Hemoglobin variants: biochemical properties and clinical correlates

Hb H disease associated with compound heterozygosity for --SEA deletion and a novel alpha globin chain variant (HBA2:c.175C>A) on the distal histidine in a Chinese family

OBJECTIVES

In clinical practice, the majority of α-thalassaemia cases arise from deletions of the α-globin genes. However, a subset of cases is attributed to rare haemoglobin variants, which can manifest with borderline or normal screening results, potentially leading to missed diagnoses in clinical practice.

METHODS

Blood samples were collected from family members and underwent haematological, DNA and RNA analysis.

RESULTS

The five-month-old proband presented a haematological phenotype consistent with Hb H disease. The mother's haematology profile was consistent with an α-thalassaemia carrier, while the father exhibited a borderline reduction in MCV and MCH. MALDI-TOF identified an abnormal α-chain in the proband. DNA analysis revealed a novel α-globin variant (HBA2:c.175C>A, α58His>Asn, Hb DG-Nancheng) affecting the distal histidine in the family. The father and the mother had α-genotype of --SEA/αα and αDG-Nanchengα/αα, respectively; while the proband inherited both mutant alleles (--SEA/αDG-Nanchengα). Sequencing of cDNA from HBA2 gene identified an equal ratio of normal and mutant alleles.

CONCLUSION

This rare case highlighted the importance of identifying rare haemoglobin variant during prenatal screening. The clinical and genetic data provides useful information on the pathogenicity of this variant and further insight into the role of distal histidine residue of α-globin.

Regional Prevalence of Hemoglobin C Across Saudi Arabia: An Epidemiological Survey

INTRODUCTION

HbC is a common structural hemoglobinopathy especially in West Africa. Prevalence and regional distribution of HbC in Saudi Arabia are widely undocumented. Patients with homozygous HbC disease may have mild hemolytic anemia whereas combination with hemoglobin S (HbS) leads to a clinically severe phenotype.

AIM

The current epidemiological study, considered the largest from Saudi Arabia, aimed to evaluate the regional prevalence of the HbC variant among the couples participating in the premarital screening program from 2011 to 2018.

METHODS

Data from the PMSGC program were obtained for premarital screening and genetic counseling. The collected data were then entered into the SEHA platform, a centralized electronic repository for the 13 designated regions in Saudi Arabia. Hemoglobin electrophoresis samples are analyzed using either HPLC, capillary electrophoresis, or a combination of both methods to confirm the presence of abnormal hemoglobin bands.

RESULTS

This study included 1,871,184 individuals from 2011 to 2018. Of those, 49.8% were males and 50.2% were females. 112,618 (6.0%) had an abnormal test. Total number of Hb C cases were 778 (0.04%). HbC trait (HbAC) was detected in 764 participants while homozygous HbC (HbCC) and combined heterozygous (HbSC) were found in 9 and 5 cases, respectively. The regions near the Red Sea have higher rates than the central and eastern regions.

CONCLUSION

HbC is a rare variant in Saudi Arabia with varying regional frequencies. HbC variant is more common in Mecca and Madina regions. The geographic area of HbC distribution differs from the areas with high prevalence of HbS, which explains why HbSC disease cases are overwhelmingly rare.

Interference of hemoglobin variants with HbA1c measurements: comparison of 6 commonly used HbA1c methods with the IFCC reference method

BACKGROUND

Glycated hemoglobin, or hemoglobin A1c (HbA1c), serves as a crucial marker for diagnosing diabetes and monitoring its progression. We aimed to assess the interference posed by common Hb variants on popular HbA1c measurement systems.

METHODS

A total of 63 variant and nonvariant samples with target values assigned by the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) reference method were included. We assessed 6 methods for measuring HbA1c in the presence of HbS, HbC, HbD, HbE, and fetal hemoglobin (HbF): 2 cation-exchange high-performance liquid chromatography (HPLC) methods (Bio-Rad D-100 and HLC-723 G8), a capillary electrophoresis (CE) method (Sebia Capillarys 3 TERA), an immunoassay (Roche c501), an enzyme assay system (Mindray BS-600M), and a boronate affinity method (Primus Premier Hb9210).

RESULTS

The HbA1c results for nonvariant samples from the 6 methods were in good agreement with the IFCC reference method results. The Bio-Rad D-100, Capillarys 3, Mindray BS-600M, Premier Hb9210, and Roche c501 showed no interference from HbS, HbC, HbD, and HbE. Clinically significant interference was observed for the HLC-723 G8 standard mode. Elevated HbF levels caused significant negative biases for all 6 methods, which increased with increasing HbF concentration.

CONCLUSION

Elevated levels of HbF can severely affect HbA1c measurements by borate affinity, immunoassays, and enzyme assays.

Uncommon Combination of Hemoglobin Jax and Hemoglobin Constant Spring Leading to Microcytic Anemia

BACKGROUND Thalassemia and hemoglobin (Hb) variants are the most common hereditary red blood cell disorders worldwide. Alpha-thalassemia and alpha-globin variants are caused by mutations of the alpha-globin genes (HBA2 and HBA1), resulting in impaired alpha-globin production and structurally abnormal globin, respectively. Clinical severity of alpha-thalassemia correlates with the number of affected alpha-globin genes, yielding a spectrum of clinical manifestations from mild to severe anemia. Routine diagnosis involves Hb analysis and PCR-based methods, yet identifying rare variants necessitates comprehensive clinical and hematologic laboratory data. The knowledge of phenotype and genotype correlation is useful for genetic counseling and treatment planning. CASE REPORT A 59-year-old Thai woman presented with chronic anemia. Her baseline Hb level ranged between 8.0 and 9.0 g/dL, with no history of transfusion. Physical examination showed mild pallor, without enlarged liver and spleen. Laboratory investigations showed microcytic, hypochromic anemia and abnormal Hb peak by Hb analysis (retention time 4.58 min by HPLC method). Common alpha-globin gene deletions, including the Southeast-Asian/Thai 3.7 kb and 4.2 kb deletions were tested using gap-PCR, with none of these deletions detected. Direct DNA sequencing revealed a compound heterozygosity of Hb Jax (HBA2: c.44G>C) and Hb Constant Spring (HBA2: c.427T>C). CONCLUSIONS Compound heterozygosity of Hb Jax and Hb Constant Spring results in microcytic anemia. Hb Jax can be identified by Hb analysis, and diagnosis can be confirmed by direct DNA sequencing method. Coinheritance of Hb Jax and alpha-globin variants should be considered in cases with microcytic anemia and a specific Hb peak seen in Hb chromatogram.

Impact of haemoglobin variants on the diagnostic sensitivity of glycated haemoglobin (HbA1c) assay methodologies in sub-Saharan Africa: a laboratory-based method validation study

Introduction

the utility of glycated haemoglobin (HbA1c) for the diagnosis and monitoring of diabetes in sub-Saharan Africa is uncertain due to limited data on the performance of the available HbA1c assay methods in this population, which has a high prevalence of haemoglobin variants. We aimed to compare the diagnostic accuracy of the major HbA1c methodologies (Boronate Affinity, Capillary Electrophoresis, High Performance Liquid Chromatography, Immunoassay) in an African population, and assess the impact of the common haemoglobin variant HbAS (sickle cell trait).

Methods

whole blood samples were obtained from 182 individuals living with type 2 diabetes in Uganda. HbA1c values for each method were compared to average glucose measured over 14 days by continuous glucose monitoring (CGM). To determine concordance, the three HbA1c assay methods were compared to the capillary electrophoresis method.

Results

there was a strong correlation between CGM average glucose levels and all four HbA1c methodologies (r=0.81-0.89) which did not differ in those with and without HbAS (present in 37/182 participants). The presence of HbAS did not alter the relationship between HbA1c and CGM glucose for any assay (p for interaction >0.2 for all methods). Diagnostic accuracy for CGM average glucose thresholds of 7 and 10mmol/L was similar across methods (area under the receiver operating characteristic curve 0.80-0.84 and 0.76-0.84 respectively). The maximum bias between the HbA1c assay methodologies was 2 mmol/mol (2.07%).

Conclusion

all major HbA1c technologies offer accurate and comparable HbA1c measurement even in this population with high prevalence of haemoglobin variants.

