FMR1 and fragile X-associated tremor/ataxia syndrome: To validate our findings in an endogenous context, we silenced IGF2BP3 in control and FXTAS patient-derived fibroblasts and found that the relative FMR1 mRNA level increases upon IGF2BP3 KD (Fig. 6A, Supplementary Fig. 6A), similarly as in cell lines with stable expression of FMRpolyG (Fig. 2A).