Defected lipid rafts suppress cavin1-dependent IFN-α signaling endosome in paroxysmal nocturnal hemoglobinuria.

Paroxysmal nocturnal haemoglobinuria (PNH) is a clonal disorder of haematopoietic stem cells caused by somatic PIGA mutations, resulting in a deficiency in glycosylphosphatidylinositol-anchored proteins (GPI-AP). Some researchers uncovered that PNH cells displayed a GPI-mediated defect in lipid-raft formation. However, Lipid rafts play a crucial role in signaling, the signaling underlying lipid rafts in PNH have not yet been addressed. In this study, we reported that, IFN-α was significantly increased in PNH plasma compared with normal controls. And PNH cells more resistant to the inhibitory colony[1]-forming activity of IFN-α. Here we have already established PIGA knock out K562 cell line by CRISPR/cas9, the most recognized in vitro model of PNH. PNH cells showed obviously defected endocytosis of IFNα/ßRs in lipid rafts, causing suppressed STAT2 activation and the inflammatory response. We further investigated the possible mechanisms of interferon signaling endosomes mediate by cavin1. Our findings provide crucial insight into the process of reduced IFNα signal transduction in PNH cells mediated by lipid rafts and suggest that cavin1 are a potential target for suppression of IFN-α inflammatory signaling. These results might further explain the growth advantage of PNH cells in an unfavorable microenvironment.

Dysplasia and PNH-type cells in bone marrow aspirates of myelodysplastic syndromes.

BACKGROUND: Flow cytometry is increasingly applied in cytopenic patients suspected for myelodysplastic syndromes (MDS). Analysis includes evaluation of antigen expression patterns in granulocytes of which, for example, partial lack of CD16 may indicate dysplasia, but presence of paroxysmal nocturnal hemoglobinuria (PNH)-type cells should be considered. However, diagnostic bone marrow (BM) samples hamper PNH analysis because immature stages in the granulo-/monocytic compartment lack expression of certain glycophosphatidyl-inositol-anchored proteins. In this prospective study, we evaluated the presence of PNH-type cells in BM next to aberrancies from routine MDS immunophenotyping. METHODS: We combined antibodies defining maturation trajectories with FLAER. Validation of the designed method against routine PNH analysis and parallel analysis of BM and blood samples revealed similar results (granulocytes: Wilcoxon p = 0.25 and p = 0.82, respectively). We analyzed BM samples from 134 MDS, 17 chronic myelomonocytic leukemia, 15 aplastic anemia (AA), 1 PNH, 51 non-clonal cytopenic controls, and 12 normal controls. RESULTS: Most AA/PNH-BM samples showed clear PNH clones: median 1.1% (0%-35%); CD16 loss on mature neutrophils paralleled PNH-clone sizes. In MDS-BM, only 3.7% of cases showed ≥0.1% PNH-type cells, whereas partial CD16 loss was more frequent and abundant. CONCLUSIONS: Our findings confirm that dysplastic features in MDS-BM may point to presence of PNH-type cells, though only few cases displayed FLAER-negative cells. We showed that identification of these cells in the granulocyte compartment of BM specimen is feasible, but-according to international guidelines-results need to be confirmed in peripheral blood.

SUZ12 participates in the proliferation of PNH clones by regulating histone H3K27me3 levels.

Paroxysmal nocturnal hemoglobinuria (PNH) is a disease involving hematopoietic stem cell membrane defects caused by acquired phosphatidylinositol glycan anchor biosynthesis class A (PIGA) mutations. In this study, 97 target genes were selected as a target gene panel and screened in 23 PNH patients via the sequencing of specific DNA target regions. Through functional analysis, we identified that suppressor-of-Zeste 12 (SUZ12) may be involved in the proliferation of PNH clones. mRNA and protein expression levels of SUZ12 and the trimethylation level of histone H3 at lysine 27 (H3K27) in CD59- peripheral blood leukocytes from PNH patients were higher than those in CD59+ cells from PNH patients and peripheral blood leukocytes from healthy controls. In addition, the relative expression of SUZ12 in PNH patients was positively correlated with Ret% and the proportion of PNH clones. When we knocked down SUZ12 expression in a PIGA knockdown THP-1 cell line (THP-1 KD cells), the trimethylation of histone H3K27(H3K27me3) and cell proliferation decreased, apoptosis increased, and cell cycle arrest occurred in G0/G1 phase. In conclusion, SUZ12 participates in the proliferation of PNH clones by regulating histone H3K27me3 levels. Our results may provide new therapeutic targets and possibilities for PNH patients.

