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Fetal hemoglobin (HbF) usually consists of 4 to 10% of total hemoglobin in adults of African descent with sickle cell anemia. Rarely, their HbF levels reach more than 30%. High HbF levels are sometimes a result of β-globin gene deletions or point mutations in the promoters of the HbF genes. Collectively, the phenotype caused by these mutations is called hereditary persistence of fetal hemoglobin, or HPFH. The pancellularity of HbF associated with these mutations inhibits sickle hemoglobin polymerization in most sickle erythrocytes so that these patients usually have inconsequential hemolysis and few, if any, vasoocclusive complications. Unusually high HbF can also be associated with variants of the major repressors of the HbF genes, BCL11A and MYB. Perhaps most often, we lack an explanation for very high HbF levels in sickle cell anemia.

Background There are challenges in generating mRNA-Seq data from whole-blood derived RNA as globin gene and rRNA are frequent contaminants. Given the abundance of erythrocytes in whole blood, globin genes comprise some 80% or more of the total RNA. Therefore, depletion of globin gene RNA and rRNA are critical steps required to have adequate coverage of reads mapping to the reference transcripts and thus reduce the total cost of sequencing. In this study, we directly compared the performance of probe hybridization (GLOBINClear Kit and Globin-Zero Gold rRNA Removal Kit) and RNAse-H enzymatic depletion (NEBNext® Globin & rRNA Depletion Kit and Ribo-Zero Plus rRNA Depletion Kit) methods from 1 μg of whole blood-derived RNA on mRNA-Seq profiling. All RNA samples were treated with DNaseI for additional cleanup before the depletion step and were processed for poly-A selection for library generation. Results Probe hybridization revealed a better overall performance than the RNAse-H enzymatic depletion method, detecting a higher number of genes and transcripts without 3′ region bias. After depletion, samples treated with probe hybridization showed globin genes at 0.5% (±0.6%) of the total mapped reads; the RNAse-H enzymatic depletion had 3.2% (±3.8%). Probe hybridization showed more junction reads and transcripts compared with RNAse-H enzymatic depletion and also had a higher correlation (R > 0.9) than RNAse-H enzymatic depletion (R > 0.85). Conclusion In this study, our results showed that 1 μg of high-quality RNA from whole blood could be routinely used for transcriptional profiling analysis studies with globin gene and rRNA depletion pre-processing. We also demonstrated that the probe hybridization depletion method is better suited to mRNA sequencing analysis with minimal effect on RNA quality during depletion procedures.

One of the most relevant pathophysiological hallmarks of β-thalassemia is the accumulation of toxic α-globin chains inside erythroid cells, which is responsible for their premature death (hemolysis). In this context, the availability of an experimental model system mimicking the excess in α-globin chain production is still lacking. The objective of the present study was to produce and characterize K562 cellular clones forced to produce high amounts of α-globin, in order to develop an experimental model system suitable for studies aimed at the reduction of the accumulation of toxic α-globin aggregates. In the present study, we produced and characterized K562 cellular clones that, unlike the original K562 cell line, stably produced high levels of α-globin protein. As expected, the obtained clones had a tendency to undergo apoptosis that was proportional to the accumulation of α-globin, confirming the pivotal role of α-globin accumulation in damaging erythroid cells. Interestingly, the obtained clones seemed to trigger autophagy spontaneously, probably to overcome the accumulation/toxicity of the α-globin. We propose this new model system for the screening of pharmacological agents able to activate the full program of autophagy to reduce α-globin accumulation, but the model may be also suitable for new therapeutical approaches targeted at the reduction of the expression of the α-globin gene.

Background Heterozygotes of HPFH and δβ thalassemia are clinically asymptomatic or have mild hemoglobin (Hb) values. However, when both HPFH and δβ‐thalassemia are coinherited with heterozygous β‐thalassemia, patients may progress to a clinical phenotype of thalassemia intermedia or thalassemia major. The purpose of this study was to characterize the genotypes and analyze the phenotypes of these disorders in Fujian Province, to offer advice for genetic counseling and accurate prenatal diagnosis in this region. A total of 55 001 subjects were participated in thalassemia screening. 142 subjects with HbF levels ≥10%, before the blood transfusion, were selected for further investigation. Methods Multiplex ligation‐dependent probe amplification (MLPA) and Gap‐PCR were used to screen for three β‐globin gene cluster deletions: Chinese Gγ(Aγδβ)0 thalassemia and Southeast Asia HPFH (SEA‐HPFH) deletion and 1357 bp deletion (NG‐000007.3:g.69997‐71353 del 1357). Results A total of 142 patients with HbF (≥10%) were enrolled to characterize the molecular basis of β‐globin gene cluster deletions in our study; 22 cases 0.04% (22/55 001) were definitively diagnosed with β‐globin gene cluster deletions. Ten cases were heterozygous for the Chinese Gγ(Aγδβ)0‐thal mutations, 10 cases were heterozygous for SEA‐HPFH, and one case was compound heterozygous for SEA‐HPFH and the α‐thal mutation. The 1357 bp deletion (NG‐000007.3:g.69997‐71353 del 1357) was detected in one case. Moreover, the hemoglobin A2 levels in patients who were heterozygous for Chinese Gγ(Aγδβ)0‐thal were statistically lower than in cases with SEA‐HPFH deletion(p < 0.05). Conclusion In Fujian Province, the prevalence of common β‐globin gene cluster deletions was 0.04%. What's more, the most common β‐globin cluster deletions are the Chinese Gγ(Aγδβ)0 and SEA‐HPFH. Figure 1 Screening for β‐globin gene cluster deletions by MLPA, A,SEA‐HPFH deletion,B,Chinese Gγ(Aγδβ)0‐thal mutation,C,1357bp deletion(NG‐000007.3:g.69997–71353 del 1357).

