FMR1 and fragile X syndrome: A study by Darnell et al. using crosslinking immunoprecipitation (HITS-CLIP) and polysome profiling to assess correspondence between FMRP and mouse brain-specific polyribosomal mRNAs, uncovered its role as a ribosomal brake, and showed that loss of the translational brake contributed to FXS (Darnell et al., 2011).