Year-end Sale % OFF 
Abstract
Mutations in genes encoding for GABAA receptor subunits is a well-established cause of genetic generalized epilepsy. GABA neurotransmission is implicated in several developmental processes including neurite outgrowth and synapse formation. Alteration in excitatory/inhibitory synaptic activities plays a critical role in epilepsy, thus here we investigated whether mutations in α1 subunit of GABAA receptor may affect dendritic spine and GABAergic bouton formation. In particular, we examined the effects of three mutations of the GABRA1 gene (D219N, A322D and K353delins18X) that were found in a cohort of French Canadian families with genetic generalized epilepsy. We used a novel single-cell genetic approach, by preparing cortical organotypic cultures from GABRA1flox/flox mice and simultaneously inactivating endogenous GABRA1 and transfecting mutant α1 subunits in single glutamatergic pyramidal cells and basket GABAergic interneurons by biolistic transfection. We found that GABRA1−/− GABAergic cells showed reduced innervation field, which was rescued by co-expressing α1-A322D and α1-WT but not α1-D219N. We further found that the expression of the most severe GABRA1 missense mutation (α1-A322D) induced a striking increase of spine density in pyramidal cells along with an increase in the number of mushroom-like spines. In addition, α1-A322D expression in GABAergic cells slightly increased perisomatic bouton density, whereas other mutations did not alter bouton formation. All together, these results suggest that the effects of different GABAAR mutations on GABAergic bouton and dendritic spine formation are specific to the mutation and cannot be always explained by a simple loss-of-function gene model. The use of single cell genetic manipulation in organotypic cultures may provide a better understanding of the specific and distinct neural circuit alterations caused by different GABAA receptor subunit mutations and will help define the pathophysiology of genetic generalized epilepsy syndromes.
Highlights
Genetic factors play a key role in the development and severity of genetic generalized epilepsy (GGE)
Alteration in excitatory/inhibitory synaptic activities plays a critical role in epilepsy, here we investigated whether mutations in α1 subunit of GABAA receptor may affect dendritic spine and GABAergic bouton formation
In order to examine how different GABRA1 mutants may affects the formation of dendritic spine and GABAergic bouton formation, we used a transgenic mouse carrying a conditional allele of GABRA1 (Vicini et al, 2001), which allows cell-type and developmental-stage restricted knockdown of GABRA1 synthesis
Summary
Genetic factors play a key role in the development and severity of genetic generalized epilepsy (GGE). GABAARs are ligand-gated ion channels that are permeable to chloride and bicarbonate anions and mediate most of cortical inhibitory neurotransmission. Their molecular structure comprises of a heteropentameric protein complex assembled from 19 different subunits (α1–6, β1–3, γ1–3, δ, ε, π, θ, and ρ1–3). We previously reported D219N, A322D, K353delins18X mutations in families with autosomal dominant genetic generalized epilepsy (Cossette et al, 2002; LachanceTouchette et al, 2011). Whether these mutations cause protein inactivation and loss of function is still unclear. Deletion of α1 in mice produced EEG spike-wave discharges and absence-like
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
