Potential new approaches to the management of the Hb Bart's hydrops fetalis syndrome: the most severe form of α-thalassemia

Use of HSC-targeted LNP to generate a mouse model of lethal α-thalassemia and treatment via lentiviral gene therapy

ABSTRACT

α-Thalassemia (AT) is one of the most commonly occurring inherited hematological diseases. However, few treatments are available, and allogeneic bone marrow transplantation is the only available therapeutic option for patients with severe AT. Research into AT has remained limited because of a lack of adult mouse models, with severe AT typically resulting in in utero lethality. By using a lipid nanoparticle (LNP) targeting the receptor CD117 and delivering a Cre messenger RNA (mRNACreLNPCD117), we were able to delete floxed α-globin genes at high efficiency in hematopoietic stem cells (HSC) ex vivo. These cells were then engrafted in the absence or presence of a novel α-globin-expressing lentiviral vector (ALS20αI). Myeloablated mice infused with mRNACreLNPCD117-treated HSC showed a complete knock out (KO) of α-globin genes. They showed a phenotype characterized by the synthesis of hemoglobin H (HbH; also known as β-tetramers or β4), aberrant erythropoiesis, and abnormal organ morphology, culminating in lethality ∼8 weeks after engraftment. Mice infused with mRNACreLNPCD117-treated HSC with at least 1 copy of ALS20αI survived long term with normalization of erythropoiesis, decreased production of HbH, and amelioration of the abnormal organ morphology. Furthermore, we tested ALS20αI in erythroid progenitors derived from α-globin-KO CD34+ cells and cells isolated from patients with both deletional and nondeletional HbH disease, demonstrating improvement in α-globin/β-globin mRNA ratio and reduction in the formation of HbH by high-performance liquid chromatography. Our results demonstrate the broad applicability of LNP for disease modeling, characterization of a novel mouse model of severe AT, and the efficacy of ALS20αI for treating AT.

Routine antenatal molecular testing for α-thalassemia at a tertiary referral hospital in China: ten years of experience

Objective

This study aimed to evaluate the efficacy of α-thalassemia gene testing as a part of an antenatal intervention program over a 10-year period.

Methods

All patients underwent α-thalassemia gene testing, which included the analysis of three types of deletions and mutations. Rare α-thalassemia gene testing was performed using Sanger sequencing, multiplex ligation-dependent probe amplification, and sequencing techniques. Prenatal diagnosis was performed in high-risk couples using chorionic villus sampling or amniocentesis.

Results

From 2010 to 2019, among the 91,852 patients examined, α-thalassemia mutations were identified in 41.78% of patients. The most frequent α0 gene mutation was--SEA, followed by--THAI. Two rare α0-thalassemia gene mutations at --32.8 and --230, were also observed. A total of 2,235 high-risk couples were identified, of which 562 were affected, including three with the--SEA/--THAI genotype and one with the--SEA/--230 genotype. Additionally, prenatal diagnosis revealed four cases of fetal anemia and/or mild edema, along with two cases of severe fetal edema. Chromosome and gene chip results were normal. Thalassemia gene testing showed an αCSα/αCSα genotype in four patients with anemia and/or mild edema, while two patients with severe fetal edema had one--SEA/αCSα genotype and one--SEA/--GX genotype. Using the cut-off points of 74.6 fL and 24.4 pg as criteria for identifying α0-thalassemia carriers and HbH disease, the detection rate of missed diagnoses in high-risk couples is consistent with national guidelines for standards, potentially saving 10,217,700 ¥.

Conclusion

Routine molecular testing for α-thalassemia in high-risk prenatal populations effectively prevented severe α-thalassemia births. Despite the high cost, the cutoff points proposed by this study suggest that implementing screening using a new parameter has the potential to reduce current expenses.

