Advances in Hemoglobinopathies and Thalassemia Evaluation.

Hemoglobin (Hb) disorders are among the most prevalent inherited diseases. Despite a limited number of involved genes, these conditions represent a broad clinical and prognostic spectrum. The menu of laboratory tests is extensive. From widely available modalities, for example, complete blood count to rather sophisticated molecular technologies, the investigation of Hb disorders recapitulates an increasing complexity of laboratory workup in other medical fields. This review highlights a current state of biochemical and molecular investigation of Hb disorders and offers a glimpse on technologies that are yet to be fully embraced in clinical practice.

Universal Targeted Haplotyping by Droplet Digital PCR Sequencing and Its Applications in Noninvasive Prenatal Testing and Pharmacogenetics Analysis.

BACKGROUND: The analysis of haplotypes of variants is important for pharmacogenomics analysis and noninvasive prenatal testing for monogenic diseases. However, there is a lack of robust methods for targeted haplotyping. METHODS: We developed digital PCR haplotype sequencing (dHapSeq) for targeted haplotyping of variants, which is a method that compartmentalizes long DNA molecules into droplets. Within one droplet, 2 target regions are PCR amplified from one template molecule, and their amplicons are fused together. The fused products are then sequenced to determine the phase relationship of the single nucleotide polymorphism (SNP) alleles. The entire haplotype of 10s of SNPs can be deduced after the phase relationship of individual SNPs are determined in a pairwise manner. We applied dHapSeq to noninvasive prenatal testing in 4 families at risk for thalassemia and utilized it to detect NUDT15 diplotypes for predicting drug tolerance in pediatric acute lymphoblastic leukemia (72 cases and 506 controls). RESULTS: For SNPs within 40 kb, phase relation can be determined with 100% accuracy. In 7 trio families, the haplotyping results for 97 SNPs spanning 185 kb determined by dHapSeq were concordant with the results deduced from the genotypes of both parents and the fetus. In 4 thalassemia families, a 19.3-kb Southeast Asian deletion was successfully phased with 97 downstream SNPs, enabling noninvasive determination of fetal inheritance using relative haplotype dosage analysis. In the NUDT15 analysis, the variant status and phase of the variants were successfully determined in all cases and controls. CONCLUSIONS: The dHapSeq represents a robust and scalable haplotyping approach with numerous clinical and research applications.

Comprehensive analysis of thalassemia alleles (CATSA) based on third-generation sequencing is a comprehensive and accurate approach for neonatal thalassemia screening.

Thalassemia is one of the most common and damaging monogenic diseases in the world. It is caused by pathogenic variants of α- and/or ß-globin genes, which disrupt the balance of these two protein chains and leads to α-thalassemia or ß-thalassemia, respectively. Patients with α-thalassemia or ß-thalassemia could exhibit a severe phenotype, with no simple and effective treatment. A three-tiered strategy of carrier screening, prenatal diagnosis and newborn screening has been established in China for the prevention and control of thalassemia, of which the first two parts have been studied thoroughly. The implementation of neonatal thalassemia screening is lagging, and the effectiveness of various screening programs has not yet been demonstrated. In this study, hemoglobin capillary electrophoresis (CE), hotspot testing method, and third-generation sequencing (TGS) were used in the variant detection of 2000 newborn samples, to assess the efficacy of these methods in neonatal thalassemia screening. Compared with CE (249, 12.45 %) and hotspot analysis (424, 21.2 %), CATSA detected the largest number of thalassemia variants (535, 26.75 %), which included 24 hotspot variants, increased copy number of α-globin gene, rare pathogenic variants, and three unreported potentially disease-causing variants. More importantly, CATSA directly determined the cis-trans relationship of variants in three newborns, which greatly shortens the clinical diagnosis time of thalassemia. CATSA showed a great advantage over other genetic tests and could become the most powerful technical support for the three-tiered prevention and control strategy of thalassemia.

