Thalassemia: the long road from the bedside through the laboratory to the community

Genetic and Epigenetic Therapies for β-Thalassaemia by Altering the Expression of α-Globin Gene

β-Thalassaemia is caused by over 300 mutations in and around the β-globin gene that lead to impaired synthesis of β-globin. The expression of α-globin continues normally, resulting in an excess of α-globin chains within red blood cells and their precursors. These unpaired α-globin chains form unstable α-hemichromes that trigger cascades of events to generate reactive oxygen species, leading to ineffective erythropoiesis and haemolysis in patients with β-thalassaemia. The clinical genetic data reported over several decades have demonstrated how the coinheritance of α-thalassaemia ameliorates the disease phenotype of β-thalassaemia. Thus, it is evident that down-regulation of the α-globin gene expression in patients with β-thalassaemia could ameliorate or even cure β-thalassaemia. Over the last few years, significant progress has been made in utilising this pathway to devise a cure for β-thalassaemia. Most research has been done to alter the epigenetic landscape of the α-globin locus or the well-characterised distant enhancers of α-globin. In vitro, pre-clinical studies on primary human erythroid cells have unveiled inhibition of histone lysine demethylation and histone deacetylation as potential targets to achieve selective downregulation of α-globin through epigenetic drug targeting. CRISPR based genome editing has been successfully used in vitro to mutate α-globin genes or enhancers of α-goblin to achieve clinically significant knockdowns of α-globin to the levels beneficial for patients with β-thalassaemia. This review summarises the current knowledge on the regulation of human α-globin genes and the clinical genetic data supporting the pathway of targeting α-globin as a treatment for β-thalassaemia. It also presents the progress of epigenetic drug and genome editing approaches currently in development to treat β-thalassaemia.

Causes of microcytic anaemia and evaluation of conventional laboratory parameters in the differentiation of erythrocytic microcytosis in blood donors candidates

CONTEXT AND OBJECTIVE

Microcytic anaemia results from defective synthesis of haemoglobin in the erythroid precursors, causing a reduction in its mean corpuscular volume (MCV). The most common causes of microcytosis, without the increase in HbA₂ levels, are iron deficiency anaemia (IDA) and α-thalassemia. The aim of this study was to identify the causes of microcytic anaemia and evaluate the haematological parameters from blood donors deemed ineligible (due to the low haematocrit level) that would differentiate the IDA and α-thal, whether isolated or in association.

METHODS

Genomic DNA was submitted to the polymerase chain reaction multiplex for the diagnosis of the most common allele deletions of α-thal and erythrogram and in order to verify haematological parameters. Iron deficiency (ID) was determined through the measurement of serum ferritin.

RESULTS

Of the 204 samples, 82 (40.2%) were identified with ID, 24 (17.8%) with α-thal and 10 (4.9%) with ID associated with α-thal. In the α-thal with ID group haemoglobin (Hb), MCV, mean corpuscular Hb concentration (MCHC) and mean corpuscular Hb (MCH) values were significantly lower compared to the isolated α-thal. In the group with ID Hb, MCV, MCHC and MCH values were significantly lower compared to those with isolated α-thal. The α-thal with ID group, showed Hb, MCV, MCHC and MCH significantly reduced when compared to those with IDA.

CONCLUSIONS

This study showed that the values of haematological parameters, especially haematocrit, Hb, MCV, MCH, MCHC and red blood cell distribution width (RDW), are lower in patients with IDA, especially when associated with α-thal and therefore it may be useful to discriminate between the different types of microcytic anaemia.

Should sex differences be considered when applying mathematical indices and formulas for discriminating β- thalassemia minor from iron deficiency?

Background

β-thalassemia minor (BTM) and iron deficiency (ID) are common disorders characterized by microcytosis and/or hypochromasia, leading to a challenge in their discrimination during mass-screening programs especially in developing countries where resources are limited. It has been shown with varying reliability that quick exclusion of either disorder could be achieved mathematically using RBC-based indices and formulas. However, none of these proposed indices and formulas considered the sex-based hematological differences. This comparative retrospective study examined the efficacy of using sex-based RBC indices in the mathematical discrimination BTM and ID in adult males and females.