The Role of T Lymphocytes in the Pathogenesis of Paroxysmal Nocturnal Hemoglobinuria.

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired hematopoietic stem cell genetic mutation disease that causes defective erythrocyte membrane hemolysis. Its pathologic basis is the mutation of the PIG-A gene, whose product is necessary for the synthesis of glycosylphosphatidylinositol (GPI) anchors; the mutation of PIG-A gene results in the reduction or deletion of the GPI anchor, which leads to the deficiency of GPI-anchored proteins (GPI-APs), such as CD55 and CD59, which are complement inhibitors. The deficiency of complement inhibitors causes chronic complement-mediated intravascular hemolysis of GPI-anchor-deficient erythrocyte. PIG-A gene mutation could also be found in bone marrow hematopoietic stem cells (HSCs) of healthy people, but they have no growth advantage; only the HSCs with PIG-A gene mutation in PNH patients have this advantage and expand. Besides, HSCs from PIG-A-knockout mice do not show clonal expansion in bone marrow, so PIG-A mutation cannot explain the clonal advantage of the PNH clone and some additional factors are needed; thus, in recent years, many scholars have put forward the theories of the second hit, and immune escape theory is one of them. In this paper, we focus on how T lymphocytes are involved in immune escape hypothesis in the pathogenesis of PNH.

Insights Into the Emergence of Paroxysmal Nocturnal Hemoglobinuria.

Paroxysmal Nocturnal Hemoglobinuria (PNH) is a disease as simple as it is complex. PNH patients develop somatic loss-of-function mutations in phosphatidylinositol N-acetylglucosaminyltransferase subunit A gene (PIGA), required for the biosynthesis of glycosylphosphatidylinositol (GPI) anchors. Ubiquitous in eukaryotes, GPI anchors are a group of conserved glycolipid molecules responsible for attaching nearly 150 distinct proteins to the surface of cell membranes. The loss of two GPI-anchored surface proteins, CD55 and CD59, from red blood cells causes unregulated complement activation and hemolysis in classical PNH disease. In PNH patients, PIGA-mutant, GPI (-) hematopoietic cells clonally expand to make up a large portion of patients' blood production, yet mechanisms leading to clonal expansion of GPI (-) cells remain enigmatic. Historical models of PNH in mice and the more recent PNH model in rhesus macaques showed that GPI (-) cells reconstitute near-normal hematopoiesis but have no intrinsic growth advantage and do not clonally expand over time. Landmark studies identified several potential mechanisms which can promote PNH clonal expansion. However, to what extent these contribute to PNH cell selection in patients continues to be a matter of active debate. Recent advancements in disease models and immunologic technologies, together with the growing understanding of autoimmune marrow failure, offer new opportunities to evaluate the mechanisms of clonal expansion in PNH. Here, we critically review published data on PNH cell biology and clonal expansion and highlight limitations and opportunities to further our understanding of the emergence of PNH clones.

Utility of FLAER and CD157 in a five-color single-tube high sensitivity assay, for diagnosis of Paroxysmal Nocturnal Hemoglobinuria (PNH)-A standalone flow cytometry laboratory experience.

BACKGROUND: FLAER-based flow cytometry assay is considered the gold standard for diagnosis of paroxysmal nocturnal hemoglobinuria (PNH). CD157 is a recently reported marker for GPI-anchored protein found both on neutrophils and monocytes. This study highlights the robustness of FLAER and CD157 combination to identify PNH clones in a high sensitivity assay. Though rare, the data shown highlight the presence of CD157 negativity in few cases re-emphasizing the importance of FLAER for PNH diagnosis. METHODS: A single 5-color tube-FLAER Alexa488/ CD157PE/ CD15PECy5/ CD64PE-Cy7 & CD45APCH7-was used for a high sensitivity PNH assay. RESULTS: Of 364 cases, 59(16.2%) cases had PNH clone in both granulocytes and monocytes. PNH clone sizes ranged from 0.02% to 96.6% in granulocytes and 0.07% to 96.3% in monocytes based on their FLAER-negative, CD157-negative phenotype. Twenty-two of the 59 PNH cases (37.3%) had WBC clone size of <1%. In addition, there were 10 cases which showed absence of CD 157 expression on both granulocytes and monocytes but on FLAER staining showed normal staining patterns. Three of these ten cases also showed a PNH clone based on absence of FLAER expression on both granulocytes and monocytes. CONCLUSION: FLAER and CD157 is a robust combination for diagnosis of clinical and subclinical PNH. Absence of CD157 expression in normal WBCs, though rare, should be kept in mind and re-emphasizes the importance of FLAER for the high sensitivity PNH assay.

