Molecular prenatal diagnosis of alpha and beta thalassemia in pregnant Hakka women in southern China.
ABSTRACT: BACKGROUND:To date, there has been no systematic study of DNA-based prenatal diagnosis of thalassemia in pregnant Hakka women in southern China. METHODS:A total of 279 pregnant Hakka women with confirmed cases of thalassemia who had been treated at the Meizhou People's Hospital in China's Guangdong Province from January 2014 to December 2016 were here enrolled. Genomic DNA was extracted from peripheral blood of couples and villus, amniotic fluid, or fetal cord blood. DNA-based diagnosis was performed on the tissues of fetuses whose parents had tested positive for ?- and ?-globin gene mutations were found using polymerase chain reaction (PCR) and flow-through hybridization technique. Follow-up visits were performed 6 months after the fetuses were born. Prenatal diagnosis was performed on 279 fetuses in at-risk pregnancies. RESULTS:Here, 211 ?-thalassemia fetuses were confirmed, including 41 (19.43%) that tested positive for Bart's hydrops syndrome and 15 (7.11%) for Hb H disease. There were 103 (48.81%) heterozygotes. ?-thalassemia was confirmed in 68 fetuses, including 23 (33.82%) with severe thalassemia and 27 (39.71%) heterozygotes. Another 12 cases were confirmed with ?+?-thalassemia, including three cases of severe ?-thalassemia. DNA-based testing prenatal diagnosis of thalassemia was found to be highly reliable. CONCLUSIONS:Our findings provide key information for clinical genetic counseling of prenatal diagnosis for major thalassemia in pregnant Hakka women in southern China.
Project description:Prenatal clinical detection of thalassemia involves gap?PCR and reverse dot blot (RDB) analysis of fetal DNA acquired through invasive methods. The present study aimed to develop a non?invasive prenatal diagnostic method for thalassemia based on next?generation sequencing (NGS). A total of eight families with proband children with thalassemia were recruited for the study during a subsequent pregnancy. The sequence of the thalassemia genes of the parents and proband were determined using NGS, based on a thalassemia AmpliSeq panel. Cell?free plasma DNA from pregnant women related to the aforementioned proband was analyzed using an NGS panel, based on thalassemia?associated capture probes. Heterozygous single nucleotide polymorphisms within the 10 kb regions flanking exons of the targeted thalassemia genes were acquired using probes or AmpliSeq and employed for parental haplotype construction using Trio?based panel sequencing. The fetal haplotype was deduced from the parental haplotypes and relative haplotype dosage, and subsequently validated using gap?PCR and RDB, based on invasively sampled amniotic fluid. A non?invasive prenatal diagnosis procedure from maternal plasma fetal DNA was successfully developed based on haplotype analysis. The deduced haplotypes of eight fetuses were identical to the results of invasive prenatal diagnosis procedures, with an accuracy rate of 100%. Taken together, the present study demonstrated the potential for non?invasive prenatal diagnosis of ?? and ??thalassemia using NGS and haplotype?assisted analysis.
Project description:Thalassemia is a dangerous hematolytic genetic disease. In south China, ?24% Chinese carry alpha-thalassemia or beta-thalassemia gene mutations. Given the fact that the invasive sampling procedures can only be performed by professionals in experienced centers, it may increase the risk of miscarriage or infection. Thus, most people are worried about the invasive operation. As such, a noninvasive and accurate prenatal diagnosis is needed for appropriate genetic counseling for families with high risks. Here we sought to develop capture probes and their companion analysis methods for the noninvasive prenatal detection of deletional and nondeletional thalassemia.Two families diagnosed as carriers of either beta-thalassemia gene or Southeast Asian deletional alpha-thalassemia gene mutation were recruited. The maternal plasma and amniotic fluid were collected for prenatal diagnosis. Probes targeting exons of the genes of interest and the highly heterozygous SNPs within the 1Mb flanking region were designed. The target capture sequencing was performed with plasma DNA from the pregnant woman and genomic DNA from the couples and their children. Then the parental haplotype was constructed by the trios-based strategy. The fetal haplotype was deduced from the parental haplotype with a hidden Markov model-based algorithm.The fetal genotypes were successfully deduced in both families noninvasively. The noninvasively constructed haplotypes of both fetuses were identical to the invasive prenatal diagnosis results with an accuracy rate of 100% in the target region.Our study demonstrates that the effective noninvasive prenatal diagnosis of alpha-thalassemia and beta-thalassemia can be achieved with the targeted capture sequencing and the haplotype-assisted analysis method.
