Rapid determination of human globin chains using reversed-phase high-performance liquid chromatography

3' UTR-truncated HMGA2 promotes erythroblasts production from human embryonic stem cells

Cultured red blood cells represent an alternative resource for blood transfusions. However, important issues such as low yields and high costs remain. Recently, gene editing of hematopoietic stem cells has been conducted to induce erythroid differentiation in vitro for producing sufficient RBCs to meet the imbalance in blood supply and demand. The differentiation and expansion of hematopoietic stem and progenitor cells are regulated by transcription factors, such as high mobility group AT-hook 2 (HMGA2). In this study, we utilized CRISPR/Cas9 to establish a doxycycline-inducible HMGA2-expressing human embryonic stem cell (hESC) line. In a defined erythroid differentiation system, HMGA2 prolonged erythroid differentiation in vitro, enabling extensive expansion of human erythroblasts. The erythroblasts derived from the HMGA2-expressing hESC line are rich in polychromatic and orthochromatic erythroblasts expressing mostly α- and γ-globin and have the capacity to differentiate into RBCs. Our findings highlight the potential of combining hematopoietic transcription factors with genome editing techniques to enhance RBC production.

The diagnosis and molecular analysis of a novel 27.2 kb deletion causing α0-thalassemia

BACKGROUND

Thalassemia, one of the most prevalent monogenic diseases worldwide, is caused by an imbalance of α-like and non-α-like globin chain production. Copy number variations, which cause the most common genotype of α-thalassemia, can be detected by multiple diagnostic methods.

CASE REPORT

The proband was a 31-year-old female who was diagnosed with microcytic hypochromic anemia by antenatal screening. Hematological analysis and molecular genotyping were conducted on the proband and the proband's family members. Gap-polymerase chain reaction, Sanger sequencing, multiplex ligation-dependent probe amplification, and next-generation sequencing were used to detect potentially pathogenic genes. Familial studies and genetic analyses revealed a novel deletion of 27.2 kb located in the α-globin gene cluster (NC_000016.9: g. 204538_231777delinsTAACA).

CONCLUSIONS

We reported a novel α-thalassemia deletion and described the process of molecular diagnosis. The novel deletion extends the thalassemia mutation spectrum, which may be helpful in genetic counseling and clinical diagnosis in the future.

A Novel Hemoglobin Variant Hb Liaobu [α107(G14)Val→Leu, HBA2: c.322G>C] Detected by Matrix-Assisted Laser Desorption Ionization-Time-of-Flight Mass Spectrometry

We here describe a novel hemoglobin (Hb) variant, Hb Liaobu [α107(G14)Val→Leu, HBA2: c.322G>C], in a Chinese family. The structurally abnormal α chain variant could not be detected using capillary electrophoresis (CE) and was subsequently characterized by matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry (MS), and further confirmed by reversed phase high performance liquid chromatography (HPLC). Sanger sequencing revealed a novel base mutation on the α2-globin gene and RNA analysis by reverse transcription polymerase chain reaction (RT-PCR) showed the presence of an abnormal HBA transcript. The isopropanol stability test indicated the stable state of this structural Hb variant. In conclusion, a new Hb variant, Hb Liaobu, was discovered and characterized. It was proven to be a nonpathogenic variant. Our study resolved the confusion in the clinical diagnosis of individuals with this novel Hb variant in this family.

The curious case of hemoglobin DC disease masquerading as sickle cell anemia

Hemoglobin D is a relatively rare disease first reported in 1951. We present the first reported case of Hemoglobin DC disease. This is a case of a Hemoglobinopathy with DC disease in a woman with a previous diagnosis of Hemoglobin SC disease. A 19-year-old woman presented to the Adult Hematology clinic at a tertiary care hospital in Northwest Louisiana for transition of care from Pediatric Hematology for a diagnosis of Hemoglobin SC disease diagnosed at the age 4. Historical data suggested no avascular necrosis, acute chest syndrome, and very few episodes of pain crisis. She has never taken hydroxyurea. Laboratory work showed persistently normal hemoglobin and white blood cell counts. All sickle cell preparations in the past were negative. Computerized tomography scan of the abdomen was reviewed and showed a spleen grossly normal in size and appearance. Given the incongruent clinical picture for sickle cell disease, repeat hemoglobinopathy evaluation with Capillary electrophoresis and confirmatory acid electrophoresis (to differentiate hemoglobins that co-migrate with Hemoglobin S) showed a probable double heterozygote for Hemoglobin D and C with suspected coexistent alpha thalassemia minor based on red blood cell indices. This case confirms the importance of the required confirmatory method to ensure a correct diagnosis since a misdiagnosis can lead to numerous adverse clinical or psychological effects for patients.

