A 6-Year Follow-up of a Chinese Child with Homozygous β0-Thalaasemia and a Heterozygous KLF1 Mutation

Patients with the genotype of β0/β0 for β-thalassemia (β-thal) usually behave as β-thal major (β-TM) phenotype which is transfusion-dependent. The pathophysiology of β-thal is the imbalance between α/β-globin chains. The degree of α/β-globin imbalance can be reduced by the more effective synthesis of γ-globin chains, and increased Hb F levels, modifying clinical severity of β-TM. We report a Chinese child who had homozygous β0-thal and a heterozygous KLF1 mutation. The patient had a moderate anemia since 6 months old, keeping a baseline Hb value of 8.0-9.0 g/dL. She had normal development except for a short stature (3rd percentile) until 6 years old, when splenomegaly and facial bone deformities occurred. Although genetic alteration of KLF1 expression in β0/β0 patients can result in some degree of disease alleviation, our case shows that it is insufficient to ameliorate satisfactorily the presentation. This point should be borne in mind for physicians who provide the genetic counseling and prenatal diagnosis to at-risk families.

Treatment with Hydroxyurea Leads to Fetal Hemoglobin Reactivation through CA1 and LIN28B Genes: An In Vitro Study

Hydroxyurea (HU) is an effective drug to increase fetal γ-globin gene (Hb F) expression, replacing the missing adult β-globin gene. The mechanism of Hb F induction by HU and improvement in clinical symptoms are still poorly understood. The current study aimed to improve the molecular understanding of drug-induced alterations and reveals genes related to HU treatment responsiveness in β-thalassemia (β-thal). We analyzed the GSE109186 dataset using system biology and weighted gene coexpression network analysis (WGCNA) to identify and quantify gene expression changes reflected in the HU-treated human erythroblastic leukemia cells. The K562 cell line was treated in 50, 100, and 150 µM concentrations of HU for 24, 48, and 72 hours with three replications. The alteration of CA1, LIN28B and Hb F gene expression in HU-treated cells was evaluated using the real-time polymerase chain (real-time PCR) technique. The results showed that LIN28B has an increase of 4.27-fold on the first day of HU-treatment in 50 µM (p < 0.01). The CA1 expression showed a decrease at all times and doses of treatment, and the most decrease happened in 48 hours and 50 µM (p < 0.04). Hb F also showed the highest increase in 100 µM after 24 hours of treatment (5.18-fold). In summary, the data suggest that alteration of LIN28B and CA1 gene expression is associated with γ-globin increasing in HU-treated cells.

The Effect of Five Single Nucleotide Polymorphisms on Hb F Variation of β-Thalassemia Traits and Hematologically Normal Individuals in Southeast Turkey

β-Thalassemia (β-thal) is caused by deficiency of β-globin chain synthesis and leads to the accumulation of unstable globin chain production. This results in a higher Hb F level in order to neutralize the excess α chains. In addition, γ-globin gene expression, due to genetic factors after birth, leads to increased Hb F levels in adulthood [hereditary persistence of fetal hemoglobin (Hb) (HPFH)]. In this study, the relationship between β-thal trait and individuals with suspected HPFH and a control group was investigated in Adıyaman, Turkey. Single nucleotide polymorphism (SNP) analyses were performed in five different polymorphic regions using real-time polymerase chain reaction (qPCR) methods [rs4671393 (G>A), rs766432 (A>C), rs9402686 (G>A), rs28384513 (T>G), rs1609812 (A>G)]. No significant difference was found between the control and β-thal group in the codominant inheritance model in the rs1609812 (A>G) polymorphism region only, while all the other polymorphic regions were found to be statistically significant. It was found that different genotype models increased Hb F levels between 1.6- and 3.06-fold in four studied polymorphic regions [rs4671393 (G>A), rs766432 (A>C), rs9402686 (G>A), rs28384513 (T>G)]. All of the polymorphic regions increased the Hb F levels from 1.86- to 24.76-fold, except rs9402686 (G>A) and rs28384513 (T>G) over dominant and rs1609812 (A>G) codominant inheritance models. The AC and AA genotypes increased Hb F levels in the B-cell CLL/lymphoma 11 A haplotype studies. It was determined that both haplotypes 2 and 4 increased Hb F levels. As a result, SNPs strongly affect the Hb F levels in both healthy individuals and β-thal trait.

