Diamond-Blackfan anemia

Hematopoietic Stem Cell Transplantation Outcomes in Diamond-Blackfan Anemia Patients Based on Myeloablative Conditioning Regimen With or Without Total Body Irradiation: A Systematic Review and Meta-Analysis

Diamond-Blackfan anemia (DBA) is a rare, congenital bone marrow failure syndrome characterized by hypoplastic anemia. Earliest descriptions of this disease date back to 1936, and since then, a plethora of treatment strategies have been used to control or treat the disease. In recent decades, hematopoietic stem cell transplantation (HSCT) has been declared the only curative treatment. Despite the time elapsing from the first time HSCT has been used in this setting, no unified standard preparative and prophylactic protocol has been established. In this article, for the first time, the published articles concerning the efficacy of the most verified conditioning regimens established for these patients, the myeloablative conditioning regimen (MAC), were systematically reviewed. A comparison of two groups, based on the presence or absence of radiation in their protocol, was performed. Electronic and manual searches were conducted on PubMed, Scopus, and Web of Science. The primary study domains, selection, and outcome were assessed using the JBI Scale quality assessment for cohort and case series studies. Cohorts were categorized into treatment groups, and the characteristics of patients and donors, in addition to intervention characteristics and outcomes, were synthesized. Among a total of 196 studies reviewed, we included five cohorts in our systematic review. The studies were heterogeneous in various aspects. In conclusion, our analysis suggests that DBA patients who underwent a MAC non-total body irradiation (TBI) conditioning regimen may experience better post-HSCT outcomes; however, the findings are inconclusive.

DNA remnants in red blood cells enable early detection of cancer

Cytoplasmic DNA emerges as a consequence of genomic instability. However, its potential role in disease diagnosis has yet to be fully explored. Here we analyzed DNA remnants in mature red blood cells (rbcDNA) from both healthy individuals and cancer patients. Our study unveiled distinct genomic profiles in rbcDNA from cancer patients with early-stage solid tumors compared to those of healthy donors. Significant changes in read counts at specific genomic regions within rbcDNA were identified in patients, which were termed tumor-associated rbcDNA features. These features demonstrated potential for highly accurate early-stage cancer detection, proposing a novel approach for cancer detection. Moreover, tumor-associated rbcDNA features were observed in tumor mouse models, with some features being conserved between mice and humans. Chronic, but not transient, up-regulation of interleukin-18 is essential for the development of these features by promoting DNA damage in bone marrow hematopoietic cells through the up-regulation of NR4A1. These results underscore the remote regulation of chromosomal stability in hematopoietic cells by solid tumors and propose tumor-associated rbcDNA features as a promising strategy for early cancer detection.

Sotatercept in pulmonary hypertension and beyond

Sotatercept binds free activins by mimicking the extracellular domain of the activin receptor type IIA (ACTRIIA). Additional ligands are BMP/TGF-beta, GDF8, GDF11 and BMP10. The binding with activins leads to the inhibition of the signalling pathway and the deactivation of the bone morphogenic protein (BMP) receptor type 2. In this way, sotatercept activates an antiproliferative signalling to the cells of the pulmonary arteries and arterioles with the aim of rebalancing the proliferative and antiproliferative pathway that characterizes the pulmonary arterial hypertension (PAH). Sotatercept is indicated for the treatment of group 1 PAH in combination with drugs that act through the endothelin receptor, nitric oxide or prostacyclin. Its effects, demonstrated in the STELLAR study, are the improvement of exercise capacity and the FC-WHO functional class, together with the reduction of the risk of clinical worsening events. In addition to its antiremodeling effects on the pulmonary circulation, sotatercept has several haematological effects that could suggest its use in the treatment of some blood disorders other than PAH. In this review, we will discuss the effects of the drug on PAH and in parallel provide an in-depth overview of its application in haematological disorders, focusing on clinical and preclinical studies.

Unveiling the role of RPS17 and SLC4A1 in diamond-Blackfan Anemia: A zebrafish-based study

Diamond-Blackfan Anemia (DBA) is a rare congenital disorder characterized by macrocytic anemia, physical abnormalities, and growth delays. Although RPS19 mutations have been more extensively studied in DBA compared to other ribosomal protein genes, the pathological mechanisms of genes such as RPS17 remain largely unexplored. This study aimed to investigate the role of RPS17 haploinsufficiency in DBA, focusing on its downstream effects on erythropoiesis and the involvement of SLC4A1, a critical erythrocyte membrane protein essential for red blood cell stability. Transcriptomic analysis of publicly available RNA sequencing data from DBA patients revealed significant downregulation of SLC4A1 in RPS17-mutated cases. To validate these findings, we generated a zebrafish model of DBA by knocking down rps17 using morpholino injections. Zebrafish embryos with rps17 knockdown exhibited reduced erythropoiesis, impaired hemoglobin synthesis, consistent with DBA. Further analysis confirmed decreased slc4a1a expression in rps17-morphants. Independent knockdown of slc4a1a in zebrafish resulted in similar erythropoietic defects, highlighting its critical role in red blood cell membrane integrity and function. This study identifies slc4a1 as a key downstream target of RPS17 haploinsufficiency and provides novel insights into the molecular mechanisms of DBA. By establishing zebrafish as an effective in vivo model, this research offers potential therapeutic targets for treating DBA and related erythropoietic disorders.

Biallelic variants in the conserved ribosomal protein chaperone gene PDCD2 are associated with hydrops fetalis and early pregnancy loss

Pregnancy loss is a major problem in clinical medicine with devastating consequences for families. Next generation sequencing has improved our ability to identify underlying molecular causes, though over half of all cases lack a clear etiology. Here, we began with clinical evaluation combined with exome sequencing across independent families to identify bi-allelic candidate genetic variants in the Programmed Cell Death 2 (PDCD2) gene in multiple fetuses with nonimmune hydrops fetalis (NIHF). PDCD2 is an evolutionarily conserved protein with no prior association with monogenic disorders. PDCD2 is known to act as a molecular chaperone for the ribosomal protein uS5, and this complex formation is important for incorporation of uS5 into the 40S subunit, a crucial step in ribosome biogenesis. Primary fibroblasts from an affected fetus and cell lines expressing PDCD2 patient variants demonstrated reduced levels of PDCD2, reduced PDCD2 binding to uS5, and altered ribosomal RNA processing. Xenopus tadpoles with Pdcd2 knockdown demonstrated developmental defects and edema, reminiscent of the NIHF seen in affected fetuses, and showed altered ribosomal RNA processing. Through genetic, biochemical, and in vivo approaches, we provide evidence that bi-allelic PDCD2 variants cause an autosomal recessive ribosomal biogenesis disorder resulting in pregnancy loss.