YTHDF2-regulated matrilin-3 mitigates post-reperfusion hemorrhagic transformation in ischemic stroke via the PI3K/AKT pathway

Hemorrhagic transformation can complicate ischemic strokes after recanalization treatment within a time window that requires early intervention. To determine potential therapeutic effects of matrilin-3, rat cerebral ischemia-reperfusion was produced using transient middle cerebral artery occlusion (tMCAO); intracranial hemorrhage and infarct volumes were assayed through hemoglobin determination and 2,3,5-triphenyltetrazoliumchloride (TTC) staining, respectively. Oxygen-glucose deprivation (OGD) modeling of ischemia was performed on C8-D1A cells. Interactions between matrilin-3 and YTH N6-methyladenosine RNA binding protein F2 (YTHDF2) were determined using RNA immunoprecipitation assay and actinomycin D treatment. Reperfusion after tMCAO modeling increased hemorrhage, hemoglobin content, and infarct volumes; these were alleviated by matrilin treatment. Matrilin-3 was expressed at low levels and YTHDF2 was expressed at high levels in ischemic brains. In OGD-induced cells, matrilin-3 was negatively regulated by YTHDF2. Matrilin-3 overexpression downregulated p-PI3K/PI3K, p-AKT/AKT, ZO-1, VE-cadherin and occludin, and upregulated p-JNK/JNK in ischemic rat brains; these effects were reversed by LY294002 (a PI3K inhibitor). YTHDF2 knockdown inactivated the PI3K/AKT pathway, inhibited inflammation and decreased blood-brain barrier-related protein levels in cells; these effects were reversed by matrilin-3 deficiency. These results indicate that YTHDF2-regulated matrilin-3 protected ischemic rats against post-reperfusion hemorrhagic transformation via the PI3K/AKT pathway and that matrilin may have therapeutic potential in ischemic stroke.

Monogenic Disorders of ROS Production and the Primary Anti-Oxidative Defense

Oxidative stress, characterized by an imbalance between the production of reactive oxygen species (ROS) and the cellular anti-oxidant defense mechanisms, plays a critical role in the pathogenesis of various human diseases. Redox metabolism, comprising a network of enzymes and genes, serves as a crucial regulator of ROS levels and maintains cellular homeostasis. This review provides an overview of the most important human genes encoding for proteins involved in ROS generation, ROS detoxification, and production of reduced nicotinamide adenine dinucleotide phosphate (NADPH), and the genetic disorders that lead to dysregulation of these vital processes. Insights gained from studies on inherited monogenic metabolic diseases provide valuable basic understanding of redox metabolism and signaling, and they also help to unravel the underlying pathomechanisms that contribute to prevalent chronic disorders like cardiovascular disease, neurodegeneration, and cancer.

Sickle Cell Disease Update: New Treatments and Challenging Nutritional Interventions

Sickle cell disease (SCD), a distinctive and often overlooked illness in the 21st century, is a congenital blood disorder characterized by considerable phenotypic diversity. It comprises a group of disorders, with sickle cell anemia (SCA) being the most prevalent and serious genotype. Although there have been some systematic reviews of global data, worldwide statistics regarding SCD prevalence, morbidity, and mortality remain scarce. In developed countries with a lower number of sickle cell patients, cutting-edge technologies have led to the development of new treatments. However, in developing settings where sickle cell disease (SCD) is more prevalent, medical management, rather than a cure, still relies on the use of hydroxyurea, blood transfusions, and analgesics. This is a disease that affects red blood cells, consequently affecting most organs in diverse manners. We discuss its etiology and the advent of new technologies, but the aim of this study is to understand the various types of nutrition-related studies involving individuals suffering from SCD, particularly in Africa. The interplay of the environment, food, gut microbiota, along with their respective genomes collectively known as the gut microbiome, and host metabolism is responsible for mediating host metabolic phenotypes and modulating gut microbiota. In addition, it serves the purpose of providing essential nutrients. Moreover, it engages in direct interactions with host homeostasis and the immune system, as well as indirect interactions via metabolites. Nutrition interventions and nutritional care are mechanisms for addressing increased nutrient expenditures and are important aspects of supportive management for patients with SCD. Underprivileged areas in Sub-Saharan Africa should be accompanied by efforts to define and promote of the nutritional aspects of SCD. Their importance is key to maintaining well-being and quality of life, especially because new technologies and products remain limited, while the use of native medicinal plant resources is acknowledged.

First report of a patient with homozygous hemoglobin Ernz: Evidence to support a non-pathogenic variant

Hemoglobin Ernz (Hb Ernz) is a missense variant in β-globin caused by a Threonine to Asparagine substitution at the 123rd amino acid position and HBB c.371C > A in gene level. Hb Ernz has been classified as Uncertain Significance (VUS) by ACMG due to limited reports and the absence of any homozygote genotypes. In our study, we found eight cases of Hb Ernz by DNA sequencing of the β-globin gene during >20 years of Thalassemia Screening in individuals with borderline hematological parameters who were possible carriers of thalassemia or their spouses. We also report the first homozygote variant of Hb Ernz. Our findings suggest that the changes in hematological parameters observed in individuals with Hb Ernz are likely due to α-globin gene mutations rather than Hb Ernz itself. These findings support the reclassification of Hb Ernz as a benign variant in variant classification.

Functional characterization of compound heterozygosity Hb S/Hb Deer Lodge in Brazil

INTRODUCTION

The Hb Deer Lodge (β2 His>Arg; HBB:c.8A>G) is a structural hemoglobin variant described in some populations around the world, characterized by increased oxygen affinity, but does not confer clinical symptoms to its carriers. The coinheritance of the Hb Deer Lodge with the most common hemoglobin variant, Hb S, has been reported only once; however, functional data were not described. Here we show a case of the Hb S and Hb Deer Lodge carrier in heterozygosity.

METHODS

The Hb S and Hb Deer Lodge association was identified by High-Performance Liquid Chromatography (HPLC), reverse phase HPLC and the β globin gene sequencing. The functional characterization of this interaction was obtained using the O2 dissociation curve, determination of the cooperativity between the globin chains and the Bohr effect in the presence and absence of organic phosphates.

RESULTS

When the Hb S and Hb Deer Lodge were associated, there was a decrease in cooperativity, no significant changes in oxygen affinity and no significant Bohr effect changes.

CONCLUSION

Despite these genetic variations, the carrier showed no hematological alterations and no clinical symptoms, possibly due to the high oxygen affinity of the Hb Deer Lodge, which interferes with the Hb S polymerization.

The First Case of Hemoglobin J-Guantanamo Reported During HbA1c Measurement by High-Performance Liquid Chromatography at Moroccan Military Hospital Mohammed V

We present a 57-year-old woman with diabetes mellitus and no other known comorbidities. HbA1c measurement by high-performance liquid chromatography (HPLC) gave unquantified results and a supernumerary peak was detected on the chromatogram. A thorough exploration of the hemoglobin profile showed the presence of an unclassified variant. Alkaline pH capillary electrophoresis revealed the presence of an abnormal peak migrating at zone 11, comprising 40.1% of total hemoglobin. An abnormal band migrating between hemoglobin A and hemoglobin F was observed by acid gel electrophoresis. Sequencing of the β-globin gene confirmed the presence of a rare hemoglobin variant, hemoglobin J-Guantanamo (HBB:c.386C>A) in the heterozygous state, which was for the first time documented in Morocco. Through this report, we emphasize the importance of careful analysis of the HPLC chromatogram for the detection of possible hemoglobin variants in HbA1c measurement.

A Novel β-Globin Variant, Hb Raklev [β 75(E19) HBB:c.227T > A (Leu→Gln)]

We present a new hemoglobin variant, Hb Raklev, characterized by the substitution of leucine with glutamine at position 75 in the β-globin chain. This variant was discovered inadvertently during an HbA1c evaluation using high performance liquid chromatography in a symptomless 54-year-old Caucasian woman, with the same variant also identified in her 16-year-old daughter. Purification of the hemoglobin revealed possibly diminished 2,3-bisphosphoglycerate (2,3-BPG) sensitivity, which may result in heightened oxygen affinity. Notably, two variants have been previously documented at this location: the unstable Hb Atlanta and the high-affinity Hb Pasadena.

