Mimicking FUS hypomethylation preferentially weakens excitatory synapses via AMPA and NMDA-receptor dysregulation

Abnormal methylation of the RNA-binding protein fused in sarcoma (FUS) has been implicated in frontotemporal lobar degeneration. Interestingly, hypomethylation has been shown to alter the biophysical interactions between FUS molecules, leading to liquid-liquid phase separation (LLPS) and the formation of irreversible condensates. Importantly, these hypomethylated FUS condensates are observed in patient postmortem tissue and are known to disrupt synapse function in animal models.

However, the extent to which FUS hypomethylation impacts specific excitatory receptor classes remains unclear. Here, we use the FUS-16R hypomethylation mimic to uncover the progression of FUS pathophysiology at excitatory synapses. We found that mimicking hypomethylation of FUS and the subsequent aberrant cytosolic LLPS drive preferential synaptic dysfunction of AMPA and NMDA ionotropic glutamate receptors.

In contrast, FUS hypomethylation did not impair metabotropic glutamate receptor 1/5 (mGluR1/5) or acetylcholine receptor (AChR) function. Collectively, these findings reveal a previously unknown selectivity of FUS hypomethylation-mediated pathophysiology on excitatory synapses in the hippocampus. Cross-linking immunoprecipitation and sequencing Miniature excitatory postsynaptic currents Special thanks to Prof.

Marc-David Ruepp for generating the FUS-16R-LLPS and -NLS mutations and to Prof. Jernej Ule for his guidance on CLIP-seq analyses. M.T. was funded by the King’s College London Medical Research Council Doctoral Training Partnership (KCL MRC DTP, grant number: 2605619).

K.C. was funded by the UK Dementia Research Institute, which receives its funding from DRI LTD, funded by the UK Medical Research Council, Alzheimer’s Society and Alzheimer’s Research UK. K.C. and P.StGH Wellcome Trust Collaborative Award 203249/Z/16/Z. Department of Basic and Clinical Neuroscience, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, SE5 9TX, UK Margarita Toneva, Fanbo Kong, Siwon Oh, Seung-Chan Kim, Scott J.

Mitchell & Kwangwook Cho Department of Medicine (Division of Neurology), University Health Network and Tanz Centre for Research in Neurodegenerative Diseases, Temerty Faculty of Medicine, University of Toronto, Toronto, ON, M5S 3H2, Canada The authors declare no competing interests. All procedures involving animals were conducted in accordance with the United Kingdom Animals Scientific Procedures Act 1986 (ASPA). All animal experiments were granted approval by the King’s College London ethics committee.