A Novel BaEVRless-Pseudotyped γ-Globin Lentiviral Vector Drives High and Stable Fetal Hemoglobin Expression and Improves Thalassemic Erythropoiesis In Vitro

It has previously been demonstrated that the self-inactivating γ-globin lentiviral vector GGHI can significantly increase fetal hemoglobin (HbF) in erythroid cells from thalassemia patients and thus improve the disease phenotype in vitro. In the present study, the GGHI vector was improved further by incorporating novel enhancer elements and also pseudotyping it with the baboon endogenous virus envelope glycoprotein BaEVRless, which efficiently and specifically targets human CD34⁺ cells. We evaluated the hypothesis that the newly constructed vector designated as GGHI-mB-3D would increase hCD34⁺ cell tropism and thus transduction efficiency at low multiplicity of infection, leading to increased transgene expression. High and stable HbF expression was demonstrated in thalassemic cells for the resulting GGHI-mB-3D/BaEVRless vector, exhibiting increased transduction efficiency compared to the original GGHI-mB-3D/VSVG vector, with a concomitant 91% mean HbF increase at a mean vector copy number per cell of 0.86 and a mean transduction efficiency of 56.4%. Transduced populations also exhibited a trend toward late erythroid, orthochromatic differentiation and reduced apoptosis, a further indication of successful gene therapy treatment. Monitoring expression of ATG5, a key link between autophagy and apoptosis, it was established that this correction correlates with a reduction of enhanced autophagy activation, a typical feature of thalassemic polychromatophilic normoblasts. This work provides novel mechanistic insights into gene therapy-mediated correction of erythropoiesis and demonstrates the beneficial role of BaEVRless envelope glycoprotein compared to VSVG pseudotyping and of the novel GGHI-mB-3D/BaEVRless lentiviral vector for enhanced thalassemia gene therapy.

Rapid and Sensitive Assessment of Globin Chains for Gene and Cell Therapy of Hemoglobinopathies

The β-hemoglobinopathies sickle cell anemia and β-thalassemia are the focus of many gene-therapy studies. A key disease parameter is the abundance of globin chains because it indicates the level of anemia, likely toxicity of excess or aberrant globins, and therapeutic potential of induced or exogenous β-like globins. Reversed-phase high-performance liquid chromatography (HPLC) allows versatile and inexpensive globin quantification, but commonly applied protocols suffer from long run times, high sample requirements, or inability to separate murine from human β-globin chains. The latter point is problematic for in vivo studies with gene-addition vectors in murine disease models and mouse/human chimeras. This study demonstrates HPLC-based measurements of globin expression (1) after differentiation of the commonly applied human umbilical cord blood-derived erythroid progenitor-2 cell line, (2) in erythroid progeny of CD34+ cells for the analysis of clustered regularly interspaced short palindromic repeats/Cas9-mediated disruption of the globin regulator BCL11A, and (3) of transgenic mice holding the human β-globin locus. At run times of 8 min for separation of murine and human β-globin chains as well as of human γ-globin chains, and with routine measurement of globin-chain ratios for 12 nL of blood (tested for down to 0.75 nL) or of 300,000 in vitro differentiated cells, the methods presented here and any variant-specific adaptations thereof will greatly facilitate evaluation of novel therapy applications for β-hemoglobinopathies.

