title: A novel polymorphism in the FMR1 gene: implications for clinical testing of fragile X syndrome.
abstract: Fragile X syndrome is the most common cause of inherited mental retardation among males. In most cases, the molecular basis of fragile X syndrome is the expansion and subsequent methylation of a CGG trinucleotide repeat in the 5' untranslated region of the fragile X mental retardation 1 (FMR1) gene. Laboratory diagnosis usually relies on a combination of Southern blot and polymerase chain reaction analyses. In this case report we describe an unusual Southern blot result in a patient who presented with developmental delay and had a normal CGG repeat number by polymerase chain reaction analysis. Further investigation revealed a novel G3310C transversion in the FMR1 gene resulting in a new recognition site for the BssHII restriction enzyme. This novel restriction site could potentially mimic a partial deletion of the FMR1 gene on Southern blot analysis and thus represents a possible pitfall in the diagnosis of fragile X syndrome.
authors.affiliation: Department of Laboratory Medicine and Pathology, University of Minnesota, 420 Delaware St SE, Minneapolis, MN 55455, USA.
authors.forename: Bharat
authors.initials: B
authors.lastname: Thyagarajan
authors.forename: Matthew
authors.initials: M
authors.lastname: Bower
authors.forename: Michael
authors.initials: M
authors.lastname: Berger
authors.forename: Sidney
authors.initials: S
authors.lastname: Jones
authors.forename: Michelle
authors.initials: M
authors.lastname: Dolan
authors.forename: Xinjing
authors.initials: X
authors.lastname: Wang
mesh_terms: D014408:Biomarkers, Tumor / Q000235:genetics / Q000378:metabolism; D015139:Blotting, Southern; D002648:Child; D004252:DNA Mutational Analysis; D051860:Fragile X Messenger Ribonucleoprotein 1 / Q000235:genetics* / Q000378:metabolism; D005600:Fragile X Syndrome / Q000097:blood / Q000175:diagnosis* / Q000235:genetics*; D020022:Genetic Predisposition to Disease; D006801:Humans; D008297:Male; D020641:Polymorphism, Single Nucleotide; D012091:Repetitive Sequences, Nucleic Acid
chemical_list: D014408:Biomarkers, Tumor; D051860:Fragile X Messenger Ribonucleoprotein 1; C497683:FMR1 protein, human