Excess ribosomal protein production unbalances translation in a model of Fragile X Syndrome
Sang Soo Seo, Susana R. Louros, Natasha Anstey, Miguel A. Gonzalez‐Lozano, Callista B. Harper, Nicholas Verity, Owen Dando, Sophie R. Thomson, Jennifer C. Darnell, Peter C. Kind, Ka Wan Li, Emily K. Osterweil
Abstract
Abstract Dysregulated protein synthesis is a core pathogenic mechanism in Fragile X Syndrome (FX). The mGluR Theory of FX predicts that pathological synaptic changes arise from the excessive translation of mRNAs downstream of mGlu 1/5 activation. Here, we use a combination of CA1 pyramidal neuron-specific TRAP-seq and proteomics to identify the overtranslating mRNAs supporting exaggerated mGlu 1/5 -induced long-term synaptic depression (mGluR-LTD) in the FX mouse model ( Fmr1 −/y ). Our results identify a significant increase in the translation of ribosomal proteins (RPs) upon mGlu 1/5 stimulation that coincides with a reduced translation of long mRNAs encoding synaptic proteins. These changes are mimicked and occluded in Fmr1 −/y neurons. Inhibiting RP translation significantly impairs mGluR-LTD and prevents the length-dependent shift in the translating population. Together, these results suggest that pathological changes in FX result from a length-dependent alteration in the translating population that is supported by excessive RP translation.