Advances in genetics and prevention of monogenic global developmental delay and intellectual disability / 中华围产医学杂志

Global developmental delay/intellectual disability (GDD/ID) is an enormous group of neurodevelopmental disorders with diverse clinical and genetic heterogeneity. The estimated prevalence of GDD/ID was 1%-3%, affecting about 150 million people. GDD/ID is one of the leading causes of disability in children worldwide. The causes of GDD/ID are complex, comprising genetic and environmental factors. It is often co-morbid with a variety of psychiatric behavioral disorders, such as autism spectrum disorder and attention deficit hyperactivity disorder. Owing to the improvement of genetic technology, monogenic GDD/ID has been one of the hot-spot research in genomic era, and the relevant preventive measures deserve extensive attention. In this review, we summarized the advances in genetics and prevention of monogenic GDD/ID.

Prenatal diagnosis of abnormal morphology of Sylvian fissure and malformations of cortical development / 中华围产医学杂志

Objective:To investigate the significance of abnormal morphology of Sylvian fissure detected by fetal neurosonogram (NSG) in prenatal diagnosis of malformations of cortical development (MCD).Methods:This retrospective study involved fetuses with abnormal morphology of Sylvian fissure on prenatal NSG in Peking University First Hospital between January 2016 and December 2021. Clinical data including the basic information as well as the results of NSG, genetic examinations and MRI were collected. The diagnosis of MCD could be made when both brain morphological abnormalities and pathogenic/likely pathogenic genetic abnormalities were presented. The association between the abnormal morphology of Sylvian fissure and MCD was analyzed by descriptive analysis.Results:Thirteen participants who had complete genetic information were included in this study [defined as those who were found with pathogenic/likely pathogenic copy number variation (CNV) or those who further underwent whole-exome sequencing (WES) as no pathogenic/likely pathogenic CNV were detected]. Twelve fetuses (12/13) were eventually diagnosed with MCD. Pathogenic CNV were found in seven fetuses and pathogenic point mutations in five, involving six pathogenic genes and four genetic syndromes. Symmetric morphologic abnormality of Sylvian fissure was detected in 10 cases by prenatal NSG with shallow and broad shape in six and abnormal angle of Sylvian fissure in four. The other two fetuses showed asymmetric abnormal morphology of Sylvian fissure that was shallow and broad shape on one side and abnormal angle on the other. The imaging features of MCD present by prenatal NSG and were consistent with those of MRI.Conclusions:Abnormal morphology of Sylvian fissure detected by prenatal NSG is important in MCD diagnosis. Genetic examination are recommended to the fetuses with abnormal morphology of Sylvian fissure. For those requiring for genetic analysis, chromosomal microarray analysis together with WES might be an optimal choice.

Parental origin verification through chromosomal microarray analysis to determine the clinical significance of copy number variations / 中华围产医学杂志

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.

Prenatal diagnosis of X-linked adrenoleukodystrophy in 20 pedigrees / 中华围产医学杂志

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.

Prenatal diagnosis of monogenic global developmental delay/intellectual disability in 43 pedigrees / 中华围产医学杂志

Objective:To summarize the prenatal diagnostic characteristics of monogenic global developmental delay/intellectual disability(GDD/ID) pedigrees.Methods:This study retrospectively collected the prenatal molecular diagnostic results of 43 pedigrees that were affected with monogenic GDD/ID in the genetic counseling clinic of Peking University First Hospital from January 2015 to June 2019. The results of prenatal molecular tests were validated after birth or pregnancy termination. Pregnancy outcomes and healthy condition of the offspring were followed up. All data were analyzed by descriptive statistical analysis.Results:Among the 43 pedigrees, 24 were affected with autosomal recessive inheritance (AR) GDD/ID, in which six (25%) fetuses were found to carry two pathogenic variants; 13 (55%) had only one pathogenic variant; five (20%) did not harbor any variant. GDD/ID inherited in an autosomal dominant inheritance (AD) pattern was found in 13 pedigrees, in which 11 fetuses carried no variants while the other two fetuses had the same variants as the proband had (in one pedigree, a low-level variant was detected in the peripheral blood sample of the father while absent in peripheral blood samples of parents in the other pedigree, so it was suspected that the variants of these two affected fetuses were inherited from parental mosaicism). In the other six pedigrees with X-linked inheritance (XL) of GDD/ID, one male fetus was found to harbor the pathogenic variant, while no variants were detected in the others. Maternal contamination was excluded in all prenatal samples using short tandem repeat for linkage analysis. Postnatal validations were consistent with the prenatal tests. All nine affected fetuses were terminated, and the other thirty-four children were delivered and in good health.Conclusions:Prenatal molecular diagnostic test is an effective method to detect pathogenic variants during the first and second trimesters for pedigrees affected by monogenic GDD/ID. For pedigrees affected with AD or XL patterns caused by de novo mutations, potential parental mosaicism should be noted and prenatal diagnostic tests are also recommended.

