title: Cascade Screening for Fragile X Syndrome/CGG Repeat Expansions in Children Attending Special Education in Sri Lanka.
abstract: Fragile X syndrome (FXS) is the commonest cause of inherited mental retardation and clinically presents with learning, emotional and behaviour problems. FXS is caused by expansion of cytosine-guanine-guanine (CGG) repeats present in the 5' untranslated region of the FMR1 gene. The aim of this study was to screen children attending special education institutions in Sri Lanka to estimate the prevalence of CGG repeat expansions. The study population comprised a representative national sample of 850 children (540 males, 310 females) with 5 to 18 years of age from moderate to severe mental retardation of wide ranging aetiology. Screening for CGG repeat expansion was carried out on DNA extracted from buccal cells using 3' direct triplet primed PCR followed by melting curve analysis. To identify the expanded status of screened positive samples, capillary electrophoresis, methylation specific PCR and Southern hybridization were carried out using venous blood samples. Prevalence of CGG repeat expansions was 2.2%. Further classification of the positive samples into FXS full mutation, pre-mutation and grey zone gave prevalence of 1.3%, 0.8% and 0.1% respectively. All positive cases were male. No females with FXS were detected in our study may have been due to the small sample size.
authors.affiliation: Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of Colombo, Kynsey road, Colombo 08, Sri Lanka.
authors.forename: C H W M R Bhagya
authors.initials: CH
authors.lastname: Chandrasekara
authors.affiliation: Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of Colombo, Kynsey road, Colombo 08, Sri Lanka.
authors.forename: W S Sulochana
authors.initials: WS
authors.lastname: Wijesundera
authors.affiliation: Department of Psychological Medicine, Faculty of Medicine, University of Colombo, Kynsey road, Colombo 08, Sri Lanka.
authors.forename: Hemamali N
authors.initials: HN
authors.lastname: Perera
authors.affiliation: Department of Pediatrics, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 119074, Singapore.|Khoo Teck Puat - National University Children's Medical Institute, National University Health System, Singapore, 119228, Singapore.|Department of Laboratory Medicine, National University Hospital, Singapore, 119074, Singapore.
authors.forename: Samuel S
authors.initials: SS
authors.lastname: Chong
authors.affiliation: Department of Pediatrics, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 119074, Singapore.
authors.forename: Indhu-Shree
authors.initials: IS
authors.lastname: Rajan-Babu
mesh_terms: D000293:Adolescent; D002648:Child; D004519:Education, Special; D005260:Female; D051860:Fragile X Messenger Ribonucleoprotein 1 / Q000235:genetics*; D005600:Fragile X Syndrome / Q000175:diagnosis* / Q000453:epidemiology* / Q000235:genetics; D005820:Genetic Testing / Q000379:methods; D006801:Humans; D008297:Male; D009061:Mouth Mucosa / Q000166:cytology; D060885:Multiplex Polymerase Chain Reaction; D013188:Sri Lanka / Q000453:epidemiology; D019680:Trinucleotide Repeat Expansion; D044465:White People / Q000235:genetics
chemical_list: D051860:Fragile X Messenger Ribonucleoprotein 1; C497683:FMR1 protein, human