RPS24 haploinsufficiency impairs erythropoiesis in the Diamond-Blackfan anemia zebrafish model via the STAT6-SATB1 pathway

Diamond-Blackfan anemia (DBA) is a rare bone marrow failure disorder primarily caused by mutations in ribosomal proteins (RPs), including RPS24, leading to impaired erythropoiesis. Despite advances in our understanding of the roles of other RPs, the mechanisms underlying RPS24-related DBA remain unclear. Therefore, in this study, we aimed to investigate the effect of RPS24 haploinsufficiency on erythropoiesis using a zebrafish model. RPS24 knockdown via morpholino injection significantly reduced the hemoglobin levels, as confirmed by O-dianisidine staining and whole-mount in situ hybridization. Further analysis revealed that RPS24 deficiency downregulated the expression of SATB homeobox 1a (satb1a), a key regulator of erythroid differentiation, by inhibiting the signal transducer and activator of transcription 6 (STAT6) signaling pathway. Western blotting analysis revealed decreased levels of pSTAT6 correlated with the decrease in downstream erythroid marker levels. satb1a knockdown further impaired erythropoiesis in zebrafish, reinforcing its critical role in DBA pathogenesis. Overall, our findings suggest that RPS24 haploinsufficiency leads to DBA by disrupting the STAT6-SATB1 axis, providing novel insights into the molecular mechanisms underlying erythropoietic failure in DBA. Furthermore, this study highlights the importance of zebrafish models for further exploration of therapeutic targets for DBA.

Hematologic Complications of Pregnancy

Hematologic complications are common in pregnancy and can significantly impact both maternal and fetal health. Recognizing and treating these complications can be challenging due to the limited evidence available to guide clinical consultants. Iron deficiency anemia is the most prevalent hematologic issue in pregnancy and often occurs due to increased maternal blood volume and the nutritional demands of the growing fetus. Thrombocytopenia is the second most commonly occurring hematologic issue in pregnancy and can be associated with increased blood loss and complications during childbirth. However, the most common type of thrombocytopenia in pregnancy is gestational thrombocytopenia, which does not typically require clinical management. Thus, it is important to distinguish gestational thrombocytopenia from other etiologies of thrombocytopenia in pregnancy that require immediate treatment, including immune thrombocytopenia, thrombotic thrombocytopenic purpura, preeclampsia, and HELLP (hemolysis, elevated liver enzyme levels, and low platelet levels) syndrome. Other important hematologic conditions in pregnancy include non-inherited anemias, such as autoimmune hemolytic anemia and aplastic anemia, as well as inherited anemias, such as sickle cell disease and thalassemia, which may require specialized management to optimize maternal and fetal outcomes. Additionally, bleeding disorders, such as von Willebrand disease and hemophilia, pose unique challenges in pregnancy, especially around the time of delivery, due to the risk of excessive bleeding. Lastly, thromboembolic disorders, such as venous thromboembolism (VTE), remain the leading cause of mortality in pregnancy in developed countries. Pregnancy-related hormonal changes, venous stasis, and hypercoagulability contribute to an increased thromboembolic risk, further exacerbated by additional risk factors such as obesity or a prior personal or family history of VTE. This review aims to summarize current guidelines and management of the most common hematologic disorders in pregnancy.

NBS1 facilitates preribosomal RNA biogenesis

Mutations in the NBS1 gene result in Nijmegen breakage syndrome (NBS), and the gene encodes NBS1 that forms a complex with MRE11 and RAD50 and participates in DNA damage repair. However, the molecular mechanism by which NBS1 mutations cause clinical phenotypes of NBS, such as craniofacial dysmorphism, is still unclear. Here, we show that NBS1 localizes at the ribosomal DNA (rDNA) loci in nucleoli and interacts with ribosomal RNA (rRNA) transcription machinery including RNA polymerase I (Pol I) and TCOF1. Loss of NBS1 impairs Pol I-dependent transcription of pre-rRNA and induces nucleolar stress. In particular, lacking Nbs1 in mouse neural crest cells not only leads to the reduction of ribosome biogenesis but also craniofacial abnormalities during prenatal development. Moreover, the C-terminus of NBS1 is associated with pre-rRNA and a number of pre-rRNA processing factors, which may also facilitate pre-rRNA maturation. Taken together, our study reveals the functions of NBS1 in rRNA biogenesis.

Balancing benefits and burdens: a systematic review on ethical and social dimensions of gene and cell therapies for hereditary blood diseases

BACKGROUND

Sickle cell disease (SCD) and Diamond-Blackfan anemia syndrome (DBAS) are two hereditary blood diseases that present significant challenges to patients, their caregivers, and the healthcare system. Both conditions cause severe health complications and have limited treatment options, leaving many individuals without access to curative therapies like hematopoietic stem cell transplantation. Recent advancements in gene and cell therapies offer the potential for a new curative option, marking a pivotal shift in the management of these debilitating diseases. However, the implementation of these therapies necessitates a nuanced understanding of the ethical and social implications.

METHODS

In this mixed methods systematic review, we explore the responsible development and implementation of gene and cell therapies for SCD and DBAS and aim to sketch a path toward ethically and socially sound implementation. Drawing upon principles of Responsible Research & Innovation and the 4A framework of availability, accessibility, acceptability, and affordability, we thematically analyze existing research to illuminate the ethical and social dimensions of these therapies. Following established PRISMA and JBI Manual guidelines, a search across multiple databases yielded 51 peer-reviewed studies with publication dates ranging from 1991 to 2023.

RESULTS

Our thematic analysis shows that the theme of acceptability is heavily shaped by interactions between patients, caregivers, healthcare professionals and researchers, influencing treatment decisions and shaping the development of curative gene and cell therapies. Despite the generally positive perspective on these therapies, factors like the limited treatment options, financial constraints, healthcare professional attitudes, and (historical) mistrust can impede stakeholder decision-making. While acceptability focuses on individual decisions, the themes of availability, accessibility, and affordability are interconnected and primarily driven by healthcare systems, where high research and development costs, commercialization and a lack of transparency challenge equitable access to these therapies. This diminishes the acceptability for patients, revealing a complex interdependence of the themes.

CONCLUSIONS

The findings suggest the need for improved communication strategies in clinical practice to facilitate informed decision-making for patients and caregivers. Policy development should focus on addressing pricing disparities and promoting international collaboration to ensure equitable access to therapies. This review has been pre-registered in PROSPERO under registration number CRD42023474305.

Immunodeficiency in children with Diamond Blackfan and Diamond Blackfan like anemia

BACKGROUND

Diamond-Blackfan anemia Syndrome (DBAS) is a ribosomopathy with erythroid failure. DBA-like picture occurs with non-ribosomal mutation and a normal rRNA maturation. Immunodeficiency in patients with DBAS is not adequately studied. We aimed to study the frequency of infections and immunoglobulins levels in children with DBAS.

