Analysis of gene inversion in Hemophilia A by Nanopore sequencing / 中华医学遗传学杂志

OBJECTIVE@#To detect gene inversion in two pedigrees affected with Hemophilia A by using Nanopore sequencing technology.@*METHODS@#Peripheral blood samples were taken from members of the two pedigrees. Following extraction of genome DNA, genetic variants of the carriers were detected by Nanopore sequencing and subjected to bioinformatic analysis.@*RESULTS@#Nanopore sequencing has identified the niece of the proband of the pedigree 1 as carrier of Hemophilia A Inv22, and the mother of the proband of the pedigree 2 as carrier of Hemophilia A Inv1, which was consistent with clinical findings. Breakpoint sites in both pedigrees were accurately mapped. Statistical analysis of the sequencing results revealed a large number of variations in the carriers' genomes including deletions, duplications, insertions, inversions and translocations.@*CONCLUSION@#Nanopore sequencing can be used to analyze gene inversions associated with Hemophilia A, which also provided a powerful tool for the diagnosis of diseases caused by gene inversions.

Prenatal cytogenetic and molecular genetic analysis of a fetus with confined placenta mosaicism for trisomy 16 / 中华医学遗传学杂志

OBJECTIVE@#To review the clinical data of a fetus with false positive result of non-invasive prenatal testing (NIPT) due to confined placental mosaicism (CPM).@*METHODS@#Amniotic fluid sample was taken from a pregnant women with high risk for chromosome 16 aneuploidy for karyotyping analysis, single nucleotide polymorphism array (SNP array) and interphase fluorescence in situ hybridization (FISH). Genetic testing was also conducted on the fetal and maternal surface of the placenta, root of umbilical cord and fetal skin tissue after induced abortion.@*RESULTS@#Cytogenetic analysis of the amniotic fluid sample yielded a normal karyotype. SNP array revealed mosaicism (20%) of trisomy 16 in the fetus. FISH confirmed the presence of mosaicism (25%) for trisomy 16. After induced labor, all sampled sites of placenta were confirmed to contain trisomy 16 by SNP array, while the analysis of fetal skin tissue yielded a negative result.@*CONCLUSION@#CPM is an important factor for false positive NIPT result. Prenatal identification of CPM and strengthened pregnancy management are important to reduce adverse pregnancy outcomes.

Application of bionano optical mapping for the diagnosis of a 16p11.2-p12.2 microdeletion / 中华医学遗传学杂志

OBJECTIVE@#To delineate chromosomal aberration caused by structural chromosomal abnormalities with bionano optical mapping.@*METHODS@#Chromosomal karyotyping, bionano optical mapping and copy number variation sequencing (CNV-seq) were used to delineate the chromosomal aberration carried by a patient.@*RESULTS@#The patient was found to have an anomalous chromosome 16 by karyotyping analysis, which was verified by bionano optical mapping and CNV-seq as loss of heterozygosity at 16p11.2-p12.2.@*CONCLUSION@#Bionano optical mapping has provided a novel tool for the detection and diagnosis of structural chromosomal aberrations.

False negative non-invasive prenatal screening result for trisomy 18: a case report / 中华围产医学杂志

We hereby reported a case of false negative non-invasive prenatal screening (NIPS) for trisomy 18. The fetus with increased nuchal translucency (3.2 mm) detected by ultrasound scan at 13+4 gestational weeks received NIPS and the result was negative in chromosomes 21, 18 and 13. A routine ultrasound examination at 22 weeks of gestation revealed multiple anomalies and a second NIPS was offered, which showed a negative result again. The pregnancy was terminated at 22+3 weeks. Multiple fetal and placental biopsies were collected for chromosome analysis using copy number variation sequencing based on high-throughput sequencing and fluorescence in situ hybridization. The fetal karyotype was shown to be 47,XY,+18 in fetal tissues (skin and liver) and umbilical cord, while no chromosomal abnormalities was detected at or near the center of the fetal and maternal surface of the placenta. Results of the chromosomal analysis along the edges of the fetal and maternal surfaces of the placenta were Chr18:47,XY,+18[60]/46,XY[40] and Chr18:47,XY,+18[35]/46,XY[65], respectively. We inferred that placental mosaicism was the cause of the false negative NIPS result. Therefore, genetic counseling before and after NIPS is necessary. Follow-up ultrasound is important for NIPS-negative patients. Invasive prenatal diagnosis is recommended when abnormal ultrasound markers with possible genetic etiology were recognized.

