FMR1 and neuroblastoma: As an example of the two opposite activities on different mRNAs, it has been shown that hippocampal FMRP protects PSD-95 mRNA from decay (Zalfa et al., 2007) in an activity-dependent manner; however, FMRP protein also facilitates the decay of nuclear RNA export factor 1 (NXF1) mRNA in mouse neuroblastoma (N2a) cells (Zhang et al., 2007).