Clinical manifestations and prenatal diagnosis of congenital muscular dystrophy / 中华围产医学杂志

Objective To summarize the clinical features of 22 probands diagnosed with congenital muscular dystrophy (CMD),and to provide genetic counseling and prenatal diagnosis for 23 fetuses of these pedigrees.Methods Data of 22 CMD patients who were treated in the Pediatric Department of Peking University First Hospital during October 2006 to March 2016 were analyzed.Informed written consents for participation in this study were obtained from the parents or guardians.Prenatal diagnosis was performed using DNA samples extracted from fetal villus cells of 12 cases at 11-13 gestational weeks and amniotic fluid of 11 cases at 18-22 gestational weeks.Direct DNA sequencing by polymerase chain reaction (PCR) and multiplex ligation-dependent probe amplification (MLPA) were used to detect CMD-related gene mutations.Linkage analysis of short tandem repeats (STRs) was used to identify maternal blood contamination and biological parents.Results Thirteen out of the 22 probands with CMD were diagnosed with congenital muscular dystrophy type 1 A (MDC1A),and all of them carried compound heterozygous mutations in LAMA2 gene.Prenatal diagnosis of 13 fetuses from these pedigrees found that four fetuses were wild-type,seven were heterozygotes and two carried the same mutations as their proband.Three probands with LMNA-related congenital muscular dystrophy (L-CMD) carried de novo mutations in LMNA gene.In these pedigrees,two fetuses were wild-type and one whose mother was mosaicism carried the same mutations as the proband.One proband with Ullrich congenital muscular dystrophy carried compound heterozygous mutations in COL6A2 gene and the fetus of the same pedigree was wild-type.Five probands were diagnosed with α-dystroglycanopathies.And among them,two cases of muscle-eye-brain disease (MEB) carried compound heterozygous mutations in POMGnT1 gene and the fetuses of the two peidgrees were heterozygotes;one case of congenital muscular dystrophy type 1C (MDC1C) had compound heterozygous mutations in FKRP gene and the fetus carried the same mutations;one patient diagnosed with POMGnT1-related congenital muscular dystrophy with mental retardation (CMD-MR) carried compound heterozygous mutations in POMGnT1 gene,and the fetus was positive for the same mutations;one proband with POMT1-related CMD-MR was positive for compound heterozygous mutations in POMT1 gene and the results of prenatal diagnosis for two fetuses of this pedigree showed that the first fetus had the same mutations as the proband,while the second was heterozygote.Conclusions No effective therapeutic method is available for CMD.Therefore,accurate genetic counseling and prenatal diagnosis are necessary to prevent CMD child from birth.

Prenatal diagnosis of mitochondrial disease: analysis of 28 pedigrees with mitochondrial DNA mutation / 中华围产医学杂志

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.

Prenatal diagnosis and genetic counseling of fragile X syndrome in four pedigrees by using high-resolution multiplex polymerase chain reaction / 中华围产医学杂志

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.

Diagnosis of MECP2 duplication syndrome with molecular genetic techniques / 中华儿科杂志

<p><b>OBJECTIVE</b>To investigate whether the four boys with delayed motor development and intellectual disability suffer from MECP 2 duplication syndrome.</p><p><b>METHOD</b>Blood specimens and clinical data of four patients and mothers of patient 2 and patient 4 were collected. Genomic DNA was extracted from peripheral blood using DNA extraction kit. At first multiplex ligation-dependent probe amplification (MLPA) was employed in 4 patients, two distinct kits SALSA P036 and P070 for sub-telomere screening, and SALSA P245 for the 22 common microdeletion and microduplication syndromes. Then array-CGH analysis was carried out. Two mothers of patients were tested by array- comparative genomic hybridization (CGH) and X chromosome inactivation analysis.</p><p><b>RESULT</b>All the 4 patients presented with severe hypotonia, delayed motor development, intellectual disability and absent or limited language. Three patients manifested recurrent pneumonia in infancy except patient 2. Four patients had duplication on chromosome Xq28 with MLPA kit SALSA P245. Array-CGH identified the size of each duplication on Xq28. The precise size of each duplication was different in the four patients: patient 1, 14.931 Mb, patient 2, 0.393 Mb, patient 3, 0.482 Mb and patient 4, 0.299 Mb. To compare Xq28 duplications with UCSC database (http://genome.ucsc.edu/) revealed that each duplication harbors the MECP 2 and HCFC 1 gene. Mothers of patient 2 and patient 4 also carried microduplication on Xq28. X chromosome inactivation analysis demonstrated completely skewed inactivation (0: 100) and it is the inactive allele that passed on to the patients.</p><p><b>CONCLUSION</b>For patients that present with delayed motor development, intellectual disability, hypotonia, absent or limited language and recurrent infection, combination of MLPA and array- CGH is effective and specific diagnostic methods of MECP 2 duplication syndrome.</p>

Association study between simple febrile seizures and gabbr1 gene and gabbr2 gene / 中华实用儿科临床杂志

Objective To investigate whether the gamma-aminobutyric acid (GABAB) receptor genes,including gabbr1 gene and gabbr2 gene,are the susceptible genes for simple febrile seizures (sFS) by screening mutation of gabbr1 gene and gabbr2 gene and to study the possible association between sFS and the 2 genes.Methods All exons and flanking introns of gabbr1 gene and gabbr2 gene were amplified with polymerase chain reaction (PCR) and sequenced to screen the possible mutation on 60 children with sFS in the northern China in Han nationality population.One hundred and one healthy children from the same area were selected as controls,and the genotypes of single nucleotiole polymorphisms (SNPS) (rs29220,rs29230,rs29267 on gabbr1 gene and rs1000440,rs3205936,rs2304391 on gabbr2 gene) were typed by PCR-restriction fragment length polymorphism.EH1.20 software was used to estimate haplotype frequency to study the association with the haplotype as genetic marker between case group and control group.Results No mutation associated with sFS was found in the 60 sFS cases.In all sequenced regions,23 SNPs were identified in both genes:6 SNPs in gabbr1 gene and 17 SNPs in gabbr2 gene.The frequencies of the 6 SNPs were complied well with the Hardy-weinberg equilibrium in sFS group and normal group.Genotype proportions and allele frequencies of 6 SNPs were not significantly different between both groups.The haplotypes of 3 SNPs in gabbr1 gene and in gabbr2 gene distributions were not significantly different between 2 groups.Conclusions No mutations and associations were identified between sFS with both GABAB receptor genes(gabbr1 gene and gabbr2 gene).They may not be the susceptibility gene for simple febrile seizures in Han nationality population in northern China.