Thalassaemia in China

Development and clinical validation of a novel detection kit for α-thalassemia in southern Chinese

Objective

This study aimed to develop and assess a novel reverse dot blot assay for the simultaneous detection of 10 types of α-thalassemia alleles in the Chinese population, including six common variants of-SEA, -α3.7, -α4.2, αCS, αQS, and αWS, and four rare variants of αααanti-4.2, αααanti-3.7, --FIL deletion and--THAI deletion.

Methods

The novel thalassemia gene assay utilized a two-tier multiplex polymerase chain reaction amplification system and one round of hybridization. Genomic DNA samples were sourced from three hospitals in southern China. Each clinically validated DNA sample was re-evaluated using the new multiplex polymerase chain reaction/reverse dot blot assay Ⅲ (M-PCR/RDB Ⅲ).

Results

The study analyzed a total of 1,148 unrelated participants, consisting of 810 thalassemia patients and 338 healthy control subjects. Valid hybridization results were obtained for 1,147 samples, with one case (thalassemia carrier) being excluded from the study due to the poor quality of DNA. All 1,147 samples, including those with α heterozygous thalassemia, α homozygous thalassemia, α compound heterozygous thalassemia, and control subjects were accurately genotyped, showing 100% concordance with the reference assays.

Conclusion

The novel M-PCR/RDB Ⅲ assay proved to be simple, rapid, and precise, indicating its potential for genetic screening and clinical diagnosis of both common and rare α-thalassemia variants in Chinese populations.

CRISPR/Cas12a-triggered ordered concatemeric DNA probes signal-on/off multifunctional analytical sensing system for ultrasensitive detection of thalassemia

Based on CRISPR/Cas12a triggered ordered concatemeric DNA probes, a "on/off" self-powered biosensor is developed to achieve highly sensitive detection of thalassemia gene CD142 through open-circuit potential-assisted visual signal output. The ingeniously constructed glucose oxidase (GOD)-functionalized ordered concatemeric DNA probe structure can significantly amplify signal output, while the coupled CRISPR/Cas12a system is served as a "signal switch" with excellent signal-transducing capabilities. When the ordered concatemeric DNA probe structure is anchored on electrode, the response signal of the sensing system is in the "signal on" mode. While, the presence of the target activates the non-specific cleavage activity of the CRISPR/Cas12a system, causing the sensing system to switch to the "signal off" mode. In the detection system, GOD catalyzes the oxidation of glucose to produce hydrogen peroxide, which further catalyzes the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) to form a color product, enabling visual signal of the target through naked-eye color contrast. By employing a multifunctional analytical mode combining electrochemical and visual signal outputs, accurate determination of the target is achieved, with linear ranges of 0.0001-100 pM, and detection limits of 48.1 aM (S/N = 3). This work provides a reference method for sensitive detection of thalassemia genes and holds great diagnostic potential in biomedical applications.

A case report on congenital hypothyroidism and alpha thalassemia in children with anemia and muscle damage as the main manifestation

RATIONALE

This study reports the first case of congenital hypothyroidism (CH) and alpha thalassemia in a child in China, with anemia and muscle damage as the main manifestations. Analyzing and studying this case is of great significance in reducing missed and misdiagnosed CH and will provide a clinical strategy for treating these patients.

PATIENT CONCERNS

Child, female, 2 years and 7 months old, the child appeared dispirited, had poor appetite, shallow complexion, reduced activities with anemia, elevated muscle enzymes, height, and growth retardation.

DIAGNOSES

The child was diagnosed with CH with alpha thalassemia.

INTERVENTIONS

The patient was treated with levothyroxine sodium and anemia correction.

OUTCOMES

The children's current spirit, appetite, red face, normal limb activity, physical development, and intelligence were significantly better than those of normal children of the same age.

CONCLUSIONS

CH with alpha thalassemia, especially anemia and muscle damage as the main manifestations, has not been reported. Administration of levothyroxine sodium is effective in correcting anemia in patients with CH and alpha thalassemia.

LESSON

Due to CH and alpha thalassemia, there are no specific symptoms and they are prone to missed diagnosis and misdiagnosis. Therefore, patients with anemia and elevated muscle enzyme levels should be routinely tested for thyroid function to diagnose them early and provide proper treatment to avoid negative consequences.