Analysis of POMT1 gene mutation in a pedigree affected with congenital muscular dystrophy / 中华医学遗传学杂志

OBJECTIVE To analyze mutation of POMT1 gene in a Chinese family affected with congenital muscular dystrophy (CMD). METHODS Peripheral blood samples of the family including one affected and two unaffected individuals, in addition with chorionic villous sample from the fetus, were collected. PCR was used to amplify exons 19 and 20 of the POMT1 gene, and the products were sequenced directly. Based on the result of genetic testing, prenatal diagnosis of the fetus was attained. RESULTS The proband was found to carry a heterozygous missense mutation c.1939G>A (p.Ala647Thr) in exon 19 of the POMT1 gene inherited from the mother and a heterozygous frameshift mutation c.2141delG (p.Trp714Ter) in exon 20 inherited from the father. Prenatal diagnosis revealed that the fetus has carried the c.1939G>A (p.Ala647Thr) missense mutation. With the disease causing mutation, the fetus was predicted to have similar phenotype as its mother. CONCLUSION The compound heterozygous mutations of c.1939G>A (p.Ala647Thr) and c.2141delG (p.Trp714Ter) probably underlie the CMD in this family. Based on the result, prenatal diagnosis may be provided.

Analysis of non-invasive prenatal screening detection in fetal chromosome aneuploidy / 中华妇产科杂志

Objective To evaluate the efficacy of non-invasive prenatal screening (NIPS) in the detection of fetal aneuploidies.Methods Cell free DNA was sequenced in 5 566 pregnant women to identify the fetal aneuploidies in the First Affiliated Hospital of Zhengzhou University from January 1st,2015 to March 15th,2016.Among them,5 230 (93.96％,5 230/5 566) were singleton pregnancies and 336 (6.04％,336/5 566) were twin pregnancies.In singleton pregnancies,1 809 (34.59％,1 809/5 230) were women with advanced maternal age,and 3 421 (65.41％,3 421/5 230) were young women.The positive results of NIPS were validated by karyotyping through invasive procedures and neonatal outcomes were followed up by telephone.Results Among the 5 566 women,69 (1.24％,69/5 566) got positive NIPS results,with 66 in singleton pregnancies and 3 in twin pregnancies.Two were monochorionic diamniotic twins and 1 was dichorionic twin pregnancy.The positive predictive value of NIPS for trisomy 21,18 and 13 were 100.0％,90.9％ and 100.0％,and was 55.6％ for sex chromosome aneuploidies.There was no false negative case found during the follow-up.In the advanced maternal age group and young women group,the prevalence rates of fetal chromosomal aneuploidies were 1.11％ (20/1 809) and 0.94％ (32/3 421),respectively.In the young women with soft markers in fetal ultrasound,the prevalence of fetal chromosomal aneuploidies was 1.44％ (7/487),and in serum high risk women,it was 0.94％ (7/747).In women with the serum screening risk with cut-off value,0.89％(9/1 016) had fetal aneuploidies,and the prevalence was 0.77％(9/1 171) in volunteers.There was no statistically significant difference among these groups (P=0.636).Conclusions There is no difference in the detection rate of fetal aneuploidies between high-risk women in serum screening and volunteers in NIPS.NIPS is more suitable as a first line screening test for women without fetal ultrasound abnormalities.It should be used carefully when there is ultrasound abnormalities.

Detection and prenatal diagnosis of TOR1A gene mutation in a Chinese family affected with dystonia / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To explore the feasibility of using PCR-based capillary electrophoresis method to analysis mutation of the TOR1A gene in a family affected with primary torsion dystonia (PTD).</p><p><b>METHODS</b>Peripheral blood sample was collected from proband and amnionic fluid from her fetus for the extraction of DNA. The 5th exon of the TOR1A gene and its flanking sequences were amplified with PCR and analyzed with agarose electrophoresis, fluorescence labeled fragment analysis and Sanger sequencing.</p><p><b>RESULTS</b>Fluorescence labeled fragment analysis was performed through capillary electrophoresis, which showed that the proband carried a c.907_909delGAG (p.Glu303del) deletional mutation of the TOR1A gene. The result was verified by Sanger sequencing. The fetus DNA was also found with the same mutation by capillary electrophoresis, inferring that the fetus was probably affected with the disease.</p><p><b>CONCLUSION</b>The mutation of c.907_909delGAG of the TOR1A gene was speculated as pathologic cause of proband in this family. Fragment analysis by capillary electrophoresis combined with DNA sequencing is an efficient test for small deletional mutations and feasible for its prenatal diagnosis.</p>