New insights on hereditary erythrocyte membrane defects

Deciphering and disrupting PIEZO1-TMEM16F interplay in hereditary xerocytosis

ABSTRACT

Cell-surface exposure of phosphatidylserine (PS) is essential for phagocytic clearance and blood clotting. Although a calcium-activated phospholipid scramblase (CaPLSase) has long been proposed to mediate PS exposure in red blood cells (RBCs), its identity, activation mechanism, and role in RBC biology and disease remain elusive. Here, we demonstrate that TMEM16F, the long-sought-after RBC CaPLSase, is activated by calcium influx through the mechanosensitive channel PIEZO1 in RBCs. PIEZO1-TMEM16F functional coupling is enhanced in RBCs from individuals with hereditary xerocytosis (HX), an RBC disorder caused by PIEZO1 gain-of-function channelopathy. Enhanced PIEZO1-TMEM16F coupling leads to an increased propensity to expose PS, which may serve as a key risk factor for HX clinical manifestations including anemia, splenomegaly, and postsplenectomy thrombosis. Spider toxin GsMTx-4 and antigout medication benzbromarone inhibit PIEZO1, preventing force-induced echinocytosis, hemolysis, and PS exposure in HX RBCs. Our study thus reveals an activation mechanism of TMEM16F CaPLSase and its pathophysiological function in HX, providing insights into potential treatment.

Case report: Whole-exome sequencing for a hereditary elliptocytosis case with an unexpectedly low HbA1c

Objectives

Hereditary elliptocytosis is a group of erythroid hereditary diseases characterized by elliptically shaped erythrocytes in peripheral blood. It is mainly inherited through autosomal dominant inheritance. This study aimed to conduct a genetic etiology analysis in a case with a clinical diagnosis of hereditary elliptocytosis and an unexpectedly low HbA1c.

Methods

Whole-exome sequencing was performed to find the possible pathogenic mutations. At the same time, bioinformatics software was used to predict the mutation function. Sanger sequencing was performed to verify the suspected pathogenic mutations.

Results

Whole-exome sequencing results showed that the proband with mild anemia had a heterozygous c.2303G>A (p.G768D) missense mutation in the 13th exon of the SPTB gene. The Sanger sequencing confirmed this heterozygous mutation. This mutation was extremely rare in the population, and multiple software's predictions were harmful. Conservative analysis revealed that this site was highly conserved in various species.

Conclusion

The c.2303G>A mutation of the SPTB gene is the suspected cause of hereditary elliptocytosis in the patient. Our data show that microscopic examination of red blood cells on blood smears is an important means of diagnosing hereditary elliptocytosis. Whole-exome sequencing is an effective tool to determine the genetic etiology of erythrocyte membrane diseases, which can promote accurate diagnosis and genetic counseling.

Case report: Genetic analysis of a novel intronic inversion variant in the SPTB gene associated with hereditary spherocytosis

Background: Hereditary spherocytosis (HS) is a congenital haemolytic anaemia attributed to dysregulation or abnormal quantities of erythrocyte membrane proteins. Currently, the most common erythrocytic gene, spectrin β (SPTB), variants are located in exons and give rise to mRNA defects. However, the genetic characteristics and pathogenic mechanisms of SPTB intronic variants are not completely understood. This study aimed to analyse a rare intronic inversion variant in the SPTB gene associated with HS, and explore the impact of the variant on SPTB mRNA splicing. Method: The clinical manifestations of the patient were summarised and analysed for spherocytosis phenotype diagnosis. The pathogenic variant was identified in the proband using targeted next-generation and Sanger sequencing. RNA sequencing was performed to analyse whether SPTB gene splicing and expression were affected. Results: Targeted next-generation sequencing identified a novel disease-associated intronic inversion variant of the SPTB gene in the proband. The inversion variant was located between intron 19 and 20, and contained the entire exon 20 and partial sequences of adjacent introns. Sanger sequencing confirmed that the intronic inversion variant only appeared in the genome of the proband, not in his parents. RNA sequencing revealed that the variant could result in the skipping of exon 20 and reduced expression of SPTB mRNA. Conclusion: This study identifies a rare intronic inversion variant in the SPTB gene associated with hereditary spherocytosis. The pathogenic variant can lead to exon 20 skipping and decreased SPTB gene expression. This finding has not been previously reported in any literature. This study can expand the intronic variant spectrum of the SPTB gene, deepen our understanding of HS pathogenesis, and contribute to the genetic diagnosis and clinical management of patients.

Next generation sequencing (NGS) interest in deciphering erythrocyte molecular defects' association in red cell disorders: Clinical and erythrocyte phenotypes of patients with mutations inheritance in PIEZO1, Spectrin ß1, RhAG and SLC4A1

We report here an instructive case referred at 16 months-old for exploration of hemolysis without anemia (compensated anemia with reticulocytosis). The biology tests confirmed the hemolysis with increased total and indirect bilirubin. The usual hemolysis diagnosis tests were normal (DAT, G6PD, PK, Hb electrophoresis) except cytology and ektacytometry suggesting an association of multiple red blood cell (RBC) membrane disorders. This led us to propose a molecular screening analysis using targeted-Next Generation Sequencing (t-NGS) with a capture technique on 93 genes involved in RBC and erythropoiesis defects. We identified 4 missense heterozygous allelic variations, all of them were described without any significance (VUS) in the SLC4A1, RhAG, PIEZO1 and SPTB genes. The study of the familial cosegregation and research functional tests allowed to decipher the role of at least two by two genes in the phenotype and the hemolytic disease of this young patient. Specialized t-NGS panel (or virtual exome/genome sequencing) in a disease-referent laboratory and the motivated collaboration of clinicians, biologists and scientists should be the gold standard for improving the diagnosis of the patients affected with RBC diseases or rare inherited anemias.

Peroxiredoxins in erythrocytes: far beyond the antioxidant role

The red blood cells (RBCs) are essential to transport oxygen (O2) and nutrients throughout the human body. Changes in the structure or functioning of the erythrocytes can lead to several deficiencies, such as hemolytic anemias, in which an increase in reactive oxidative species generation is involved in the pathophysiological process, playing a significant role in the severity of several clinical manifestations. There are important lines of defense against the damage caused by oxidizing molecules. Among the antioxidant molecules, the enzyme peroxiredoxin (Prx) has the higher decomposition power of hydrogen peroxide, especially in RBCs, standing out because of its abundance. This review aimed to present the recent findings that broke some paradigms regarding the three isoforms of Prxs found in RBC (Prx1, Prx2, and Prx6), showing that in addition to their antioxidant activity, these enzymes may have supplementary roles in transducing peroxide signals, as molecular chaperones, protecting from membrane damage, and maintenance of iron homeostasis, thus contributing to the overall survival of human RBCs, roles that seen to be disrupted in hemolytic anemia conditions.

