• Journal of Genetic Medicine
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• v.5 no.1
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• pp.41-46
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• 2008

Purpose : Fragile X syndrome (FXS) is the most common heritable cause of cognitive impairment. FXS is caused by hyperexpansion and hypermethylation of a polymorphic CGG trinucleotide repeat in the 5' untranslated region of the fragile X mental retadation-1(FMR1) gene. Combination of Southern blotting and simple polymerase chain reaction(PCR) amplification of the FMR1 repeat region is commonly used for diagnosis in females. To give a definite diagnosis in a female child suspected of having FXS, we carried out the molecular diagnostic test for FXS using the recently developed Abbott Molecular Fragile X PCR Kit. Methods : The PCR amplification of the FMR1 repeat region was performed using the Abbott Mdecular Fragile X PCR Kit. The amplified products were analyzed by size-separate analysis on 1.5% agarose gels and by DNA fragment analysis using Gene scan. Results : Agarose gel and Gene scan analyses of PCR products of the FMR1 repeat region showed that the patient had two heterozygous alleles with a normal 30 repeats and full mutation of >200 repeats whereas her mother had two heterozygous alleles with the normal 30 repeats and premutation of 108 repeats, suggesting that the premutation of 108 repeats in her mother may have led to the full mutation of >200 repeats in the patient. Conclusion : We diagnosed FXS in a female patient using a simplified molecular diagnostic test. This commercially available diagnostic test for FXS, based on PCR, may be a suitable alternative or complement method to Southern blot analysis and PCR analysis and/or methylation specific(MS)-PCR analysis for the molecular diagnosis of FXS in both males and females.

• Journal of the Korean Academy of Child and Adolescent Psychiatry
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• v.11 no.1
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• pp.3-15
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• 2000

Objectives：There has been a rapid expansion of studies aimed at elucidating the genetic basis of autistic disorder, especially it’ relationship to fragile-X syndrome. The detection of fragile X chromosome(Xq27.3) by cytogenetic analysis has revealed many difficulties in testing. Therefore, to explore the relationship between autistic disorder and fragile X syndrome, this study administered molecular biologic methods which examined an unstable CGG repeat within the fragile X mental retardation-1(FMR-1) gene. Methods：Ninety nine autistic children and eight normal control children were tested. The number of CGG repeats within FMR-1 gene was measured after amplification by PCR, and cytogenetic analysis was also carried out to detect fragile site Xq27.3. Southern blot hybridization, using StB12.3 and/or Pfxa3 probe, was done for the patients showing expansion of more than 50 CGG repeats (premutation). Results：All but two autistic patients had no expansion in CGG repeats by PCR and there was no significant statistical difference in number of CGG repeat in comparison with normal control. Two autistic patients, considered as premutation by PCR analysis, had no full mutation or premutation by Southern blot hybridization. All autistic children tested did not have any abnormal karyotype or fragile site Xq27.3. Conclusions：These results suggest that autistic patients may not have abnormality in FMR-1 gene or abnormal expansion in CGG repeat. In conclusion, fragile X syndrome may not be antecedent of autistic disorder.

• BMB Reports
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• v.39 no.6
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• pp.766-773
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• 2006

Fragile-X-syndrome (FXS) is the most common type of inherited cognitive impairment. The underlying molecular alteration consists of a CGG-repeat amplification within the FMR-1 gene. The phenotype is only apparent once a threshold in the number of repeats has been exceeded (full mutation). The aim of this study was to characterize the FMR-1 CGG-repeat status in Argentine patients exhibiting mental retardation. A total of 330 blood samples from patients were analyzed by PCR and Southern blot analysis. Initially, DNA from 78 affected individuals were studied by PCR. Since this method is unable to detect high molecular weight alleles, however, we undertook a second approach using the Southern blotting technique to analyze the CGG repeat number and methylation status. Southern blot analysis showed an altered pattern in 14 out of 240 (6%) unrelated patients, with half of them presenting a mosaic pattern. Eight out of 17 families (47%) showed a (suggest deleting highlight). The characteristic FXS pattern was identified in 8/17 families (47%), and in 4 of these families 25% of the individuals presented with a mosaic model. The expansion from pre-mutation to full mutation was shown to occur both at the pre and post zygotic levels. The detection of FXS mutations has allowed us to offer more informed genetic counseling, prenatal diagnosis and reliable patient follow-up.