Interplay between α-thalassemia and β-hemoglobinopathies: Translating genotype-phenotype relationships into therapies

α-Thalassemia represents one of the most important genetic modulators of β-hemoglobinopathies. During this last decade, the ongoing interest in characterizing genotype-phenotype relationships has yielded incredible insights into α-globin gene regulation and its impact on β-hemoglobinopathies. In this review, we provide a holistic update on α-globin gene expression stemming from DNA to RNA to protein, as well as epigenetic mechanisms that can impact gene expression and potentially influence phenotypic outcomes. Here, we highlight defined α-globin targeted strategies and rationalize the use of distinct molecular targets based on the restoration of balanced α/β-like globin chain synthesis. Considering the therapies that either increase β-globin synthesis or reactivate γ-globin gene expression, the modulation of α-globin chains as a disease modifier for β-hemoglobinopathies still remains largely uncharted in clinical studies.

Appropriate whole genome amplification and pathogenic loci detection can improve the accuracy of preimplantation genetic diagnosis for deletional α-thalassemia

Objective

To improve the accuracy of preimplantation genetic testing (PGT) in deletional α-thalassemia patients.

Design

Article.

Patients

fifty-two deletional α-thalassemia couples.

Interventions

Whole genome amplification (WGA), Next-generation sequencing (NGS) and PCR mutation loci detection.

Main outcome measures

WGA, Single nucleotide polymorphism (SNP) and PCR mutation loci detection results; Analysis of embryo chromosome copy number variation (CNV).

Results

Multiple Displacement Amplification (MDA) and Multiple Annealing and Looping-Based Amplification Cycles (MALBAC) methods for PGT for deletional α-thalassemia. Blastocyst biopsy samples (n = 253) were obtained from 52 deletional α-thalassemia couples. The results of the comparison of experimental data between groups MALBAC and MDA are as follows: (i) The average allele drop-out (ADO) rate, MALBAC vs. MDA = 2.27% ± 3.57% vs. 0.97% ± 1.4%, P=0.451); (ii) WGA success rate, MALBAC vs. MDA = 98.61% vs. 98.89%, P=0.851; (iii) SNP haplotype success rate, MALBAC vs. MDA = 94.44% vs. 96.68%, P=0.409; (iv) The result of SNP haplotype analysis is consistent with that of Gap-PCR/Sanger sequencing results, MALBAC vs. MDA = 36(36/72, 50%) vs. 151(151/181, 83.43%), P=0; (v) Valid SNP loci, MALBAC vs. MDA = 30 ± 9 vs. 34 ± 10, P=0.02; (vi) The mean CV values, MALBAC vs. MDA = 0.12 ± 0.263 vs. 0.09 ± 0.40, P=0.916; (vii) The average number of raw reads, MALBAC vs. MDA =3244259 ± 999124 vs. 3713146 ± 1028721, P=0; (viii) The coverage of genome (%), MALBAC vs. MDA = 5.02 ± 1.09 vs. 5.55 ± 1.49, P=0.008.

Conclusions

Our findings indicate that MDA is superior to MALBAC for PGT of deletional α-thalassemia. Furthermore, SNP haplotype analysis combined with PCR loci detection can improve the accuracy and detection rate of deletional α-thalassemia.

Quantification of human embryonic ζ-globin chains in Southeast Asian deletion (--SEA) carriers

AIMS

Reactivation of embryonic ζ-globin is a promising strategy for genetic treatment of α-thalassaemia. However, quantification of ζ-globin as a quantitative trait in α-thalassaemia carriers and patients remains incompletely understood. In this study, we aimed to set up a reliable approach for the quantification of ζ-globin in α-thalassaemia carriers, followed by a population study to investigate its expression patterns.

METHODS

ζ-globin was purified as monomers from cord blood haemolysate of a Hb Bart's fetus, followed by absolute protein quantification, which was then tested by in-house ELISA system and introduced as protein standard. It was then used for large-scale quantification in peripheral blood samples from 6179 individuals. Finally, liquid chromatography-tandem mass spectrometry (LC-MS/MS) introduced as an independent validating approach by measuring ζ-globin expression in a second cohort of 141-SEA/αα carriers.