Plasmodium knowlesi (Pk) Malaria: A Review & Proposal of Therapeutically Rational Exchange (T-REX) of Pk-Resistant Red Blood Cells

Plasmodium knowlesi (Pk) causes zoonotic malaria and is known as the "fifth human malaria parasite". Pk malaria is an emerging threat because infections are increasing and can be fatal. While most infections are in Southeast Asia (SEA), especially Malaysia, travelers frequently visit this region and can present with Pk malaria around the world. So, clinicians need to know (1) patients who present with fever after recent travel to SEA might be infected with Pk and (2) Pk is often misdiagnosed as P. malariae (which typically causes less severe malaria). Here we review the history, pathophysiology, clinical features, diagnosis, and treatment of Pk malaria. Severe disease is most common in adults. Signs and symptoms can include fever, abdominal pain, jaundice, acute kidney injury, acute respiratory distress syndrome, hyponatremia, hyperparasitemia, and thrombocytopenia. Dengue is one of the diseases to be considered in the differential. Regarding pathophysiologic mechanisms, when Pk parasites invade mature red blood cells (RBCs, i.e., normocytes) and reticulocytes, changes in the red blood cell (RBC) surface can result in life-threatening cytoadherence, sequestration, and reduced RBC deformability. Since molecular mechanisms involving the erythrocytic stage are responsible for onset of severe disease and lethal outcomes, it is biologically plausible that manual exchange transfusion (ET) or automated RBC exchange (RBCX) could be highly beneficial by replacing "sticky" parasitized RBCs with uninfected, deformable, healthy donor RBCs. Here we suggest use of special Pk-resistant donor RBCs to optimize adjunctive manual ET/RBCX for malaria. "Therapeutically-rational exchange transfusion" (T-REX) is proposed in which Pk-resistant RBCs are transfused (instead of disease-promoting RBCs). Because expression of the Duffy antigen on the surface of human RBCs is essential for parasite invasion, T-REX of Duffy-negative RBCs-also known as Fy(a-b-) RBCs-could replace the majority of the patient's circulating normocytes with Pk invasion-resistant RBCs (in a single procedure lasting about 2 h). When sequestered or non-sequestered iRBCs rupture-in a 24 h Pk asexual life cycle-the released merozoites cannot invade Fy(a-b-) RBCs. When Fy(a-b-) RBC units are scarce (e.g., in Malaysia), clinicians can consider the risks and benefits of transfusing plausibly Pk-resistant RBCs, such as glucose-6-phosphate dehydrogenase deficient (G6PDd) RBCs and Southeast Asian ovalocytes (SAO). Patients typically require a very short recovery time (<1 h) after the procedure. Fy(a-b-) RBCs should have a normal lifespan, while SAO and G6PDd RBCs may have mildly reduced half-lives. Because SAO and G6PDd RBCs come from screened blood donors who are healthy and not anemic, these RBCs have a low-risk for hemolysis and do not need to be removed after the patient recovers from malaria. T-REX could be especially useful if (1) antimalarial medications are not readily available, (2) patients are likely to progress to severe disease, or (3) drug-resistant strains emerge. In conclusion, T-REX is a proposed optimization of manual ET/RBCX that has not yet been utilized but can be considered by physicians to treat Pk malaria patients.

adducin 1 is essential for the survival of erythroid precursors via regulating p53 transcription in zebrafish

Adducin 1 (Add1) is known as a membrane cytoskeletal protein, but its nuclear function remains unclear. In this study, we generated add1-deficient zebrafish to investigate its role in hematopoiesis. Lack of add1 impaired both primitive and definitive hematopoiesis, preventing healthy erythrocyte development. RNA sequencing revealed activation of the p53 pathway in add1-depleted erythroblast cells, leading to apoptosis at the 14-somites stage and 24 hpf. Interestingly, partial rescue of the anemic phenotype and apoptosis was observed with p53 insufficiency. Mechanistically, ADD1 was found to regulate promoter activity. These findings demonstrate that Add1 plays a crucial role in zebrafish erythropoiesis, involving the p53-mediated apoptotic pathway, expanding its regulatory role beyond cytoskeletal functions.

Pentaclethra eetveldeana Leaves from Four Congo-Brazzaville Regions: Antioxidant Capacity, Anti-Inflammatory Activity and Proportional Accumulation of Phytochemicals

Oxidative stress and inflammation play a key role in the occurrence of neurodegenerative diseases. Traditionally, Pentaclethra eetveldeana leaves are used in dementia treatment. Therefore, this study aimed to evaluate the antioxidant and anti-inflammatory activities as well as the phytochemical composition of Pentaclethra eetveldeana leaves from four Congo-Brazzaville regions. The 1.2-diphenyl-1-picrylhydrazyl radical-scavenging, β-carotene bleaching and molybdenum reduction assays were used to assess the antioxidant activity. The protein denaturation and erythrocyte membrane stabilization tests were used to analyze the anti-inflammatory activity. Phytochemical screening, the quantification of polyphenols by spectrophotometry, as well as the determination of extraction yields were carried out. It was found that the extracts reduced molybdenum; furthermore, compared to ascorbic acid, they showed better antiradical activity and inhibited lipid peroxidation. Moreover, globally, the membrane-stabilizing power of the aqueous extracts was superior or comparable to diclofenac, while the same extracts were less effective for the inhibition of denaturation. All of the aqueous extracts contained polyphenols, saponins, alkaloids, anthraquinones, reducing sugar and cardiotonic glycosides. The total polyphenols, tannins and proanthocyanidins are produced proportionally from one region to another. Finally, the leaves from Brazzaville and Boundji contain flavonols, while those from Makoua and Owando contain flavones. Thus, Pentaclethra eetveldeana leaves contribute to traditional dementia treatment through their antioxidant and anti-inflammatory properties.

Splenectomy improves erythrocyte functionality in spherocytosis based on septin abundance, but not maturation defects

Splenectomy improves the clinical parameters of patients with hereditary spherocytosis, but its potential benefit to red blood cell (RBC) functionality and the mechanism behind this benefit remain largely overlooked. Here, we compared 7 nonsplenectomized and 13 splenectomized patients with mutations in the β-spectrin or the ankyrin gene. We showed that hematological parameters, spherocyte abundance, osmotic fragility, intracellular calcium, and extracellular vesicle release were largely but not completely restored by splenectomy, whereas cryohemolysis was not. Affected RBCs exhibited decreases in β-spectrin and/or ankyrin contents and slight alterations in spectrin membrane distribution, depending on the mutation. These modifications were found in both splenectomized and nonsplenectomized patients and poorly correlated with RBC functionality alteration, suggesting additional impairments. Accordingly, we found an increased abundance of septins, small guanosine triphosphate-binding cytoskeletal proteins. Septins-2, -7, and -8 but not -11 were less abundant upon splenectomy and correlated with the disease severity. Septin-2 membrane association was confirmed by immunolabeling. Except for cryohemolysis, all parameters of RBC morphology and functionality correlated with septin abundance. The increased septin content might result from RBC maturation defects, as evidenced by (1) the decreased protein 4.2 and Rh-associated glycoprotein content in all patient RBCs, (2) increased endoplasmic reticulum remnants and endocytosis proteins in nonsplenectomized patients, and (3) increased lysosomal and mitochondrial remnants in splenectomized patients. Our study paves the way for a better understanding of the involvement of septins in RBC membrane biophysical properties. In addition, the lack of restoration of septin-independent cryohemolysis by splenectomy may call into question its recommendation in specific cases.

Anemia and Associated Risk Factors in Pediatric Patients

Anemia is the most common hematologic abnormality identified in children and represents a major global health problem. A delay in diagnosis and treatment might place patients with anemia at risk for the development of rare but serious complications, including chronic and irreversible cognitive impairment. Identified risk factors contributing to the development of anemia in children include the presence of nutritional deficiencies, environmental factors, chronic comorbidities, and congenital disorders of hemoglobin or red blood cells. Pediatricians, especially those in the primary care setting, serve a particularly critical role in the identification and care of those children affected by anemia. Prompt recognition of these risk factors is crucial for developing appropriate and timely therapeutic interventions and prevention strategies.