Mitoxantrone ameliorates ineffective erythropoiesis in a β-thalassemia intermedia mouse model

ABSTRACT

β-thalassemia is a condition characterized by reduced or absent synthesis of β-globin resulting from genetic mutations, leading to expanded and ineffective erythropoiesis. Mitoxantrone has been widely used clinically as an antitumor agent considering its ability to inhibit cell proliferation. However, its therapeutic effect on expanded and ineffective erythropoiesis in β-thalassemia is untested. We found that mitoxantrone decreased α-globin precipitates and ameliorated anemia, splenomegaly, and ineffective erythropoiesis in the HbbTh3/+ mouse model of β-thalassemia intermedia. The partially reversed ineffective erythropoiesis is a consequence of effects on autophagy as mitochondrial retention and protein levels of mTOR, P62, and LC3 in reticulocytes decreased in mitoxantrone-treated HbbTh3/+ mice. These data provide significant preclinical evidence for targeting autophagy as a novel therapeutic approach for β-thalassemia.

Prevalence of anemia of varying severity, geographic variations, and association with metabolic factors among women of reproductive age in China: a nationwide, population-based study

To investigate the epidemiological characteristics of anemia of varying severity among women of reproductive age, we conducted a nationwide, cross-sectional study between January 1, 2019 and December 31, 2019, including 4 184 547 nonpregnant women aged 18-49 years from all 31 provinces in the mainland of China. Anemia was defined as having hemoglobin concentration < 120.0 g/L and categorized as mild, moderate, and severe. Multivariate logistic models with cluster effect were used to explore the association of anemia and metabolic risk factors. The standardized prevalence of anemia and moderate and worse anemia among women of reproductive age in China was 15.8% (95% CI 15.1%-16.6%) and 6.6% (6.3%-7.0%), respectively. The prevalence of anemia and the proportion of moderate and worse anemia significantly increased with age. We also observed great geographic variations in the prevalence of anemia, with a high likelihood in south, central, and northwest China. Moderate and/or severe anemia was positively associated with overweight and obesity, diabetes, and impaired kidney function. In conclusion, anemia remains a significant challenge for women of reproductive age in China. Geographic variations and metabolic risk factors should be considered in the comprehensive and targeting strategy for anemia reduction.

Identification of a Novel 16.8Kb Deletion of the α-Globin Gene Cluster by Third-Generation Sequencing

α-thalassemia major (α-TM) often causes Hb Bart's (c4) hydrops fetalis and severe obstetric complications in the mother. Step-wise screening for couples at risk of having offspring(s) affected by α-TM is the efficient prevention method but some rare genotypes of thalassemia cannot be detected. A 32-year-old male with low HbA2 (2.4%) and mild anemia was performed real-time PCR-based multicolor melting curve analysis (MMCA) because his wife was -SEA deletion carrier. The result of multiplex ligation-dependent probe amplification (MLPA) suggested the existence of -SEA deletion in the proband. A novel deletion of the α-globin gene cluster was found using self-designed MLPA probes combined with longer PCR, which was further accurately described to be 16.8Kb (hg38, Chr16:1,65,236-1,82,113) deletion by the third-generation sequencing. A fragment ranging from 1,53,226 to 1,54,538(GRch38/hg38) was identified which suggested the existence of the homologous recombination event. The third-generation sequencing is accurate and efficient in obtaining accurate information for complex structural variations.

β-Thalassemia gene editing therapy: Advancements and difficulties

β-Thalassemia is the world's number 1 single-gene genetic disorder and is characterized by suppressed or impaired production of β-pearl protein chains. This results in intramedullary destruction and premature lysis of red blood cells in peripheral blood. Among them, patients with transfusion-dependent β-thalassemia face the problem of long-term transfusion and iron chelation therapy, which leads to clinical complications and great economic stress. As gene editing technology improves, we are seeing the dawn of a cure for the disease, with its reduction of ineffective erythropoiesis and effective prolongation of survival in critically ill patients. Here, we provide an overview of β-thalassemia distribution and pathophysiology. In addition, we focus on gene therapy and gene editing advances. Nucleic acid endonuclease tools currently available for gene editing fall into 3 categories: zinc finger nucleases, transcription activator-like effector nucleases, and regularly interspaced short palindromic repeats (CRISPR-Cas9) nucleases. This paper reviews the exploratory applications and exploration of emerging therapeutic tools based on 3 classes of nucleic acid endonucleases in the treatment of β-thalassemia diseases.

Molecular Characterization of α- and β-Thalassemia Among Children Less Than 18 Years Old in Guizhou, China

BACKGROUND

Thalassemia is an inherited hemolytic disease, the complications and sequelae of which have posed a huge impact on both patients and society. But limited studies have investigated the molecular characterization of α- and β-thalassemia in children from Guizhou, China.

METHODS

Between January 2019 and December 2022, a total of 3301 children, aged 6 months to 18 years, suspected of having thalassemia underwent molecular analysis.

