Fragile X Mental Retardation Protein: broadening the possibilities for studying Fragile X Syndrome

• Main Author: Oliveira, Bárbara
• Publication Date: 2010
• Other Authors: Marques, Isabel, Loureiro, Joana, Santos, Rosário, Jorge, Paula
• Language: eng
• Source: Repositórios Científicos de Acesso Aberto de Portugal (RCAAP)
• Download full: http://hdl.handle.net/10400.18/698
• topic: Doenças Genéticas; Fragile-X Syndrome

The presence of chromosomal fragility in locus FRAXA, located at Xq27.3, is directly related with Fragile X Syndrome (FXS), where the main symptoms include intellectual and emotional disabilities. The main cause of this monogenic disorder is the transcriptional silencing of the FMR1 gene, due to an expansion of more than 200 CGG repeats, found in the 5’-untranslated region, and its consequent hypermethylation which extends to the promoter region. The diagnostic complexity of FXS is proportional to the heterogeneity underlying this disease. In situations that strongly suggest a clinical diagnosis of FXS, but in which the repetitive region is not expanded, studying the presence of the encoded protein has proved to be very helpful as a complement to the molecular diagnosis. The Fragile X Mental Retardation Protein (FMRP), a selective RNA-binding protein that negatively regulates local protein synthesis in neuronal dendrites, may be detected applying specific antibodies either by immunocytochemistry or Western Blot analysis. The aim of the present work was to optimize such techniques, so as to complement the routine molecular procedures employed in prenatal and postnatal FXS diagnosis. In order to test the efficacy of the procedure, different types of biological samples were used, namely leukocytes from peripheral blood, human brain tissue, cultured amniocytes and chorionic villi. Additionally, slide preparation and detection method for immunocytochemistry, as well as protein isolation for Western Blot, were optimized resorting to several approaches. Both immunocytochemistry and Western Blot techniques allowed the detection of FMRP and were equally suitable. The advantages and disadvantages of the implementation of these techniques in terms of laboratory workflow and specimen type as well as in diagnostic and research context are discussed herein.