Background Thalassemia is common in Southeast Asian countries, including China. Hb A2‐Melbourne is a rare hemoglobin variant and has never been reported in China. Here, we report a Hb A2‐Melbourne combined with β‐thalassemia in Chinese individuals which is the second case described in the published reports. Methods Complete blood counts (CBC) of a 28‐year‐old female showed signs of thalassemia during a routine screening. Hemoglobin analysis was subsequently performed using capillary electrophoresis (CE) and high‐performance liquid chromatography (HPLC). Four common deletional α‐thalassemia detection was carried out using a gap‐polymerase chain reaction (PCR). PCR and reverse dot‐blot were used to detect three non‐deletional α‐thalassemia and 17 types of point mutations in β‐thalassemia. Finally, it was identified by Sanger sequencing. Her husband also had CBC, hemoglobin analysis, and genetic diagnosis. Results CBC of the couple showed Hb 103 and 139 g/L, mean corpuscular volume 58 and 63.1 fL, mean corpuscular hemoglobin 19.7 and 20.4 pg, respectively. Hemoglobin analysis revealed Hb X 2.4%, Hb A2 2.8% by CE and Hb X 2.9%, Hb A2 2.4% by HPLC in the female. The results of her husband were Hb A93.5%, Hb A2 5.7%, Hb F 0.8% by CE. Genetic analysis of both spouses detected the same CD 41/42 mutations in β‐globin gene. Sanger sequencing of female identified a mutation of the δ‐globin gene (HBD:c.130G>A), corresponding to Hb A2‐Melbourne. Conclusion Hb A2‐Melbourne can lead to misdiagnosis of β‐thalassemia. δ‐globin gene mutation must be carefully examined in routine thalassemia screening.

Beta-like globin gene expression is developmentally regulated during life by transcription factors, chromatin looping and epigenome modifications of the β-globin locus. Epigenome modifications, such as histone methylation/demethylation and acetylation/deacetylation and DNA methylation, are associated with up- or down-regulation of gene expression. The understanding of these mechanisms and their outcome in gene expression has paved the way to the development of new therapeutic strategies for treating various diseases, such as β-hemoglobinopathies. Histone deacetylase and DNA methyl-transferase inhibitors are currently being tested in clinical trials for hemoglobinopathies patients. However, these approaches are often uncertain, non-specific and their global effect poses serious safety concerns. Epigenome editing is a recently developed and promising tool that consists of a DNA recognition domain (zinc finger, transcription activator-like effector or dead clustered regularly interspaced short palindromic repeats Cas9) fused to the catalytic domain of a chromatin-modifying enzyme. It offers a more specific targeting of disease-related genes (e.g., the ability to reactivate the fetal γ-globin genes and improve the hemoglobinopathy phenotype) and it facilitates the development of scarless gene therapy approaches. Here, we summarize the mechanisms of epigenome regulation of the β-globin locus, and we discuss the application of epigenome editing for the treatment of hemoglobinopathies.

