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*

OBJECTIVE: To explore the genetic basis for a child with febrile seizures. METHODS: Peripheral venous blood samples were taken from the child and his parents for the analysis of chromosomal karyotype and dynamic variant of the FMR1 gene. The family trio was also subjected to target capture and next generation sequencing (NGS) with a gene panel related to developmental retardation, mental retardation, language retardation, epilepsy and special facial features. RESULTS: The child was found to have a normal karyotype by conventional cytogenetic analysis (400 bands). No abnormal expansion was found with the CGG repeats of the FMR1 gene. NGS revealed that the child has carried a heterozygous c.864+1 delG variant of the MEF2C gene, which may lead to abnormal splicing and affect its protein function. The same variant was found in neither parent, suggesting that it has a de novo origin. Based on the American College of Medical Genetics and Genomics standards and guidelines, c.864+1delG variant of MEF2C gene was predicted to be pathogenic (PVS1+PS2+PM2). CONCLUSION MEF2C, as the key gene for chromosome 5q14.3 deletion syndrome which was speculated as a cause for febrile seizures, has an autosomal dominant effect. The c.864+1delG variant of the MEF2C gene may account for the febrile seizures in this patient.
Child ; Chromosome Deletion ; Chromosome Disorders ; Epilepsy ; Fragile X Mental Retardation Protein ; Humans ; Intellectual Disability/genetics* ; Karyotyping ; MEF2 Transcription Factors/genetics*

OBJECTIVE: To explore the correlation between Fragile X mental retardation gene-1 (FMR1) gene CGG repeats with diminished ovarian reserve (DOR). METHODS: For 214 females diagnosed with DOR, DNA was extracted from peripheral blood samples. FMR1 gene CGG repeats were determined by PCR and capillary electrophoresis. RESULTS: Three DOR patients were found to carry FMR1 premutations, and one patient was found to carry gray zone FMR1 repeats. After genetic counseling, one patient and the sister of another patient, both carrying FMR1 permutations, conceived naturally. Prenatal diagnosis showed that both fetuses have carried FMR1 permutations. CONCLUSION FMR1 gene permutation may be associated with DOR. Determination of FMR1 gene CGG repeats in DOR patients can provide a basis for genetic counseling and guidance for reproduction.
Female ; Fragile X Mental Retardation Protein/metabolism* ; Fragile X Syndrome/genetics* ; Humans ; Ovarian Diseases ; Ovarian Reserve/genetics* ; Primary Ovarian Insufficiency/genetics* ; Trinucleotide Repeats/genetics*

OBJECTIVE: To analyze the (CGG)n repeats of FMR1 gene among patients with unexplained mental retardation. METHODS: For 201 patients with unexplained mental retardation, the (CGG)n repeats of the FMR1 gene were analyzed by PCR and FragilEase RESULTS: For the 201 patients with unexplained mental retardation, 15 were identified with full mutations of the FMR1 gene. The prevalence of fragile X syndrome (FXS) in patients with unexplained mental retardation was determined as 7.5% (15/201). Prenatal diagnosis was provided for 6 pregnant women with pre- or full mutations. Analysis revealed that women with mental retardation and full FMR1 mutations exhibited a skewed XCI pattern with primary expression of the X chromosome carrying the mutant allele. CONCLUSION FXS has a high incidence among patients with unexplained mental retardation. Analysis of FMR1 gene (CGG)n repeats in patients with unexplained mental retardation can facilitate genetic counseling and prenatal diagnosis for their families. FMR1 gene (CGG)n repeats screening should be recommended for patients with unexplained mental retardation.
Female ; Fragile X Mental Retardation Protein/genetics* ; Fragile X Syndrome/genetics* ; Humans ; Intellectual Disability/genetics* ; Mutation ; Pregnancy ; Prenatal Diagnosis

OBJECTIVE: To screen for mutations of fragile X mental retardation 1 (FMR1) gene during early and middle pregnancy and provide prenatal diagnosis for those carrying high-risk CGG trinucleotide expansions. METHODS: Peripheral blood samples of 2316 pregnant women at 12 to 21(+6) gestational weeks were collected for the extraction of genomic DNA. CGG repeats of the FMR1 gene were detected by fluorescence PCR and capillary electrophoresis. Genetic counseling and prenatal diagnosis were provided for 3 women carrying the premutations. RESULTS: The carrier rate of CGG repeats of the FMR1 gene was 1 in 178 for the intermediate type and 1 in 772 for the premutation types. The highest frequency allele of CGG was 29 repeats, which accounted for 49.29%, followed by 30 repeats (28.56%) and 36 repeats (8.83%). In case 1, the fetus had a karyotype of 45,X, in addition with premutation type of CGG expansion of the FMR1 gene. Following genetic counseling, the couple chose to terminate the pregnancy through induced labor. The numbers of CGG repeats were respectively 70/- and 29/30 for the husband and wife. In case 2, amniocentesis was performed at 20 weeks of gestation. The number of CGG repeats of the FMR1 gene was 29/-. No abnormality was found in the fetal karyotype and chromosomal copy number variations. The couple chose to continue with the pregnancy. Case 3 refused prenatal diagnosis after genetic counseling and gave birth to a girl at full term, who had a birth weight of 2440 g and no obvious abnormality found during follow-up. CONCLUSION Pregnant women should be screened for FMR1 gene mutations during early and middle pregnancy, and those with high-risk CGG expansions should undergo prenatal diagnosis, genetic counseling and family study.
DNA Copy Number Variations ; Female ; Fragile X Mental Retardation Protein/genetics* ; Fragile X Syndrome/genetics* ; Genetic Counseling ; Humans ; Mutation ; Pregnancy ; Trinucleotide Repeat Expansion ; Trinucleotide Repeats

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 screen for CGG repeats in the FMR1 gene among patients with fragile X syndrome and carriers of pre-mutations.

