Introduction: Sequencing of the fragile X mental retardation 1 (FMR1) gene and the measurements of the gene product FMRP, have enabled protein quantification of variations within the FMR1 gene and FMRP-clinical correlations.
Development: This paper will review our knowledge of the regulation of FMR1 gene expression and the genotype-phenotype relationships. The clinical variability is related to several factors including: 1) molecular variations at FMR1 leading to a range of FMRP levels, 2) the combined effect of background genes interacting directly or indirectly with FMRP, 3) environmental factors which can either enhance or impede development and the degree of dysfunction which ensues.
Conclusion: Advances in neuroimaging, neurosciences, and knockout mice further our understanding of the gene-brain-behavior relationships in Fragile X Syndrome.