Activation of pyruvate kinase as therapeutic option for rare hemolytic anemias: Shedding new light on an old enzyme

Novel developments in therapies for various hereditary hemolytic anemias reflect the pivotal role of pyruvate kinase (PK), a key enzyme of glycolysis, in red blood cell (RBC) health. Without PK catalyzing one of the final steps of the Embden-Meyerhof pathway, there is no net yield of adenosine triphosphate (ATP) during glycolysis, the sole source of energy production required for proper RBC function and survival. In hereditary hemolytic anemias, RBC health is compromised and therefore lifespan is shortened. Although our knowledge on glycolysis in general and PK function in particular is solid, recent advances in genetic, molecular, biochemical, and metabolic aspects of hereditary anemias have improved our understanding of these diseases. These advances provide a rationale for targeting PK as therapeutic option in hereditary hemolytic anemias other than PK deficiency. This review summarizes the knowledge, rationale, (pre)clinical trials, and future advances of PK activators for this important group of rare diseases.

Molecular insights into hereditary elliptocytosis and pyropoikilocytosis: NGS uncovers multiple potential candidate genes

Hereditary elliptocytosis (HE) and pyropoikilocytosis (HPP) are considered a group of hemolytic anemias (HE/HPP) due to inherited abnormalities of erythrocyte membrane proteins with a worldwide distribution. Most cases are associated with molecular abnormalities linked to spectrin, band 4.1, and ankyrin. The present study aimed to identify significant molecular signatures on a target panel of 8 genes using whole exome sequencing (WES) in 9 Bahraini patients with elliptocytosis. Case selection was based on presence of anemia not associated with iron deficiency or hemoglobinopathy and demonstrating > 50% elliptocytes in blood smears. The c.779 T > C mutation of SPTA1 (Spectrin alpha), which is a known deleterious missense mutation that inhibits normal association of spectrin molecules to form tetramers, was seen in 4 patients in homozygous (n = 1) and heterozygous (n = 3) states. The αLELY abnormality in association with compound heterozygous mutations in SPTA1 was present in 5 patients (2 associated with the SPTA1 c.779 T > C variant; 3 with c.3487 T > G and various other SPTA1 mutations of uncertain/unknown significance). Seven patients had SPTB (Spectrin beta) mutations, predicted as likely benign by in silico analysis. A novel EPB41 (Erythrocyte Membrane Protein Band 4.1) mutation with potential deleterious impact was also seen. Finally, 2 cases showed an InDel (insertion-deletion mutations) abnormality in the gene that codes for the mechanosensitive ion-channel PIEZO (Piezo Type Mechanosensitive Ion Channel Component 1). PIEZO mutations are reported to cause red cell dehydration but have not been previously described in HE/HPP. Results of this study confirm the involvement of previously reported abnormalities in SPTA1 and suggest possible involvement of other candidate genes in a disorder involving polygenic interactions.

Proteome alterations in erythrocytes with PIEZO1 gain-of-function mutations

Gain-of-function mutations in PIEZO1 cause dehydrated hereditary stomatocytosis (DHS) or hereditary xerocytosis, an autosomal dominant hemolytic anemia characterized by high reticulocyte count, a tendency to macrocytosis, and mild jaundice, as well as by other variably penetrant clinical features, such as perinatal edema, severe thromboembolic complications after splenectomy, and hepatic iron overload. PIEZO1 mutations in DHS lead to slowed inactivation kinetics of the ion channel and/or facilitation of channel opening in response to physiological stimuli. To characterize the alterations of red blood cell proteome in patients with mutated PIEZO1, we used a differential approach to compare the proteome of patients with DHS (16 patients from 13 unrelated ancestries) vs healthy individuals. We identified new components in the regulation of the complex landscape of erythrocytes ion and volume balance mediated by PIEZO1. Specifically, the main impaired processes in patients with DHS were ion homeostasis, transmembrane transport, regulation of vesicle-mediated transport, and the proteasomal catabolic process. Functional assays demonstrated coexpression of PIEZO1 and band 3 when PIEZO1 was activated. Moreover, the alteration of the vesicle-mediated transport was functionally demonstrated by an increased vesiculation rate in patients with DHS compared with healthy controls. This finding also provides an explanation of the pathogenetic mechanism underlying the increased thrombotic rate observed in these patients. Finally, the newly identified proteins, involved in the intracellular signaling pathways altered by PIEZO1 mutations, could be used in the future as potential druggable targets in DHS.

Molecular diagnosis of hereditary hemolytic anemias: Recent updates

Hereditary hemolytic anemia (HHA) is a heterogeneous group of disorders due to genetically caused defects in red blood cell membrane structure, enzymes, heme and globin synthesis, erythroid proliferation, and differentiation. Traditionally, the diagnostic process is complex and includes a plethora of tests from routine to highly specialized ones. The inclusion of molecular testing has significantly improved the diagnostic yield. The value of molecular testing is broader than just rendering the correct diagnosis, as it may also guide therapeutic decisions. As more molecular modalities become available for clinical use, it is imperative to understand their benefits and disadvantages pertaining to the HHA diagnostics. Re-evaluation of the traditional diagnostic workflow may also bring forth additional benefits. This review focuses on the current state of molecular testing for HHA.

Erythrocyte pyruvate kinase activation in red cell disorders

PURPOSE OF REVIEW

In red cells, pyruvate kinase is a key enzyme in the final step of glycolytic degradative process, which generates a constant energy supply via ATP production. This commentary discusses recent findings on pyruvate kinase activators as new therapeutic option in hereditary red cell disorders such as thalassemic syndromes or sickle cell disease (SCD).

RECENT FINDINGS

Mitapivat and etavopivat are two oral pyruvate kinase activators. Studies in a mouse model for β thalassemia have shown beneficial effects of mitapivat on both red cell survival and ineffective erythropoiesis, with an amelioration of iron homeostasis. This was confirmed in a proof-of-concept study in patients with nontransfusion-dependent thalassemias. Both mitapivat and etavopivat have been evaluated in mouse models for SCD, showing an increased 2-3DPG/ATP ratio and a reduction in haemolysis as well as in sickling. These data were confirmed in proof-of-concept clinical studies with both molecules carried in patients with SCD.

SUMMARY

Preclinical and clinical evidence indicate that pyruvate kinase activators represent new therapeutic option in hemoglobinopathies or SCD. Other red cell disorders such as hereditary spherocytosis or hereditary anaemias characterized by defective erythropoiesis might represent additional areas to investigate the therapeutic impact of pyruvate kinase activators.

Variant spectrum of PIEZO1 and KCNN4 in Japanese patients with dehydrated hereditary stomatocytosis

Hereditary stomatocytosis (HSt) is a type of congenital hemolytic anemia caused by abnormally increased cation permeability of erythrocyte membranes. Dehydrated HSt (DHSt) is the most common subtype of HSt and is diagnosed based on clinical and laboratory findings related to erythrocytes. PIEZO1 and KCNN4 have been recognized as causative genes, and many related variants have been reported. We analyzed the genomic background of 23 patients from 20 Japanese families suspected of having DHSt using a target capture sequence and identified pathogenic/likely pathogenic variants of PIEZO1 or KCNN4 in 12 families.

Five Years' Experience with Gene Panel Sequencing in Hereditary Hemolytic Anemia Screened by Routine Peripheral Blood Smear Examination

BACKGROUND

Hereditary hemolytic anemia (HHA) is defined as a group of heterogeneous and rare diseases caused by defects of red blood cell (RBC) metabolism and RBC membrane, which leads to lysis or premature clearance. The aim of this study was to investigate individuals with HHA for potential disease-causing variants in 33 genes reported to be associated with HHA.

METHODS

A total of 14 independent individuals or families diagnosed with suspected HHA, and in particular, RBC membranopathy, RBC enzymopathy, and hemoglobinopathy, were collected after routine peripheral blood smear testing. A custom designed panel, including the 33 genes, was performed using gene panel sequencing on the Ion Torrent PGM™ Dx System. The best candidate disease-causing variants were confirmed by Sanger sequencing.