[Analysis of rare mutations associated with Thalassemia and their hematological characteristics in Chenzhou region of Hunan Province].

OBJECTIVE: To explore the distribution and hematological characteristics of rare thalassemia-associated mutations in Chenzhou region of Hunan Province with an aim to provide a basis for genetic counseling and effective prevention. METHODS: A total of 37 370 individuals enrolled from January 2015 to December 2021 were screened by routine blood test and hemoglobin electrophoresis. The genotypes were determined with high-throughput sequencing. RESULTS: A total of 8 455 thalassemia mutations (including 185 rare ones) were detected, which had involved 27 mutational types. Rare type α-Thalassemia --THAI and CD31 (AGG>AAG) have the typical microcytic hypochromic hematological features, whilst SEA-HPFH, CD14 (CTG>-TG), CD37 (TGG>TAG), -90(C>T), Codon 15 (G>A), IVS-I-128 (T>G), CD86 (GCC>GC-) and Chinese Gγ+(Aγδß)0 had typical microcytic hypochromic and ß-thalassemia-associated hematological features of elevated HbA2 or HbF. In addition, the -50（G>A）heterozygotes of ß-thalassemia had normal or slightly decreased MCV and MCH without an increase in HbA2. CONCLUSION: Various forms of thalassemia-associated mutations have been identified in the Chenzhou region of Hunan Province. Above finding has facilitated development of preventive and control strategies for thalassemia as well as birth health programs.

Noninvasive Prenatal Diagnosis of SEA-Thalassemia by Combining 1000 Genomes Database and Relative Haplotype Dosage.

To explore a noninvasive method for diagnosis of SEA-thalassemia and to investigate whether the regional factors affect the accuracy of this method. The method involved using a public database and bioinformatics software to construct parental haplotypes for proband and predicting fetal genotypes using relative haplotype dosage. We screened and downloaded sequencing data of couples who were both SEA-thalassemia carriers from the China National Genebank public data platform, and matched the sequencing data format with that of the reference panel using Ubuntu system tools. We then used Beagle software to construct parental haplotypes, predicted fetal haplotypes by relative haplotype dosage. Finally, we used Hidden Markov Model and Viterbi algorithm to determine fetal pathogenic haplotypes. All noninvasive fetal genotype diagnosis results were compared with gold standard gap-PCR electrophoresis results. Our method was successful in diagnosing 13 families with SEA-thalassemia carriers. The best diagnostic results were obtained when Southern Chinese Han was used as the reference panel, and 10 families showed full agreement between our noninvasive diagnostic results and the gap-PCR electrophoresis results. The accuracy of our method was higher when using a Chinese Han as the reference panel for haplotype construction in the Southern Chinese Han region as opposed to Beijing Chinese region. The combined use of public databases and relative haplotype dosage for diagnosing SEA-thalassemia is a feasible approach. Our method produces the best noninvasive diagnostic results when the test samples and population reference panel are closely matched in both ethnicity and geography. When constructing parental haplotypes with our method, it is important to consider the effect of region in addition to population background alone.

[Progress in the Genetic Detection of Thalassemia Based on Third-Generation Gene Sequencing --Review].

Thalassemia is most widely distributed single gene autosome recessive genetic disease in the world, whose clinical manifestation was changed from asymptomatic anemia to severe anemia requiring continous blood transfusion to maintain life, thus resulting in a serious economic burden to society and families. Therefore, it is necessary to carry out the corresponding prentatal screening and diagnosis. Most of the conventional detection methods can only detect the common thalassemia genotype, it can easy to cause misdiagnosis or missed diagnosis for those rate genetic variantions. The third-generation sequecing (TGS) has been applied to the detection of thalassemia genes, which is more accurate, reliable and superior to the converntional detection methods. This article reviews the latest research progress of the TGS technology in genetic testing of thalassemia.

Regulation of N6-methyladenosine modification in erythropoiesis and thalassemia.