Structural stability of R-state conformation of carbonmonoxyl sickle and normal hemoglobin dimer

A mutation at the sixth residue, glutamic acid to valine, in beta chain of hemoglobin distorts the entire shape of hemoglobin into a sickle shape. The investigation of the binding mechanisms of different chains of hemoglobin under the mutated condition can give an understanding of the molecular distortion. In this work, we have studied the binding mechanism between two chains in the dimer structure of the R-state conformation of carbonmonoxyl sickle hemoglobin and is compared with that of normal hemoglobin by using molecular dynamics simulations. The binding strength between α-chain (PROA) and β-chain (PROB) in hemoglobin dimer has been analyzed by estimating hydrogen bonds, salt bridges, hydrophobic interactions and non-bonded interactions (electrostatics and van der Waals). The quantitative estimation of aforementioned interactions depicts that the structural stability of normal hemoglobin dimer is found to be greater than that of sickle one. The outcomes of such interactions are also supported by the estimated free energy between the chains in R-state conformation of the dimers. The difference of binding free energy, calculated by utilizing the umbrella sampling technique, is found to be ≈ (0.67 ± 0.06) kcal/mol.Communicated by Ramaswamy H. Sarma.

ReDirection: an R-package to compute the probable dissociation constant for every reaction of a user-defined biochemical network

Biochemical networks integrate enzyme-mediated substrate conversions with non-enzymatic complex formation and disassembly to accomplish complex biochemical and physiological functions. The choice of parameters and constraints used in most of these studies is numerically motivated and network-specific. Although sound in theory, the outcomes that result depart significantly from the intracellular milieu and are less likely to retain relevance in a clinical setting. There is a need for a computational tool which is biochemically relevant, mathematically rigorous, and unbiased, and can ascribe functionality to and generate potentially testable hypotheses for a user-defined biochemical network. Here, we present "ReDirection," an R-package which computes the probable dissociation constant for every reaction of a biochemical network directly from a null space-generated subspace of the stoichiometry number matrix of the modeled network. "ReDirection" delineates this subspace by excluding all trivial and redundant or duplicate occurrences of non-trivial vectors, combinatorially summing the vectors that remain and verifying that the upper or lower bounds of the sequence of terms formed by each row of this subspace belong to the open real-valued intervals - ∞ , - 1 or 1 , ∞ or whether the number of terms that are differently signed are almost equal. "ReDirection" iterates these steps until these bounds are consistent and unambiguous for all reactions of the modeled biochemical network. Thereafter, "ReDirection" filters the terms from each row of this subspace, bins them to outcome-specific subsets, sums and maps this to an outcome-specific reaction vector, and computes the p1-norm, which is the probable dissociation constant for a reaction. "ReDirection" works on first principles, does not discriminate between enzymatic and non-enzymatic reactions, offers a biochemically relevant and mathematically rigorous environment to explore user-defined biochemical networks under baseline and perturbed conditions, and can be used to address empirically intractable biochemical problems. The utility and relevance of "ReDirection" are highlighted by numerical studies on stoichiometric number models of biochemical networks of galactose metabolism and heme and cholesterol biosynthesis. "ReDirection" is freely available and accessible from the comprehensive R archive network (CRAN) with the URL (https://cran.r-project.org/package=ReDirection).

Human cellular model systems of β-thalassemia enable in-depth analysis of disease phenotype

β-thalassemia is a prevalent genetic disorder causing severe anemia due to defective erythropoiesis, with few treatment options. Studying the underlying molecular defects is impeded by paucity of suitable patient material. In this study we create human disease cellular model systems for β-thalassemia by gene editing the erythroid line BEL-A, which accurately recapitulate the phenotype of patient erythroid cells. We also develop a high throughput compatible fluorometric-based assay for evaluating severity of disease phenotype and utilize the assay to demonstrate that the lines respond appropriately to verified reagents. We next use the lines to perform extensive analysis of the altered molecular mechanisms in β-thalassemia erythroid cells, revealing upregulation of a wide range of biological pathways and processes along with potential novel targets for therapeutic investigation. Overall, the lines provide a sustainable supply of disease cells as research tools for identifying therapeutic targets and as screening platforms for new drugs and reagents.

The blood count as a compass to navigate in the ever-changing landscape of the carrier state of hemoglobinopathies: a single-center Italian experience

Introduction

Approximately 7% of the worldwide population exhibits variations in the globin genes. The recent migration of populations from countries where hemoglobin disorders are endemic has resulted in important epidemiological changes with the diffusion of newly discovered or poorly characterized genetic variants and new combinations and very heterogeneous clinical phenotypes. The aim of our study is to assess the parameters that are more significant in predicting a positive genetic testing outcome for hemoglobinopathies in a pediatric population of patients presenting with anemia or microcythemia, without a definite diagnosis.

Methods and materials

This study included patients evaluated in our hematological outpatient clinic for anemia and/or microcythemia despite normal ferritin levels. A screening of pathological hemoglobins using high-performance liquid chromatography (HPLC) was performed for the entire population of the study. Subsequently, patients with hemoglobin (Hb) S trait and patients with an HPLC profile compatible with beta thalassemia trait were excluded from the study. Genetic screening tests for hemoglobinopathies were performed on the remaining patients, which involved measuring the red blood cell (RBC) counts, red blood cells distribution width (RDW), reticulocyte count, and mean corpuscular volume of reticulocytes (MCVr).

Results

This study evaluated a total of 65 patients, consisting of nine patients with negative genetic analysis results and 56 patients with positive genetic analysis results. The Hb and RDW values in these two groups did not demonstrate statistical significance. On the other hand, there were statistically significant differences observed in the mean corpuscular volume (MCV), RBC count, reticulocyte count, and MCVr between the two groups. Furthermore, in the group of patients with positive genetic test results, specific genetic findings associated with different HPLC results were observed. In particular, 13 patients with positive genetic test results had normal HPLC findings.

Discussion

This study has demonstrated that HPLC, while serving as a valuable first-level test, has some limitations. Specifically, it has been observed that some patients may exhibit a negative HPLC result despite a positive genetic analysis. In addition to the presence of low levels of Hb and HPLC alterations, other parameters could potentially indicate the underlying mutations in the globin genes. Therefore, we propose that the complete blood cell count be utilized as a widely available parameter for conducting targeted genetic analyses to avoid the risk of overlooking rare hemoglobinopathies.

The dependence of maximum oxygen uptake and utilization (V̇O2 max) on hemoglobin-oxygen affinity and altitude

Oxygen transport from the lungs to peripheral tissue is dependent on the affinity of hemoglobin for oxygen. Recent experimental data have suggested that the maximum human capacity for oxygen uptake and utilization (V̇O2 max) at sea level and altitude (~3000 m) is sensitive to alterations in hemoglobin-oxygen affinity. However, the effect of such alterations on V̇O2 max at extreme altitudes remains largely unknown due to the rarity of mutations affecting hemoglobin-oxygen affinity. This work uses a mathematical model that couples pulmonary oxygen uptake with systemic oxygen utilization under conditions of high metabolic demand to investigate the effect of hemoglobin-oxygen affinity on V̇O2 max as a function of altitude. The model includes the effects of both diffusive and convective limitations on oxygen transport. Pulmonary oxygen uptake is calculated using a spatially-distributed model that accounts for the effects of hematocrit and hemoglobin-oxygen affinity. Systemic oxygen utilization is calculated assuming Michaelis-Menten kinetics. The pulmonary and systemic model components are solved iteratively to compute predicted arterial and venous oxygen levels. Values of V̇O2 max are predicted for several values of hemoglobin-oxygen affinity and hemoglobin concentration based on data from humans with hemoglobin mutations. The model predicts that increased hemoglobin-oxygen affinity leads to increased V̇O2 max at altitudes above ~4500 m.