RESULTS

Several variants of the HHA-associated genes were detected in 10 out of 14 suspected HHA individuals. After excluding those variants predicted to be benign, 10 pathogenic variants and 1 variant of uncertain significance (VUS) were confirmed in 10 individuals with suspected HHA. Of these variants, the p.Trp704Ter nonsense variant of EPB41 and missense p.Gly151Asp variant of SPTA1 were identified in two out of four hereditary elliptocytoses. The frameshift p.Leu884GlyfsTer27 variant of ANK1, nonsense p.Trp652Ter variant of the SPTB, and missense p.Arg490Trp variant of PKLR were detected in all four hereditary spherocytosis cases. Missense p.Glu27Lys, nonsense p.Lys18Ter variants, and splicing errors such as c.92 + 1G > T and c.315 + 1G > A within HBB were identified in four beta thalassemia cases.

CONCLUSIONS

This study provides a snapshot of the genetic alterations in a cohort of Korean HHA individuals and demonstrates the clinical utility of using gene panels in HHA. Genetic results can provide precise clinical diagnosis and guidance regarding medical treatment and management for some individuals.

[Hereditary Spherocytosis and Pregnancy: A Case Report]

Even though it is a rare condition, hereditary spherocytosis (EH) is the main inherited cause of haemolytic anaemia and presents with a broad spectrum of symptoms. In the few reported cases of pregnancy and EH, maternal and foetal outcomes are controversial. Particularly, reports of pregnancies with EH associated with thrombosis or portal hypertension are scarce. We present a case of a woman who underwent splenectomy with EH and non-cirrhotic portal hypertension. Our patient presented polymorphisms of the methylenetetrahydrofolate reductase (MTHFR) and plasminogen activator inhibit-1 that have a controversial impact on thrombotic risk. During pregnancy, the woman showed no signs of haemodynamical or cirrhosis deterioration. Concerning the foetus, late-onset foetal growth restriction was diagnosed but did not determine preterm delivery. Five weeks post-partum after an episode of acute abdominal pain, mesenteric venous thrombosis was diagnosed. In this case report, we describe our experience in managing pregnancy, labour and post-partum of a woman with EH, highlighting potential complications of this condition.

A novel variant of SLC4A1 for hereditary spherocytosis in a Chinese family: a case report and systematic review

BACKGROUND

The incidence of hereditary spherocytosis (HS) is approximately 1:2000 in the western population, while it is much lower in the Chinese population. It is difficult to make a definite diagnosis due to the variable genotypic features and the lack of well-documented evidence for HS patients. Gene sequence examination is helpful for clear diagnosis.

CASE PRESENTATION

We presented the case of a 29-year-old male HS patient with skin yellowness, anorexia, and cholecystolithiasis as the first manifestations. Laboratory examination of the patient and his parents showed a mild reduction in hemoglobin and mean corpuscular hemoglobin concentration, increased reticulocytes, and promotion of indirect bilirubin in the patient and his father. Furthermore, small globular red blood cells with increased osmotic fragility were observed. In particular, the eosin-5'-maleimide binding test provided the strong evidence that band 3 protein was deleted in the erythrocyte membrane. Next-generation sequencing (NGS) and Sanger sequencing further demonstrated a heterozygous nonsense variant (exon16, c.G1985A: p.W662X) in SLC4A1, inherited from his father. Thus, the patient was diagnosed with HS, and then was effectively treated. After splenectomy, the anemia was relieved without any obvious unpleasant side effects.

CONCLUSION

We report an extremely rare case of HS in China that presented with hereditary hemolytic anemia with band 3 deletion resulting from a novel variant of SLC4A1, and systematically review a large number of related literatures. This study, therefore, significantly contributes to the literature on HS.

A rare mutation (p.F149del) of the NT5C3A gene is associated with pyrimidine 5'-nucleotidase deficiency

Pyrimidine 5'-nucleotidase deficiency is a rare erythrocyte enzymopathy. Here we report two cases of hemolytic anemia in brothers of Polish origin that are associated with a very rare mutation. Heterozygous deletion in the NT5C3A gene (c.444_446delGTT), inherited most likely from their asymptomatic mother, resulted in a single amino acid residue deletion (p.F149del) in cytosolic pyrimidine 5'-nucleotidase. However, only the mutated transcript was present in the reticulocyte transcriptome of both patients. Only residual activity of pyrimidine 5'-nucleotidase in the brothers' erythrocytes could be observed when compared with the controls, including their asymptomatic father and sister. Western blot showed no sign of the presence of 5'-nucleotidase protein in the erythrocytes of both studied patients. The 2.5-fold reduction of the purine/pyrimidine ratio observed only in the brothers' erythrocytes confirms the correlation of the results of molecular analysis, including whole-exome sequencing, with the phenotype of the pyrimidine 5'-nucleotidase deficiency. Altogether, our results may substantiate the hypothesis of the heterogeneity of the molecular basis of the defect involving both the mutation presented here and negative regulation of expression of the "normal" allele.

Sustained hyperkalemia in an asymptomatic primary care patient. When to suspect familial pseudohyperkalemia

Objectives

Study and management of a case with elevated potassium levels without apparent clinical causes in successive follow-up visits.

Case presentation

We present the case of a primary care female patient who persistently exhibited elevated levels of potassium (5.3-5.9 mmol/L) in successive control laboratory tests, without an apparent clinical cause. The patient was ultimately referred to the Unit of Nephrology, where a potassium-low diet was indicated. Diet did not have any effect on potassium levels. After a thorough study, the cause of hyperkalemia could not be determined.

Conclusions

The inconsistency between elevated potassium levels and the reason of consultation, and exclusion of other pre-analytical or pathological causes raised suspicion of familial pseudohyperkalemia. The sample was incubated at different times and temperatures to demonstrate their influence on levels of potassium in blood. Familial pseudohyperkalemia was established as the most probable diagnosis. Finally, the patient was discharged from the Unit of Nephrology and instructed to follow a normal diet.

The role of mechanosensitive Piezo1 channel in diseases

Mechanotransduction is associated with organ development and homoeostasis. Piezo1 and Piezo2 are novel mechanosensitive ion channels (MSCs) in mammals. MSCs are membrane proteins that are critical for the mechanotransduction of living cells. Current studies have demonstrated that the Piezo protein family not only functions in volume regulation, cellular migration, proliferation, and apoptosis but is also important for human diseases of various systems. The complete loss of Piezo1 and Piezo2 function is fatal in the embryonic period. This review summarizes the role of Piezo1 in diseases of different systems and perspectives potential treatments related to Piezo1 for these diseases.