Methods

The CBC of randomly selected eight hundred adults diagnosed with BTM or ID (200M & 200F BTM, and 200M & 200F ID) were used in the comparisons. The discrimination power, in terms of sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, and Youden index were calculated for all subjects and separately for males and females for 20 mathematical indices and formulas.

Results

Data revealed significant differences in the RBC-based indices between males and females for both BTM and ID groups. Significant variation in reliability indicators for the different indices and formulas were discovered between males and females samples.

Conclusion

Sex-based indices and formulas are necessary to improve the reliability in mathematically discriminating between BTM and ID in mass screening programs. We also advocate for a large–scale multicenter study to establish the parameters of such indices and formulas with sex and age.

Hemoglobinopathies in newborns in the southern region of the Triângulo Mineiro, Brazil. Cross-sectional study

CONTEXT AND OBJECTIVE

Hemoglobinopathies are among the commonest and most widespread genetic disorders worldwide. Their prevalence varies according to ethnic composition and/or geographical region. The aim of this study was to investigate the presence of hemoglobinopathies and their association with ethnicity among 1,004 newborns, to confirm the guideline of the Brazilian National Neonatal Screening Program.

DESIGN AND SETTING

Cross-sectional study conducted in a public referral hospital in the Triângulo Mineiro region, Minas Gerais, Brazil.

METHODS

Qualitative assessment of hemoglobin was performed through electrophoresis on cellulose acetate: at alkaline pH to identify the hemoglobin (Hb) profile and at acid pH to differentiate Hb S from Hb D and Hb C from Hb E and others that migrate to similar positions at alkaline pH. Neutral pH was used to detect Hb Bart's identified in alpha thalassemia (α-thal). The elution method after electrophoresis was used to quantitatively assess hemoglobins.

RESULTS

There was predominance of α-thal, with 105 cases (10.46%), followed by Hb S with 61 cases (6.08%, comprising 46 Hb AS, 2 Hb SS and 13 Hb S/α-thal), 9 cases (0.9%) of Hb AC and 6 cases (0.6%) suggestive of beta thalassemia (β-thal). The frequency of hemoglobinopathies was significantly higher among Afro-descendants.

CONCLUSIONS

These findings corroborated of the National Neonatal Screening Program for diagnosing sickle cell disease and Hb C, Hb D, Hb E and β-thal hemoglobinopathies.

Regulatory Fe(II/III) heme: the reconstruction of a molecule's biography

More than 20 years of research on heme as a temporary effector molecule of proteins have revealed its widespread impact on virtually all primary functions in the human organism. As our understanding of this influence is still growing, a comprehensive overview of compiled data will give fresh impetus for creativity and developing new strategies in heme-related research. From known data concerning heme-regulated proteins and their involvement in the development of diseases, we provide concise information of Fe(II/III) heme as a regulator and the availability of "regulatory heme". The latter is dependent on the balance between free and bound Fe(II/III) heme, here termed "hemeostasis". Imbalance of this system can lead to the development of diseases that were not always attributed to this small molecule. Diseases such as cancer or Alzheimer's disease highlight the reawakened interest in heme, whose function was previously believed to be completely understood.

Non-invasive prenatal diagnostics using next generation sequencing: technical, legal and social challenges

INTRODUCTION

Newly developed non-invasive prenatal diagnostic techniques, using maternal blood samples, have the potential to reduce or obviate the need for invasive prenatal diagnostic practices such as amniocentesis or chorionic villous sampling. This will lead to a change in how obstetric care is extended by health care providers to pregnant women at-risk of bearing an aneuploid child.

AREAS COVERED

The process leading to the development of fetal aneuploidy detection via the analysis of cell-free DNA in maternal plasma by massive parallel sequencing. Optimization of these strategies and approaches used in the recent or up-coming commercial launches. In addition, this review provides insight into legal implications, potential patent disputes, ethical and societal concerns raised by this development, such as whole genome data storage, retrieval and access.

EXPERT OPINION

There is a need for engagement by professional societies, to ensure correct usage of these newly emerging technologies and their restriction to high-risk pregnancies. National agencies need to ensure the necessary degree of high quality required for prenatal diagnosis.