Article in press - uncorrected proof BioMol Concepts, Vol. 2 (2011), pp. 343–352 • Copyright ᮊ by Walter de Gruyter • Berlin • Boston. DOI 10.1515/BMC.2011.033 Review Fragile X family members have important and non-overlapping functions Claudia Winograd2 and Stephanie Ceman1,2,* member, FMR1, was isolated by positional cloning of the X 1 Department of Cell and Developmental Biology, chromosomal region containing the inducible fragile site in University of Illinois, 601 S. Goodwin Avenue, individuals with fragile X syndrome (1). Cloning of the gene Urbana–Champaign, IL 61801, USA revealed the molecular defect to be a trinucleotide (CGG) 2 Neuroscience Program and College of Medicine, repeat expansion in exon 1 (2). Normally, individuals have University of Illinois, 601 S. Goodwin Avenue, less than 45 repeats with an average around 30 repeats; how- Urbana–Champaign, IL 61801, USA ever, expansion to greater than 200 repeats leads to aberrant methylation of the cytosines, leading to recruitment of * Corresponding author histone deacetylases with consequent transcriptional silenc- e-mail:
[email protected] ing of the FMR1 locus (3). Thus, individuals with fragile X syndrome do not express transcript from the FMR1 locus. Abstract To identify the Xenopus laevis ortholog of FMR1 for further use in developmental studies, the human FMR1 gene was The fragile X family of genes encodes a small family of used to screen a cDNA library prepared from Xenopus laevis RNA binding proteins including FMRP, FXR1P and FXR2P ovary. In addition to identifying the Xenopus laevis ortholog that were identified in the 1990s. All three members are of FMR1, the first autosomal paralog FXR1 was discovered encoded by 17 exons and show alternative splicing at the 39 because of its sequence similarity to FMR1 (4).