High throughput human genotyping for variants associated with malarial disease outcomes using custom targeted amplicon sequencing

Malaria has exhibited the strongest known selective pressure on the human genome in recent history and is the evolutionary driving force behind genetic conditions, such as sickle-cell disease, glucose-6-phosphatase deficiency, and some other erythrocyte defects. Genomic studies (e.g., The 1000 Genomes project) have provided an invaluable baseline for human genetics, but with an estimated two thousand ethno-linguistic groups thought to exist across the African continent, our understanding of the genetic differences between indigenous populations and their implications on disease is still limited. Low-cost sequencing-based approaches make it possible to target specific molecular markers and genes of interest, leading to potential insights into genetic diversity. Here we demonstrate the versatility of custom dual-indexing technology and Illumina next generation sequencing to generate a genetic profile of human polymorphisms associated with malaria pathology. For 100 individuals diagnosed with severe malaria in Northeast Tanzania, variants were successfully characterised on the haemoglobin subunit beta (HBB), glucose-6-phosphate dehydrogenase (G6PD), atypical chemokine receptor 1 (ACKR1) genes, and the intergenic Dantu genetic blood variant, then validated using pre-existing genotyping data. High sequencing coverage was observed across all amplicon targets in HBB, G6PD, ACKR1, and the Dantu blood group, with variants identified at frequencies previously observed within this region of Tanzania. Sequencing data exhibited high concordance rates to pre-existing genotyping data (> 99.5%). Our work demonstrates the potential utility of amplicon sequencing for applications in human genetics, including to personalise medicine and understand the genetic diversity of loci linked to important host phenotypes, such as malaria susceptibility.

Z-flipon variants reveal the many roles of Z-DNA and Z-RNA in health and disease

Identifying roles for Z-DNA remains challenging given their dynamic nature. Here, we perform genome-wide interrogation with the DNABERT transformer algorithm trained on experimentally identified Z-DNA forming sequences (Z-flipons). The algorithm yields large performance enhancements (F1 = 0.83) over existing approaches and implements computational mutagenesis to assess the effects of base substitution on Z-DNA formation. We show Z-flipons are enriched in promoters and telomeres, overlapping quantitative trait loci for RNA expression, RNA editing, splicing, and disease-associated variants. We cross-validate across a number of orthogonal databases and define BZ junction motifs. Surprisingly, many effects we delineate are likely mediated through Z-RNA formation. A shared Z-RNA motif is identified in SCARF2, SMAD1, and CACNA1 transcripts, whereas other motifs are present in noncoding RNAs. We provide evidence for a Z-RNA fold that promotes adaptive immunity through alternative splicing of KRAB domain zinc finger proteins. An analysis of OMIM and presumptive gnomAD loss-of-function datasets reveals an overlap of Z-flipons with disease-causing variants in 8.6% and 2.9% of Mendelian disease genes, respectively, greatly extending the range of phenotypes mapped to Z-flipons.

Case report: Curing a rare, unstable hemoglobin variant Hb Bristol-Alesha using haploidentical hematopoietic stem cell transplantation

Unstable hemoglobinopathies are a rare, heterogeneous group of diseases that disrupt the stability of hemoglobin (Hb), leading to chronic hemolysis and anemia. Patients with severe phenotypes often require regular blood transfusions and iron chelation therapy. Although rare, studies have reported that hematopoietic stem cell transplantation (HSCT) seems to be an available curative approach in transfusion-dependent patients with unstable hemoglobinopathies. Here, we describe successful haploidentical HSCT for the treatment of an unstable Hb variant, Hb Bristol-Alesha, in a 6-year-old boy with severe anemia since early childhood. Two years after transplantation, he had a nearly normal hemoglobin level without evidence of hemolysis. DNA analysis showed complete chimerism of the donor cell origin, confirming full engraftment with normal erythropoiesis.

The Hemoglobin Wayne Variant and Association With Falsely Elevated HbA1c

The objective of this work is to explain the effect of the clinically silent hemoglobinopathy hemoglobin Wayne (Hb Wayne) variant on glycated hemoglobin A1c (HbA1c) assay. This variant can result in falsely high HbA1c values among euglycemic individuals without diabetes mellitus (DM). We discuss 3 patients who were diagnosed with type 2 DM based on spuriously high HbA1c values due to the presence of Hb Wayne. All 3 patients were found to have elevated HbA1c values that did not correlate with other glycemic parameters such as capillary blood sugar, 2-hour oral glucose tolerance test, and fructosamine levels. Hemoglobin electrophoresis revealed that each patient had a rare hemoglobinopathy called Hb Wayne variant. These patients were reassured that they did not have DM and were able to avoid unnecessary treatment. These cases emphasize the importance of clinical judgment in recognizing the limitations and caveats of the HbA1c test. It is always necessary to investigate further any discordance between HbA1c values and the clinical picture or other glycemic parameters.

Interference of hemoglobin variants in HbA1c quantification

Fasting blood glucose and glycated hemoglobin (HbA_1c) are routine biomarkers to screen and monitor diabetes mellitus. HbA_1c results from glycation at the N-terminus of the β globin chain of tetrameric human hemoglobin. Fasting blood glucose level varies with the nature and amount of food intake, physical exercise, etc., and, accordingly, is a short-term measure of glucose control. In contrast, HbA_1c provides an average measure of glucose control for the long-term (8-12 weeks). Unfortunately, genetic variants of hemoglobin may interfere with HbA_1c quantification using ion exchange chromatography, capillary electrophoresis, immunoassay and boronate affinity chromatography. Mass spectrometry, however, measures total glycation of hemoglobin across both α and β globin chains and correlates well with the ion exchange based method. Additionally, mass spectrometry based quantification is not impacted by the presence of genetic variants of hemoglobin and thus might be a better analytical choice for diabetes mellitus.

Transient neonatal hemolytic anemia due to the novel gamma globin gene mutation HBG2:C.290T>C, p.Leu97Pro (hemoglobin Wareham)

Unstable gamma globin variants can cause transient neonatal hemolytic anemia. We have identified a novel variant in a newborn who presented with jaundice and anemia requiring phototherapy and red blood cell transfusion. The patient was found to be heterozygous for the mutation HGB2:c.290T>C, p.Leu97Pro, which we have termed hemoglobin (Hb) Wareham. This substitution is expected to generate an unstable hemoglobin with increased oxygen affinity based on the homologous mutation previously described in the beta globin gene, which is termed as Hb Debrousse. The patient fully recovered by 9 months of age as expected with the transition from fetal to adult hemoglobin.

Core-Shell Structured Hemoglobin Nanoparticles as Artificial O2 Carriers

This paper describes the synthesis and O₂ binding properties of core-shell structured hemoglobin (Hb) nanoparticles (NPs), artificial O₂ carriers of five types, as designed for use as red blood cell (RBC) substitutes. Human adult Hbs were polymerized using α-succinimidyl-ω-maleimide and dithiothreitol in spheroidal shapes to create parent particles. Subsequent covalent wrapping of the sphere with human serum albumin (HSA) yielded 100 nm-diameter Hb nanoparticles (HbNPs). The HbNP showed higher O₂ affinity than that of RBC, but NPs prepared under a N₂ atmosphere exhibited low O₂ affinity. Entirely synthetic particles comprising recombinant human adult Hb and recombinant HSA were also fabricated. Using a recombinant Hb (rHb) variant in which Leu-β28 of the heme pocket had been replaced with Phe, we found somewhat low O₂ affinity of rHb(βL28F)NP. Particles made of stroma-free Hb (SFHb) containing natural antioxidant enzyme catalase (SFHbNP) formed a very stable O₂ complex, even in aqueous H₂O₂ solution. The SFHbNP showed good blood compatibility and did not affect the blood cell component functionality. The circulation half-life of SFHbNP in rats was considerably longer than that of naked Hb. All results indicate these Hb-based NPs as useful alternative materials for RBC and as a useful O₂ therapeutic reagent in diverse medical scenarios.

Congenital Disorders of Red Blood Cells

See Bonus NeoBriefs videos and downloadable teaching slides Understanding the physiologic process of red blood cell development in utero and subsequent erythropoiesis in the neonate is crucial as this determines red blood cell structure and therefore function, which is vital to neonatal health. Infants frequently experience anemia, and special consideration must be given to the evaluation of these infants to determine the correct etiology. Traditionally, anemia is conceptualized in terms of inadequate red blood cell production, increased red blood cell destruction, or whole blood loss. This framework translates well to inherited red blood cell defects, which include genetic abnormalities in bone marrow productivity or structure of the red blood cell membrane, enzymes, or hemoglobin. This article highlights fetal and neonatal erythropoiesis and the underlying etiologies of the inherited red blood cell disorders, as well as reviews the appropriate diagnostic evaluation and next steps in management. It is imperative that neonatal clinicians remain informed about these disorders to enable early recognition and treatment, and ultimately to improve outcomes in affected infants.