METHODS

Children and adolescents with DBAS were included. Infections were scored according to the immunodeficiency related score (IDR). Total serum immunoglobulin A (IgA), IgG and IgM were measured. Molecular studies were done to a group of patients.

RESULTS

Thirty-four patients had a median age at diagnosis of 3.6 month-old. Fourteen (41 %) patients had an IDR score of ≥6, and 4 of them (28.6 %) had low immunoglobulin levels. Patients with IDR score > 6 had significantly lower IgG (471 versus 1057 mg/dl, p = 0,032) and serum IgA (24 versus 98.5 mg/dl, p = 0.015) than IDR < 6 group. We report mortality in 8 (23.5 %) patients, two of them were related to infection. Molecular analyses were performed in 8 probands and 17 relatives (5 families); 7 of the probands carried CECR1/ADA2 gene mutation and one patient carried a pathogenic variant in RPL36 gene.

CONCLUSION

We highlight the presence of underlying immunodeficiency in a group of patients with DBA and DBA-like disease.

Elucidating loss-of-function mechanisms of monoallelic EPAS1 mutations underlying congenital hypoplastic anaemia in a paediatric anaemia cohort

HIF-2α, encoded by EPAS1, plays a dominant role in regulating erythropoietin (EPO) production, maintaining the dynamic balance of erythropoiesis. Gain-of-function mutations in EPAS1 cause erythrocytosis. However, anaemia caused by EPAS1 loss-of-function mutations has been confined to only one case report, and the underlying mechanism remains unclear. Herein, the reanalysis of high-throughput sequencing data from 311 patients with anaemia identified three monoallelic EPAS1 variants from three unrelated families in a paediatric anaemia cohort. The probands showed highly consistent clinical phenotypes with normocytic and normochromic anaemia, reticulocytopenia and relative deficiency of serum EPO, characterised as congenital hypoplastic anaemia. In vitro studies suggested that defects in steady-state protein abundance, nuclear localisation and binding with co-activator in EPAS1 variants lead to impaired EPO transcriptional activation. Therefore, loss-of-function mutations in EPAS1 can cause erythroid hypoplasia in an EPO-dependent manner. This study identified a new causative gene for congenital hypoplastic anaemia and clarified the molecular aetiology of loss-of-function EPAS1 mutations.

Genome sequencing in the management of myelodysplastic syndromes and related disorders

Myeloid neoplasms originate from the clonal proliferation of hematopoietic stem cells, which is driven by the acquisition of somatic genetic mutations. Within these disorders, myelodysplastic syndromes (MDS) are specifically characterized by morphological abnormalities (dysplasia) and impaired maturation of myeloid precursors (ineffective hematopoiesis), resulting in peripheral blood cytopenia. Several studies have advanced the field of MDS, with a few landmark papers leading to a paradigm shift, opening new avenues of research and enabling a molecular revolution. These seminal papers include the first description of the 5q- syndrome, the identification of somatic mutations of TET2 in myeloid neoplasms, the detection of common pathway mutations in the splicing machinery, and the discovery of clonal hematopoiesis. The somatic genomic landscape of MDS is now well defined. Genes that are recurrently mutated include epigenetic regulators, as well as genes of RNA splicing machinery, transcription regulation, DNA repair control, cohesin complex, and signal transduction. Furthermore, several disorders with a germline genetic predisposition to MDS have been identified, collectively accounting for up to 15% of all MDS cases. Genomic profiling can significantly improve the diagnostic approach to MDS, allowing the identification of distinct nosological entities such as SF3B1-mutant or TP53-mutant MDS. The Molecular International Prognostic Scoring System for MDS has already proven to be a valuable tool for individualized risk assessment and treatment decisions. In addition, the recently developed molecular taxonomy of MDS will likely facilitate the implementation of precision medicine approaches for these disorders. This will necessitate the establishment of specialized infrastructures within public health systems, involving close collaboration between healthcare institutions, academia, and the life-sciences industry.

Expert consensus on classification and diagnosis of congenital orofacial cleft

Congenital orofacial cleft, the most common birth defect in the maxillofacial region, exhibits a wide range of prognosis depending on the severity of deformity and underlying etiology. Non-syndromic congenital orofacial clefts typically present with milder deformities and more favorable treatment outcomes, whereas syndromic congenital orofacial clefts often manifest with concomitant organ abnormalities, which pose greater challenges for treatment and result in poorer prognosis. This consensus provides an elaborate classification system for varying degrees of orofacial clefts along with corresponding diagnostic and therapeutic guidelines. Results serve as a crucial resource for families to navigate prenatal screening results or make informed decisions regarding treatment options while also contributing significantly to preventing serious birth defects within the development of population.

A role for the kinetochore protein, NUF2, in ribosome biogenesis

Ribosome biogenesis (RB) is an intricate and evolutionarily conserved process that takes place mainly in the nucleolus and is required for eukaryotic cells to maintain homeostasis, grow in size, and divide. Our laboratory has identified the NUF2 protein, part of the mitotic kinetochore, in a genome-wide siRNA screen for proteins required for making ribosomes in MCF10A human breast epithelial cells. After rigorous validation and using several biochemical and cell-based assays, we find a role for NUF2 in pre-rRNA transcription, the primary and rate-limiting step of RB. siRNA depletion of other components of the NUF2 kinetochore sub-complex, NDC80, SPC24, and SPC25, also reduce pre-rRNA transcription. Interestingly, essential protein components for pre-rRNA transcription, including the largest subunit of RNA polymerase I, POLR1A, are reduced upon siRNA depletion of NUF2 and its protein partners. Their reduced levels are a likely mechanism for the decrease in pre-rRNA transcription. siRNA depletion of NUF2 and NDC80 also cause increased TP53 and CDKN1A (p21) mRNA levels, which can be restored by codepletion of RPL5, indicating activation of the nucleolar stress pathway (NSP). These results reveal a new connection between proteins with a known role in mitosis to the function of the nucleolus in RB during interphase.

Human oncostatin M deficiency underlies an inherited severe bone marrow failure syndrome

Oncostatin M (OSM) is a cytokine with the unique ability to interact with both the OSM receptor (OSMR) and the leukemia inhibitory factor receptor (LIFR). On the other hand, OSMR interacts with IL31RA to form the interleukin-31 receptor. This intricate network of cytokines and receptors makes it difficult to understand the specific function of OSM. While monoallelic loss-of-function (LoF) mutations in OSMR underlie autosomal dominant familial primary localized cutaneous amyloidosis, the in vivo consequences of human OSM deficiency have never been reported so far. Here, we identified 3 young individuals from a consanguineous family presenting with inherited severe bone marrow failure syndromes (IBMFS) characterized by profound anemia, thrombocytopenia, and neutropenia. Genetic analysis revealed a homozygous 1 base-pair insertion in the sequence of OSM associated with the disease. Structural and functional analyses showed that this variant causes a frameshift that replaces the C-terminal portion of OSM, which contains the FxxK motif that interacts with both OSMR and LIFR, with a neopeptide. The lack of detection and signaling of the mutant OSM suggests a LoF mutation. Analysis of zebrafish models further supported the role of the OSM/OSMR signaling in erythroid progenitor proliferation and neutrophil differentiation. Our study provides the previously uncharacterized and unexpectedly limited in vivo consequence of OSM deficiency in humans.