Diagnostic significance of flow cytometry scales in diagnostics of myelodysplastic syndromes.

BACKGROUND: Myelodysplastic syndromes (MDS) can present a challenge for clinicians. Multicolor flow cytometry (MFC) can aid in establishing a diagnosis. The aim of this study was to determine the optimal MFC approach for MDS. METHODS: The study included 102 MDS (39 low-grade MDS), 83 cytopenic patients without myeloid neoplastic disorders (control group), and 35 healthy donors. Bone marrow was analyzed using a six-color MFC. Analysis was conducted according to the "Ogata score," "Wells score," and the integrated flow cytometry (iFC) score. RESULTS: The respective sensitivity and specificity values were 77.5% and 90.4% for the Ogata score, 79.4% and 81.9% for the Wells score, and 87.3% and 87.6% for the iFC score. Specificity was not 100% due to deviations of MFC parameters in the control group. Patients with paroxysmal nocturnal hemoglobinuria (PNH) had higher levels of CD34+ CD7+ myeloid cells than donors. Aplastic anemia and PNH were characterized by a high proportion of CD56+ cells among CD34+ precursors and neutrophils. The proportion of MDS-related features increased with the progression of MDS. The highest number of CD34+ blasts was found in MDS with excess blasts. MDS with isolated del(5q) was characterized by a high proportion of CD34+ CD7+ cells and low granularity of neutrophils. In 39 low-grade MDS, the sensitivities were 53.8%, 61.5%, and 71.8% for Ogata score, Wells score, and iFC, respectively. CONCLUSION: The results support iFC as a useful diagnostic tool in MDS.

FLAER-negative CD15+ neutrophils can be used for the simplified screening of suspected PNH cases.

BACKGROUND: The flow cytometry analysis of GPI-linked proteins on red blood cells and leukocytes is crucial for paroxysmal nocturnal hemoglobinuria (PNH) diagnostics. However, the commonly used multicolor panels cannot be implemented in low-resourced hematology laboratories. In order to develop a simple prediagnostic test for PNH screening, we analyzed the diagnostic accuracy of the two-color (FLAER/CD15) detection of GPI-deficient neutrophils. METHODS: We reanalyzed multicolor data set of 1594 peripheral blood samples of patients screened for PNH applying only two markers (FLAER/CD15). The quantitative positivity/negativity was reported. Then, these results were compared in a blinded manner with previously obtained multicolor data from the same samples. RESULTS: Among the 1594 samples included in the study, 507 samples were PNH-positive by the multicolor assay. The two-color method revealed 510 PNH-positive samples. The detailed examination of this discrepancy revealed 12 false-positives and 9 false-negatives. Therefore, FLAER/CD15 screening method displayed 98.90% of the diagnostic specificity and 98.22% of the sensitivity. CONCLUSION: This simple two-color evaluation of FLAER-negative neutrophils is a highly effective screening test for PNH. Although this approach is not intended to replace the multicolor diagnostic procedure, it could minimize the number of patients requiring a conventional multicolor flow cytometric assay.

Disease modeling of bone marrow failure syndromes using iPSC-derived hematopoietic stem progenitor cells.

The plasticity of induced pluripotent stem cells (iPSCs) with the potential to differentiate into virtually any type of cells and the feasibility of generating hematopoietic stem progenitor cells (HSPCs) from patient-derived iPSCs (iPSC-HSPCs) has many potential applications in hematology. For example, iPSC-HSPCs are being used for leukemogenesis studies and their application in various cell replacement therapies is being evaluated. The use of iPSC-HSPCs can now provide an invaluable resource for the study of diseases associated with the destruction of HSPCs, such as bone marrow failure syndromes (BMFSs). Recent studies have shown that generating iPSC-HSPCs from patients with acquired aplastic anemia and other BMFSs is not only feasible, but is also a powerful tool for understanding the pathogenesis of these disorders. In this article, we highlight recent advances in the application of iPSCs for disease modeling of BMFSs and discuss the discoveries of these studies that provide new insights in the pathophysiology of these conditions.

