FMR1 and fragile X syndrome: Two members of the cytoplasmic fragile X mental retardation 1 (FMR1)-interacting protein family, CYFIP1 and CYFIP2 (also referred to as SRA1 and PIR121, respectively), are evolutionarily highly conserved proteins which were originally identified as direct binding partners of FMR Protein (Schenck et al., 2001), an RNA-binding protein whose loss causes fragile X syndrome (Bagni and Zukin, 2019).