Biallelic variation in the choline and ethanolamine transporter FLVCR1 underlies a severe developmental disorder spectrum

PURPOSE

FLVCR1 encodes a solute carrier protein implicated in heme, choline, and ethanolamine transport. Although Flvcr1-/- mice exhibit skeletal malformations and defective erythropoiesis reminiscent of Diamond-Blackfan anemia (DBA), biallelic FLVCR1 variants in humans have previously only been linked to childhood or adult-onset ataxia, sensory neuropathy, and retinitis pigmentosa.

METHODS

We identified individuals with undiagnosed neurodevelopmental disorders and biallelic FLVCR1 variants through international data sharing and characterized the functional consequences of their FLVCR1 variants.

RESULTS

We ascertained 30 patients from 23 unrelated families with biallelic FLVCR1 variants and characterized a novel FLVCR1-related phenotype: severe developmental disorders with profound developmental delay, microcephaly (z-score -2.5 to -10.5), brain malformations, epilepsy, spasticity, and premature death. Brain malformations ranged from mild brain volume reduction to hydranencephaly. Severely affected patients share traits, including macrocytic anemia and skeletal malformations, with Flvcr1-/- mice and DBA. FLVCR1 variants significantly reduce choline and ethanolamine transport and/or disrupt mRNA splicing.

CONCLUSION

These data demonstrate a broad FLVCR1-related phenotypic spectrum ranging from severe multiorgan developmental disorders resembling DBA to adult-onset neurodegeneration. Our study expands our understanding of Mendelian choline and ethanolamine disorders and illustrates the importance of anticipating a wide phenotypic spectrum for known disease genes and incorporating model organism data into genome analysis to maximize genetic testing yield.

Pituitary hemochromatosis in the clinical setting of secondary amenorrhea in a patient with Diamond-Blackfan anemia

Secondary amenorrhea is the absence of menses for more than 3 months in women who previously had regular menstrual cycles or 6 months for those with irregular cycles. Workup of secondary amenorrhea includes laboratory analysis to assess pituitary function, specifically luteinizing hormone (LH) and follicle stimulating hormone (FSH). If low, structural evaluation of the pituitary gland with MRI is recommended. We report a case of a 31-year-old female with history of transfusion-dependent Diamond-Blackfan anemia and type 2 diabetes that reported amenorrhea for 1 year following intrauterine device (IUD) removal. Due to low LH and FSH, the patient underwent an MRI of the pituitary gland. Imaging demonstrated complete absence of MRI signal within the pituitary parenchyma, which confirmed pituitary dysfunction from secondary hemochromatosis, presumably due to iron overload from multiple transfusions. As a result of her imaging and laboratory assessment, she was placed on an iron chelator and oral contraception.

Diagnosis of Diamond-Blackfan anemia in adulthood: case series and review of the literature

Diamond-Blackfan anemia (DBA) is a rare constitutional inherited bone marrow failure syndrome (iBMF) characterized by progressive severe non-regenerative anemia and congenital abnormalities. Diagnosis is made by identification of a DBA-causing variant, typically in a ribosomal protein gene. More than 99% of patients are diagnosed in the pediatric age, but clinical manifestation may be mild and severe anemia can occur later in the patient's life. Moreover, the expanding availability of molecular testing is increasing the ability to identify DBA variants also in adults with a non-canonical DBA phenotype. Therefore, adult hematologists must maintain a high clinical suspicion and awareness towards possible DBA diagnosis in adulthood. In this context, the most common differential diagnoses are acquired BMFs such as pure red cell aplasia (PRCA) or hypoplastic myelodysplastic syndrome (MDS). Here, we present three adult patients diagnosed with DBA, where the identification of the causative mutation occurred several years from PRCA misdiagnosis or was made after screening for an affected relative. We also provide a review of 16 cases available in the literature and give hints on possible treatment strategies.

Preclinical development of lentiviral vector gene therapy for Diamond-Blackfan anemia syndrome

Diamond-Blackfan anemia syndrome (DBAS) is an inherited bone marrow failure disorder caused by haploinsufficiency of ribosomal protein genes, most commonly RPS19. Limited access to patient hematopoietic stem and progenitor cells (HSPCs) is a major roadblock to developing novel therapies for DBAS. We developed a self-inactivating third-generation RPS19-encoding lentiviral vector (LV) called SJEFS-S19 for DBAS gene therapy. To facilitate LV design, optimize transduction, and assess potential therapeutic efficacy, we leveraged a human cellular model of DBAS based on heterozygous disruption of RPS19 in healthy donor CD34+ HSPCs. We show that SJEFS-S19 LV can rescue DBAS-associated defects in ribosomal RNA processing, erythropoiesis, and competitive bone marrow repopulation. Transduction of RPS19+/- CD34+ HSPCs with SJEFS-S19 LV followed by xenotransplantation into immunodeficient mice generated a polyclonal HSPC population with normal multilineage differentiation and a diverse integration site profile resembling that of clinically proven LVs. Overall, these preclinical studies demonstrate the safety and efficacy of SJEFS-S19, a novel LV for future DBAS gene therapy.

A novel nonsense RPS26 mutation in a patient with Diamond-Blackfan anemia: a case report

BACKGROUND

Diamond-Blackfan anemia is a rare congenital disorder characterized by erythroid hypoplasia and is associated with mutations in ribosomal protein genes. This case report describes a novel variant in the RPS26 gene, which, to our knowledge, has not been previously documented. Reporting this case adds to the understanding of Diamond-Blackfan anemia's genetic diversity and phenotypic manifestations.

CASE PRESENTATION

A 16-month-old Turkish girl presented with pallor and macrocytosis. There was no familial history of anemia. Hemoglobin electrophoresis showed hemoglobin F at 10.8%, hemoglobin A2 at 1.7%, and hemoglobin A at 87.5% (normal range 0-2%). Peripheral smear demonstrated macrocytosis and reticulocytopenia. Bone marrow examination revealed marked erythroid hypoplasia and dyserythropoiesis. Targeted next-generation sequencing, which included genes such as RPL11, RPL15, RPL26, RPL35A, RPL5, RPS10, RPS17, RPS19, RPS24, RPS26, RPS28, RPS29, RPS7, and TSR2, identified a heterozygous c.221G>T (p.C74F) variant in the RPS26 gene. This variant is reported here for the first time.