RESULTS

The ELISA system was proved sensitive in distinguishing individuals with varied extent of ζ-globin. Large scale quantitative study of this --SEA/αα carrier cohort indicated the high diversity of ζ-globin expression ranging from 0.00155 g/L to 1.48778 g/L. Significant positive correlation between ELISA and LC-MS/MS (R=0.400, p<0.001) was observed and it is more sensitive in distinguishing the samples with extreme expression of ζ-globin (R=0.650, p<0.001).

CONCLUSION

Our study has reported reliable approaches for the quantification of ζ-globin and presented the expression patterns of ζ-globin among the --SEA/αα carrier population, which might lay a foundation on subsequent genotype-phenotype studies on mechanisms of delayed haemoglobin switch in α-thalassaemia.

Ten years' experience in prenatal diagnosis of α-thalassemia in a municipal hospital and retrospective analysis of ultrasonic abnormalities

OBJECTIVE

This study reviewed and analyzed the prenatal diagnosis experience of thalassemia in our center over the past decade and the abnormal ultrasonic characteristics of fetuses with hemoglobin (Hb) Bart's hydrops fetalis.

METHODS

Pregnant women and their partners who tested positive for α0-thalassemia or were diagnosed with thalassemia intermedia (HbH diseases) underwent genetic counseling, and a prenatal diagnostic procedure for α-thalassemia was recommended. Ultrasonography was performed before prenatal diagnosis.

RESULTS

Invasive prenatal α-thalassemia diagnosis and ultrasonography were performed in 1049 patients at risk for Hb Bart's hydrops fetalis syndrome at our hospital from 2012 to 2021. Chorionic villus sampling (CVS) was performed in 58 cases (5.5%), amniocentesis in 902 cases (86%), and cordocentesis in 89 cases (8.5%). Hb Bart's hydrops fetalis syndrome was diagnosed in 280 fetuses. The most common body cavity effusion was pericardial effusion, ascites, and fetal systemic edema.

CONCLUSIONS

The extensive experience at our center shows that carrier screening, molecular diagnostics, genetic counseling, and prenatal diagnosis are effective measures to prevent Hb Bart's hydrops fetalis syndrome. The ultrasonographic abnormalities in fetuses with Hb Bart's hydrops are mainly caused by an increase in cardiac output, which leads to the body cavity effusion from various organs.

Diagnosis of α-thalassaemia by colorimetric gap loop mediated isothermal amplification

α-Thalassaemia is an inherited haemoglobin disorder that results from the defective synthesis of α-globin protein. Couples whom both carry the α-thalassaemia 1 gene are at risk of having a foetus with the most severe thalassaemia, Hb Bart's hydrops fetalis, with a risk of maternal mortality. However, haematological parameters alone cannot distinguish between a α-thalassaemia 1 carrier and a homozygous α-thalassaemia 2, in which one α-globin gene has been deleted on each chromosome. A rapid and accurate molecular detection assay is essential for prevention of the disease in populations where α-thalassaemia 1 is common. Multiplex Gap-PCR analysis is widely used for diagnosis of α-thalassaemia. However, the technique requires a thermocycler and post-amplification processing, which limits its application in primary care or in rural areas in developing countries. Loop mediated isothermal amplification (LAMP) amplifies target DNA at a constant temperature and does not require a thermocycler. This study developed a colorimetric Gap-LAMP using malachite green to allow naked eye visualization of two deletional α-thalassaemia 1 commonly found in Asian populations, the Southeast Asian type (--^SEA) and the Thai type (--^THAI) deletions. The Gap-LAMP was performed on DNA samples from 410 individuals carrying various α-thalassaemia gene defects with 100% concordance with conventional Gap-PCR analysis. This method eliminates post-amplification processing or the use of expensive sophisticated equipment and allows screening large populations for the prevention and control of α-thalassaemia.

Molecular Basis and Genetic Modifiers of Thalassemia

Thalassemia syndromes are common monogenic disorders and represent a significant health issue worldwide. In this review, the authors elaborate on fundamental genetic knowledge about thalassemias, including the structure and location of globin genes, the production of hemoglobin during development, the molecular lesions causing α-, β-, and other thalassemia syndromes, the genotype-phenotype correlation, and the genetic modifiers of these conditions. In addition, they briefly discuss the molecular techniques applied for diagnosis and innovative cell and gene therapy strategies to cure these conditions.

