Hb Lepore-Leiden: A New δ/β Rearrangement Associated with a β-Thalassemia Minor Phenotype

Molecular characterization of similar Hb Lepore Boston-Washington in four Chinese families using third generation sequencing

Hemoglobin (Hb) Lepore is a rare deletional δβ-thalassemia caused by the fusion between delta-beta genes, and cannot be identified by traditional thaltassemia gene testing technology. The aim of this study was to conduct molecular diagnosis and clinical analysis of Hb Lepore in four unrelated Chinese families using third generation sequencing. Decreased levels of mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH) and an abnormal Hb band were observed in the probands of the four families. However, no common α and β-thalassemia variants were detected in the enrolled families using polymerase chain reaction-reverse dot blot hybridization based traditional thalassemia gene testing. Further third-generation sequencing revealed similar Hb Lepore-Boston-Washington variants in all the patients, which were resulted from partial coverage of the HBB and HBD globin genes, leading to the formation of a delta-beta fusion gene. Specific gap-PCR and Sanger sequencing confirmed that all the patients carried a similar Hb Lepore-Boston-Washington heterozygote. In addition, decreased levels of MCH and Hb A2 were observed in the proband's wife of family 2, an extremely rare variant of Hb Nanchang (GGT > AGT) (HBA2:c.46G > A) was identified by third-generation sequencing and further confirmed by Sanger sequencing. This present study was the first to report the similar Hb Lepore-Boston-Washington in Chinese population. By combining the utilization of Hb capillary electrophoresis and third-generation sequencing, the screening and diagnosis of Hb Lepore can be effectively enhanced.

Plasma metabolomics and proteomics reveal novel molecular insights and biomarker panel for cholelithiasis

BACKGROUND

Cholelithiasis is a gastrointestinal disease that is associated with the highest socioeconomic cost. A diagnosis of cholelithiasis based on clinical features is significantly limited, and direct molecular insights into cholelithiasis and the relationship between cholelithiasis and clinical biochemical parameters are unclear.

OBJECTIVES

Uncovering direct molecular insights into cholelithiasis and the relationship between cholelithiasis and clinical biochemical parameters. Identifying sensitive and specific biomarkers for this disease.

METHODS

Parallel metabolomic and proteomic analyses of plasma from cholelithiasis patients (CPs) and healthy control individuals (HCs) without cholelithiasis were performed using ultrahigh-performance liquid chromatography-tandem mass spectrometry. A multimodule coexpression network analysis and integrated machine learning methods, including least absolute shrinkage and selection operator, random forest, and support vector machine, were used for bioinformatic analyses. An independent cohort and the cross-validation of the combination of two cohorts were used to evaluate the diagnostic performance of the panel.

RESULTS

Arachidonic acid metabolism was significantly different between the CP and HC groups. Glyceraldehyde-3-phosphate dehydrogenase, actin beta, phosphoglycerate mutase 1, Enolase 1, Myeloperoxidase, and actin alpha 1 were identified as potential proteins related to cholelithiasis. The correlation between the merged modules and clinical biochemical tests was calculated. A diagnostic panel composed of four candidate biomarkers, including 3-oxotetradecanoic acid, 12-hydroxydodecanoic acid, hemoglobin subunit delta (HBD), and fibrinogen beta chain (FGB), was proposed based on three modules that were significantly associated with cholelithiasis. The classification according to the diagnostic panel detected CPs with an area under the curve (AUC) of 0.955. External validation in an independent cohort resulted in similar accuracy (AUC=0.995).

CONCLUSIONS

This study provided some direct molecular insights into cholelithiasis by showing the differences in plasma metabolic and protein profiles between CPs and HCs and presented a potential biomarker panel with two metabolites (3-oxotetradecanoic acid, 12-hydroxydodecanoic acid) and two proteins (HBD, FGB) for predicting cholelithiasis. We also explored the potential correlation of clinical biochemical parameters with combined modules. These findings may provide some reference for the diagnosis of cholelithiasis in clinical practice.

Thalassemias: From gene to therapy

Thalassemias (α, β, γ, δ, δβ, and εγδβ) are the most common genetic disorders worldwide and constitute a heterogeneous group of hereditary diseases characterized by the deficient synthesis of one or more hemoglobin (Hb) chain(s). This leads to the accumulation of unstable non-thalassemic Hb chains, which precipitate and cause intramedullary destruction of erythroid precursors and premature lysis of red blood cells (RBC) in the peripheral blood. Non-thalassemic Hbs display high oxygen affinity and no cooperativity. Thalassemias result from many different genetic and molecular defects leading to either severe or clinically silent hematologic phenotypes. Thalassemias α and β are particularly diffused in the regions spanning from the Mediterranean basin through the Middle East, Indian subcontinent, Burma, Southeast Asia, Melanesia, and the Pacific Islands, whereas δβ-thalassemia is prevalent in some Mediterranean regions including Italy, Greece, and Turkey. Although in the world thalassemia and malaria areas overlap apparently, the RBC protection against malaria parasites is openly debated. Here, we provide an overview of the historical, geographic, genetic, structural, and molecular pathophysiological aspects of thalassemias. Moreover, attention has been paid to molecular and epigenetic pathways regulating globin gene expression and globin switching. Challenges of conventional standard treatments, including RBC transfusions and iron chelation therapy, splenectomy and hematopoietic stem cell transplantation from normal donors are reported. Finally, the progress made by rapidly evolving fields of gene therapy and gene editing strategies, already in pre-clinical and clinical evaluation, and future challenges as novel curative treatments for thalassemia are discussed.