Project description:We propose antenatal blood tests using high-resolution DNA melting (HRM) analysis for beta thalassemia mutation detection after hemoglobin A2 estimation as a modified strategy for the identification of beta thalassemia at-risk couples. Antenatal blood samples of 1,115 couples were transferred from the antenatal care clinic. Hemoglobin A2 was quantified, and proportions ?3.5% were further assessed for beta thalassemia mutation using HRM analysis. Twelve types of beta thalassemia mutations, including hemoglobin E, were identified. There were 23 couples who were detected as at-risk. All at-risk couples were identified within 7 working days after sample receipt. Prenatal diagnosis revealed 6 affected fetuses. One fetus was homozygous CD17 (AT), and five fetuses exhibited beta0 - thalassemia/hemoglobin E disease. These results were consistent with the outcomes calculated using the Hardy-Weinberg equation. Antenatal blood tests for mutation detection using high-resolution DNA melting analysis after hemoglobin A2 estimation is a feasible laboratory method for the recruitment of couples with a fetus that is at risk for beta thalassemia. This modified strategy is cost-effective and may be beneficial for use in a beta thalassemia prevention program.
Project description:We report two unrelated cases of compound heterozygosity for hemoglobin (Hb) variant Broomhill and the Southeast Asian (- - <sup>SEA</sup>/) ?-thalassemia deletion, whose clinical features and laboratory findings have never been reported. Hematological analyses revealed abnormal values for both cases as ?-thalassemia traits, and capillary electrophoresis suggested an abnormal peak that was incompletely separated from the Hb A peak. A suspension array system and Sanger sequencing were used to characterize the genotypes. Sanger sequencing confirmed the presence of Hb Broomhill [?114(GH2)Pro?Ala; <i>HBA1</i>: c.343C>G]. Eventually, both cases were accurately diagnosed as compound heterozygotes for Hb Broomhill and the (- - <sup>SEA</sup>/) ?-thalassemia deletion, which is the first known report of these variants. This information will be useful when providing appropriate genetic counselling and prenatal diagnosis.
Project description:<b>Background:</b> Prenatal genetic counseling can be difficult, especially when it is related to fetuses with a rare thalassemia. An intronic variant located far from obvious regulatory sequences in the <i>HBB</i> gene could be very difficult to evaluate as it may affect the mRNA processing or cause β-thalassemia (β-thal). In the present study, a Chinese pregnant woman with HbJ-Bangkok and a very rare change in the second intron of the <i>HBB</i> gene [IVS-II-806(G>C), NM_000518.4, <i>HBB</i>: c.316-45G>C] in combination with α+-thalassemia was reported, which can assist in prenatal genetic counseling. <b>Case Report:</b> A 26-year-old pregnant woman presented at the obstetric clinic for a routine pregnancy check at 12 weeks of gestation. Red blood counts and high-performance liquid chromatography (HPLC) were consistent with clinical manifestations of anemia. Multiplex gap-polymerase chain (gap-PCR) displayed rightward deletion (-α<sup>3.7</sup>/αα). Direct DNA sequencing of the δ-globin gene showed no mutation. Sanger sequencing of the β-globin gene showed a previously undescribed condition of double heterozygosity for HbJ-Bangkok and a very rare change in the second intron of the <i>HBB</i> gene [IVS-II-806(G>C), NM_000518.4, <i>HBB</i>: c.316-45G>C] that has not been previously reported in the HbVar database. Thus, a rare combination of α+-thal and a compound heterozygosity of HbJ-Bangkok and [IVS-II-806(G>C)] with α+-thal (-α<sup>3.7</sup>/αα) was finally diagnosed. Prenatal genetic counseling was made based on the genotype and phenotype analyses. <b>Conclusion:</b> This study enlarges the mutation spectrum of β-globin gene and emphasizes DNA analysis in resolving unusual patterns in Hb analysis and the importance of sharing the observed rare undefined mutations and the possible interactions with known molecular defects, which can assist in prenatal genetic counseling.