Hemosiderin tubulopathy-induced acute kidney injury - A rare initial manifestation of paroxysmal nocturnal hemoglobinuria.

Paroxysmal nocturnal hemoglobinuria (PNH) is characterized by episodes of intravascular hemolysis, infections, and thromboembolic complications. Renal abnormalities are rare which occur either due to hemolytic crisis or repeated thrombotic episodes involving small venules. Acute kidney injury (AKI) requiring hemodialysis due to toxic effects of hemoglobinuria, with a stable disease is exceptional. We describe a case of an elderly gentleman presenting with features of severe AKI requiring hemodialysis due to hemosiderin tubulotoxicity as the first manifestation of PNH. The diagnosis was challenging because of the rarity and unfamiliarity with this entity. The outcome was complete recovery of renal function with hemodialysis.

Introduction to Acquired and Inherited Bone Marrow Failure.

Acquired aplastic anemia and inherited bone marrow failure syndromes both present with pancytopenia and must be distinguished because they have differences in treatment decisions and continued monitoring requirements. Advances in the genetic interrogation of patient samples have led to identification of inherited germline diseases and appreciation that patients with inherited bone marrow failure disorders may be normal in appearance with few expected clinical clues. Somatic mutations in aplastic anemia may have prognostic value. Hematopoietic stem cells from inherited marrow failure diseases can correct the proliferative defect and may develop further somatic mutations that progress to myelodysplastic syndrome or acute myeloid leukemia.

Evaluation and Management of Hematopoietic Failure in Dyskeratosis Congenita.

Dyskeratosis congenita (DC) is a rare, inherited bone marrow failure (BMF) syndrome characterized by variable manifestations and ages of onset, and predisposition to cancer. DC is one of a spectrum of diseases caused by mutations in genes regulating telomere maintenance, collectively referred to as telomere biology disorders (TBDs). Hematologic disease is common in children with DC/TBD. Timely diagnosis of underlying TBD in patients with BMF affects treatment and has been facilitated by increased awareness and availability of diagnostic tests in recent years. This article summarizes the pathophysiology, evaluation, and management of hematopoietic failure in patients with DC and other TBDs.

Germline GATA2 Mutation and Bone Marrow Failure.

GATA2 deficiency is an immunodeficiency and bone marrow failure disorder caused by pathogenic variants in GATA2. It is inherited in an autosomal-dominant pattern or can be due to de novo sporadic germline mutation. Patients commonly have B-cell, dendritic cell, natural killer cell, and monocytopenias, and are predisposed to myelodysplastic syndrome, acute myeloid leukemia, and chronic myelomonocytic leukemia. Patients may suffer from disseminated human papilloma virus and mycobacterial infections, pulmonary alveolar proteinosis, and lymphedema. The bone marrow eventually takes on a characteristic hypocellular myelodysplasia with loss of monocytes and hematogones, megakaryocytes with separated nuclear lobes, micromegakaryocytes, and megakaryocytes with hypolobated nuclei.

Diseases of complement dysregulation-an overview.

Atypical hemolytic uremic syndrome (aHUS), C3 glomerulopathy (C3G), and paroxysmal nocturnal hemoglobinuria (PNH) are prototypical disorders of complement dysregulation. Although complement overactivation is common to all, cell surface alternative pathway dysregulation (aHUS), fluid phase alternative pathway dysregulation (C3G), or terminal pathway dysregulation (PNH) predominates resulting in the very different phenotypes seen in these diseases. The mechanism underlying the dysregulation also varies with predominant acquired autoimmune (C3G), somatic mutations (PNH), or inherited germline mutations (aHUS) predisposing to disease. Eculizumab has revolutionized the treatment of PNH and aHUS although has been less successful in C3G. With the next generation of complement therapeutic in late stage development, these archetypal complement diseases will provide the initial targets.

ICCS/ESCCA consensus guidelines to detect GPI-deficient cells in paroxysmal nocturnal hemoglobinuria (PNH) and related disorders part 4 - assay validation and quality assurance.

Over the past six years, a diverse group of stakeholders have put forth recommendations regarding the analytical validation of flow cytometric methods and described in detail the differences between cell-based and traditional soluble analyte assay validations. This manuscript is based on these general recommendations as well as the published experience of experts in the area of PNH testing. The goal is to provide practical assay-specific guidelines for the validation of high-sensitivity flow cytometric PNH assays. Examples of the reports and validation data described herein are provided in Supporting Information. © 2017 International Clinical Cytometry Society.