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Objective:To summarize the characteristics of genetic variation and prenatal diagnosis in pedigrees with X-linked adrenoleukodystrophy (X-ALD) and elucidate the value of prenatal diagnosis in preventing the birth of children with X-ALD.Methods:Twenty pedigrees, clinically diagnosed with X-ALD in Peking University First Hospital from November 2012 and March 2019, were included in this retrospective study. Genomic DNA was extracted from peripheral blood and amniotic fluid or chorionic villi samples of probands and their families for detecting variants in ATP-binding cassette subfamily D member 1 ( ABCD1) gene using polymerase chain reaction (PCR)-Sanger sequencing. Linkage analysis was also performed on five microsatellite markers near ABCD1 gene to exclude maternal contamination. Characteristics of ABCD1 gene variants and prenatal diagnosis of X-ALD pedigrees were summarized by descriptive statistics. Results:Twenty ABCD1 gene variants were identified in the 20 pedigrees. The variants in three probands that were not detected by next-generation sequencing were identified by PCR-Sanger sequencing. Among the mothers of the 20 probands, 17 carried ABCD1 variants and three did not. We performed 24 prenatal diagnoses on 20 pregnancies (24 fetuses) and identified eight fetuses with variants who were finally terminated. The 16 cases without variants were born alive. The validation results obtained after termination or delivery were consistent with those performed prenatally. Conclusions:No hotspot variants in ABCD1 gene are detected in these X-ALD patients and most variants are maternally inherited. PCR-Sanger sequencing is an effective method for detecting ABCD1 variants. Prenatal diagnosis for mothers who had a body with X-ALD could prevent another one from birth.
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Objective:To explore the role of parental origin verification in chromosomal microarray analysis (CMA) on the determination of the clinical significance of copy number variations (CNVs).Methods:This retrospective study collected clinical information from 73 core families who underwent prenatal diagnosis at Peking University First Hospital from November 2017 to December 2019. Indications for prenatal diagnosis included ultrasound abnormality in 54 cases (including 12 with thickened nuchal translucency (≥2.5 mm), four with fetal growth restriction, seven with abnormal pregnancy history, and 31 with isolated ultrasound abnormality), NIPT indicated high-risk in four cases, advanced age in nine cases, abnormal pregnancy history alone in three cases, intrauterine death in two cases and one with maternal mental retardation. Genomic DNA of amniotic fluid sample, chorionic villi, cord blood, fetal tissues, and fetal heart blood were extracted using genomic DNA extraction kit. The CNVs of prenatal samples in 73 subjects were analyzed using array-based comparative genomic hybridization (array-CGH) analysis and single nucleotide polymorphism array (SNP-array). Peripheral blood DNA of the couples, and relevant families if necessary, were collected and analyzed in the same way. The results of parental origin detection in CMA were summarized.Results:A total of 76 CNVs were detected in these 73 samples, out of which nine were pathogenic and parental origin detection revealed that six were de novo, two were maternally, and one was paternally inherited; six CNVs were likely pathogenic, including three de novo, two maternally inherited and one paternally inherited; 20 CNVs were variants of uncertain significance, including five paternally inherited, three maternally inherited and 12 de novo; 41 CNVs were likely benign, among which 38 were inherited from parents with normal phenotype. Conclusions:Parental origin verification plays an important role in explaining the clinical significance of detected fetal CNVs and thereby can help to analyze its clinical effect and reproductive risk.
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Objectives To provide prenatal diagnosis and genetic counseling for four athigh-risk pregnant women with a suspected family or personal history of fragile X syndrome (FXS) by genetic screening of fragile X mental retardation (FMR1) gene.Methods This study was conducted on four pregnant women (No.l to 4) who received outpatient treatment in Peking University First Hospital from August 2014 to June 2016.Genomic DNA was extracted from peripheral blood samples of the pregnant women and six of their family members,four of which were suspected or confirmed FXS and the other two were FMR1 gene carriers.Amplide X kits were used to detect CGG repeat size in FMR1 gene.Two amniocytes and one chorionic villi samples were collected from three pregnant women to extract DNAs for FMR1 gene and karyotyping analyses.Results There were patients diagnosed with FXS in all the families by detecting CGG repeat numbers in FMR1 gene.The pregnant woman No.1 was a permutation carrier;No.2 carried normal FMR1 alleles while her brother had a mutation with over 20 CGG repeats in FMRI gene at chromosome X.No.3 and 4 were full mutation carriers with over 200 CGG repeats in FMR1 gene.After genetic counseling,No.3 decided to terminate the pregnancy due to abnormal fetal karyotype (47,XY,+21) and full mutation of FMR1 alleles.No.1 and 4 continued to pregnancy as their fetuses were normal in FMR1 alleles and karyotype.No.2 continued to pregnancy as her fetus was free of FXS risk.Conclusions Prenatal diagnosis and genetic counseling should be conducted on women at highrisk for FXS to avoid birth defects.People with a family history of FXS should be tested for FMR1 gene carrier status.
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Objective To perform a prenatal diagnosis for the second fetuses from 28 pedigrees with proband of mitochondrial disease due to mitochondrial DNA (mtDNA) mutation.Methods From April 2011 to November 2015,peripheral blood samples of 28 probands and their parents,urine samples of these probands and their mothers as well as amniotic fluid samples of the second fetuses from the 28 pedigrees were collected in Peking University First Hospital.DNA sequencing was used to identify mtDNA mutations.Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was performed to verify mutation sites,calculate mutation loads,and further confirm the diagnosis after birth.Microsatellite maker analysis was also performed on five short tandem repeats located in nuclear genes to exclude maternal contamination.Statistical analysis was carried out using independent t-test.Results In the 15 pedigrees carrying A3243G mutation,13 mothers and nine fetuses carried A3243G mutation.Neither the other two mothers nor their fetuses were positive for A3243G mutation.Among the 12 pedigrees with T8993G mutation,there were eight mothers carrying T8993G mutation and all of their fetuses carried the same mutation;and the other four mothers and their fetuses were negative for T8993G mutation.T10191C mutation was only found in one proband and the second fetus of that pedigree,but not in the mother.None of the fathers had mtDNA mutation.Results of PCR-RFLP were consistent with those of DNA sequencing.Short tandem repeat analysis demonstrated that amniocyte samples were from fetuses without maternal contamination.No mtDNA mutations were found in the six newborns who were negative for mtDNA mutations in prenatal diagnosis.The mean mutation load in urine samples of the six mothers without A3243G mutation in amniocytes was significantly lower than that of the nine mothers with A3243G mutation [(10.1 ±4.8) ％ vs (28.2 ± 15.1) ％,t=2.290,P=0.043].Conclusions The lower the mtDNA mutation load in maternal urine samples,the less the possibility she bears a child with mtDNA mutation.However,prenatal diagnosis of mitochondrial disease is necessary.