Background: Haemoglobinopathies such as beta-thalassemia (β-thal), alpha-thalassemia (α-thal) and sickle cell disease (SCD) are characterised by pathogenic gene variations (mutations) in the globin genes. Patients with haemoglobinopathies have the same disease-causing coding variations with very different disease phenotypes, from requiring blood transfusions to being non-symptomatic. The gap between the expected clinical outcomes based on primary coding mutations (the genotype) and the actual observed symptoms (the phenotype) often remains unexplained. We refer to the contribution of secondary genetic modifiers—specifically, non-coding variants of the genome that alter globin gene expression and pathophysiology—as the “missing heritability” of the clinical presentation [Primary Mutation + Missing Heritability (Non-Coding Variants) = Actual Clinical Phenotype]. Objectives: This systematic review aims to find evidence connecting genetic differences outside of the protein-coding region, as in promoters, enhancers or untranslated regions (UTRs), to the clinical severity (phenotype) of beta-thalassemia, alpha-thalassaemia and SCD. We summarise the molecular basis of phenotypic variation among haemoglobinopathy patients with identical variations to reveal their missing heritability and to enhance our understanding of prognostic strategies. Methods: This systematic review was performed in accordance with the PRISMA 2020 guidelines. We used search terms related to haemoglobinopathies, non-coding variation, SNP, promoters, enhancers and clinical severity to search major databases (PubMed and Google Scholar) as of October 2025. A total of 527 (out of 572) abstracts were fit for initial screening to identify the eligible reports. Due to heterogeneity in study designs and reported outcomes, findings were synthesised descriptively and grouped by variant mechanism (cis-acting and trans-acting). The final analysis included 89 articles that demonstrated a direct association between a non-coding genomic variant and a quantitative measure of clinical severity. Results: Two main groups of non-coding variants (NCVs) that modulate foetal haemoglobin (HbF) induction were identified. The first major group comprises cis-acting variants within globin gene clusters (HBG2 promoter XmnI polymorphism, HBB promoter mutations and α-globin enhancer variants), while the second major group comprises trans-acting quantitative trait loci (QTLs) (BCL11A and HBS1L-MYB loci). Non-globin NCVs in the UGT1A1 promoter were also found to influence the severity measures in β-thal and SCD. NCVs primarily alter the binding of transcription factors and the looping dynamics of chromatin, modulating the α/β chain balance ratio and γ-globin repression. The XmnI polymorphism is the most prominent cis-acting modifier associated with β-thal intermedia. The promoter polymorphisms in TNF-α and VCAM1 are associated with vascular complications in SCD. Conclusions: NCVs are fundamental when determining the clinical measures of haemoglobinopathies, in addition to coding variants. NCV screening should be integrated for clinical prognosis for the accurate prediction of haemoglobinopathy severity and associated high-risk complications. NCVs may represent promising targets for next-generation gene editing and therapeutic intervention strategies aimed at modifying the severity of β-thal, α-thal and SCD.

Background: Hemoglobin A (Hb A) (α2β2) in the normal adult subject constitutes 96–98% of hemoglobin, and Hb F is normally less than 1%, while for hemoglobin A2 (Hb A2) (α2δ2), the normal reference values are between 2.0 and 3.3%. It is important to evaluate the presence of possible delta gene mutations in a population at high risk for globin gene defects in order to correctly diagnose the β-thalassemia carrier. Methods: The most used methods for the quantification of Hb A2 are based on automated high performance liquid chromatography (HPLC) or capillary electrophoresis (CE). In particular Hb analyses were performed by HPLC on three dedicated devices. DNA analyses were performed according to local standard protocols. Results: Here, we described eight new δ-globin gene variants discovered and characterized in some laboratories in Northern Italy in recent years. These new variants were added to the many already known Hb A2 variants that were found with an estimated frequency of about 1–2% during the screening tests in our laboratories. Conclusions: The knowledge recognition of the delta variant on Hb analysis and accurate molecular characterization is crucial to provide an accurate definitive thalassemia diagnosis, particularly in young subjects who would like to ask for a prenatal diagnosis or preimplantation genetic diagnosis.

Beta-thalassemia is one of the most prevalent inherited diseases and a public health problem in Malaysia. Malaysia is geographically divided into West and East Malaysia. In Sabah, a state in East Malaysia, there are over 1000 estimated cases of β-thalassemia major patients. Accurate population frequency data of the molecular basis of β-thalassemia major are needed for planning its control in the high-risk population of Sabah. Characterization of β-globin gene defects was done in 252 transfusion dependent β-thalassemia patients incorporating few PCR techniques. The study demonstrates that β-thalassemia mutations inherited are ethnically dependent. It is important to note that 86.9% of transfusion-dependent β-thalassemia major patients in Sabah were of the indigenous population and homozygous for a single mutation. The Filipino β(0)-deletion was a unique mutation found in the indigenous population of Sabah. Mutations common in West Malaysia were found in 11 (4.3%) patients. Four rare mutations (Hb Monroe, CD 8/9, CD 123/124/125 and IVS I-2) were also found. This study is informative on the population genetics of β-thalassemia major in Sabah.

The α- and β-globin gene clusters have been extensively studied 1 , 2 , 3 . Regulation of these genes ensures that proteins derived from both loci are produced in balanced amounts, and that expression is tissue-restricted and specific to developmental stages. Here we compare the subnuclear location of the endogenous α- and β-globin loci in primary human cells in which the genes are either actively expressed or silent. In erythroblasts, the α- and β-globin genes are localized in areas of the nucleus that are discrete from α-satellite-rich constitutive heterochromatin. However, in cycling lymphocytes, which do not express globin genes, the distribution of α- and β-globin genes was markedly different. β-globin loci, in common with several inactive genes studied here (human c -fms and SOX-1) and previously (mouse λ5, CD4, CD8α, RAGs, TdT and Sox-1) 4 , 5 , were associated with pericentric heterochromatin in a high proportion of cycling lymphocytes. In contrast, α-globin genes were not associated with centromeric heterochromatin in the nucleus of normal human lymphocytes, in lymphocytes from patients with α-thalassaemia lacking the regulatory HS-40 element or entire upstream region of the α-globin locus, or in mouse erythroblasts and lymphocytes derived from human α-globin transgenic mice. These data show that the normal regulated expression of α- and β-globin gene clusters occurs in different nuclear environments in primary haemopoietic cells.