Project description:?-Thalassemia (?-thal) is a major public health problem in Albania as it is in many Mediterranean countries. We determined the different ?-thal alleles that are present in the Albanian population by using the temporal temperature gradient electrophoresis (TTGE) method because of its high throughput, cost-effectiveness, sensitivity and simplicity. DNA from blood of 68 patients with ?-thal, 26 with sickle cell anemia or sickle cell ?-thal, 54 parents of these patients and 14 heterozygotes related to these families. We found the IVS-I-110 (G>A), codon 39 (C>T), IVS-I-6 (T>C), IVS-I-1 (G>A) and codon 44 (-C) mutations that accounted for nearly 90% of the ?-thal alleles. Their frequencies were similar to those found in other studies in the Albanian population. This method has permitted the detection of heterozygotes for ?-thal in this population and offers a prenatal diagnosis with a probability of 90% accuracy.
Project description:PURPOSE: Preimplantation genetic diagnosis (PGD) is an alternative to prenatal diagnosis (PND) giving couples at risk a chance to start a pregnancy with a disease-free baby. This study aimed to develop a new PGD protocol for alpha-thalassemia(-SEA) mutation, the commonest Mendelian disorder. PATIENTS AND METHODS: Multiplex fluorescent PCR was employed for mutation, contamination and linkage analysis. A couple experienced termination of pregnancy following positive PND decided to join the project. RESULTS: Novel primers for alpha-thalassemia(-SEA) mutation amplifying 5 DNA fragments were developed. Two PGD cycles were performed, resulting in an un-affected baby. PND confirmed the heterozygous result. From 24 embryos, 87.5% of affected genotype were of best quality compared to 0% and 18.2% of those with normal and heterozygous, respectively. CONCLUSIONS: A novel PCR protocol for the common alpha-thalassemia(-SEA) mutation is reported. This test should be widely applicable. Interestingly, a potential effect of alpha-thalassemia(-SEA) mutation on preimplantation embryonic development was noticed.
Project description:We propose using a modified amplification refractory mutation system real-time polymerase chain reaction (ARMS RTPCR) technique to exclude the invasive prenatal diagnosis for a non-paternally inherited beta thalassemia mutation in couples atrisk for having a baby with CHBT. The ARMS RT-PCR method was performed for 36 at-risk couples by using isolated fetal cell-free DNA from maternal plasma. The modified ARMS RT-PCR primers targeted one of the following paternally inherited beta thalassemia mutation: -28 A?G, CD17 A?T, CD 26 G?A, IVS1-1 G?T and CD 41-42 -CTTT. The method could be successfully employed for NIPST starting with the 7th week of gestation. The results showed that 19 pregnant women were negative for PIBTM (53%). After an on-track and on-time of one year, including postnatal thalassemia blood tests, none of the babies showed symptoms or signs of beta thalassemia disease. We concluded that the modified ARMS RT-PCR method was an accurate, cost-effective and feasible method for use as a NIPST for at-risk couples with the potential of having a baby with CHBT.