RESULTS

Out of the total sample, 824 (25%) children were found to carry thalassemia mutations. The carrier rates of α-thalassemia, β-thalassemia, and α + β-thalassemia were determined as 8.1%, 15.6%, and 1.3%, respectively. Approximately 96.5% of the α-thalassemia gene mutations were --SEA (51%), ααCS (20.9%), -α3.7 (19.6%), and -α4.2 (5.0%). The most prevalent mutations of β-thalassemia were βCD17(A>T) (41.5%), βCD41-42(-TTCT) (37.7%), and βIVS-II-654(C>T) (11.3%). Additionally, we identified rare cases, including one case with ααHb Nunobiki/αα, two cases with triplicated α-thalassemia (one case with ααα/ααα and βCD41-42/βN and the other with ααα-3.7/αα and βE CD26/βN), and also one case with α Q-Thailandα/-α4.2 and βCD41-42/βN.

CONCLUSIONS

Our study findings provide important insights into the heterogeneity of thalassemia carrier rates and molecular profiles among children in the Guizhou region. The findings support the development of prevention strategies to reduce the incidence of severe thalassemia in the future.

Development of preimplantation genetic testing for monogenic reference materials using next-generation sequencing

OBJECTIVE

Preimplantation genetic testing for monogenic disorders (PGT-M) has been used for over 20 years to detect many serious genetic conditions. However, there is still a lack of reference materials (RMs) to validate the test performance during the development and quality control of PGT-M.

METHOD

Sixteen thalassemia cell lines from four thalassemia families were selected to establish the RMs. Each family consisted of parents with heterozygous mutations for α- and/or β-thalassemia and two children, at least one of whom carried a homozygous thalassemia mutation (proband). The RM panel consisted of 12 DNA samples (parents and probands in 4 families) and 4 simulated embryos (cell lines constructed from blood samples from the four nonproband children). Four accredited genetics laboratories that offer verification of thalassemia samples were invited to evaluate the performance of the RM panel. Furthermore, the stability of the RMs was determined by testing after freeze‒thaw cycles and long-term storage.

RESULTS

PGT-M reference materials containing 12 genome DNA (gDNA) reference materials and 4 simulated embryo reference materials for thalassemia testing were successfully established. Next-generation sequencing was performed on the samples. The genotypes and haplotypes of all 16 PGT-M reference materials were concordant across the four labs, which used various testing workflows. These well-characterized PGT-M reference materials retained their stability even after 3 years of storage.

CONCLUSION

The establishment of PGT-M reference materials for thalassemia will help with the standardization and accuracy of PGT-M in clinical use.

Genetic epidemiology of thalassemia in couples of childbearing age: over 6 years of a thalassemia intervention project

BACKGROUND

Shenzhen is one of the most populated metropolises in southern China where thalassemia is highly prevalent. The prevention of thalassemia inheritance is an ambition of child-bearing couples.

METHODS AND RESULTS

A total of 22,098 peripheral blood samples were collected from 11,049 potentially at-risk couples of childbearing age from Shenzhen. Thalassemia mutations were determined by PCR-based flow-through hybridization. The results identified 45.02% of the participants (9948 out of 22,098) as harboring globin gene mutations, distributed into 18 α-thalassemia alleles detected in 71.48% (7111 out of 9948) and 15 β-thalassemia alleles detected in 32.68% (3252 out of 9948) of all mutant individuals, among which 415 individuals carried both α- and β-thalassemia alleles. The most frequent phenotypes for α-globin variations were --SEA/αα (63.37%), -α3.7/αα (18.66%), and -α4.2/αα (7.31%), and those for β-globin variations were β41-42/βN (34.96%), β654/βN (28.11%), and β17/βN (13.84%). A total of 970 high-risk couples who could possibly give birth to offspring with thalassemia intermedia or major were identified. In addition, the hematological indices were compared among thalassemia genotypes. Significant differences in MCH, MCV, Hb A, and Hb A2 levels among α-thalassemia minor (α+), trait (α0), and intermediate phenotypes (P < 0.05) and between βE/βN and the other β-thalassemia phenotypes (P < 0.05) were found. Moreover, GAP-PCR and next-generation sequencing further identified 42 rare mutations, 13 of which were first reported in the Chinese population. A novel mutation in the β-globin gene (HBB: c.246 C > A (rs145669504)) was also discovered.

CONCLUSIONS

This study presented a comprehensive analysis of thalassemia variations in a population from Shenzhen and may offer valuable insights for thalassemia control and intervention strategies in this area.