Objective: To determine the CGG repeat number and methylation status of FMR1 gene for fetuses whose mothers have carried a FMR1 mutation. Methods: For 30 pregnant women, the fetal CGG repeat number was determined with a GC-rich PCR system by using chorionic villus, amniotic fluid or umbilical blood samples. The methylation status of the FMR1 gene was confirmed with Southern blotting. Results: In total 30 prenatal diagnoses were performed for 29 carriers of FMR1 gene mutations and 1 with FMR1 gene deletion mosaicism. Three fetuses were found to carry premutations, 9 were with full mutations and 1 with mosaicism of premutation and full mutations. Eighteen fetuses were normal. Conclusion Considering the genetic complexity of Fragile X syndrome (FXS), single method may not suffice accurate determination of their genetic status. The pitfalls and technical limitations of protocols requires adoption of personalized strategy for its prenatal diagnosis.

OBJECTIVETo assess the value of genetic testing for Fragile X syndrome (FXS).

METHODSA domestically made diagnostic kit based Tri-primer-PCR method was used to detect mutations of the FMR1 gene among 6 pedigrees with unexplained intellectual disability. The results were verified by methylation PCR and Southern blotting.

RESULTSPedigrees 1 and 6 were positive for the screening. In pedigree 1, a full-mutation allele with methylation was identified in the proband and his mother, which was passed on to the fetus. In pedigree 6, the proband was mosaic for a full-mutation allele and a pre-mutation allele. His sister was asymptomatic with a full-mutation. His mother carried pre-mutation allele, while his father and sister's baby were normal. The number of CGG repeats of the pedigrees 2 to 5 were in the normal range.

CONCLUSIONGenetic testing can provide an effective way to prevent FXS caused by FMR1 mutations and enable prenatal diagnosis for families with a high risk for the disease.

OBJECTIVE: To determine the CGG repeat number and methylation status of FMR1 gene for fetuses whose mothers have carried a FMR1 mutation. METHODS: For 30 pregnant women, the fetal CGG repeat number was determined with a GC-rich PCR system by using chorionic villus, amniotic fluid or umbilical blood samples. The methylation status of the FMR1 gene was confirmed with Southern blotting. RESULTS: In total 30 prenatal diagnoses were performed for 29 carriers of FMR1 gene mutations and 1 with FMR1 gene deletion mosaicism. Three fetuses were found to carry premutations, 9 were with full mutations and 1 with mosaicism of premutation and full mutations. Eighteen fetuses were normal. CONCLUSION Considering the genetic complexity of Fragile X syndrome (FXS), single method may not suffice accurate determination of their genetic status. The pitfalls and technical limitations of protocols requires adoption of personalized strategy for its prenatal diagnosis.
Female ; Fragile X Mental Retardation Protein ; genetics ; Fragile X Syndrome ; diagnosis ; Heterozygote ; Humans ; Mutation ; Pregnancy ; Prenatal Diagnosis

OBJECTIVETo study the pattern of CGG repeat instability within germline cells derived from two male fetuses affected with Fragile X syndrome (FXS).

METHODSThe length and methylation status of CGG repeats within the testes of a fetus carrying a full FXS mutation and another fetus carrying mosaicism FXS mutation were analyzed with Southern blotting and AmplideX FMR1 PCR. Immunohistochemistry was also applied for the measurement of FMR1 protein (FMRP) expression within the testes.

RESULTSFor the fetus carrying the full mutation, Southern blotting analysis of the PCR product has detected an expected band representing the full mutation in its brain and a premutation band of > 160 CGG repeats in its testis. Whereas the pattern of premutation/full mutation in mosaic testis was similar to that in peripheral blood and no sign of contracted fragment was found other than a band of about 160 CGG repeats. Immunohistochemistry assay with a FMRP-specific antibody demonstrated a number of FMRP-positive germ cells, which suggested a contraction from full mutation to premutation alleles.

CONCLUSIONThis study has clarified the instability pattern of CGG repeat and expression of FMRP protein within the testes of fetuses affected with FXS, confirming that the CGG repeat can contract progressively within the germline. The FMRP expression in the testis is consistent with spermatogonium proliferation, and thus the contraction from full mutation to unmethylated premutations may occur for the requirement of FMRP expression during spermatogenesis. The better understanding of FMRP function during germ cell proliferation may elucidate the mechanism underlying the contraction of full FXS mutation in male germline.