Placenta-Derived Extracellular Vesicles in Pregnancy Complications and Prospects on a Liquid Biopsy for Hemoglobin Bart's Disease

Extracellular vesicles (EVs) are nano-scaled vesicles released from all cell types into extracellular fluids and specifically contain signature molecules of the original cells and tissues, including the placenta. Placenta-derived EVs can be detected in maternal circulation at as early as six weeks of gestation, and their release can be triggered by the oxygen level and glucose concentration. Placental-associated complications such as preeclampsia, fetal growth restriction, and gestational diabetes have alterations in placenta-derived EVs in maternal plasma, and this can be used as a liquid biopsy for the diagnosis, prediction, and monitoring of such pregnancy complications. Alpha-thalassemia major ("homozygous alpha-thalassemia-1") or hemoglobin Bart's disease is the most severe form of thalassemia disease, and this condition is lethal for the fetus. Women with Bart's hydrops fetalis demonstrate signs of placental hypoxia and placentomegaly, thereby placenta-derived EVs provide an opportunity for a non-invasive liquid biopsy of this lethal condition. In this article, we introduced clinical features and current diagnostic markers of Bart's hydrops fetalis, extensively summarize the characteristics and biology of placenta-derived EVs, and discuss the challenges and opportunities of placenta-derived EVs as part of diagnostic tests for placental complications focusing on Bart's hydrop fetalis.

The impact of in utero transfusions on perinatal outcomes in patients with alpha thalassemia major: the UCSF registry

Alpha thalassemia major (ATM) is a hemoglobinopathy that usually results in perinatal demise if in utero transfusions (IUTs) are not performed. We established an international registry (NCT04872179) to evaluate the impact of IUTs on survival to discharge (primary outcome) as well as perinatal and neurodevelopmental secondary outcomes. Forty-nine patients were diagnosed prenatally, 11 were diagnosed postnatally, and all 11 spontaneous survivor genotypes had preserved embryonic zeta-globin levels. We compared 3 groups of patients; group 1, prenatally diagnosed and alive at hospital discharge (n = 14), group 2, prenatally diagnosed and deceased perinatally (n = 5), and group 3, postnatally diagnosed and alive at hospital discharge (n = 11). Group 1 had better outcomes than groups 2 and 3 in terms of the resolution of hydrops, delivery closer to term, shorter hospitalizations, and more frequent average or greater neurodevelopmental outcomes. Earlier IUT initiation was correlated with higher neurodevelopmental (Vineland-3) scores (r = -0.72, P = .02). Preterm delivery after IUT was seen in 3/16 (19%) patients who continued their pregnancy. When we combined our data with those from 2 published series, patients who received ≥2 IUTs had better outcomes than those with 0 to 1 IUT, including resolution of hydrops, delivery at ≥34 weeks gestation, and 5-minute appearance, pulse, grimace, activity, and respiration scores ≥7. Neurodevelopmental assessments were normal in 17/18 of the ≥2 IUT vs 5/13 of the 0 to 1 IUT group (OR 2.74; P = .01). Thus, fetal transfusions enable the survival of patients with ATM and normal neurodevelopment, even in those patients presenting with hydrops. Nondirective prenatal counseling for expectant parents should include the option of IUTs.

Erythroid overproduction of erythroferrone causes iron overload and developmental abnormalities in mice