Effects of SPTA1 Gene Variants on the Hematological Phenotype of Mexican Patients with Hereditary Spherocytosis

Introduction: Hereditary spherocytosis (HS) is a common hereditary hemolytic anemia characterized by chronic hemolysis, increased indirect serum bilirubin, the presence of reticulocytes and spherocytes in blood smears, and great heterogeneity at the clinical, biochemical, and molecular levels. The molecular pathology of HS includes genetic variants at five genes: ANK1, EPB42, SLC4A1, SPTA1, and SPTB. Alpha spectrin (SPTA1) deficiency is the second leading cause of HS in Mexican patients. Aim: To assess the effects of five SPTA1 variants on the hematological phenotype of Mexican patients with HS. Materials and Methods: This study included a retrospective cohort of 227 biologically unrelated patients with HS. Variants c.4339-99C>T and c.6531-12C>T in SPTA1 were identified by the amplification-refractory mutation system polymerase chain reaction (ARMS-PCR), and variants c.5572C>T, c.5992C>G, and c.6794T>C were identified by quantitive Real Time-Polymerase Chain Reaction (qRT-PCR) allelic discrimination. Risk tests were performed for each variant with respect to HS clinical severity. Results: The SPTA1 c.5992C>G variant showed association with moderately severe HS (p = 0.006, odds ratio = 5.67, confidence interval95% = 1.6-19.9); the risk increased when the variant was in compound heterozygosity with αLELY and c.6794T>C. Lower hematological levels were observed in simple αLely (c.5572C>T and c.6531-12C>T), and c.5992C>G heterozygotes (red blood cell [RBC] p = 0.028 and 0.010; hemoglobin [Hb] p = 0.030 and 0.002; packed cell volume [PCV] p = 0.034 and 0.002 respectively), and in c.5992C>G+c.6794T>C compound heterozygotes (RBC p = 0.043; Hb p = 0.033; PCV p = 0.043). Additional genetic traits were observed: 15% had HS+Gilbert syndrome and 13% HS+thalassemia. Conclusion: Although most of the studied variants are considered benign, we observed significant associations with phenotypic severity. Therefore, we recommend the inclusion of these variants in molecular screening for HS.

Clinical and Genetic Etiologies of Neonatal Unconjugated Hyperbilirubinemia in the China Neonatal Genomes Project

OBJECTIVE

To investigate the clinical and genetic causes of neonatal unconjugated hyperbilirubinemia.

STUDY DESIGN

We included 1412 neonates diagnosed with unconjugated hyperbilirubinemia (total serum bilirubin >95 percentile for age), from the China Neonatal Genomes Project between August 2016 and September 2019, in the current study. Clinical data and targeted panel sequencing data on 2742 genes including known unconjugated hyperbilirubinemia genes were analyzed.

RESULTS

Among the 1412 neonates with unconjugated hyperbilirubinemia, 37% had severe unconjugated hyperbilirubinemia, with total serum bilirubin levels that met the recommendations for exchange transfusion. Known clinical causes were identified for 68% of patients. The most common clinical cause in the mild unconjugated hyperbilirubinemia group was infection (17%) and in the severe group was combined factors (21%, with infection combined with extravascular hemorrhage the most common). A genetic variant was observed in 55 participants (4%), including 45 patients with variants in genes associated with unconjugated hyperbilirubinemia and 10 patients with variants that were regarded as additional genetic findings. Among the 45 patients identified with unconjugated hyperbilirubinemia-related variants, the genes were mainly associated with enzyme deficiencies, metabolic/biochemical disorders, and red blood cell membrane defects. G6PD and UGT1A1 variants, were detected in 34 of the 45 patients (76%).

CONCLUSIONS

Known clinical causes, which varied with bilirubin levels, were identified in approximately two-thirds of the patients. Genetic findings were identified in 4% of the patients, including in patients with an identified clinical cause, with G6PD and UGT1A1 being the most common genes in which variants were detected.

Case Report: Familial Pseudohyperkalemia Due to Red Blood Cell Membrane Leak in a Chinese Patient

Hyperkalemia is a critical condition requiring careful evaluation and timely intervention. Many conditions could manifest as pseudohyperkalemia and it's important to differentiate them as inappropriate potassium-lowering therapy might lead to detrimental outcomes. A 56-year-old female was admitted for hyperkalemia (5.62–8.55 mmol/L). She had no symptoms or signs of hyperkalemia. A comprehensive work-up of hyperkalemia retrieved no valuable findings. Her blood samples underwent incubation tests at different temperatures and revealed temperature-dependent potassium leaks from red blood cells. Based on all test results, a diagnosis of hyperkalemia caused by red blood cell membrane defects was suspected. Whole-genome sequencing revealed a heterozygous c.1123C>T (p. R375W) mutation in the ABCB6 gene and confirmed the diagnosis of familial pseudohyperkalemia (FP). FP is an inherited benign condition in which red blood cells have increased cold-induced permeability to potassium. The patient was discharged with no additional treatment and she was suggested avoiding blood donation.

Erythroid differentiation in mouse erythroleukemia cells depends on Tmod3-mediated regulation of actin filament assembly into the erythroblast membrane skeleton

Erythroid differentiation (ED) is a complex cellular process entailing morphologically distinct maturation stages of erythroblasts during terminal differentiation. Studies of actin filament (F-actin) assembly and organization during terminal ED have revealed essential roles for the F-actin pointed-end capping proteins, tropomodulins (Tmod1 and Tmod3). Tmods bind tropomyosins (Tpms), which enhance Tmod capping and F-actin stabilization. Tmods can also nucleate F-actin assembly, independent of Tpms. Tmod1 is present in the red blood cell (RBC) membrane skeleton, and deletion of Tmod1 in mice leads to a mild compensated anemia due to mis-regulated F-actin lengths and membrane instability. Tmod3 is not present in RBCs, and global deletion of Tmod3 leads to embryonic lethality in mice with impaired ED. To further decipher Tmod3's function during ED, we generated a Tmod3 knockout in a mouse erythroleukemia cell line (Mel ds19). Tmod3 knockout cells appeared normal prior to ED, but showed defects during progression of ED, characterized by a marked failure to reduce cell and nuclear size, reduced viability, and increased apoptosis. Tmod3 does not assemble with Tmod1 and Tpms into the Triton X-100 insoluble membrane skeleton during ED, and loss of Tmod3 had no effect on α1,β1-spectrin and protein 4.1R assembly into the membrane skeleton. However, F-actin, Tmod1 and Tpms failed to assemble into the membrane skeleton during ED in absence of Tmod3. We propose that Tmod3 nucleation of F-actin assembly promotes incorporation of Tmod1 and Tpms into membrane skeleton F-actin, and that this is integral to morphological maturation and cell survival during erythroid terminal differentiation.

Clinical and genetic diagnosis of thirteen Japanese patients with hereditary spherocytosis

Hereditary spherocytosis is the most frequent cause of hereditary hemolytic anemia and is classified into five subtypes (SPH1-5) according to OMIM. Because the clinical and laboratory features of patients with SPH1-5 are variable, it is difficult to classify these patients into the five subtypes based only on these features. We performed target capture sequencing in 51 patients with hemolytic anemia associated with/without morphological abnormalities in red blood cells. Thirteen variants were identified in five hereditary spherocytosis-related genes (six in ANK1 [SPH1]; four in SPTB [SPH2]; and one in each of SPTA1 [SPH3], SLC4A1 [SPH4], and EPB42 [SPH5]). Among these variants, seven were novel. The distribution pattern of the variants was different from that reported previously in Japan but similar to those reported in other Asian countries. Comprehensive genomic analysis would be useful and recommended, especially for patients without a detailed family history and those receiving frequent blood transfusions due to chronic hemolytic anemia.

Differential diagnosis of hereditary anemias from a fraction of blood drop by digital holography and hierarchical machine learning

Anemia affects about the 25% of the global population and can provoke severe diseases, ranging from weakness and dizziness to pregnancy problems, arrhythmias and hearth failures. About 10% of the patients are affected by rare anemias of which 80% are hereditary. Early differential diagnosis of anemia enables prescribing patients a proper treatment and diet, which is effective to mitigate the associated symptoms. Nevertheless, the differential diagnosis of these conditions is often difficult due to shared and overlapping phenotypes. Indeed, the complete blood count and unaided peripheral blood smear observation cannot always provide a reliable differential diagnosis, so that biomedical assays and genetic tests are needed. These procedures are not error-free, require skilled personnel, and severely impact the financial resources of national health systems. Here we show a differential screening system for hereditary anemias that relies on holographic imaging and artificial intelligence. Label-free holographic imaging is aided by a hierarchical machine learning decider that works even in the presence of a very limited dataset but is enough accurate for discerning between different anemia classes with minimal morphological dissimilarities. It is worth to notice that only a few tens of cells from each patient are sufficient to obtain a correct diagnosis, with the advantage of significantly limiting the volume of blood drawn. This work paves the way to a wider use of home screening systems for point of care blood testing and telemedicine with lab-on-chip platforms.