In eukaryotic RNA, N6-methyladenosine (m6A) is a prevalent form of methylation modification. The m6A modification process is reversible and dynamic, written by m6A methyltransferase complex, erased by m6A demethylase, and recognized by m6A binding proteins. Through mediating RNA stability, decay, alternative splicing, and translation processes, m6A modification regulates gene expression at the post-transcriptional level. Erythropoiesis is the process of hematopoietic stem cells undergoing proliferation, a series of differentiation and maturation to form red blood cells (RBCs). Thalassemia is a common monogenic disease characterized by excessive production of ineffective RBCs in the peripheral circulation, resulting in hemolytic anemia. Increasing evidence suggests that m6A modification plays a crucial role in erythropoiesis. In this review, we comprehensively summarize the function of m6A modification in erythropoiesis and further generalize the mechanism of m6A modification regulating ineffective erythropoiesis and fetal hemoglobin expression. The purpose is to improve the understanding of the pathogenesis of erythroid dysplasia and offer new perspectives for the diagnosis and treatment of thalassemia.

Systematic review of hematopoietic stem cell gene therapy approach in thalassemia: Comparative analysis in animal models.

Hematopoietic stem cell (HSC) gene therapy has shown potential as a therapeutic approach for thalassemia in recent years. However, a comparison of the varying gene therapy methods of HSC gene therapy in thalassemia has never been reviewed. This study aims to evaluate the utilization of HSC gene therapy approaches in animal models of thalassemia. A systematic review was conducted in five databases: PubMed, EBSCOHost, Science Direct, SCOPUS, and Proquest using a combination of the terms hematopoietic stem cell or hematopoietic stem cell or HSC, thalassemia, genetic therapy or gene therapy and animal model. Only journals published in English between 2008 and 2023 were included. This literature included six studies analyzing the use of HSC gene therapy in thalassemic mice models. The three outcomes being assessed in this review were globin levels, hematological parameters, and red blood cell (RBC) phenotypes. Gene therapy approaches for thalassemia using HSC showed significant improvement in ß-globin levels and RBC phenotypes. Phenotypic improvements were also observed. These outcomes indicate good efficacy in gene therapy for thalassemia in mice models. Furthermore, more studies assessing the efficacy of HSC gene therapy in the human model should be done in future studies.

Retrospective study on the distribution of hemoglobinopathies in Karnataka-A laboratory experience.

AIMS: The importance of screening for hemoglobinopathies is well-documented in India. However, information on the distribution of hemoglobinopathies in Karnataka is lacking. The present study focuses on determining the spectrum of hemoglobinopathies for various districts of Karnataka. MATERIALS AND METHODS AND RESULTS: A retrospective analysis of samples registered for hemoglobinopathies for a period of 5 years (2017-2021) was carried out. A total of 17066 records registered only from the Karnataka region, were anonymized and retrieved. The data included gender, age, district, and results of the tests. The results were based on complete blood count, peripheral smear, and capillary electrophoresis (CE) pattern. The data were revalidated by pathologists, and the unambiguous data were analyzed for the study. One-fourth of the records (25%) showed abnormal hematological parameters. The number of female records (66%) was twice that of males and both genders showed higher distribution of thalassemia, followed by variants and double heterozygotes (DH). Several cases of thalassemia major were identified below the age of 17 years. The majority of thalassemia cases were ß thal and 93% of them were ß thal trait. Among the variants, HbS was more prevalent than HbE. Among the districts, Hassan had a 35.2% thal, Mysuru had a 7.2% variant, and Chitradurga had a 5.5% DH. Thalassemia, variants, and DH were distributed across several districts of Karnataka to various levels. CONCLUSION: The comprehensive retrospective analysis of the spectrum of hemoglobinopathies in various districts of Karnataka serves as evidence to carry out a prospective study on population screening where the incidence of thalassemia and structural variants is high.

Misdiagnosis of ß-Thalassemia Major Due to Chinese Gγ+(Aγδß)0-Thalassemia Combined with ß0-Thalassemia.