The hormone erythroferrone (ERFE) is produced by erythroid cells in response to hemorrhage, hypoxia, or other erythropoietic stimuli, and it suppresses the hepatic production of the iron-regulatory hormone hepcidin, thereby mobilizing iron for erythropoiesis. Suppression of hepcidin by ERFE is believed to be mediated by interference with paracrine bone morphogenetic protein (BMP) signaling that regulates hepcidin transcription in hepatocytes. In anemias with ineffective erythropoiesis, ERFE is pathologically overproduced, but its contribution to the clinical manifestations of these anemias is not well understood. We generated 3 lines of transgenic mice with graded erythroid overexpression of ERFE and found that they developed dose-dependent iron overload, impaired hepatic BMP signaling, and relative hepcidin deficiency. These findings add to the evidence that ERFE is a mediator of iron overload in conditions in which ERFE is overproduced, including anemias with ineffective erythropoiesis. At the highest levels of ERFE overexpression, the mice manifested decreased perinatal survival, impaired growth, small hypofunctional kidneys, decreased gonadal fat depots, and neurobehavioral abnormalities, all consistent with impaired organ-specific BMP signaling during development. Neutralizing excessive ERFE in congenital anemias with ineffective erythropoiesis may not only prevent iron overload but may have additional benefits for growth and development.

Alpha Globin Gene Copy Number Is Associated with Prevalent Chronic Kidney Disease and Incident End-Stage Kidney Disease among Black Americans

BACKGROUND

α-Globin is expressed in endothelial cells of resistance arteries, where it limits endothelial nitric oxide signaling and enhances α-adrenergic-mediated vasoconstriction. α-Globin gene (HBA) copy number is variable in people of African descent and other populations worldwide. Given the protective effect of nitric oxide in the kidney, we hypothesized that HBA copy number would be associated with kidney disease risk.

METHODS

Community-dwelling Black Americans aged ≥45 years old were enrolled in a national longitudinal cohort from 2003 through 2007. HBA copy number was measured using droplet digital PCR. The prevalence ratio (PR) of CKD and the relative risk (RR) of incident reduced eGFR were calculated using modified Poisson multivariable regression. The hazard ratio (HR) of incident ESKD was calculated using Cox proportional hazards multivariable regression.

RESULTS

Among 9908 participants, HBA copy number varied from 2 to 6. In analyses adjusted for demographic, clinical, and genetic risk factors, a one-copy increase in HBA was associated with 14% greater prevalence of CKD (PR, 1.14; 95% CI, 1.07 to 1.21; P<0.0001). While HBA copy number was not associated with incident reduced eGFR (RR, 1.06; 95% CI, 0.94 to 1.19; P=0.38), the hazard of incident ESKD was 32% higher for each additional copy of HBA (HR, 1.32; 95% CI, 1.09 to 1.61; P=0.005).

CONCLUSIONS

Increasing HBA copy number was associated with a greater prevalence of CKD and incidence of ESKD in a national longitudinal cohort of Black Americans.

Advances in the management of α-thalassemia major: reasons to be optimistic

α-Thalassemia major (ATM) is a severe disease resulting from deletions in all 4 copies of the α-globin gene. Although it is usually fatal before birth, the advent of in utero transfusions has enabled survival of a growing number of children. Postnatal therapy consists of chronic transfusions or stem cell transplantation, similar to patients with β-thalassemia major. In this review, we discuss the experience with postnatal stem cell transplantation in patients with ATM, as well as the ongoing phase 1 clinical trial of in utero stem cell transplantation for this condition.

Prenatal diagnosis of thalassemia in 695 pedigrees from southeastern China: a 10-year follow-up study

Thalassaemia is highly prevalent in southeastern China. This 10-year follow-up study aimed to characterize the genotype and karyotype of thalassaemia in fetal samples derived from thalassemia carriers in Fujian province, southeastern China. A total of 476 prenatal samples from 472 couples carrying α-thalassaemia traits and 224 samples from 223 couples carrying β-thalassaemia traits were collected for STR analysis, detection of thalassemia genotypes and karyotyping. The common deletional α-thalassemias and rare thalassemia genotypes were detected using Gap-PCR assay, and the common β-globin gene mutations were detected using PCR-RDB assay. We detected 43.49% prevalence of α-thalassaemia minor, 26.05% prevalence of α-thalassaemia intermediate and major and 1.89% prevalence of rare form among the 476 prenatal samples from couples with α-thalassaemia, and 85 fetuses with β-thalassemia heterozygote, 16 with homozygote and 21 with double heterozygote, and a rare β^{IVS-2-654(C→T)} /Chinese G_γ (^A γδβ)⁰  genotype among the 224 prenatal samples from couples with β-thalassemia. Karyotyping showed 7 fetuses with abnormal karyotypes. Totally 153 pregnancies were terminated, and genetic diagnosis of thalassemia using fetal umbilical cord blood following induction of labor showed consistent results with prenatal diagnosis. No thalassemia phenotypes were identified in normal infants half a year after birth, and the infants with α-thalassemia and β-thalassemia minor had no or mild anemia symptoms, but normal development, while 15 babies with hemoglobin H disease presented moderate anemia symptoms. Our data suggest the pregestational screening of thalassemia, notably compound and rare forms of thalassemia, for couples carrying thalassemia traits.