Identification of a rare compound heterozygous hemoglobin variant β0-thal [β17(A14) Lys>Stop, HBB: c.52A>T] and Hb J-Lome [β59(E3) Lys>Asn, HBB: c.180G>C]

BACKGROUND

HbA1c is the validated biomarker for glycemic management in diabetic individuals. Here, we report a compound heterozygote for β⁰-thal and Hb J-Lomeand evaluate its effect on HbA1c measurements.

METHODS

A 51-year-old female was suspected of harboring a hemoglobin variant following no value of HbA1c levelby Arkray HA-8180 V (48s HbA1c mode), abnormal hematological data, and abnormalhemoglobin analysison capillary electrophoresis (Capillarys 2 Flex Piercing, Hb program). Sanger sequencing of the α and β genes was subsequently performed on the proband.HbA1c was reanalyzed using D10 (Bio-Rad), Capillarys 2 Flex Piercing (Sebia), and Roche Cobas c501 (Roche Diagnostics).

RESULTS

Sanger sequencing identified a compound heterozygote for β⁰-thal [β17(A14) Lys > Stop, HBB: c.52A > T] and Hb J-Lome [β59(E3) Lys > Asn, HBB: c.180G > C].HbA1c values ⁣⁣determinedby D10, Capillarys 2 Flex Piercing (HbA1c program), and Roche Cobas c501were 2.3%, no HbA1c value, and 5.1 (32 mmol/mol), respectively. During pedigree analysis, the son of the proband was found to have normal blood glucose (5.55 mmol/L), decreased HbA1c (3.6%, 16 mmol/mol)by Arkray HA-8180 V (48s HbA1c mode), an abnormal band on the electrophoretogram of Capillarys2 (Hb program), and the Hb J-Lome mutation in the β globin gene.Subsequently, HbA1c values ⁣⁣determinedby D10, Capillarys 2 Flex Piercing (HbA1c program), and Roche Cobas c501 were4.0% (20 mmol/mol), no HbA1c value, and 5.0 (31 mmol/mol), respectively.

CONCLUSION

Atypically low HbA1c levels or a discrepancy between blood glucose and HbA1c levels should raise concerns about hemoglobin variations.

First study to describe a novel HbA2: c.400A > C mutation and Hb Dongguan heterozygote in two unrelated Chinese families

OBJECTIVES

Here we report two rare α-globin chain variants in two unrelated families: Hb Val de Marne [α133(H16) Ser > Arg (AGC > CGC); HBA2: c.400A > C] and Hb Dongguan [α52(E6) Ser > Cys (TCT > TGT); HBA1: c.158C > G]. Notably, HBA2: c.400A > C is an unreported new variant in the third exon of the α₂ gene, and simple heterozygous unstable Hb Dongguan haematological characteristics are proposed for the first time.

METHODS

Hb analysis was performed by using capillary electrophoresis (CE). Twenty-three common mutations were detected using a suspension array system. Mutations were identified by DNA sequencing.

RESULTS

The CE results showed an abnormal peak with incomplete separation from Hb A at zone 8 in two members of Family 1. DNA sequencing confirmed the presence of Hb Val de Marne [α133(H16) Ser > Arg (AGC > CGC); HBA2: c.400A > C]. Five members of Family 2 exhibited an abnormal peak at zone 11, and DNA sequencing confirmed the presence of Hb Dongguan [α52(E6) Ser > Cys (TCT > TGT); HBA1: c.158C > G].

CONCLUSIONS

The discovery of HBA2: C.400A > C expands the existing spectrum of α-globin variants. The carriers of simple heterozygous Hb Dongguan generally do not have obvious clinical symptoms. The information in this study will help clinicians understand the screening, molecular diagnosis and clinical significance of Hb variants.

Identification of Pulmonary Hypertension Animal Models Using a New Evolutionary Machine Learning Framework Based on Blood Routine Indicators

Pulmonary Hypertension (PH) is a global health problem that affects about 1% of the global population. Animal models of PH play a vital role in unraveling the pathophysiological mechanisms of the disease. The present study proposes a Kernel Extreme Learning Machine (KELM) model based on an improved Whale Optimization Algorithm (WOA) for predicting PH mouse models. The experimental results showed that the selected blood indicators, including Haemoglobin (HGB), Hematocrit (HCT), Mean, Platelet Volume (MPV), Platelet distribution width (PDW), and Platelet-Large Cell Ratio (P-LCR), were essential for identifying PH mouse models using the feature selection method proposed in this paper. Remarkably, the method achieved 100.0% accuracy and 100.0% specificity in classification, demonstrating that our method has great potential to be used for evaluating and identifying mouse PH models.

Effect of Different Gas-Stunning Conditions on Heme Pigment Solutions and on the Color of Blood, Meat, and Small Intestine of Rabbits

The objectives of this study were to elucidate the effect of different high-concentration levels of inert gases (Ar and N2) on heme-pigment solutions and on the color of the blood, meat, and small intestine of rabbits; and to figure out the proper concentration level of inert gas (Ar or N2) for the complete stunning of the rabbit. To observe the changing of color attributes, a research study was conducted in the abattoir of the National Institute of Animal Science (NIAS), RDA, Republic of Korea. This experiment had 2 parts, (i) A trial on heme-pigment solutions (hemoglobin and myoglobin solution) was conducted in a gas chamber with different high-concentration levels of carbon dioxide, argon, nitrogen, and normal air; and (ii) a rabbit experiment was conducted—stunning with different high-concentration levels of carbon dioxide, argon, nitrogen, and the Halal method (non-stunning). A small-size digital gas chamber was used for this experiment (size: width 850 mm × depth 1350 mm). Artificial hemoglobin (Hb) and myoglobin (Mb) solutions were created from “porcine hemoglobin lyophilized powder” and “equine skeletal muscle myoglobin lyophilized powder”, respectively. In the heme-pigment solutions trial, 10 treatments were used: (i) 80% carbon dioxide (T1), (ii) 85% carbon dioxide (T2), (iii) 90% carbon dioxide (T3), (iv) 80% argon (T4), (v) 85% argon (T5), (vi) 90% argon (T6), (vii) 80% nitogen (T7), (viii) 85% nitogen (T8), (ix) 90% nitogen (T9), and (x) normal air (T10). Heme-pigment solutions (both Hb and Mb) were exposed with each treatment for four separate durations of time (30 s, 1 min, 2 min, and 4 min); and every sample (Hb and Mb) was exposed during each duration of time for 10 times (n = 10). In the rabbit experiment, seven treatments were used (i) 85% carbon dioxide (T1), (ii) 90% carbon dioxide (T2), (iii) 85% argon (T3), (iv) 90% argon (T4), (v) 96% nitrogen (T5), (vi) 98% nitogen (T6), and (vii) the Halal method (non-stunning) (T7). Forty-two rabbits (mixed-breed) were collected from the nearest commercial farm and randomly selected for a treatment group (n = 6). The average body weight was 2.3 kg. For stunning, each individual rabbit was separately kept in a gas chamber, after which each specific gas was used to fulfill the desired level in the pit. After reaching the desired level of concentration, rabbits were stunned within a very short time. It was observed that the time required for stunning in the T1, T2, T3, T4, T5 and T6 treatment was 79−82, 68−73, 97−103, 88−91, 164−173, and 108−115 s, respectively. In the case of the Halal method (non-stunning), as per the rules of Islam, rabbits were slaughtered without stunning. After slaughtering, in all treatments, the blood, meat, and small intestine of each animal were collected carefully and kept in a cool room in which the temperature was −2 °C, and after 24 h, the color attributes—lightness (L*), redness (a*), and yellowness (b*)—were measured via a Chroma Meter. It was found that in both experiments (trial on heme-pigment solutions and rabbit stunning), the color values (L*, a* and b*) showed a significant difference (p < 0.05) among the treatment groups. The CO2-treated groups showed high redness (a*) and low lightness (L*) and yellowness (b*), which indicated a dark-red color, and N2-treated groups showed high lightness (L*) and yellowness (b*) and low redness (a*), which implied a bright-red color. The effect of the Ar was in between the CO2- and N2-treated groups. These phenomena were observed both in the heme-pigment solutions (Hb and Mb) and in the blood, meat, and small intestine of the rabbits. N2-stunned animals fulfill the fundamental desire of consumers to purchase bright red-colored fresh meat. Therefore, in view of color attributes, consumer satisfaction, and animal welfare, N2 gas can be thought of as a valuable alternative to stunning. Considering the time required for complete stunning and desirable color attributes, a 98% concentration of N2 is best for rabbit stunning. As such, it could be used as a better option for the gas stunning of animals.

