FMR1 and fragile X syndrome: Two different options for developing an effective treatment for FXS are possible: (i) compensating for the loss of FMRP function by identifying and normalizing the altered pathways, and (ii) restoring FMRP expression either by reactivating the silenced FMR1 gene or by providing exogenous FMRP using gene therapy or mRNA-based approaches (Figure 1).