Development of Icephilic ACTIVE Glycopeptides for Cryopreservation of Human Erythrocytes

Ice formation and recrystallization exert severe impairments to cellular cryopreservation. In light of cell-damaging washing procedures in the current glycerol approach, many researches have been devoted to the development of biocompatible cryoprotectants for optimal bioprotection of human erythrocytes. Herein, we develop a novel ACTIVE glycopeptide of saccharide-grafted ε-poly(L-lysine), that can be credited with adsorption on membrane surfaces, cryopreservation with trehalose, and icephilicity for validity of human erythrocytes. Then, by Borch reductive amination or amidation, glucose, lactose, maltose, maltotriose, or trehalose was tethered to ε-polylysine. The synthesized ACTIVE glycopeptides with intrinsic icephilicity could localize on the membrane surface of human erythrocytes and improve cryopreservation with trehalose, so that remarkable post-thaw cryosurvival of human erythrocytes was achieved with a slight variation in cell morphology and functions. Human erythrocytes (∼50% hematocrit) in cryostores could maintain high cryosurvival above 74%, even after plunged in liquid nitrogen for 6 months. Analyses of differential scanning calorimetry, Raman spectroscopy, and dynamic ice shaping suggested that this cryopreservation protocol combined with the ACTIVE glycopeptide and trehalose could enhance the hydrogen bond network in nonfrozen solutions, resulting in inhibition of recrystallization and growth of ice. Therefore, the ACTIVE glycopeptide can be applied as a trehalose-associated "chaperone", providing a new way to serve as a candidate in glycerol-free human erythrocyte cryopreservation.

Potential Applications of Computational Fluid Dynamics for Predicting Hemolysis in Mitral Paravalvular Leaks

Paravalvular leaks (PVLs) may lead to hemolysis. In vitro shear stress forces above 300 Pa cause erythrocyte destruction. PVL channel dimensions may determine magnitude of shear stress forces that affect erythrocytes; however, this has not been tested. It remains unclear how different properties of PVL channels contribute to presence of hemolysis. A model of a left ventricle was created based on data from computer tomography with Slicer software PVLs of various shapes and sizes were introduced. Blood flow was simulated using ANSYS Fluent software. The following variables were examined: wall shear stress, shear stress in fluid, volume of PVL channel with shear stress exceeding 300 Pa, and duration of exposure of erythrocytes to shear stress values above 300 Pa. In all models, shear stress forces exceeded 300 Pa. Shear stress increased with blood flow rates and cross-sectional areas of any PVL. There was no linear relationship between cross-sectional area of a PVL and volume of a PVL channel with shear stress > 300 Pa. Blood flow through mitral PVLs is associated with shear stress above 300 Pa. Cross-sectional area of a PVL does not correlate with volume of a PVL channel with shear stress > 300 Pa and duration of exposure of erythrocytes to shear stress > 300 Pa.

Hematological and molecular analysis of patients with G6PD deficiency revealed coexistent hereditary spherocytosis and alpha thalassemia

BACKGROUND

Glucose-6-phosphate dehydrogenase (G6PD) deficiency, hereditary spherocytosis (HS), and alpha thalassemia (α-thal) are frequent erythrocyte pathologies with different geographic distributions worldwide. Our aim is to report hematological and molecular findings of G6PD deficient Mexican patients in coinheritance with suggestive hereditary spherocytosis (sHS) and α-thal.

METHODS

We studied 78 G6PD deficiency patients. Hematological parameters, acidified glycerol lysis test, erythrocyte morphology, electrophoresis, and hemoglobin quantification were obtained. G6PD and HBA2/HBA1 variants were identified using ARMS-PCR, Gap-PCR, or Sanger sequencing.

RESULTS

Nine G6PD variants were identified; A^-202A/376G , A^-376G/968C , and A^+376G as the most frequent. G6PD Santiago de Cuba^1339A and Kamiube^1387T were detected in Mexicans for first time. Hematological analysis revealed additional erythrocyte pathologies in 52 patients, 32 with positive osmotic fragility test and spherocytes in blood smear (suggestive hereditary spherocytosis, sHS), 12 with microcytosis and 8 with all three defects who had the most severe phenotype, with significantly lower hematological parameters (Hb, PCV, MCV, and MCH). α-thal variants (α^Hph α, α^-59C>T α and -α^3.7 ) were observed in 65% of patients with microcytosis.

CONCLUSION

Additional erythrocyte defects were observed in 69.3% of G6PD deficiency patients. We stress the importance of searching for the presence of additional erythrocyte hereditary diseases in patients with G6PD deficiency.

Efficacy of cytochemical tests in gene analysis of hereditary spherocytosis: a case study of six patients with different disease subtypes

OBJECTIVES

In this study, clinical and biochemical methods were utilized to predict the final diagnosis of hereditary spherocytosis (HS), correlate the diagnosis with splenectomy, and examine the usefulness of this approach.

METHODS

We biochemically and cytochemically analysed erythrocyte membrane proteins before making a final HS diagnosis based on gene analysis to compare diagnostic approaches. The clinical features of six patients with various subtypes of HS and symptoms were observed by blood analysis using eosin-5'-maleimide staining, biochemical analysis using sodium dodecyl sulphate - polyacrylamide gel electrophoresis with western blotting, and mass spectrometry. Finally, diagnostic membrane gene analysis was performed.

RESULTS

Five of the six patients showed mild to moderate or severe anaemia, and the other patient was non-anaemic; all six patients showed faint eosin-5'-maleimide staining. In western blotting of erythrocyte membrane proteins, all six patients (three with β-spectrin, two with ankyrin, and one with SLC4A1 anomalies) showed low-molecular-weight peptide fragments, which were confirmed by mass spectrometry in the region corresponding to the band 3 protein. The two patients with an ankyrin gene anomaly exhibited severe anaemia, and two patients with simultaneous SLC4A1, SPTB, and UGT1A1 anomalies exhibited mild anaemia and hyperbilirubinemia.

DISCUSSION

We determined the relationship among clinical features, cytochemical parameters, and gene anomalies in six patients with newly diagnosed HS while referring to previously published cases.

CONCLUSION

These findings reveal a close relationship between clinical features and membrane characteristics in HS, which can facilitate diagnosis and inform treatment.

Cell Physiology and Molecular Mechanism of Anion Transport by Erythrocyte Band 3/AE1

The major transmembrane protein of the red blood cell, known as band 3, AE1, and SLC4A1, has two main functions: 1) catalysis of Cl^-/HCO₃^- exchange, one of the steps in CO₂ excretion; 2) anchoring the membrane skeleton. This review summarizes the 150 year history of research on red cell anion transport and band 3 as an experimental system for studying membrane protein structure and ion transport mechanisms. Important early findings were that red cell Cl^- transport is a tightly coupled 1:1 exchange and band 3 is labeled by stilbenesulfonate derivatives that inhibit anion transport. Biochemical studies showed that the protein is dimeric or tetrameric (paired dimers) and that there is one stilbenedisulfonate binding site per subunit of the dimer. Transport kinetics and inhibitor characteristics supported the idea that the transporter acts by an alternating access mechanism with intrinsic asymmetry. The sequence of band 3 cDNA provided a framework for detailed study of protein topology and amino acid residues important for transport. The identification of genetic variants produced insights into the roles of band 3 in red cell abnormalities and distal renal tubular acidosis. The publication of the membrane domain crystal structure made it possible to propose concrete molecular models of transport. Future research directions include improving our understanding of the transport mechanism at the molecular level and of the integrative relationships among band 3, hemoglobin, carbonic anhydrase, and gradients (both transmembrane and subcellular) of HCO₃^-, Cl^-, O₂, CO₂, pH, and NO metabolites during pulmonary and systemic capillary gas exchange.