CONCLUSIONS

The identification of the c.221G>T (p.C74F) variant in RPS26 provides new insights into the genetic underpinnings of Diamond-Blackfan anemia. This finding underscores the importance of genetic testing in diagnosing Diamond-Blackfan anemia and highlights the potential for new mutations to contribute to the clinical presentation of the disease. Further research into RPS26 mutations may enhance the understanding of Diamond-Blackfan anemia's pathogenesis and lead to improved diagnostic and therapeutic strategies.

Annexin A1: a key regulator of T cell function and bone marrow adiposity in aplastic anaemia

This study investigates the role of Annexin A1 (ANXA1) in regulating T cell function and its implications in bone marrow adiposity in aplastic anaemia (AA). Utilizing single-cell sequencing analysis, we compared bone marrow tissues from AA patients and healthy individuals, focusing on T cell subgroups and their impact on bone marrow pathology. Our findings reveal a significant activation of CD8+ T cells in AA, driven by reduced ANXA1 expression. This heightened T cell activity promotes adipogenesis in bone marrow-derived mesenchymal stem cells via IFN-γ secretion. Overexpression of ANXA1 was found to suppress this process, suggesting its therapeutic potential in AA treatment. The study highlights ANXA1 as a crucial regulator in the AA-associated immune microenvironment and bone marrow adiposity. KEY POINTS: This study found that ANXA1 is significantly downregulated in AA and provides detailed insights into its critical role in the disease. The study demonstrates the excessive activation of CD8+ T cells in the progression of AA. The research shows that the overexpression of ANXA1 can effectively inhibit the activation of CD8+ T cells. The study confirms that overexpression of ANXA1 reduces the secretion of the cytokine IFN-γ, decreases adipogenesis in bone marrow-derived mesenchymal stem cells and may improve AA symptoms. This research provides new molecular targets for the treatment of AA.

Case report: Rethinking NGS analysis in diagnosing Diamond-Blackfan anemia syndrome

Diamond-Blackfan anemia syndrome (DBAS) is a rare inherited bone marrow failure (BMF) syndrome characterized by erythroid aplasia, congenital malformations, and cancer predisposition. With its genetic heterogeneity, variable penetrance and expressivity, DBAS poses significant diagnostic challenges, necessitating advancements in genetic testing for improved accuracy. Here, we present the case of an 18-year-old male with a long-standing macrocytic anemia that remained undiagnosed despite standard whole exome sequencing (WES). Revisiting a family-trio WES analysis with clinical insight led to the identification of a likely pathogenic variant in the Ribosomal Protein S17 (RPS17) gene, previously masked due to analytical challenges and conservative filter settings. This variant, an initiation codon mutation, was confirmed in heterozygosity in both the proband and his mother through Sanger sequencing. Comprehensive imaging studies showed no malformations or organ anomalies in either individual, except for mild esophageal stenosis observed in both. RPS17 mutations, particularly those affecting the initiation codon, have previously been linked to the DBAS phenotype, but strong pathogenic association has not yet been firmly established. Our case warns of potential underdiagnosis of RPS17 variants in DBAS, highlighting the importance of clinical context and interdisciplinary collaboration in interpreting WES data to avoid false-negative results.

RPS19 and RPL5, the most commonly mutated genes in Diamond Blackfan anemia, impact DNA double-strand break repair

Diamond Blackfan anemia (DBA) is caused by germline heterozygous loss-of-function pathogenic variants (PVs) in ribosomal protein (RP) genes, most commonly RPS19 and RPL5. In addition to red cell aplasia, individuals with DBA are at increased risk of various cancers. Importantly, the mechanism(s) underlying cancer predisposition are poorly understood. We found that DBA patient-derived lymphoblastoid cells had persistent γ-H2AX foci following ionizing radiation (IR) treatment, suggesting DNA double-strand break (DSB) repair defects. RPS19- and RPL5-knocked down (KD) CD34+ cells had delayed repair of IR-induced DSBs, further implicating these RPs in DSB repair. Assessing the impact of RPS19- and RPL5-KD on specific DSB repair pathways, we found RPS19-KD decreased the efficiency of pathways requiring extensive end-resection, whereas RPL5-KD increased end-joining pathways. Additionally, RAD51 was reduced in RPS19- and RPL5-KD and RPS19- and RPL5-mutated DBA cells, whereas RPS19-deficient cells also had a reduction in PARP1 and BRCA2 proteins. RPS19-KD cells had an increase in nuclear RPA2 and a decrease in nuclear RAD51 foci post-IR, reflective of alterations in early, critical steps of homologous recombination. Notably, RPS19 and RPL5 interacted with poly(ADP)-ribose chains noncovalently, were recruited to DSBs in a poly(ADP)-ribose polymerase activity-dependent manner, and interacted with Ku70 and histone H2A. RPL5's recruitment, but not RPS19's, also required p53, suggesting that RPS19 and RPL5 directly participate in DSB repair via different pathways. We propose that defective DSB repair arising from haploinsufficiency of these RPs may underline the cancer predisposition in DBA.

Osteosarcoma through the Lens of Bone Development, Signaling, and Microenvironment

In this work, we review the multifaceted connections between osteosarcoma (OS) biology and normal bone development. We summarize and critically analyze existing research, highlighting key areas that merit further exploration. The review addresses several topics in OS biology and their interplay with normal bone development processes, including OS cell of origin, genomics, tumor microenvironment, and metastasis. We examine the potential cellular origins of OS and how their roles in normal bone growth may contribute to OS pathogenesis. We survey the genomic landscape of OS, highlighting the developmental roles of genes frequently altered in OS. We then discuss the OS microenvironment, emphasizing the transformation of the bone niche in OS to facilitate tumor growth and metastasis. The role of stromal and immune cells is examined, including their impact on tumor progression and therapeutic response. We further provide insights into potential development-informed opportunities for novel therapeutic strategies.

DNA damage repair in megakaryopoiesis: molecular and clinical aspects

INTRODUCTION

Endogenous DNA damage is a significant factor in the damage of hematopoietic cells. Megakaryopoiesis is one of the pathways of hematopoiesis that ends with the production of platelets and plays the most crucial role in hemostasis. Despite the presence of efficient DNA repair mechanisms, some endogenous lesions can lead to mutagenic alterations, disruption of pathways of hematopoiesis including megakaryopoiesis and potentially result in human diseases.