Hb Lepore-Hong Kong: First Report of a Novel δ/β-Globin Gene Fusion in a Chinese Family

We describe a new δ/β fusion gene causing β-thalassemia (β-thal) trait and its formation mechanism. The proband was a 39-year-old woman who presented with persistent microcytic microcytosis without iron deficiency. Molecular diagnoses revealed a δβ configuration within a 54 bp region between the Cap site (+22) and codon 8, causing a deletion (NG_000007.3: g.63154_70565del). This results in a variant that has been named Hb Lepore-Hong Kong and shows a decreased β-globin mRNA in carriers compared to that of normal subjects. It is assumed that combination of this variant with β-thal may cause severe β-thal syndrome.

Severe Drug-Induced Hemolysis in a Patient with Compound Heterozygosity for Hb Peterborough (HBB: c.334G>T) and Hb Lepore-Boston-Washington (NG_000007.3: g.63632_71046del)

Unstable hemoglobins (Hbs) are often overlooked in the differential diagnoses of drug-induced hemolysis. Hb Peterborough [β111(G13)Val→Phe; HBB: c.334G>T] is a rare unstable Hb variant, predominantly found in individuals of Italian descent, due to a structural defect involving a single amino acid substitution (phenylalanine for valine at position 111 of the β-globin chain). Unstable Hb variants are often inherited in the heterozygous state with Hb A (α2β2) and rarely in compound heterozygosity with other Hb variants. The presence of another variant Hb often alters the phenotype, occasionally resulting in more severe disease. Using a combination of molecular techniques; multiplex ligation-dependent probe amplification (MLPA) and Sanger sequencing, we identified a compound heterozygosity for Hb Peterborough and Hb Lepore-Boston-Washington (Hb LBW) [δ87, β116; NG_000007.3: g.63632_71046del] in a middle-aged gentleman with a history of chronic microcytic anemia and splenomegaly, presenting with severe drug-induced hemolysis, which was managed conservatively. The clinical history and presentation reflect the dual pathology due to the presence of two variant Hbs and their associated phenotypes. In this article, we discuss the phenotype resulting from the interaction of Hb Peterborough and Hb LBW and emphasize the importance of molecular testing in the diagnosis of rare Hb variants.

Biochemical and Molecular Analysis of the Hb Lepore Boston Washington in a Syrian Homozygous Child

Hemoglobin (Hb) Lepore is composed of two normal α chains and two δβ fusion globins that arise from unequal crossover events between the δ- and β-globin genes. The Hb Lepore is widespread all over the world and in many ethnic groups. It includes some of the few clinically significant Hb variants that are associated with a β-thalassemia phenotype. Here, we describe the first occurrence of Hb Lepore Boston Washington in a Syrian individual. The patient, a 10-year-old child, shows severe anemia with a Hb level of 6.85 g/dL and typical thalassemic red cell indices. The diagnostic procedure implies hematological, biochemical, and molecular analysis, including multiplex ligation-dependent probe amplification (MLPA) assay, GAP-PCR, and DNA sequencing. This latter allowed us to define the correct structure of the hybrid δβ-globin gene. The knowledge of the spectrum of mutations associated with different geographical areas is the prerequisite to set up large-scale screening programs and be able to offer genetic counseling to couples at risk.

Strategies for basic laboratory diagnostics of the hemoglobinopathies in multi-ethnic societies: interpretation of results and pitfalls

The consistent multi-ethnic migrations of the last decades have considerably changed the epidemiology of the hemoglobinopathies. Healthy carriers of these conditions are present today in many nonendemic parts of the world, and severely affected children are now born where these diseases were previously rare or unknown. Improving the competence in carrier diagnostics at the laboratory level is one of the first concerns when introducing management and primary prevention of the severe conditions in nonendemic areas. This review describes how and when carriers should be correctly diagnosed and informed. The essential technologies needed for basic carrier diagnostics in different situations are summarized in some detail, and interpretation of the results and a number of related problems are discussed. The role of the hematology laboratory is essential, particularly in nonendemic areas where the first line of health care is often insufficiently aware of hemoglobinopathy management. Carriers living in nonendemic areas can be appropriately diagnosed and informed regarding genetic risk and prevention by well-organized laboratories. Both basic and specialized diagnostics are needed for the correct treatment for the anemic carriers, for primary prevention in couples at risk and for state-of-the art care of severely affected patients.

Occurrence of common and rare δ-globin gene defects in two multiethnic populations: thirteen new mutations and the significance of δ-globin gene defects in β-thalassemia diagnostics

INTRODUCTION

The aim of this review is to study the frequency of common and the occurrence of rare and novel mutations of the delta-globin gene and of Hb Lepore defects that might interfere with thalassemia diagnostics and to report the rationale of HbA2 estimation in the presence of delta- or alpha-gene mutations.

METHODS

A total of 135 cases suspected to have a delta-globin gene defect collected in a diagnostic center in the USA and in a reference laboratory in the Netherlands were characterized by molecular analysis.

RESULTS

Hb B2 was found at a frequency of at least 0.5% in the USA and 0.87% in the Netherlands. Known variants such as Hb A2-Babinga, Hb A2-Sphakia, Hb A2-Fitzroy, Hb A2-Flatbush, Hb A2-NYU, Hb A2-Grovetown, HbA2-Yialousa, Hb A2-Indonesia and several delta-thalassemia mutations were found together with 13 new mutations and two new polymorphisms, while Hb Lepores were regularly observed.

CONCLUSION

HbA2 mutations either structurally stable and visible or undetectable because of a thalassemia effect or instability are clinically asymptomatic but may compromise the diagnosis of beta-thalassemia minor. Stable mutations result in two HbA2 fractions of about half of the expected value. Expression defects are undetectable as a protein fraction but reduce the amount of HbA2 by half.