Missense mutation of Fmr1 results in impaired AMPAR-mediated plasticity and socio-cognitive deficits in mice
Marta Curto Prieto, Alessandra Folci, Gwénola Poupon, Sara Schiavi, Valeria Buzzelli, Marie Pronot, Urielle François, Paula A. Pousinha, N. Lattuada, Sophie Abélanet, Sara Castagnola, Magda Chafaï, Anouar Khayachi, Carole Gwizdek, Frédéric Brau, Emmanuel Deval, Maura Francolini, Barbara Bardoni, Yann Humeau, Viviana Trezza, Stéphane Martin
Abstract
Abstract Fragile X syndrome (FXS) is the most frequent form of inherited intellectual disability and the best-described monogenic cause of autism. CGG-repeat expansion in the FMR1 gene leads to FMR1 silencing, loss-of-expression of the Fragile X Mental Retardation Protein (FMRP), and is a common cause of FXS. Missense mutations in the FMR1 gene were also identified in FXS patients, including the recurrent FMRP-R138Q mutation. To investigate the mechanisms underlying FXS caused by this mutation, we generated a knock-in mouse model ( Fmr1 R138Q ) expressing the FMRP-R138Q protein. We demonstrate that, in the hippocampus of the Fmr1 R138Q mice, neurons show an increased spine density associated with synaptic ultrastructural defects and increased AMPA receptor-surface expression. Combining biochemical assays, high-resolution imaging, electrophysiological recordings, and behavioural testing, we also show that the R138Q mutation results in impaired hippocampal long-term potentiation and socio-cognitive deficits in mice. These findings reveal the functional impact of the FMRP-R138Q mutation in a mouse model of FXS.