AREAS COVERED

The complex regulation of DNA repair mechanisms plays a central role in maintaining genomic integrity during megakaryopoiesis and influences platelet production efficiency and quality. Moreover, anomalies in DNA repair processes are involved in several diseases associated with megakaryopoiesis, including myeloproliferative disorders and thrombocytopenia.

EXPERT OPINION

In the era of personalized medicine, diagnosing diseases related to megakaryopoiesis can only be made with a complete assessment of their molecular aspects to provide physicians with critical molecular data for patient management and to identify the subset of patients who could benefit from targeted therapy.

Erythropoiesis: insights from a genomic perspective

Erythropoiesis, the process underlying the production of red blood cells, which are essential for oxygen transport, involves the development of hematopoietic stem cells into mature red blood cells. This review focuses on the critical roles of transcription factors and epigenetic mechanisms in modulating gene expression critical for erythroid differentiation. It emphasizes the significance of chromatin remodeling in ensuring gene accessibility, a key factor for the orderly progression of erythropoiesis. This review also discusses how dysregulation of these processes can lead to erythroid disorders and examines the promise of genome editing and gene therapy as innovative therapeutic approaches. By shedding light on the genomic regulation of erythropoiesis, this review suggests avenues for novel treatments for hematological conditions, underscoring the need for continued molecular studies to improve human health.

Generation of iPSC lines and isogenic gene-corrected lines from two individuals with RPS19-mutated Diamond-Blackfan anemia syndrome

Diamond-Blackfan anemia syndrome (DBAS) is an inherited bone marrow failure disorder that typically presents in infancy as hypoplastic anemia and developmental abnormalities in approximately 50% of cases. DBAS is caused by haploinsufficiency in one of 24 ribosomal protein genes, with RPS19 mutations accounting for 25% of cases. We generated iPSC lines from two patients with different heterozygous RPS19 mutations (c.191T > C and c.184C > T) and isogenic lines in which the mutations were corrected by Cas9-mediated homology directed repair.

Reduced anti-Müllerian hormone levels in males with inherited bone marrow failure syndromes

Fanconi anemia (FA), dyskeratosis congenita-related telomere biology disorders (DC/TBD), and Diamond-Blackfan anemia (DBA) are inherited bone marrow failure syndromes (IBMFS) with high risks of bone marrow failure, leukemia, and solid tumors. Individuals with FA have reduced fertility. Previously, we showed low levels of anti-Müllerian hormone (AMH), a circulating marker of ovarian reserve, in females with IBMFS. In males, AMH may be a direct marker of Sertoli cell function and an indirect marker of spermatogenesis. In this study, we assessed serum AMH levels in pubertal and postpubertal males with FA, DC/TBD, or DBA and compared this with their unaffected male relatives and unrelated healthy male volunteers. Males with FA had significantly lower levels of AMH (median: 5 ng/mL, range: 1.18-6.75) compared with unaffected male relatives (median: 7.31 ng/mL, range: 3.46-18.82, P = 0.03) or healthy male volunteers (median: 7.66 ng/mL, range: 3.3-14.67, P = 0.008). Males with DC/TBD had lower levels of AMH (median: 3.76 ng/mL, range: 0-8.9) compared with unaffected relatives (median: 5.31 ng/mL, range: 1.2-17.77, P = 0.01) or healthy volunteers (median: 5.995 ng/mL, range: 1.57-14.67, P < 0.001). Males with DBA had similar levels of AMH (median: 3.46 ng/mL, range: 2.32-11.85) as unaffected relatives (median: 4.66 ng/mL, range: 0.09-13.51, P = 0.56) and healthy volunteers (median: 5.81 ng/mL, range: 1.57-14.67, P = 0.10). Our findings suggest a defect in the production of AMH in postpubertal males with FA and DC/TBD, similar to that observed in females. These findings warrant confirmation in larger prospective studies.

Updates on clinical and laboratory aspects of hereditary dyserythropoietic anemias

Hereditary dyserythropoietic anemias, or congenital dyserythropoietic anemias (CDAs), are rare disorders disrupting normal erythroid lineage development, resulting in ineffective erythropoiesis and monolinear cytopenia. CDAs include three main types (I, II, III), transcription-factor-related forms, and syndromic forms. The widespread use of next-generation sequencing in the last decade has unveiled novel causative genes and unexpected genotype-phenotype correlations. The discovery of the genetic defects underlying the CDAs not only facilitates accurate diagnosis but also enhances understanding of CDA pathophysiology. Notable advancements include identifying a hepatic-specific role of the SEC23B loss-of-function in iron metabolism dysregulation in CDA II, deepening CDIN1 dysfunction during erythroid differentiation, and uncovering a recessive CDA III form associated with RACGAP1 variants. Current treatments primarily rely on supportive measures tailored to disease severity and clinical features. Comparative studies with pyruvate kinase deficiency have illuminated new therapeutic avenues by elucidating iron dyshomeostasis and dyserythropoiesis mechanisms. We herein discuss recent progress in diagnostic methodologies, novel gene discoveries, and enhanced comprehension of CDA pathogenesis and molecular genetics.

Bayesian estimation of gene constraint from an evolutionary model with gene features

Measures of selective constraint on genes have been used for many applications, including clinical interpretation of rare coding variants, disease gene discovery and studies of genome evolution. However, widely used metrics are severely underpowered at detecting constraints for the shortest ~25% of genes, potentially causing important pathogenic mutations to be overlooked. Here we developed a framework combining a population genetics model with machine learning on gene features to enable accurate inference of an interpretable constraint metric, shet. Our estimates outperform existing metrics for prioritizing genes important for cell essentiality, human disease and other phenotypes, especially for short genes. Our estimates of selective constraint should have wide utility for characterizing genes relevant to human disease. Finally, our inference framework, GeneBayes, provides a flexible platform that can improve the estimation of many gene-level properties, such as rare variant burden or gene expression differences.

An atypical form of 60S ribosomal subunit in Diamond-Blackfan anemia linked to RPL17 variants

Diamond-Blackfan anemia syndrome (DBA) is a ribosomopathy associated with loss-of-function variants in more than 20 ribosomal protein (RP) genes. Here, we report the genetic, functional, and biochemical dissection of 2 multigenerational pedigrees with variants in RPL17, a large ribosomal subunit protein-encoding gene. Affected individuals had clinical features and erythroid proliferation defects consistent with DBA. Further, RPL17/uL22 depletion resulted in anemia and micrognathia in zebrafish larvae, and in vivo complementation studies indicated that RPL17 variants were pathogenic. Lymphoblastoid cell lines (LCLs) derived from patients displayed a ribosomal RNA maturation defect reflecting haploinsufficiency of RPL17. The proteins encoded by RPL17 variants were not incorporated into ribosomes, but 10%-20% of 60S ribosomal subunits contained a short form of 5.8S rRNA (5.8SC), a species that is marginal in normal cells. These atypical 60S subunits were actively engaged in translation. Ribosome profiling showed changes of the translational profile, but those are similar to LCLs bearing RPS19 variants. These results link an additional RP gene to DBA. They show that ribosomes can be modified substantially by RPL17 haploinsufficiency but support the paradigm that translation alterations in DBA are primarily related to insufficient ribosome production rather than to changes in ribosome structure or composition.