Project description:<h4>Purpose</h4>This study aimed to explore the value of chromosomal microarray analysis (CMA) and whole exome sequencing (WES) in the prenatal diagnosis of fetal isolated nasal bone absence (INBA) or isolated nasal bone hypoplasia (INBH). We hope to provide additional relevant information for clinical counseling.<h4>Patients and methods</h4>From November 1, 2018, to March 1, 2020, 55 pregnant women with isolated nasal bone dysplasia were admitted to the Changzhou Maternity and Child Health Care Hospital. Based on the degree of abnormality, the patients were divided into two groups: INBA and INBH. CMA was performed on all patients. The clinical data and prenatal genetic diagnoses of the two groups were retrospectively analyzed. According to the requirements of WES for samples, 12 cases with negative CMA results were selected for the WES test.<h4>Results</h4>A total of 55 cases with INBA or INBH met the inclusion criteria. In 35INBA fetuses, there was one case of trisomy 21 and one case of 10q11.22 deletion (5.7Mb), and the abnormality rate was 5.71% (2/35). Compared with INBA fetuses, the abnormality rate was increased in the fetuses with INBH [15.00% (3/20)] (15.00% vs 5.71%); there was one case of 1q21.1 duplication (1.3Mb), one case of Xp22.31 duplication (1.67Mb), and one case of 4p deletion (7.6Mb). In a later retrospective study, two pathogenic variants were identified in two cases after the WES test; the abnormality rate was 16.67% (2/12), which involved <i>RUNX2</i> and <i>CDH4</i> genes, respectively.<h4>Conclusion</h4>A preliminary study confirmed that molecular prenatal diagnosis should be performed in fetuses with INBA or INBH. CMA followed by WES is an effective method.
Project description:<h4>Background</h4>Fetal echogenic bowel (FEB) is associated with an increased risk of poor pregnant outcomes; however, karyotyping fails to detect copy number variations (CNVs) in FEB. This study aimed to evaluate the performance of chromosomal microarray analysis (CMA) for detection of FEB.<h4>Methods</h4>The medical records of 147 pregnant women with FEB recruited during December 2015 to December 2018 were retrospectively reviewed, and prenatal samples were collected for karyotyping and CMA. The detection of chromosomal abnormality was compared between karyotyping and CMA.<h4>Results</h4>Karyotyping identified eight cases with abnormal karyotypes (5.44% prevalence), including four fetuses with pathogenic aneuploidy, three with chromosome polymorphism and one with balanced chromosome translocation. CMA identified 13 abnormal CNVs (8.84% prevalence), including 4 fetuses with pathogenic aneuploidy as detected by karyotyping and 9 additional CNVs with normal karyotypes; however, CMA failed to detect chromosome polymorphism and balanced chromosome translocation. In fetuses with isolated FEB, no cases presented pathogenic findings and CMA detected two cases with variants of uncertain significance (VOUS). In cases presenting FEB along with other ultrasound abnormalities, CMA detected three cases with pathogenic CNVs and four cases with VOUS in addition to four cases with aneuploidy. There was no significant difference in the detection of abnormal CNVs between the fetuses with echogenic bowel alone and along with other ultrasound abnormalities (10% vs 8.67%, <i>P</i> > 0.05). Except 9 fetuses lost to the follow-up, the other 138 fetuses with echogenic bowel were successfully followed up. Pregnancy was terminated in 5 fetuses with chromosomal abnormality, 2 with pathogenic CNVs and 1 with VOUS, and other 16 with normal karyotypes and CMA findings but showing ultrasound abnormalities or multiple malformations.<h4>Conclusion</h4>Isolated FEB is associated with a good prognosis, and a satisfactory pregnant outcome is expected for fetuses with echogenic bowel that are negative for chromosomal anomalies and other severe structure abnormalities. CMA shows an important value in the genetic diagnosis of FEB. As a supplement to karyotyping, CMA may improve the accuracy of prenatal diagnosis of fetal intestinal malformations in pregnant women with FEB.