Piezo1 mediates endothelial atherogenic inflammatory responses via regulation of YAP/TAZ activation

The vascular endothelium plays a key role in the pathobiology of atherosclerotic cardiovascular disease. Endothelial cell Piezo1 mediates blood vessel formation, angiogenesis and regulation of blood pressure. However, changes of Piezo1 expression in atherosclerosis (AS) and the role of Piezo1 in the progression of atherosclerotic diseases remains obscure. Thus, the current study is to elucidate the role and mechanism of which Piezo1 mediates vascular inflammation in atherosclerotic mice and vascular endothelial inflammation induced by oxidized low density lipoprotein (ox-LDL) in vitro. Here, we have shown that the expression of Piezo1 was significantly increased in the stenotic carotid artery of ApoE-/- mice fed by high-fat diet (HFD). Pharmacological inhibition of Piezo1 (GsMTx-4) attenuated plaque formation, decreased the level of inflammation related factors (JNK, TNF-α, NF-κB, VCAM-1) of carotid plaque in atherosclerotic mice. Meanwhile, ox-LDL also upregulates Piezo1 and inflammation proteins (NF-κB, JNK and TNF-α) in endothelium cells (ECs). YAP/TAZ is activated accompanied by the enhanced Piezo1 activity in ECs induced by ox-LDL. Interference by siRNA of Piezo1 abolished the expression of YAP/TAZ and inflammation proteins (JNK, NF-κB and TNF-α). In addition, Ca²⁺ influx in ECs induced by ox-LDL was increased than control group, Piezo1 siRNA can reduce the calcium content. Piezo1 agonist Yoda1 increased Ca²⁺ influx and promote YAP nucleus translocation in ECs, genetic deletion of Piezo1 reversed it. Our results indicate that Piezo1 could mediate endothelial atherogenic inflammatory responses via regulation of YAP/TAZ activation and nuclear localization. Piezo1 may be a potential therapeutic target for atherosclerotic diseases in the future.

Emerging Role of Piezo Ion Channels in Cardiovascular Development

Mechanical cues are crucial for vascular development and the proper differentiation of various cell types. Piezo1 and Piezo2 are mechanically activated cationic channels expressed in various cell types, especially in vascular smooth muscle and endothelial cells. It is present as a transmembrane homotrimeric complex, regulating calcium influx. Local blood flow associated shear stress, in addition to blood pressure associated cell membrane stretching are key Piezo channel activators. There is rising proof, showcasing Piezo channels significance in myocytes, cardiac fibroblast, vascular tone maintenance, atherosclerosis, hypertension, NO generation, and baroreceptor reflex. Here, we review the role of Piezo channels in cardiovascular development and its associated clinical disorders. Also, emphasizing on Piezo channel modulators which might lead to novel therapies for cardiovascular diseases. This article is protected by copyright. All rights reserved.

Complex Modes of Inheritance in Hereditary Red Blood Cell Disorders: A Case Series Study of 155 Patients

Hereditary erythrocytes disorders include a large group of conditions with heterogeneous molecular bases and phenotypes. We analyzed here a case series of 155 consecutive patients with clinical suspicion of hereditary erythrocyte defects referred to the Medical Genetics Unit from 2018 to 2020. All of the cases followed a diagnostic workflow based on a targeted next-generation sequencing panel of 86 genes causative of hereditary red blood cell defects. We obtained an overall diagnostic yield of 84% of the tested patients. Monogenic inheritance was seen for 69% (107/155), and multi-locus inheritance for 15% (23/155). PIEZO1 and SPTA1 were the most mutated loci. Accordingly, 16/23 patients with multi-locus inheritance showed dual molecular diagnosis of dehydrated hereditary stomatocytosis/xerocytosis and hereditary spherocytosis. These dual inheritance cases were fully characterized and were clinically indistinguishable from patients with hereditary spherocytosis. Additionally, their ektacytometry curves highlighted alterations of dual inheritance patients compared to both dehydrated hereditary stomatocytosis and hereditary spherocytosis. Our findings expand the genotypic spectrum of red blood cell disorders and indicate that multi-locus inheritance should be considered for analysis and counseling of these patients. Of note, the genetic testing was crucial for diagnosis of patients with a complex mode of inheritance.

Clinical and molecular genetic analysis of a Chinese family with hereditary elliptocytosis caused by a novel mutation in the EPB41 gene

BACKGROUND

Hereditary elliptocytosis (HE) is a heterogeneous red blood cell membrane disorder characterized by the presence of elliptocytes on a peripheral blood smear. Clinical manifestations of HE vary widely from asymptomatic carriers to patients with severe transfusion-dependent anemia. Most patients are asymptomatic or have mild anemia, which hinders diagnosis. The proband in this case had mild anemia and jaundice over a period of 4 years, the etiology of which was unclear. Hence, he was admitted to our hospital for further diagnosis.

METHODS

Peripheral blood smears and routine blood tests were performed and biochemical parameters of the proband, and his family members were determined. To confirm the diagnosis, gene mutations were screened in the proband using next-generation sequencing (NGS) and verified by Sanger sequencing in other family members.

RESULTS

A novel mutation (c.1294delA, p.Ser432 fs) in exon 15 of the EPB41 gene was detected in the proband and his family members. This mutation results in a frameshift and a premature stop codon at position 455, encoding a truncated protein. The variant was likely pathogenic according to the criteria of the American College of Medical Genetics and Genomics. SWISS-MODEL protein structure prediction indicated partial loss of the spectrin and actin binding and C-terminal domains.

CONCLUSION

A heterozygous mutation 1294delA in exon 15 of the EPB41 gene was identified using NGS and Sanger sequencing in members of a Chinese family. This identification expands the spectrum of EPB41 mutations and contributes to the genetic diagnosis of families with HE.

Familial pseudohyperkalemia induces significantly higher levels of extracellular potassium in early storage of red cell concentrates without affecting other standard measures of quality: A case control and allele frequency study

BACKGROUND

Familial pseudohyperkalemia (FP) is characterized by an increased rate of potassium leakage in refrigerated red cells and is associated with the minor allele of the single nucleotide polymorphism rs148211042 (R723Q) in the ABCB6 gene. The study aims were to obtain the minor allele frequencies of ABCB6 variants and to measure supernatant potassium accumulation, and other red cell storage parameters, in red cell concentrates (RCC) from carriers of variant rs148211042 under standard blood bank conditions.

STUDY DESIGN

Whole blood units were collected from 6 FP individuals and 11 controls and processed into RCC in additive solution. RCC were sampled and tested over cold storage for full blood count, extracellular potassium, glucose, lactate, microvesicle release, deformability, hemolysis, pH, adenosine triphosphate, and 2,3-diphosphoglycerate.

RESULTS

Screening of genotyped cohorts identified that variant rs148211042 is present in 1 in 394 British citizens of European ancestry. FP RCC had significantly higher supernatant potassium at all time points from day 3 onwards (p < .001) and higher mean cell volume (p = .032) than controls. The initial rate of potassium release was higher in FP RCC; supernatant potassium reached 46.0 (23.8-57.6) mmol/L (mean [range]) by day 5, increasing to 68.9 (58.8-73.7) mmol/L by day 35. Other quality parameters were not significantly different between FP RCC and controls.