δß-thalassemia is a rare type of thalassemia characterized by increased Hb F levels, including mainly Chinese Gγ(Aγδß)0-thalassemia, Yunnanese Gγ(Aγδß)0-thalassemia, Cantonese Gγ(Aγδß)0-thalassemia in China. Due to the low rate of δß-thalassemia carriers, there are few reports of δß-thalassemia combined with ß-thalassemia causing ß-thalassemia major. Herein, we described the combination of Chinese Gγ(Aγδß)0-thalassemia and ß-thalassemia leading to ß-thalassemia major in a Chinese patient. Hemoglobin analysis was performed by capillary electrophoresis (CE). Routine genetic analysis was carried out by gap-polymerase chain reaction (Gap-PCR) and PCR and reverse dot blot (PCR-RDB). Multiple ligation-dependent probe amplification (MLPA) was used to detect the large deletion, and Gap-PCR confirmed the deletion. A CE result showed an elevated Hb F level of 98.7% and 11.7% in the proband and her mother, but the proband was diagnosed with ßCD17M/ßCD17M using routine genetic analysis. However, her father was heterozygous for CD17 in ß-globin, and her mother was detected as SEA heterozygous. The further analysis presented that the proband had actually missed the diagnosis of Chinese Gγ(Aγδß)0-thalassemia by MLPA and PCR-RDB. Finally, the genotype of the proband was corrected from ßCD17M/ßCD17M to ßCD17M/ßGγ(Aγδß)0. This is the first report of Chinese Gγ(Aγδß)0-thalassemia combined with ß-thalassemia resulting in ß-thalassemia major in China. Screening for δß-thalassemia by Hb analysis could be an effective method.

Carrier frequency estimation of pathogenic variants of autosomal recessive and X-linked recessive mendelian disorders using exome sequencing data in 1,642 Thais.

BACKGROUND: People with autosomal recessive disorders often were born without awareness of the carrier status of their parents. The American College of Medical Genetics and Genomics (ACMG) recommends screening 113 genes known to cause autosomal recessive and X-linked conditions in couples seeking to learn about their risk of having children with these disorders to have an appropriate reproductive plan. METHODS: We analyzed the exome sequencing data of 1,642 unrelated Thai individuals to identify the pathogenic variant (PV) frequencies in genes recommended by ACMG. RESULTS: In the 113 ACMG-recommended genes, 165 PV and likely PVs in 60 genes of 559 exomes (34%, 559/1642) were identified. The carrier rate was increased to 39% when glucose-6-phosphate dehydrogenase (G6PD) was added. The carrier rate was still as high as 14.7% when thalassemia and hemoglobinopathies were excluded. In addition to thalassemia, hemoglobinopathies, and G6PD deficiency, carrier frequencies of > 1% were found for Gaucher disease, primary hyperoxaluria, Pendred syndrome, and Wilson disease. Nearly 2% of the couples were at risk of having offsprings with the tested autosomal recessive conditions. CONCLUSIONS: Based on the study samples, the expanded carrier screening, which specifically targeted common autosomal recessive conditions in Thai individuals, will benefit clinical outcomes, regarding preconception/prenatal genetic carrier screening.

[Research progress on differential diagnosis of thalassemia trait and iron deficiency anemia by blood erythrocyte parameters].

Thalassemia trait is an autosomal recessive genetic disease, which is a hemolytic anemia caused by disturbance of erythrocyte hemoglobin production caused by gene mutation or deletion. Iron deficiency anemia is caused by a lack of iron in the body due to an imbalance between the demand and supply of iron. The laboratory manifestations of both are microcytic hypochromic anemia, but the treatment schemes are completely different, and it is difficult to distinguish them from the results of blood count. Erythrocyte parameters can be used to establish a formula or model to differentiate them, which can achieve the purpose of early screening, early diagnosis and early treatment,preventing the occurrence of severe anemia and providing a scientific basis for the thalassemia and iron deficiency anemia prevention. This article will review the research progress of using erythrocyte parameters to distinguish thalassemia trait with iron deficiency anemia.