Development of a capillary zone electrophoresis method for rapid determination of human globin chains in α and β-thalassemia subjects

Thalassemia is an inherited autosomal recessive blood disorder characterized by the underproduction of globin chains as a consequence of globin gene defects, resulting in malfunctioning red blood cells and oxygen transport. Analysis of globin chains is an important aspect of thalassemia research. In this study we developed a capillary zone electrophoresis (CZE) method for human globin determination in the diagnosis of thalassemia and hemoglobin variants. To demonstrate the utility of this approach, α/β area ratios were determined for samples from 310 thalassemia patients and healthy controls. The separation was performed on uncoated capillary with simple preparation. Distinct globin peaks were resolved in 17 min, and coefficients of variation (CV) for migration time and areas ranged from 0.37%-1.69% and 0.46%-6.71%, respectively. Receiver operating characteristic (ROC) curve analysis of the α/β area ratios gave 100% sensitivity and specificity for indicating β-TI/TM, and 100% sensitivity and 97.4% specificity for Hb H disease. Hemoglobin G-Honolulu (Hb G-Honolulu) and Hb Westmead (Hb WS) were successfully detected using this CZE method. This automated methodology is simple, rapid and cost-effective for the fast determination of human globin chains, which could be an important diagnostic tool in the field of hemoglobinopathies.

Hemoglobin D-Punjab: origin, distribution and laboratory diagnosis

This review discusses hemoglobin D-Punjab, also known as hemoglobin D-Los Angeles, one of the most common hemoglobin variants worldwide. It is derived from a point mutation in the beta-globin gene (HBB: c.364G>C; rs33946267) prevalent in the Punjab region, Northwestern Indian. Hemoglobin D-Punjab can be inherited in heterozygosis with hemoglobin A causing no clinical or hematological alterations, or in homozygosis, the rarest form of inheritance, a condition that is commonly not related to clinical symptomatology. Moreover, this variant can exist in association with other hemoglobinopathies, such as thalassemias; the most noticeable clinical alterations occur when hemoglobin D-Punjab is associated to hemoglobin S. The clinical manifestations of this association can be similar to homozygosis for hemoglobin S. Although hemoglobin D-Punjab is a common variant globally with clinical importance especially in cases of double heterozygosis, hemoglobin S/D-Punjab is still understudied. In Brazil, for example, hemoglobin D-Punjab is the third most common hemoglobin variant. Thus, this paper summarizes information about the origin, geographic distribution, characterization and occurrence of hemoglobin D-Punjab haplotypes to try to improve our knowledge of this variant. Moreover, a list of the main techniques used in its identification is provided emphasizing the importance of complementary molecular analysis for accurate diagnosis.

Compound heterozygosity for KLF1 mutations is associated with microcytic hypochromic anemia and increased fetal hemoglobin

Krüppel-like factor 1 (KLF1) regulates erythroid lineage commitment, globin switching, and the terminal maturation of red blood cells. Variants in human KLF1 have been identified as an important causative factor in a wide spectrum of phenotypes. This study investigated two unrelated male children in China who had refractory anemia associated with poikilocythemia. These were accompanied by an upregulation of biochemical markers of hemolysis, along with abnormal hemoglobin (Hb) level and elevated reticulocyte counts. Next-generation sequencing revealed that the patients were compound heterozygotes for a KLF1 frameshift mutation c.525_526insCGGCGCC (p.(Gly176ArgfsTer179)) and one of two missense variants, c.892 G>C (p.(Ala298Pro)) and c.1012C>T (p.(Pro338Ser)). The subjects had microcytic hypochromic anemia, and their healthy parents had single mutation. The two missense mutations affected a highly conserved codon in the zinc finger DNA-binding domain of KLF1, but the protein stability was unaffected in K-562 cells. A KLF1-targeted promoter-reporter assay showed that the two mutations reduce the expression of the HBB, BCL11A, and CD44 genes involved in erythropoiesis, with consequent dyserythropoiesis and an α/non-α chain imbalance. A systematic analysis was performed of the phenotypes associated with the KLF1 mutations in the two families, and the clinical characteristics and differential diagnoses of the disease are presented. This is the first report of an autosomal recessive anemia presenting with microcytic hypochromia, abnormal Hb profile, and other distinctive erythrocyte phenotypes, and provides insight into the multiple roles of KLF1 during erythropoiesis.