METHODSPotential full and pre-mutations of the FMR1 gene were detected with a Tri-primer-florescence PCR-Sanger sequencing method. The results were validated with positive and negative controls.

RESULTSAll positive and negative controls were confirmed. A male patient was found to have > 200 CGG repeats (full mutation). For a pregnant women who was heterozygous for 35/115 CGG repeats, > 200 CGG repeats were also found with amniotic fluid sample from her fetus who was a male. The result was confirmed by following selective abortion with informed consent.

CONCLUSIONTri-primer-florescence PCR-Sanger sequencing is a simple, effective and reliable method for routine screening of patients/carriers with full/pre-mutations of the FMR1 gene in the population.

DNA Primers ; genetics ; Female ; Fluorescence ; Fragile X Mental Retardation Protein ; genetics ; Fragile X Syndrome ; genetics ; Humans ; Male ; Mutation ; genetics ; Polymerase Chain Reaction ; methods

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

OBJECTIVETo analyze a patient with unexplained mental retardation by using three primer PCR (TP-PCR) and single nucleotide polymorphisms array (SNP-array), and to correlate the genotype with phenotype.

METHODSPeripheral blood sample was taken from the patient for the extraction of DNA. TP-PCR was used to determine the copy number of CGG repeats in the 5'UTR of the FMR1 gene. SNP array was used for high resolution analysis of the patient's genome.

RESULTSTP-PCR has shown no abnormal amplification of CGG in the 5'UTR of FMR1 gene. Hence, Fragile X syndrome was excluded as the cause for mental retardation. SNP array analysis has identified a 0.93 Mb duplication at 7q36.1-q36.2 and a 2.2 Mb deletion at 12p13.1-p13.2 in the patient.

CONCLUSIONThe microduplication and microdeletion discovered in the patient probably underlies the intelligence disability. The high-resolution SNP array can provide accurate information for the identification of pathogenesis, and is the preferred method for the diagnosis of unexplained mental retardation.

Child ; Cytogenetic Analysis ; Fragile X Mental Retardation Protein ; genetics ; Humans ; Intellectual Disability ; genetics ; Male ; Oligonucleotide Array Sequence Analysis ; Polymorphism, Single Nucleotide

ObjectiveTo investigate the clinical (including reproductive) manifestations and genetic characteristics of familial fragile X syndrome (FXS).

METHODSWe collected the clinical data about a case of familial FXS by inquiry, testicular ultrasonography, semen analysis, determination of sex hormone levels, and examinations of the peripheral blood karyotype and Y chromosome microdeletions. Using Southern blot hybridization, we measured the size of the CGG triple repeat sequence of the fragile X mental retardation-1 (FMR1) gene and determined its mutation type of the pedigree members with a genetic map of the FXS pedigree.

RESULTSAmong the 34 members of 4 generations in the pedigree, 3 males and 1 female (11.76%) carried full mutation and 9 females (26.47%) premutation of the FMR1 gene. Two of the males with full FMR1 mutation, including the proband showed a larger testis volume (>30 ml) and a higher sperm concentration (>250 ×10⁶/ml), with a mean sperm motility of 50.5%, a mean morphologically normal sperm rate of 17.5%, an average sperm nuclear DNA fragmentation index (DFI) of 18.5%, a low level of testosterone, normal karyotype in the peripheral blood, and integrity of the azoospermia factor (AZF) region in the Y chromosome. One of the second-generation females carrying FMR1 premutation was diagnosed with premature ovarian failure and another 3 with uterine myoma.

CONCLUSIONSSome of the FXS males in the pedigree may present macroorchidism and polyzoospermia but with normal semen parameters. In the intergenerational transmission, premutation might extend to full mutation, with even higher risks of transmission and extension of mutation in males, especially in those with >80 CGG triple repeat sequences. Therefore, it is recommended that the couples wishing for childbearing receive genetic testing, clinical guidance, and genetic counseling before pregnancy and, if necessary, prenatal diagnosis and preimplantation genetic diagnosis.

Chromosome Deletion ; Chromosomes, Human, Y ; genetics ; DNA Fragmentation ; Female ; Fragile X Mental Retardation Protein ; genetics ; Fragile X Syndrome ; genetics ; Genetic Testing ; Humans ; Infertility, Male ; genetics ; Karyotyping ; Male ; Mutation ; Organ Size ; Pedigree ; Pregnancy ; Preimplantation Diagnosis ; Risk ; Sex Chromosome Aberrations ; Sex Chromosome Disorders of Sex Development ; genetics ; Sperm Count ; Testis ; diagnostic imaging ; pathology