of Plc1 in the TRN leads to decreased excitability and impairs normal inhibitory neuronal function, thereby disrupting feedforward inhibition of the TC circuitry, which is sufficient to cause hypersynchrony of the TC system and eventually leads to spontaneous absence seizures. Our study not only provides a novel mechanism for the induction of SWDs in Plc1-deficient patients but also offers guidance for the development of diagnostic and therapeutic tools for absence epilepsy.
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Chang et al. (2022) studied Absence seizures. Deletion of Plcβ1 in the thalamic reticular nucleus (TRN) vs. Wild-type or control mice (GFP control, scrambled shRNA) was evaluated on Number of spike-and-wave discharges (SWDs) per hour (p=<0.001). TRN-specific deletion of Plcβ1 in mice led to the development of spontaneous spike-and-wave discharges (153±8 per hour) and absence seizures by reducing the intrinsic excitability of TRN neurons.
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