Allele distribution of FMR1 gene in Korean women / 대한산부인과학회잡지

OBJECTIVE: Fragile X syndrome is the most common form of familial mental retardation, attributable to (CGG)n expansion in the FMR1 gene. This study was undertaken to ascertain the distribution of FMR1 CGG repeat in the general Korean women and to identify ethnic difference in FMR1 CGG repeat number. Material and METHOD: Between January 1999 and December 1999, we evaluated 1,000 low risk women who visited Gachon Medical School Hospital. DNA samples were extracted from the venous bloods by routine methods, and G-C specific Polymerase Chain Reaction (PCR)s were performed to evaluate FMR1 CGG repeat number. RESULTS: Mean FMR1 CGG repeat number was 26.9 (6-50), single PCR bands were detected in 776 cases (77.7%). There were two more bands in 22.3% of the cases. Most of the cases are located between 21 and 35 repeats, especially 21-25 repeats. The pattern of distribution of CGG repeat is dispersed. In 13 cases, we could not obtain the PCR results. CONCLUSION: Low risk of transmission rate of the FRX in Korea can be expected.

Prenatal Diagnosis of Fragile X Syndrome using Amniotic Fluid DNA / 대한산부인과학회잡지

BACKGROUND: The fragile X syndrome is the most common cause of inherited mental retardation, is almost always caused by abnormal CGG trinucleotide amplication within the FMR1(fragile X mental retardation) gene located in Xq27.3 METHODS: DNA samples were obtained from the amniotic fluids of known carrier mother and 35 mothers without risk factors of the fragile X syndrome. Polymerase chain reaction(PCR) and Southern blot analysis were performed to evaluate the number of CGG repeats in the FMR1 gene. RESULTS: The DNA samples from the carrier mother gave a large fragment over 300 repeats by PCR. All 35 control samples showed fragments sized under 35 repeats. CONCLUSIONS: Prenatal diagnosis of the fragile X syndrome could be done with mid-trimester amniotic fluid using PCR and Southern blot method.