Hb Nivaria: A New Hemoglobin Variant with a Shortened -Globin Chain [139(HC1)LysStop; HBA1: c.418A>T]

We report a novel hemoglobin (Hb) variant found in a Spanish individual from Santa Cruz de Tenerife, the Canary Islands in Spain. The proband was a 39-year-old male. High performance liquid chromatography (HPLC) displayed an unknown peak (19.3%) at a retention time of 1.3 min. eluting before Hb A₀. Capillary zone electrophoresis (CZE) showed an abnormal peak (20.0%) in zone 12. Direct DNA sequencing of the α-globin genes revealed heterozygosity for a nonsense mutation at codon 139 (AAA>TAA), causing a lysine to stop codon substitution [α139(HC1)Lys→Stop; HBA1: c.418A>T]. We decided to name the variant Hb Nivaria (Tenerife) for the place of birth and residence of the proband.

Iron stores in steady-state sickle cell disease children accessing care at a sickle cell disease clinic in Kumasi, Ghana: A cross-sectional study

Background and Aims

Children with sickle cell disease (SCD) have an increased risk of multiple hemotransfusions and this can predispose them to elevated iron stores. The objectives of the study were to determine the extent of elevated iron stores and the associated risk factors in a population of steady-state SCD children in Ghana.

Methods

This cross-sectional study was conducted at the pediatric sickle cell clinic at the Komfo Anokye Teaching Hospital. Complete blood count and serum ferritin assay were performed for (n = 178) steady-state SCD children. Descriptive and multivariate logistic regression analysis were performed. Elevated iron stores were defined as serum ferritin levels >300 ng/ml. Statistical significance was considered at p < 0.05.

Results

The mean (standard deviation) age of the participants was 9.61 (±4.34) years, and 51% of them were males. About 17% of SCD children had elevated iron stores and receiving at least three hemotransfusions during the last 12 months was strongly associated with elevated iron stores (p < 0.001). History of chronic hemotransfusion increased the odds of having elevated iron store (adjusted odds ratio [aOR] = 11.41; 95% confidence interval [CI] = 3.11-30.85; p < 0.001) but SCD patients on hydroxyurea treatment had reduced-odds of having elevated iron stores (aOR = 0.18; 95% CI = 0.06-0.602; p = 0.006). Moreover, red blood cell (Coef. = -0.84; 95% CI = -0.37, -1.32; p = 0.001), hemoglobin (Coef. = -0.83; 95% CI = -0.05, -1.61; p = 0.04), hematocrit (Coef. = -0.85; 95% CI = -0.08, -1.63; p = 0.03), mean cell volume (Coef. = 0.02; 95% CI = 0.01, 0.03; p = 0.001) and mean cell hemoglobin (Coef. = 0.04; 95% CI = 0.01, 0.07; p = 0.002) could significantly predict serum ferritin levels.

Conclusion

The magnitude of elevated iron stores was high among children with SCD in steady-state. Red cell indices could provide invaluable information regarding the risk of elevated iron stores. SCD children who have a history of chronic hemotransfusion or had received at least three hemotransfusions in a year should be monitored for elevated iron stores.

Novel insights into heme binding to hemoglobin

Under hemolytic conditions, hemoglobin and subsequently heme are rapidly released, leading to the toxic effects characterizing diseases such as β-thalassemia and sickle cell disease. Herein, we provide evidence that human hemoglobin can bind heme in a transient fashion via surface-exposed sequence motifs. Following the synthesis of potential heme-binding motifs (HBMs) as peptides, their heme-binding capacity was investigated by UV-vis spectroscopy and ranked according to their binding affinity. Heme binding to human hemoglobin was subsequently studied by UV-vis and surface plasmon resonance (SPR) spectroscopy, revealing a heme-binding affinity in the sub- to micromolar range and a stoichiometry that clearly exceeds a 1:1 ratio. In silico molecular docking and simulation studies confirmed heme binding to the respective motifs in the β-chain of hemoglobin. Finally, the peroxidase-like activity of hemoglobin and the hemoglobin-heme complex was monitored, which indicated a much higher activity (>1800%) than other heme-peptide/protein complexes reported so far. The present study provides novel insights into the nature of intact hemoglobin concerning its transient interaction with heme, which suggests for the first time potential heme-scavenging properties of the protein at concomitant disassembly and, consequently, a potentiation of hemolysis and related processes.

Hb Wanjiang: A New β-Globin Chain Variant with Two Amino Acid Substitutions (HBB: c.255_264delinsTTTTTCTCAG)

We report a new hemoglobin (Hb) variant that we have named Hb Wanjiang (HBB: c.255_264delinsTTTTTCTCAG). We identified this variant in a Chinese man by the next-generation sequencing (NGS) method. The father of the proband also carried the same variant. This variant results from a 10 bp deletion at codons 84-87 of the β-globin chain, replaced with 10 nucleotides coming from the δ-globin gene at the same position, leading to the substitution of two amino acids in the peptide chain with no change in the β-globin chain length. The heterozygotes had a normal hematological feature with no abnormal Hb variant detectable on capillary electrophoresis (CE) and high performance liquid chromatography (HPLC). The combination of Hb Wanjiang and β-thalassemia (β-thal) was not found to aggravate anemia.

Noninvasive hemoglobin sensing and imaging: optical tools for disease diagnosis

SIGNIFICANCE

Measurement and imaging of hemoglobin oxygenation are used extensively in the detection and diagnosis of disease; however, the applied instruments vary widely in their depth of imaging, spatiotemporal resolution, sensitivity, accuracy, complexity, physical size, and cost. The wide variation in available instrumentation can make it challenging for end users to select the appropriate tools for their application and to understand the relative limitations of different methods.

AIM

We aim to provide a systematic overview of the field of hemoglobin imaging and sensing.

APPROACH

We reviewed the sensing and imaging methods used to analyze hemoglobin oxygenation, including pulse oximetry, spectral reflectance imaging, diffuse optical imaging, spectroscopic optical coherence tomography, photoacoustic imaging, and diffuse correlation spectroscopy.

RESULTS

We compared and contrasted the ability of different methods to determine hemoglobin biomarkers such as oxygenation while considering factors that influence their practical application.

CONCLUSIONS

We highlight key limitations in the current state-of-the-art and make suggestions for routes to advance the clinical use and interpretation of hemoglobin oxygenation information.

Adapting the ACMG/AMP variant classification framework: A perspective from the ClinGen Hemoglobinopathy Variant Curation Expert Panel

Accurate and consistent interpretation of sequence variants is integral to the delivery of safe and reliable diagnostic genetic services. To standardize the interpretation process, in 2015, the American College of Medical Genetics and Genomics (ACMG) and the Association for Molecular Pathology (AMP) published a joint guideline based on a set of shared standards for the classification of variants in Mendelian diseases. The generality of these standards and their subjective interpretation between laboratories has prompted efforts to reduce discordance of variant classifications, with a focus on the expert specification of the ACMG/AMP guidelines for individual genes or diseases. Herein, we describe our experience as a ClinGen Variant Curation Expert Panel to adapt the ACMG/AMP criteria for the classification of variants in three globin genes (HBB, HBA2, and HBA1) related to recessively inherited hemoglobinopathies, including five evidence categories, as use cases demonstrating the process of specification and the underlying rationale.