Transient erythroblastopenia of childhood after COVID-19 infection: a case report

BACKGROUND

Transient erythroblastopenia of childhood (TEC) is an acquired, self-limited pure red cell aplasia that usually occurs in children 4 years old and younger. This clinical condition has been priorly described to be linked to numerous viral and immunologic mechanisms. COVID-19, caused by the coronavirus SARS-CoV-2, was initially discovered in China in December 2019. The disease quickly spread worldwide, resulting in pandemic.

CASE PRESENTATION

This manuscript reports a new clinically relevant condition associated to COVID-19, describing a child with clinical and biochemical signs of Pure Red Blood cells aplasia and complete absence of erythroblasts at the bone marrow needle aspiration with signs of erythrophagocytosis, resembling morphological signs such as in hemophagocytic lymphohistiocytosis (HLH), temporally associated to SARS-CoV-2 infection.

CONCLUSION

This report highlights a newly described continuum laboratory and clinical spectrum of immune/hematological dysregulations secondary to SARS-CoV-2. SARS-CoV-2 infection-linked TEC has never been described in literature, but, according to our findings, should be considered in all the patients with transient erythroblastopenia without congenital red blood cell abnormalities and serology negative for major infections associated with TEC. This condition must be considered in the same spectrum of MIS-C and the inter-links among the two clinical manifestations, as well as a potential interdependence among them, should be considered in the future.

Erythroid-intrinsic activation of TLR8 impairs erythropoiesis in inherited anemia

Inherited non-hemolytic anemia is a group of rare bone marrow disorders characterized by erythroid defects. Although concerted efforts have been made to explore the underlying pathogenetic mechanisms of these diseases, the understanding of the causative mutations are still incomplete. Here we identify in a diseased pedigree that a gain-of-function mutation in toll-like receptor 8 (TLR8) is implicated in inherited non-hemolytic anemia. TLR8 is expressed in erythroid lineage and erythropoiesis is impaired by TLR8 activation whereas enhanced by TLR8 inhibition from erythroid progenitor stage. Mechanistically, TLR8 activation blocks annexin A2 (ANXA2)-mediated plasma membrane localization of STAT5 and disrupts EPO signaling in HuDEP2 cells. TLR8 inhibition improves erythropoiesis in RPS19+/- HuDEP2 cells and CD34+ cells from healthy donors and inherited non-hemolytic anemic patients. Collectively, we identify a gene implicated in inherited anemia and a previously undescribed role for TLR8 in erythropoiesis, which could potentially be explored for therapeutic benefit in inherited anemia.

The CRISPR-Cas System and Clinical Applications of CRISPR-Based Gene Editing in Hematology with a Focus on Inherited Germline Predisposition to Hematologic Malignancies

Clustered regularly interspaced short palindromic repeats (CRISPR)-based gene editing has begun to transform the treatment landscape of genetic diseases. The history of the discovery of CRISPR/CRISPR-associated (Cas) proteins/single-guide RNA (sgRNA)-based gene editing since the first report of repetitive sequences of unknown significance in 1987 is fascinating, highly instructive, and inspiring for future advances in medicine. The recent approval of CRISPR-Cas9-based gene therapy to treat patients with severe sickle cell anemia and transfusion-dependent β-thalassemia has renewed hope for treating other hematologic diseases, including patients with a germline predisposition to hematologic malignancies, who would benefit greatly from the development of CRISPR-inspired gene therapies. The purpose of this paper is three-fold: first, a chronological description of the history of CRISPR-Cas9-sgRNA-based gene editing; second, a brief description of the current state of clinical research in hematologic diseases, including selected applications in treating hematologic diseases with CRISPR-based gene therapy, preceded by a brief description of the current tools being used in clinical genome editing; and third, a presentation of the current progress in gene therapies in inherited hematologic diseases and bone marrow failure syndromes, to hopefully stimulate efforts towards developing these therapies for patients with inherited bone marrow failure syndromes and other inherited conditions with a germline predisposition to hematologic malignancies.

Associated Congenital Abnormalities and Physical Phenotype in Patients with Diamond-Blackfan Anemia May Be Overlooked

Diamond-Blackfan anemia (DBA) is a rare and inherited form of erythroid aplasia, characterized by severe macrocytic anemia, congenital malformations, and predisposition to cancer. The purpose of this study is to determine the congenital abnormalities and dysmorphological features of DBA patients in a cross-sectional manner. The study group included patients who had diagnosis of DBA between 1983 and 2017. Dysmorphological examinations of the patients were performed by an experienced dysmorphologist and also echocardiography and abdominal ultrasonography were performed in order to figure out cardiac and urogenital abnormalities. A total of 45 patients were examined in this study. Dysmorphological examination, echocardiography, and abdominal ultrasonography revealed the rate of congenital abnormalities as high as 88.7%. In consideration of the congenital abnormalities, the most common findings were craniofacial, followed by skeletal abnormalities. The rate of anomalies was found higher in our series of patients than that have been previously reported, most probably due to the evaluations being performed by a dysmorphologist in our cohort and not only depending on patient records or hematologists' physical examination.

Implementation of and Systems-Level Barriers to Guideline-Driven Germline Genetic Evaluation in the Care of Patients With Myelodysplastic Syndrome and Acute Myeloid Leukemia

PURPOSE

Knowledge of an inherited predisposition to myelodysplastic syndrome (MDS) and AML has important clinical implications for treatment decisions, surveillance, and care of at-risk relatives. National Comprehensive Cancer Network (NCCN) guidelines recently incorporated recommendations for germline genetic evaluation of patients with MDS/AML on the basis of personal and family history features, but the practicality of implementing these recommendations has not been studied.

METHODS

A hereditary hematology quality improvement (QI) committee was formed to implement these guidelines in a prospective cohort of patients diagnosed with MDS/AML. Referral for germline genetic testing was recommended for patients meeting NCCN guideline criteria. Referral patterns and genetic evaluation outcomes were compared with a historical cohort of patients with MDS/AML. Barriers to evaluation were identified.

RESULTS

Of the 90 patients with MDS/AML evaluated by the QI committee, 59 (66%) met criteria for germline evaluation. Implementation of the QI committee led to more referrals for germline evaluation in accordance with NCCN guidelines (31% v 14%, P = .03). However, the majority of those meeting criteria were never referred due to high medical acuity or being deceased or in hospice at the time of QI committee recommendations. Despite this, two (17%) of the 12 patients undergoing genetic testing were diagnosed with a hereditary myeloid malignancy syndrome.