Abortion, Eugenic ; Blotting, Southern ; Brain ; embryology ; metabolism ; DNA Methylation ; Fatal Outcome ; Fetus ; cytology ; metabolism ; Fragile X Mental Retardation Protein ; genetics ; metabolism ; Fragile X Syndrome ; diagnosis ; genetics ; Humans ; Immunohistochemistry ; Male ; Mosaicism ; Mutation ; Polymerase Chain Reaction ; Spermatozoa ; metabolism ; Testis ; cytology ; embryology ; metabolism ; Trinucleotide Repeat Expansion ; genetics

Objective To compare the CGG-repeat-length and its methylation status in fetal tissues and to explicate the heterogeneity of CGG repeats.Method Multiple tissues from a full mutation (August 2013) and a mosaic aborted fetus of 23-week gestation(May 2012) were collected and genomic DNA from these tissues was extracted.The CGG-repeat-length and methylation status in fetal tissues were determined by a combined strategy of Southern blotting and GC-Rich PCR.FMR1 expression was measured by real time PCR and Western blotting.Result CGG-repeat-length in different tissues of each fetus was similar.A major methylated band in the full mutation range (540 CGG repeats) was detected in the brain,skin,testis and kidney tissues of Case 1.An unmethylated premutation band with 160 CGG repeats,and another two bands with 470 and 1 100 CGG repeats in the full mutation range were shown in the brain,skin,testis,lung,stomach,gut,liver,kidney,heart and blood of Case 2.However,the methylation status of CGG repeats in the mosaic fetus was heterogeneous among different tissues.The lowest premutation ratio was in the brain of the mosaic fetus compared with other tissues,and correspondingly FMR1 expression in its brain was minimum.Conclusion This study clarify the tissue heterogeneity of CGG repeats and provides information for the genetic counseling and clinical diagnosis in fragile X syndrome.Based on the fact that the mosaic fetus' mother is a carrier of full mutation,it is speculated that the maternal CGG repeat has contracted before the differentiation of trilaminar germ disc.

Fragile X syndrome (FXS) is the leading inherited cause of intellectual disability, resulting from the lack of functional fragile X mental retardation protein (FMRP), an mRNA binding protein mainly serving as a translational regulator. Loss of FMRP leads to dysregulation of target mRNAs. The Drosophila model of FXS show an abnormal circadian rhythm with disruption of the output pathway downstream of the clock network. Yet the FMRP targets involved in circadian regulation have not been identified. Here, we identified collapsing response mediator protein (CRMP) mRNA as a target of FMRP. Knockdown of pan-neuronal CRMP expression ameliorated the circadian defects and abnormal axonal structures of clock neurons (ventral lateral neurons) in dfmr1 mutant flies. Furthermore, specific reduction of CRMP in the downstream output insulin-producing cells attenuated the aberrant circadian behaviors. Molecular analyses revealed that FMRP binds with CRMP mRNA and negatively regulates its translation. Our results indicate that CRMP is an FMRP target and establish an essential role for CRMP in the circadian output in FXS Drosophila.

Fragile X syndrome (FXS) is the most common monogenic form of inherited intellectual disability and autism spectrum disorder (ASD). More than 99% of individuals with FXS are caused by the unstable expansion of CGG repeats located within the 5'-untranslated region of the FMR1 gene. The clinical features of FXS include various degrees of cognitive deficit, physical, behavioral and psychiatric problems. Early treatment and prevention from having further affected children can be guided by molecular genetic testing of the FMR1 gene. The following guideline has combined the relevant research, guidelines and consensus worldwide, and summarized the genetic knowledge and clinical treatment for FXS in order to achieve a standardized diagnosis, treatment and prevention for patients and families affected by this disease.
Child ; Humans ; Autism Spectrum Disorder/therapy* ; Fragile X Mental Retardation Protein/genetics* ; Fragile X Syndrome/therapy* ; Intellectual Disability/genetics*