CONCLUSION

These data suggest that if a blood donor has FP, reducing the RCC shelf-life to 5 days may be insufficient to reduce the risk of hyperkalemia in clinical scenarios such as neonatal large volume transfusion.

A novel essential splice site variant in SPTB in a large hereditary spherocytosis family

BACKGROUND

We studied a large family with 22 individuals affected with autosomal dominant hereditary spherocytosis (HS).

METHODS

Genome-wide linkage, whole-genome sequencing (WGS), Sanger sequencing, RT-PCR, and ToPO TA cloning analyses were performed.

RESULTS

We revealed a heterozygous G>A transition in the 14q23 locus, at position +1 of the intron 8 donor splice site of the spectrin beta, erythrocytic (SPTB) gene. This splice variant (SPTB c.1064+1G>A) was confirmed by Sanger sequencing and showed complete co-segregation with HS in the family. Further RT-PCR reactions and sequencing analysis indicated that the variant leads to the exclusion of exon 8 and subsequent frameshift in exon 9 and a premature stop codon in SPTB. Translation of the altered allele would lead to a truncation with a loss of all spectrin repeat domains in SPTB protein.

CONCLUSION

This variant is novel and has not been found in any databases. We propose that this splice variant explains the spherocytosis phenotype observed in this large family.

Red cell membrane disorders: structure meets function

The mature red blood cell (RBC) lacks a nucleus and organelles characteristic of most cells, but it is elegantly structured to perform the essential function of delivering oxygen and removing carbon dioxide from all other cells while enduring the shear stress imposed by navigating small vessels and sinusoids. Over the past several decades, the efforts of biochemists, cell and molecular biologists, and hematologists have provided an appreciation of the complexity of RBC membrane structure, while studies of the RBC membrane disorders have offered valuable insights into structure-function relationships. Within the last decade, advances in genetic testing and its increased availability have made it possible to substantially build upon this foundational knowledge. Although disorders of the RBC membrane due to altered structural organization or altered transport function are heterogeneous, they often present with common clinical findings of hemolytic anemia. However, they may require substantially different management depending on the underlying pathophysiology. Accurate diagnosis is essential to avoid emergence of complications or inappropriate interventions. We propose an algorithm for laboratory evaluation of patients presenting with symptoms and signs of hemolytic anemia with a focus on RBC membrane disorders. Here, we review the genotypic and phenotypic variability of the RBC membrane disorders in order to raise the index of suspicion and highlight the need for correct and timely diagnosis.

The Interplay between Drivers of Erythropoiesis and Iron Homeostasis in Rare Hereditary Anemias: Tipping the Balance

Rare hereditary anemias (RHA) represent a group of disorders characterized by either impaired production of erythrocytes or decreased survival (i.e., hemolysis). In RHA, the regulation of iron metabolism and erythropoiesis is often disturbed, leading to iron overload or worsening of chronic anemia due to unavailability of iron for erythropoiesis. Whereas iron overload generally is a well-recognized complication in patients requiring regular blood transfusions, it is also a significant problem in a large proportion of patients with RHA that are not transfusion dependent. This indicates that RHA share disease-specific defects in erythroid development that are linked to intrinsic defects in iron metabolism. In this review, we discuss the key regulators involved in the interplay between iron and erythropoiesis and their importance in the spectrum of RHA.

Genetics and Genomics Approaches for Diagnosis and Research Into Hereditary Anemias

The hereditary anemias are a relatively heterogeneous set of disorders that can show wide clinical and genetic heterogeneity, which often hampers correct clinical diagnosis. The classical diagnostic workflow for these conditions generally used to start with analysis of the family and personal histories, followed by biochemical and morphological evaluations, and ending with genetic testing. However, the diagnostic framework has changed more recently, and genetic testing is now a suitable approach for differential diagnosis of these patients. There are several approaches to this genetic testing, the choice of which depends on phenotyping, genetic heterogeneity, and gene size. For patients who show complete phenotyping, single-gene testing remains recommended. However, genetic analysis now includes next-generation sequencing, which is generally based on custom-designed targeting panels and whole-exome sequencing. The use of next-generation sequencing also allows the identification of new causative genes, and of polygenic conditions and genetic factors that modify disease severity of hereditary anemias. In the research field, whole-genome sequencing is useful for the identification of non-coding causative mutations, which might account for the disruption of transcriptional factor occupancy sites and cis-regulatory elements. Moreover, advances in high-throughput sequencing techniques have now resulted in the identification of genome-wide profiling of the chromatin structures known as the topologically associating domains. These represent a recurrent disease mechanism that exposes genes to inappropriate regulatory elements, causing errors in gene expression. This review focuses on the challenges of diagnosis and research into hereditary anemias, with indications of both the advantages and disadvantages. Finally, we consider the future perspectives for the use of next-generation sequencing technologies in this era of precision medicine.

Atypical hereditary spherocytosis phenotype associated with pseudohypokalaemia and a new variant in the band 3 protein

Red blood cell (RBC) membrane disorders are predominantly caused by mutations resulting in decreased RBC deformability and permeability. We present a family in which, the proband and his daughter presented with pseudohypokalaemia. Studies on the temperature dependence of pseudohypokalaemia suggested a maximum decrease in serum potassium when whole blood is stored at 37°C. Routine haematology suggested mild haemolysis with a hereditary spherocytosis phenotype. These two cases present a novel variant in temperature-dependent changes in potassium transport. A new variant was identified in the SLC4A1 gene which codes for band 3 protein (anion exchanger 1) in RBC membrane which may contribute to the phenotype. This is the first report of familial pseudohypokalaemia associated with changes in RBC membrane morphology. The clinical implications of pseudohypokalaemia are that it can lead to inappropriate investigation or treatment. However, many questions remain to be solved and other RBC membrane protein genes should be studied.

Genetic diagnosis history and osteoarticular phenotype of a non-transfusion secondary hemochromatosis

BACKGROUND

It is not easy to identify the cause of various iron overload diseases because the phenotypes overlap. Therefore, it is important to perform genetic testing to determine the genetic background of patients.

AIM

To investigate the genetic background of a patient with hemochromatosis complicated by psoriasis on both lower extremities.

METHODS

Ten years ago, a 61-year-old male presented with iron overload, jaundice, hemolytic anemia and microcytic hypochromic anemia. Computed tomography of the left knee joint showed enlargement of the tibial medullary cavity and thinned bone cortices. Magnetic resonance imaging showed hepatic hemochromatosis, extensive abnormal signals from bone marrow cavities and nodular lesions in the lateral medullary cavity of the upper left lateral tibia. Single photon emission computed tomography showed radial dots of abnormal concentration in the upper end of the left tibia and radial symmetry of abnormal concentrations in joints of the extremities. The patient showed several hot spot mutations of the HFE and G6PD genes detected by next-generation sequencing, but no responsible gene mutation was found. The thalassemia gene was detected by gap-PCR.

RESULTS

The patient was found to carry the -α^4.2 and --^SEA deletion mutations of the globin gene. These two mutations are common causes of Southeast Asian α-thalassemia, but rarely cause severe widespread non-transfusion secondary hemochromatosis osteoarthropathy. The simultaneous presence of an auxiliary superposition effect of a rare missense mutation of the PIEZO1 gene (NM_001142864, c.C4748T, p.A1583V) was considered. Moreover, several rare mutations of the IFIH1, KRT8, POFUT1, FLG, KRT2, and TGM5 genes may be involved in the pathogenesis of psoriasis.

CONCLUSION

The selection of genetic detection methods for hemochromatosis still needs to be based on an in-depth study of the clinical manifestations of the disease.