Reactivation of a developmentally silenced embryonic globin gene

The α- and β-globin loci harbor developmentally expressed genes, which are silenced throughout post-natal life. Reactivation of these genes may offer therapeutic approaches for the hemoglobinopathies, the most common single gene disorders. Here, we address mechanisms regulating the embryonically expressed α-like globin, termed ζ-globin. We show that in embryonic erythroid cells, the ζ-gene lies within a ~65 kb sub-TAD (topologically associating domain) of open, acetylated chromatin and interacts with the α-globin super-enhancer. By contrast, in adult erythroid cells, the ζ-gene is packaged within a small (~10 kb) sub-domain of hypoacetylated, facultative heterochromatin within the acetylated sub-TAD and that it no longer interacts with its enhancers. The ζ-gene can be partially re-activated by acetylation and inhibition of histone de-acetylases. In addition to suggesting therapies for severe α-thalassemia, these findings illustrate the general principles by which reactivation of developmental genes may rescue abnormalities arising from mutations in their adult paralogues.

A Small Key for a Heavy Door: Genetic Therapies for the Treatment of Hemoglobinopathies

Throughout the past decades, the search for a treatment for severe hemoglobinopathies has gained increased interest within the scientific community. The discovery that ɤ-globin expression from intact HBG alleles complements defective HBB alleles underlying β-thalassemia and sickle cell disease, has provided a promising opening for research directed at relieving ɤ-globin repression mechanisms and, thereby, improve clinical outcomes for patients. Various gene editing strategies aim to reverse the fetal-to-adult hemoglobin switch to up-regulate ɤ-globin expression through disabling either HBG repressor genes or repressor binding sites in the HBG promoter regions. In addition to these HBB mutation-independent strategies involving fetal hemoglobin (HbF) synthesis de-repression, the expanding genome editing toolkit is providing increased accuracy to HBB mutation-specific strategies encompassing adult hemoglobin (HbA) restoration for a personalized treatment of hemoglobinopathies. Moreover, besides genome editing, more conventional gene addition strategies continue under investigation to restore HbA expression. Together, this research makes hemoglobinopathies a fertile ground for testing various innovative genetic therapies with high translational potential. Indeed, the progressive understanding of the molecular clockwork underlying the hemoglobin switch together with the ongoing optimization of genome editing tools heightens the prospect for the development of effective and safe treatments for hemoglobinopathies. In this context, clinical genetics plays an equally crucial role by shedding light on the complexity of the disease and the role of ameliorating genetic modifiers. Here, we cover the most recent insights on the molecular mechanisms underlying hemoglobin biology and hemoglobinopathies while providing an overview of state-of-the-art gene editing platforms. Additionally, current genetic therapies under development, are equally discussed.

