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This study investigated GNB1 encephalopathy, a rare neurodevelopmental disorder caused by mutations in the G protein subunit Gβ1. Researchers found that mice carrying the disease-causing I80T mutation exhibited behavioral abnormalities and altered neuronal function in the hippocampus, specifically showing simplified dendrites, reduced inhibitory signaling through GABAB receptors, and increased dendritic excitability leading to prolonged calcium spikes. Treatment with ML297, a GIRK channel activator, successfully reversed the abnormal dendritic calcium activity, suggesting a potential therapeutic approach.
Why it matters
The findings identify dendritic hyperexcitability as a key mechanism underlying both seizures and learning deficits in GNB1 encephalopathy, and demonstrate that pharmacologically activating GIRK channels can normalize this dysfunction. This provides a potential therapeutic target for treating patients with this rare genetic disorder, which currently has limited treatment options.
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⚠️ Preprint – Noch nicht peer-reviewed
Dieser Artikel wurde noch nicht von unabhängigen Experten begutachtet. Die Ergebnisse sind vorläufig und sollten mit Vorsicht interpretiert werden.
GNB1 encephalopathy (GNB1-E) is a rare neurodevelopmental disorder associated with motor dysfunction, epilepsy and learning disability caused by mutations in the gene encoding the G protein subunit G{beta}1. Previous work has shown that altered G{beta}1 can disrupt activation of G-protein-coupled inwardly rectifying potassium (GIRK) channels, dysregulate neuronal excitability and cause seizures. However, the relevant upstream regulators of G{beta}1 and the consequences of GIRK dysfunction for neuronal synaptic, cellular and circuit function have not been characterized. Here we report that mice of both sexes carrying the deleterious p.I80T mutation in Gnb1 present features consistent with GNB1-E, including developmental delay, decreased locomotion and increased anxiety. Using histology, whole-cell patch-clamp electrophysiology and pharmacology in ex vivo brain slices, we find that hippocampal neurons in heterozygous Gnb1I80T/+ mice exhibit simplified dendritic morphologies, decreased synaptic inhibition mediated by metabotropic GABAB receptors and increased dendritic excitability. These phenotypes result in longer duration dendritic calcium spikes in response to synaptic afferent stimulation, an effect that is reversed by a specific activator of GIRK channels, ML297. Given the known roles of dendritic calcium spikes in driving burst firing and inducing synaptic plasticity, these findings suggest that targeting dendritic excitability has therapeutic potential to address both the seizure susceptibility and learning deficits associated with GNB1-E.