Role of Genomic Biomarkers in Increasing Fetal Hemoglobin Levels Upon Hydroxyurea Therapy and in β-Thalassemia Intermedia: A Validation Cohort Study

Hemoglobinopathies exhibit a remarkable phenotypic diversity in terms of disease severity, while individual genetic background plays a key role in differential response to drug treatment. In the last decade, genomic variants in genes located within, as well as outside the human β-globin cluster have been shown to be significantly associated with Hb F increase, in relation to hydroxyurea (HU) therapy in patients with these diseases. Here, we aim to determine the effect of genomic variants located in genes, such as MAP3K5, ASS1, NOS2A, TOX, PDE7B, NOS1, FLT1 and ARG2, previously shown to modulate fetal hemoglobin (Hb F) levels in patients with β type hemoglobinopathies and reflecting disease severity and response to HU therapy in an independent cohort of Greek patients with these diseases. We recruited and genotyped 45 β-thalassemia patients (β-thal), either transfusion-dependent (TDT) or non transfusion-dependent (NTDT), 42 Hb S (HBB: c.20A>T)-β-thal compound heterozygotes, who were treated with HU, as well as 53 healthy individuals, all of Hellenic origin. Our study showed that genomic variants of the MAP3K5, NOS2A and ARG2 gene are associated with HU therapy efficacy in Hb S-β-thal compound heterozygotes. We have also shown that FLT1 and ARG2 genomic variants are associated with the mild phenotype of NTDT patients. Our findings provide evidence that MAP3K5, NOS2A, ARG2 and FLT1 genomic variants could be considered as genomic biomarkers to predict HU therapy efficacy in Hb S-β-thal compound heterozygotes and also to describe disease severity in patients with β type hemoglobinopathies.

KFL1 Gene Variants in α-Thalassemia Individuals with Increased Fetal Hemoglobin in a Chinese Population

Krüppel-like factor 1 (KLF1) is a pleiotropic erythroid transcription factor that is a regulator of definitive erythropoiesis. The aim of this study was to detect KLF1 gene variants in α-thalassemia (α-thal) carriers with an increased Hb F level in a Chinese population, and determine the changes of hematological parameters as a result of interactions between KLF1 gene mutations and α-thal. Subjects with α-thal and Hb F levels of ≥1.0% were selected for further investigation. Direct sequencing was used to detect KLF1 gene mutations. Hematological parameters of subjects with α-thal and concomitant KLF1 gene mutations and those with α-thal alone were compared. The KLF1 gene variants were detected in 46 of 275 (16.7%) individuals with α-thal and Hb F levels of ≥1.0%. The detection rate of KLF1 gene mutations rose correspondingly when the Hb F level increased. For α⁰-thal carriers, significantly lower mean corpuscular volume (MCV) and mean corpuscular hemoglobin (Hb) (MCH) values were observed in KLF1 gene mutation-positive carriers than that in KLF1 gene mutation-free carriers; conversely, significantly higher Hb A₂ and Hb F levels were observed in the former condition rather than in the latter condition. The results of this study indicate that KLF1 gene variants are common in Chinese subjects with α-thal and increased Hb F levels, and KLF1 gene mutations decreased the red blood cell (RBC) indices in α-thal carriers as that in normal adults.

Fetal Hemoglobin in the Maternal Circulation - Contribution of Fetal Red Blood Cells

The major hemoglobin (Hb) during fetal life is fetal Hb (Hb F). It is mostly replaced by adult Hbs before birth and during the first year of life. In adults, where Hb F comprises <2.0% of the total Hb, it is not homogenously distributed among the red blood cells (RBCs) but is concentrated in a few RBCs, termed F-cells. Interestingly, for reasons that are unclear, Hb F increases in the maternal circulation during pregnancy. This increased Hb F could have two potential origins that are not mutually exclusive: A) maternal origin, due to inducing environment of Hb F in the maternal erythroid precursors; B) fetal origin, due to fetal cells crossing the placenta and entering the maternal circulation. The question we present herein is whether the observed increased Hb F in the maternal circulation during pregnancy is, at least partially, derived from the fetal origin. Peripheral blood was obtained from normal neonates (1-3 days old), adult men and pregnant and non pregnant women. The RBCs were stained for Hb F and carbonic anhydrase (CA) using a fetal cell count kit and analyzed by flow cytometry. Fetal and adult F-cells were distinguished by their expression of Hb F and CA. Fetal F-cells were Hb F⁺⁺/CA^-, while adult F-cells were Hb F⁺/CA⁺. Comparing pregnant and non pregnant women samples (n = 10), we found six samples of pregnant women with 0.2-1.7% fetal cells, but none in the non pregnant group. These results support the possibility that at least part of the increase in Hb F during pregnancy is due to fetal cells entering the maternal circulation.