Nature Reviews Neuroscience 16, 264–277 (2015)

In Box 2 of this article, the sentence “In FXS, a polyglutamine (CGG) expansion in the nuclear fragile X mental retardation 1 (Fmr1) gene results in its methylation and silencing which lead to loss of the protein encoded by FMR1, FMRP.” should have read “In FXS, a trinucleotide (CGG) expansion in the nuclear fragile X mental retardation 1 (FMR1) gene results in its methylation and silencing, which lead to loss of the protein encoded by this gene, FMRP.” The article has been corrected online.