Metabolic Reprogramming in Sickle Cell Diseases: Pathophysiology and Drug Discovery Opportunities

Sickle cell disease (SCD) is a genetic disorder that affects millions of individuals worldwide. Chronic anemia, hemolysis, and vasculopathy are associated with SCD, and their role has been well characterized. These symptoms stem from hemoglobin (Hb) polymerization, which is the primary event in the molecular pathogenesis of SCD and contributes to erythrocyte or red blood cell (RBC) sickling, stiffness, and vaso-occlusion. The disease is caused by a mutation at the sixth position of the β-globin gene, coding for sickle Hb (HbS) instead of normal adult Hb (HbA), which under hypoxic conditions polymerizes into rigid fibers to distort the shapes of the RBCs. Only a few therapies are available, with the universal effectiveness of recently approved therapies still being monitored. In this review, we first focus on how sickle RBCs have altered metabolism and then highlight how this understanding reveals potential targets involved in the pathogenesis of the disease, which can be leveraged to create novel therapeutics for SCD.

Significantly High HbA1c in Diabetic Patient with Hb J: Case Report

Glycated hemoglobin (HbA_1c) is used to monitor the long-term management of diabetes and reflects the average blood glucose level over the past three months. Hb J is an alpha-globin gene variant that occurs less commonly but can interfere with the HbA_1c result. This case report presents two cases of abnormally high HbA_1c in patients with Hb J using the high-performance liquid chromatography (HPLC) method and repeated value using the capillary electrophoresis (CE) method. The first case was a 26 years old female Malay patient, presenting at 25 weeks gestation with diabetes mellitus (DM). Her HbA_1c results from HPLC showed persistently high level (> 18.5%, > 179 mmol/mol) despite optimum diabetic control (fasting blood sugar (FBS) range 4.0–6.1 mmol/L). The second case was a 62-year-old female Malay with type 2 DM. Her HbA_1c results from HPLC was also persistently high (> 18.5%, > 1;79 mmol/mol) despite good diabetic control (FBS average 5.0–7.0 mmol/L). Both patients’ hemoglobin analysis reports were suggestive of Hb J. Repeated HbA_1c using CE were 6.0% (42 mmol/mol) and 8.1% (65 mmol/mol), respectively, and supported the presence of the Hb J variant peak. HbA_1c measurement in patients with a variant should be interpreted with caution to avoid misdiagnosis and mismanagement in these kinds of patients.

Improvement of Protein Solubility in Macromolecular Crowding during Myoglobin Evolution

The inside of living cells is crowded by extremely high concentrations of biomolecules, and thus globular proteins should have been developed to increase their solubility under such crowding conditions during organic evolution. The O₂-storage protein myoglobin (Mb) is known to be expressed in myocytes of diving mammals in much larger quantities than those of land mammals. We have previously resurrected ancient whale and pinniped Mbs and experimentally demonstrated that the diving animal Mbs have evolved to maintain high solubility under the crowding conditions or to increase their tolerance against macromolecular precipitants, rather than solubility in a dilute buffer solution. However, the detail of chemical mechanisms of the precipitant tolerance remains unclear. Here, we investigated pH dependence of the precipitant tolerance (β, slope of the solubility against precipitant concentration) of extant Mbs and plotted the β values, as well as those of ancestral Mbs, against their surface net charges (Z_Mb). The results demonstrated that the precipitant tolerance was approximated by the square of Z_Mb, that is, β = aZ_Mb² + b, in which a and b are constants. This effect of Z_Mb against the precipitation is not predicted by a classical excluded volume theory that gives constant β for Mbs but can be explained by electrostatic repulsion between Mb molecules. The present study elucidates how Mb molecules have evolved to increase their in vivo solubility and shows the physiological significance of either neutral or basic isoelectric points (pI) of the natural Mbs, rather than acidic pI.

Using total RNA quality metrics for time since deposition estimates in degrading bloodstains

The physicochemical changes occurring in biomolecules in degrading bloodstains can be used to approximate the time since deposition (TSD) of bloodstains. This would provide forensic scientists with critical information regarding the timeline of the events involving bloodshed. Our study aims to quantify the timewise degradation trends and temperature dependence found in total RNA from bloodstains without the use of amplification, expanding the scope of the RNA TSD research which has traditionally targeted mRNA and miRNA. Bovine blood with ACD-A anticoagulant was deposited and stored in plastic microcentrifuge tubes at 21 or 4°C and tested over different timepoints spanning 1 week. Total RNA was extracted from each sample and analyzed using automated high sensitivity gel electrophoresis. Nine RNA metrics were visually assessed and quantified using linear and mixed models. The RNA Integrity Number equivalent (RINe) and DV200 were not influenced by the addition of anticoagulant and demonstrated strong negative trends over time. The RINe model fit was high (R²  = 0.60), and while including the biological replicate as a random effect increased the fit for all RNA metrics, no significant differences were found between biological replicates stored at the same temperature for the RINe and DV200. This suggests that these standardized metrics can be directly compared between scenarios and individuals, with DV200 having an inflection point at approximately 28 h. This study provides a novel approach for blood TSD research, revealing metrics that are not affected by inter-individual variation, and improving our understanding of the rapid RNA degradation occurring in bloodstains.

Hemoglobin Rothschild – Unimpaired physical performance and oxygen uptake – A case report with literature review

Asymptomatic patients with hemoglobin (Hb) variants can be detected by low oxygen levels in pulse oximetry (SpO₂).

Depending on the type of Hb variant, low SpO₂ values are either falsely low, with corresponding normal arterial oxygen saturation (SaO₂), or truly low, with low SaO₂ values, as observed in Hb variants with low oxygen binding affinity. In this context, attention must be paid to the method of determining SaO₂.

Low oxygen affinity Hb variants such as Hb Rothschild (HbR) might compensate for low oxygen loading in the lung through unloading more oxygen in peripheral tissues. This is the first case report to illustrate that maximal oxygen uptake and the workload are unimpaired in HbR variant patients.

Novel mutations in EPO-R and oxygen-dependent degradation (ODD) domain of EPAS1 genes-a causative reason for Congenital Erythrocytosis

Congenital Erythrocytosis (CE) can be primary or secondary due to the mutations in genes involved in the erythropoietin receptor and oxygen sensing pathway. In this study, 42 patients with 38 unrelated patients and one family (4 patients) who were JAK-2 mutation (both exon 12 and exon 14) negative with high haematocrit values were investigated. The Endogenous Erythroid colony (EEC) assay was performed in all patients, interestingly EEC colonies were high in EPAS1 and EPOR mutated patients compared to non-mutated patients. The sequence analysis of EPAS1 (exon 12), EPO-R (exon-8), VHL (exon-3), and EGLN1 (exon-1) genes in all these patients showed 19% of patients (8/42) had mutations, in exon12 of EPAS1 and exon 8 of EPO-R genes. Two novel missense mutations MW_600850:c.1183G>C, MW_600851:c.1028A>C in EPO-R gene were observed in the study group. One new MW_600849:c.1969C>T nonsense mutation and five MW_619914:c.1715A>G, MW_619915:c.1694G>T, MW_619916:c.1634T>C, MW_600852:c.1771C>G, MW_600848:c.1859G>A novel missense mutations were observed in the EPAS1 gene. Among them, 4 mutations p. (Gln572Arg), p. (Ser565Ile), p. (Ile545Thr), p. (Gln591Glu) in the ODD (Oxygen-dependent degradation) domain of HIF2α, all these variations contributed to the formation of non-functional HIF2α. No mutations were observed in VHL and EGLN1 genes. Using in silico analysis we observed that these mutations contributed to major conformational changes in the HIF2α protein making it non-functional. The mutations in the EPAS1 gene were heterozygous and show autosomal dominant inheritance patterns and we observed in one family. These novel mutations in the EPAS1 (75% (6/8)) and 25% (2/8) EPO-R genes correlating with EEC positivity were observed for the first time in India in CE patients.

