NMD abnormalities during brain development in the Fmr1-knockout mouse model of fragile X syndrome

Background: Fragile X syndrome (FXS) is an intellectual disability attributable to loss of fragile X protein (FMRP). We previously demonstrated that FMRP binds mRNAs targeted for nonsense-mediated mRNA decay (NMD) and that FMRP loss results in hyperactivated NMD and inhibition of neuronal differentiation in human stem cells. Results: We show here that NMD is hyperactivated during the development of the cerebral cortex, hippocampus, and cerebellum in the Fmr1-knockout (KO) mouse during embryonic and early postnatal periods. Our findings demonstrate that NMD regulates many neuronal mRNAs that are important for mouse brain development. Conclusions: We reveal the abnormal regulation of these mRNAs in the Fmr1-KO mouse, a model of FXS, and highlight the importance of early intervention.