Fragile X messenger ribonucleoprotein 1 (FMRP/FMR1), and its paralogues, FXR1 and FXR2 (RNA-binding protein FXR1 and 2, respectively), comprise a family of RNA-binding proteins [].FMR1 protein is a multifunctional polyribosome-associated protein that plays a central role in neuronal development and synaptic plasticity. It regulates alternative mRNA splicing, mRNA stability, mRNA dendritic transport and postsynaptic local protein synthesis of a subset of mRNAs [, , ]. FMR1 is thought to bind target mRNA in the nucleus to form a ribonucleoprotein complex which is transported to dendrites and spines []. It is also required for ovary development and function []. FMR1 has also been shown to interact with components of the miRNA pathway []. A large expansion of the CGG trinucleotide repeat in the 5'-untranslated region of the FMR1 gene causes Fragile X syndrome (FXS), an inherited developmental disorder that causes a broad range of intellectual and physical challenges [].FXR1 and FXR2 interact with FMR1 and seem to have a related role; therefore they are likely to play important roles in the function of FMR1 and in the pathogenesis of the FXS syndrome [, ]. FXR1 is highly expressed in vertebrates muscle cells and is required for proper development of this tissue [, ].