Third-generation sequencing identified two rare α-chain variants leading to hemoglobin variants in Chinese population.

BACKGROUND: Rare and novel variants of HBA1/2 and HBB genes resulting in thalassemia and hemoglobin (Hb) variants have been increasingly identified. Our goal was to identify two rare Hb variants in Chinese population using third-generation sequencing (TGS) technology. METHODS: Enrolled in this study were two Chinese families from Fujian Province. Hematological screening was conducted using routine blood analysis and Hb capillary electrophoresis analysis. Routine thalassemia gene testing was carried out to detect the common mutations of α- and ß-thalassemia in Chinese population. Rare or novel α- and ß-globin gene variants were further investigated by TGS. RESULTS: The proband of family 1 was a female aged 32, with decreased levels of mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), Hb A2, and abnormal Hb bands in zone 5 and zone 12. No common thalassemia mutations were detected by routine thalassemia analysis, while a rare α-globin gene variant Hb Jilin [α139(HC1)Lys>Gln (AAA>CAA); HBA2:c.418A>C] was identified by TGS. Subsequent pedigree analysis showed that the proband's son also harbored the Hb Jilin variant with slightly low levels of MCH, Hb A2, and abnormal Hb bands. The proband of family 2 was a male at 41 years of age, exhibiting normal MCV and MCH, but a low level of Hb A2 and an abnormal Hb band in zone 12 without any common α- and ß-thalassemia mutations. The subsequent TGS detection demonstrated a rare Hb Beijing [α16(A14)Lys>Asn (AAG>AAT); HBA2:c.51G>T] variant in HBA2 gene. CONCLUSION: In this study, for the first time, we present two rare Hb variants of Hb Jilin and Hb Beijing in Fujian Province, Southeast China, using TGS technology.

A proposed methodology of health education for inherited genetic disorders: Bag and Ball technique.

The life-threatening genetic blood disorder, thalassaemia, which causes decreased haemoglobin production, is preventable. Sociocultural determinants and the level of public health awareness must be used to adopt control measures of prevention. Identifying information gaps and educating the community about screening should be a priority, especially in areas with high disease burdens. A relevant health education technique, with which the audience can identify, can effectively bring understanding necessary effectively to sensitise the community. We propose the 'Bag and Ball' method, which includes role-play for health education specifically concerning inherited genetic disorders.

Identification of Hb Lepore, Hb anti-Lepore, and α-globin gene triplications by long-read single-molecule real-time sequencing.

OBJECTIVES: Hemoglobin (Hb) Lepore and Hb anti-Lepore are infrequent fusion gene variants that result from nonhomologous crossovers during meiosis. Conventional molecular testing methods may face challenges in identifying these variants. During Hb analysis using capillary electrophoresis, we encountered 6 cases with unusual Hb variants. Our aim was to identify the alterations in their globin genes. METHODS: Gap-polymerase chain reaction (PCR), reverse dot-blot assay (RDB), Sanger sequencing, multiplex ligation-dependent probe amplification (MLPA), and long-read single-molecule real-time (SMRT) sequencing were used to confirm the presence of globin gene alterations. RESULTS: The routine thalassemia gene test kit using the gap-PCR and RDB techniques did not detect common gene variations. Direct sequencing failed to identify any known or unknown globin gene alterations. The MLPA analysis, however, revealed the possible presence of α-globin gene triplications as well as 2 types of fusion gene alterations. Further analysis using long-read SMRT sequencing accurately identified 3 rare gene variations: αααanti-3.7, Hb Lepore-Boston-Washington, and Hb anti-Lepore P-India. CONCLUSIONS: Conventional methods may overlook rare thalassemias or Hb variants. Long-read SMRT sequencing has the potential to identify breakpoints in fusion genes, demonstrating that it is a promising technique for detecting rare thalassemias.