On the Origin of Hemoglobin Cooperativity under Non-equilibrium Conditions

Abnormal hemoglobins can have major consequences for tissue delivery of oxygen. Correct diagnosis of hemoglobinopathies with altered oxygen affinity requires a determination of hemoglobin oxygen dissociation curve, which relates the hemoglobin oxygen saturation to the partial pressure of oxygen in the blood. Determination of the oxygen dissociation curve of human hemoglobin is typically carried out under conditions in which hemoglobin is in equilibrium with O2 at each partial pressure. However, in the human body due to the fast transit of red blood cells through tissues hemoglobin oxygen exchanges occur under non-equilibrium conditions. We describe the determination of non-equilibrium oxygen dissociation curve and show that under these conditions the true nature of hemoglobin cooperativity is revealed as emerging solely from the consecutive binding of oxygen to each one of the four subunits of hemoglobin until the entire tetramer is saturated. We call this form of cooperativity the sequential cooperativity of hemoglobin and define the simplest model that includes it as the minimalist model of hemoglobin. A single instantiation of this model accounts for ~70% of hemoglobin cooperativity under non-equilibrium conditions. The total cooperativity of hemoglobin can be viewed more correctly as the summation of two instantiations of the minimalist model (each one corresponding to a tetramer of low and high affinity for O2, respectively) in equilibrium with each other, as in the Monod-Wyman-Changeux model of hemoglobin. In addition to offering new insights on the nature of hemoglobin reaction with oxygen, the methodology described here for the determination of hemoglobin non-equilibrium oxygen dissociation curve provides a simple, fast, low-cost alternative to complex spectrophotometric methods, which is expected to be particularly valuable in regions where hemoglobinopathies are a significant public health problem, but where highly specialized laboratories capable of determining a traditional oxygen dissociation curve are not easily accessible.

Two co-inherited hemoglobin variants revealed by capillary electrophoresis during quantification of glycated hemoglobin

OBJECTIVES

The observation of numerous new structural defects in hemoglobin (Hb) has often been linked to the evolution and development of device technologies used for the separation and quantification of hemoglobin components. However, the increased use of preventive tests for hemoglobinopathies and separative methods to quantify glycated hemoglobin (HbA_1c) also contributed to these observations, as demonstrated by the case described here. Our aim is to emphasize that different separative method can provide more useful information in patient management.

METHODS

A 64-year-old diabetic woman of Moroccan descent was examined in the context of HbA_1c monitoring. The test was performed using high performance liquid chromatography (HPLC) and capillary electrophoresis (CE) systems. Molecular characterization was performed by direct sequencing of the β and α globin genes.

RESULTS

The two methods used showed the presence of an anomalous fraction identified as HbS, already observed previously, but only through CE it was possible to observe the presence of another variant and its hybrid components. Direct sequencing of β and α globin genes confirmed heterozygous HbS [β6 (A3) Glu→Val; HBB: c.20A>T] and allowed to identify a mutation on the α ₂, [α114 (GH2) Pro→Leu gene; HBA2: c.344C>T] corresponding to the rare Hb Nouakchott variant.

CONCLUSIONS

The two Hb variants highlighted by the EC and the molecular characterization therefore allowed adequate advice, the correct assessment of HbA_1c and metabolic status and therefore better clinical management of the patient. The availability of different instruments in the same laboratory, confirming situations of diagnostic uncertainty, represents a valuable opportunity that should be encouraged.

A Rare Hemoglobin Variant (β51Pro → His) Causing Misleading Measurements of Hemoglobin A1c

Glycated hemoglobin A_1c (HbA_1c) is considered the standard of care for the testing and monitoring of diabetes. Its ability to accurately reflect glycemia, however, is imperfect. Hemoglobin variants—mutant forms of hemoglobin caused by genetic variation present in 7% of the population—are known to adversely affect the ability of HbA_1c measurement to reflect glycemic control. We report an illustrative case of a 64-year-old nondiabetic man with a steadily decreasing HbA_1c and no symptoms of hypoglycemia or concerning family history. Preliminary investigative workup returned nothing of significance. Genetic sequencing, however, identified a rare benign hemoglobin variant: a heterozygous missense mutation in the gene encoding the hemoglobin β chain (c.155C > A, p.Pro51His). This variant has been reported only once previously, and the report predates genetic sequence data of the variant. Although this variant had no clinical implications for the patient, it was the cause of falsely low HbA_1c levels on high-performance ion-exchange chromatography. This case highlights the importance of considering the effect of hemoglobin variants on the measurement of HbA_1c. When available, family history should be carefully considered. Clinicians should suspect hemoglobin variants when HbA_1c is too high or low, or discordant with the clinical picture.

Associations between HbA1c-derived estimated average glucose and fasting plasma glucose in patients with normal and abnormal hemoglobin patterns

Fasting plasma glucose (FPG) and HbA1c are well-known tests for monitoring short and long-term glycemic control, respectively. Estimated average glucose (eAG) is derived from the HbA1c for expression in the same units as FPG. The present study aimed to evaluate the association between eAG and FPG values. This retrospective study was performed on 1285 patients who measured the FPG and HbA1c (capillary electrophoresis method) values on the same day. They were initially divided into 3 hemoglobin-pattern groups, normal, HbE, and high HbA₂, and then these 3 groups were further subdivided into whole group, subgroup 1 (HbA1c ≤ 7%) and subgroup 2 (HbA1c >7%) for analytical comparisons. The eAG values were calculated using Nathan's equation. The differences, agreements, and correlations between eAG and FPG were evaluated. Good agreements and strong positive correlations between eAG and FPG values were observed in all 3 whole groups. In subgroup analysis, the degrees of agreement and correlation depended on the level of glycemic control, as all associations became stronger with better glycemic control. Additionally, the HbA1c levels and different eAG-FPG values between the normal and other groups were not significantly different in either whole group or subgroup comparisons. Our study found good agreements and strong positive correlations between eAG and FPG in all groups, indicating that high HbA₂ or HbE did not affect the HbA1c levels or thus the associations between eAG and FPG. Reporting the eAG together with the HbA1c value should help improve the understanding of glycemic status in patients, leading to improved blood glucose control.

Hemoglobin bio-adhesive nanoparticles as a colon-specific delivery system for sustained release of 5-aminosalicylic acid in the effective treatment of inflammatory bowel disease

A colonic drug delivery system was developed to specifically deliver 5-aminosalicylic acid (5-ASA) to the inflamed site by conjugating with hemoglobin nanoparticles (HbNPs). The 5-ASA-HbNPs (eight 5-ASA molecules per Hb molecule) with the size of 220 nm and zeta potential of -14.6 mV is a tailored nanoparticle able to pass through the mucus layer. The 5-ASA-HbNPs do not undergo chemical and enzymatic hydrolysis in the simulated gastrointestinal fluids over 6 h. Significantly higher cellular uptakes and prolonged release was seen for the 5-ASA-HbNPs in Caco-2 cells, compared to free 5-ASA over 72 h. In addition, 5-ASA-HbNPs revealed similar therapeutic effectiveness with free 5-ASA against tumor necrosis factor and showed less inhibitory concentration (IC50) for myeloperoxidase enzyme activity. In vivo imaging of mouse demonstrated the localization of drug in the descending colon after oral administration and about 15% of the administered dose was recovered as 5-ASA from urine in 6 h. The use of these nanoparticles with the mucus adhesion properties and permeability to intestinal epithelial cells can be a good candidate with potential application in the colonic drug delivery field.

Characterization of Structural Hemoglobin Variants by Top-Down Mass Spectrometry and R Programming Tools for Rapid Identification

Hemoglobinopathies are one of the most prevalent genetic disorders, affecting millions throughout the world. These are caused by pathogenic variants in genes that control the production of hemoglobin (Hb) subunits. As the number of known Hb variants has increased, it has become more challenging to obtain unambiguous results from routine chromatographic assays employed in the clinical laboratory. Top-down proteomic analysis of Hb by mass spectrometry is a definitive method to directly characterize the sequences of intact subunits. Here, we apply "chimeric ion loading" to characterize Hb β subunit variants. In this technique, product ions derived from complementary dissociation techniques are accumulated in a multipole storage device before delivery to a 21 T Fourier-transform ion cyclotron resonance mass spectrometer for simultaneous detection. To further improve the efficiency of identification of Hb variants and localization of the mutation site(s), we developed an R programming script, "Variants Identifier", to search top-down data against a database containing accurate intact mass differences and diagnostic ions from investigated Hb variants. A second R script, "PredictDiag", was developed and employed to determine relevant diagnostic ions for additional Hb variants with known sequences. These two R scripts were successfully applied to the identification of a Hb δ-β fusion protein and other Hb variants. The combination of chimeric ion loading and the above R scripts enables rapid and reliable interpretation of top-down mass spectrometry data, regardless of activation type, for Hb variant identification.