Long noncoding RNA CCDC26 as a modulator of transcriptional switching between fetal and embryonic globins

The CCDC26 gene is considered to encode a functional noncoding RNA associated with acute myeloid leukemia and other cancers. However, investigations into the physiological roles of CCDC26 are rare. Previously, we reported that CCDC26 regulated proliferation and cell death of leukemia cells through KIT, a receptor tyrosine kinase, by using K562 leukemia cells and their derivative CCDC26-knockdown (KD) cells. Here we propose a new role of CCDC26 in the differentiation of erythroid cells. We showed that expression of embryonic (ε- and ζ-) globins was markedly upregulated in CCDC26-KD cells compared with K562 control cells during hemin-induced differentiation. In contrast, expression of fetal-type γ-globin, a major globin expressed in original K562 cells, was decreased. These changes in the expression of globin genes mainly took place at the transcriptional level, with significant suppression of transcription of adult (β-, δ-) globins in CCDC26-KD cells. Re-introduction of exogenous CCDC26 into the CCDC26-KD cells recovered low-level expression of the embryonal globins. These results suggest CCDC26 has a role in switching transcription of globin genes in the differentiation of erythroid cells. The expression profile of the CCDC26-KD cells and control cells suggests FOG-2, a transcriptional modulator, as a candidate for a mediator of the CCDC26-associated regulation. We showed that both embryonic globins were transcriptionally activated in FOG-2-KD K562 cells. The KIT inhibitor ISCK03 suppressed the production of hemoglobin in K562 cells but did not affect transcription of globin genes. To summarize, FOG-2, but not KIT, is responsible for globin transcriptional regulation by CCDC26.

Electrophoresis features and genotypes of Hb bart's hydrops fetalis

Hydrops fetalis syndrome (Hb Bart's disease) is one of the common fetal development abnormalities and the most severe form of α-thalassemia. It causes fetal death during the third trimester or shortly after birth. The aim of this study is to investigate the feature of Hb Bart's disease by Capillary electrophoresis (CE) and its genotypes. A total of 38 cases of suspected fetal Hb Bart's disease were analyzed by B-ultrasound and CE, including 17 with 24-28 weeks of pregnancy, 9 with 29-32 weeks of pregnancy, and 12 with 33-38 weeks of pregnancy. All cases were then identified by DNA analysis. The minimum concentration of Hb Bart's was 72.2% and the highest 90.9%. Hb Bart's fraction increased while that of Hb Portland decreased with the duration of pregnancy. In order to avoid serious maternal morbidity, it is necessary to diagnose Hb Bart's disease as soon as possible and CE can be used as a method of rapid diagnosis.

Genetic investigation of haemoglobinopathies in a large cohort of asymptomatic individuals reveals a higher carrier rate for β-thalassaemia in Sichuan Province (Southwestern China)

The incidence of haemoglobinopathy is high in China, especially south of the Yangtze River. However, the exact status of haemoglobinopathy in Sichuan is unknown. To carry out a detailed research of haemoglobinopathy in individuals living in Sichuan, 13,298 subjects without clinical symptoms who were living in Sichuan Province, with an age distribution of 5–73 years, were included in this study. Between March 2014 and July 2017, these subjects received examinations at the Medical Lab of Chengdu Women's & Children's Central Hospital. Mean corpuscular volume (MCV) < 82 fL or mean corpuscular haemoglobin (MCH) < 27 pg was used to indicate haemoglobinopathy carriers. Abnormal haemoglobin was screened by electrophoresis, and genes were sequenced to identify genotypes. Genotype diagnosis of alpha- and beta-thalassaemia was carried out by using PCR and shunt hybridization. There were 638 suspected haemoglobinopathy carriers (4.80%, 638/13,298). DNA sequencing identified 6 subjects with abnormal haemoglobin genotypes and 15 subjects with Hb E. The frequency of heterozygosity for thalassaemia was 4.12% (1.48% for α-thalassaemia and 2.61% for β-thalassaemia) in Sichuan Province. The mutation spectrum of α-thalassaemia consisted of the five most common mutations: --^SEA, -α^3.7, -α^4.2, α^CS, and α^QS. Seven types of β-thalassaemia mutation were found in this study: CD41-42 (-TTCT) was the most frequent (28.47%), followed by 17 (A > T), −28 (A > G), and IVS-II-654 (C > T). The main abnormal haemoglobin genotype (HbE) and thalassaemia genotype (--^SEA, CD41-42 (-TTCT)) were consistent with those in other regions of China, but the carrier rate of β-thalassaemia in Sichuan was higher than that of α-thalassaemia.