• Journal of Genetic Medicine
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• v.13 no.1
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• pp.14-19
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• 2016

Purpose: We examined the prevalence and CGG/AGG repeat structure of expanded alleles of the FMR1 gene in preconceptional and pregnant Korean women. Materials and Methods: The CGG repeats in the FMR1 genes of 1,408 women were analyzed by polymerase chain reaction and Southern blot analysis. To estimate the prevalence of expansion alleles, the individuals were divided into low risk and high risk group. Results: Within this population, 98.4% had normal alleles and 1.6% had abnormal alleles including intermediate (0.6%), premutation (0.5%), full mutation (0.1%), and hemizygous (0.4%) alleles. There were 2 premutation alleles (1:666, 95% confidence interval [CI] 1:250-1,776) in the low risk group and 5 premutation alleles (1:15, 95% 1:6-36) in the high risk group. There were 8 intermediate alleles (1:167, 95% CI 1:130-213) in the low risk group and 1 intermediate alleles (1:76, 95% CI 1:11-533) in the high group. Six of the 7 premutation alleles did not contain AGG interruptions within the repeats and 1 had a single AGG interruption. Four of the 9 intermediate alleles contained 2-3 AGG, 4 had a single AGG, and 1 had no AGG interruptions. Conclusion: Our study demonstrates the prevalence and CGG/AGG structure of expansion alleles in Korean women. The identified premutation prevalence is higher than that of other Asian populations and lower than that of Caucasian populations. Although our study is limited by size and population bias, our findings could prove useful for genetic counseling of preconceptional or pregnant women.

• Clinical and Experimental Reproductive Medicine
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• v.34 no.3
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• pp.179-188
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• 2007

Objectives: Many neurological diseases are known to be caused by expansion of trinucleotide repeats (TNRs). It is hard to diagnose the alteration of TNRs with single cell level for preimplantation genetic diagnosis (PGD). In this study, we describe methods optimized for PGD of TNRs related diseases such as Huntington's disease (HD), spinocerebellar ataxia 3 (SCA3) and fragile X syndrome (FXS). Methods: We performed the preclinical assays with heterozygous patient's lymphocytes by single cell PCR strategy. Fluorescent semi-nested PCR and fragment analysis using automatic genetic analyzer were applied for HD and SCA 3. Whole genome amplification with multiple displacement amplification (MDA) method and fluorescent PCR were carried out for FXS. Amplification and allele drop-out (ADO) rate were evaluated in each case. Results: The fluorescent semi-nested PCR of single lymphocyte showed 100.0% of amplification and 14.0% of ADO rate in HD, and 94.7% of amplification and 5.6% of ADO rate in SCA3, respectively. We could not detect the PCR product of CGG repeats in FXS using the fluorescent semi-nested PCR alone. After applying the MDA method in FXS, 84.2% of amplification and 31.3% of ADO rate were achieved. Conclusions: Fluorescent semi-nested PCR is a reliable method for PGD of HD and SCA3. The advanced MDA method overcomes the problem of amplification failure in CGG repeats of FXS case. Optimization of methods for single cell analysis could improve the sensitivity and reliability of PGD for complicated single gene disorders of TNRs.

• Journal of Genetic Medicine
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• v.9 no.2
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• pp.73-77
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• 2012

Purpose: Fragile X carrier detection before or at early pregnancy through a wide screening program may not only confer a risk of having offspring with Fragile X syndrome (FXS), but may also confer a risk for Fragile X-associated primary ovarian insufficiency and Fragile X-associated tremor/ataxia syndrome. However, prior to the implementation of such a program, the carrier prevalence in a population and the availability of effective screening test should be evaluated. The aim of our study was to determine the prevalence of premutation carriers and to evaluate the feasibility of screening test. Materials and Methods: The blood samples were obtained from 8,641 pregnant women with no family history of mental retardation. We performed a three-primer CGG repeat primed (RP) PCR using the AmplideX$^{TM}$ FMR1 PCR kit (Asuragen, Inc. Austin, TX, USA). Samples showing full mutation alleles were reflexed to Southern blot analysis for methylation status and sizing. Results: Among the 8,641 women, we found 8 premutation carriers (1:1,090, 0.09%) and 46 women with an intermediate allele (1:190, 0.53%). No woman was found to carry the fully mutated allele. All the detected alleles were within the CGG repeat range of 8-117. Among the 8,641 samples, 29 and 30 CGG repeats represent 66.6% of all cases. The CGG RP PCR method provides robust detection of expanded alleles and resolves allele zygosity, thus minimizing the number of samples that require Southern blot analysis. Conclusion: This is the first study that has focused on the prevalence of FXS premutation carriers and FMR1 allele distribution in normal pregnant women. These data have important implications for population-based fragile X carrier screening in Korea.