Fragile X mental retardation protein (FMRP) is enriched in the brain and testes (Devys et al., 1993; Bakker et al., 2000), in accordance with the mental retardation and macroorchidism exhibited by most patients with FXS (Hagerman, 1987; Martin and Arici, 2008; Saldarriaga et al., 2014). Here, FMR1 is linked to fragile X syndrome.