CONCLUSION

Current NCCN guidelines resulted in two thirds of patients with MDS/AML meeting criteria for germline evaluation. A hereditary hematology-focused QI committee aided initial implementation and modestly improved NCCN guideline adherence. However, the high morbidity and mortality and prolonged inpatient stays associated with MDS/AML challenged traditional outpatient genetic counseling models. Further improvements in guideline adherence require innovating new models of genetic counseling and testing for this patient population.

Towards a Cure for Diamond-Blackfan Anemia: Views on Gene Therapy

Diamond-Blackfan anemia (DBA) is a rare genetic disorder affecting the bone marrow's ability to produce red blood cells, leading to severe anemia and various physical abnormalities. Approximately 75% of DBA cases involve heterozygous mutations in ribosomal protein (RP) genes, classifying it as a ribosomopathy, with RPS19 being the most frequently mutated gene. Non-RP mutations, such as in GATA1, have also been identified. Current treatments include glucocorticosteroids, blood transfusions, and hematopoietic stem cell transplantation (HSCT), with HSCT being the only curative option, albeit with challenges like donor availability and immunological complications. Gene therapy, particularly using lentiviral vectors and CRISPR/Cas9 technology, emerges as a promising alternative. This review explores the potential of gene therapy, focusing on lentiviral vectors and CRISPR/Cas9 technology in combination with non-integrating lentiviral vectors, as a curative solution for DBA. It highlights the transformative advancements in the treatment landscape of DBA, offering hope for individuals affected by this condition.

Lentivirus-mediated gene therapy corrects ribosomal biogenesis and shows promise for Diamond Blackfan anemia

This study lays the groundwork for future lentivirus-mediated gene therapy in patients with Diamond Blackfan anemia (DBA) caused by mutations in ribosomal protein S19 (RPS19), showing evidence of a new safe and effective therapy. The data show that, unlike patients with Fanconi anemia (FA), the hematopoietic stem cell (HSC) reservoir of patients with DBA was not significantly reduced, suggesting that collection of these cells should not constitute a remarkable restriction for DBA gene therapy. Subsequently, 2 clinically applicable lentiviral vectors were developed. In the former lentiviral vector, PGK.CoRPS19 LV, a codon-optimized version of RPS19 was driven by the phosphoglycerate kinase promoter (PGK) already used in different gene therapy trials, including FA gene therapy. In the latter one, EF1α.CoRPS19 LV, RPS19 expression was driven by the elongation factor alpha short promoter, EF1α(s). Preclinical experiments showed that transduction of DBA patient CD34+ cells with the PGK.CoRPS19 LV restored erythroid differentiation, and demonstrated the long-term repopulating properties of corrected DBA CD34+ cells, providing evidence of improved erythroid maturation. Concomitantly, long-term restoration of ribosomal biogenesis was verified using a potentially novel method applicable to patients' blood cells, based on ribosomal RNA methylation analyses. Finally, in vivo safety studies and proviral insertion site analyses showed that lentivirus-mediated gene therapy was nontoxic.

Treatment of refractory/relapsed Diamond-Blackfan anaemia with eltrombopag

Diamond-Blackfan anaemia (DBA) is a rare, inherited bone marrow failure syndrome with a ribosomal defect causing slowed globin chain production with normal haem synthesis, causing an overabundance of reactive iron/haem and erythroid-specific cellular toxicity. Eltrombopag, a non-peptide thrombopoietin receptor agonist, is a potent intracellular iron chelator and induced a robust durable response in an RPS19-mutated DBA patient on another trial. We hypothesized eltrombopag would improve RBC production in DBA patients. We conducted a single-centre, single-arm pilot study (NCT04269889) assessing safety and erythroid response of 6 months of daily, fixed-dose eltrombopag for DBA patients. Fifteen transfusion-dependent (every 3-5 weeks) patients (median age 18 [range 2-56]) were treated. One responder had sustained haemoglobin improvement and >50% reduction in RBC transfusion frequency. Of note, 7/15 (41%) patients required dose reductions or sustained discontinuation of eltrombopag due to asymptomatic thrombocytosis. Despite the low response rate, eltrombopag has now improved erythropoiesis in several patients with DBA with a favourable safety profile. Dosing restrictions due to thrombocytosis may cause insufficient iron chelation to decrease haem production and improve anaemia in most patients. Future work will focus on erythropoiesis dynamics in patients and use of haem synthesis inhibitors without an impact on other haematopoietic lineages.

Macrocytic anemias

PURPOSE OF REVIEW

Over the last century, the diseases associated with macrocytic anemia have been changing with more patients currently having hematological diseases including malignancies and myelodysplastic syndrome. The intracellular mechanisms underlying the development of anemia with macrocytosis can help in understanding normal erythropoiesis. Adaptations to these diseases involving erythroid progenitor and precursor cells lead to production of fewer but larger red blood cells, and understanding these mechanisms can provide information for possible treatments.

RECENT FINDINGS

Both inherited and acquired bone marrow diseases involving primarily impaired or delayed erythroid cell division or secondary adaptions to basic erythroid cellular deficits that results in prolonged cell division frequently present with macrocytic anemia.

SUMMARY OF FINDINGS

In marrow failure diseases, large accumulations of iron and heme in early stages of erythroid differentiation make cells in those stages especially susceptible to death, but the erythroid cells that can survive the early stages of terminal differentiation yield fewer but larger erythrocytes that are recognized clinically as macrocytic anemia. Other disorders that limit deoxynucleosides required for DNA synthesis affect a broader range of erythropoietic cells, but they also lead to macrocytic anemia. The source of macrocytosis in other diseases remains uncertain.

Bayesian estimation of gene constraint from an evolutionary model with gene features

Measures of selective constraint on genes have been used for many applications including clinical interpretation of rare coding variants, disease gene discovery, and studies of genome evolution. However, widely-used metrics are severely underpowered at detecting constraint for the shortest ∼25% of genes, potentially causing important pathogenic mutations to be overlooked. We developed a framework combining a population genetics model with machine learning on gene features to enable accurate inference of an interpretable constraint metric, shet. Our estimates outperform existing metrics for prioritizing genes important for cell essentiality, human disease, and other phenotypes, especially for short genes. Our new estimates of selective constraint should have wide utility for characterizing genes relevant to human disease. Finally, our inference framework, GeneBayes, provides a flexible platform that can improve estimation of many gene-level properties, such as rare variant burden or gene expression differences.

Modeling primitive and definitive erythropoiesis with induced pluripotent stem cells

ABSTRACT

During development, erythroid cells are produced through at least 2 distinct hematopoietic waves (primitive and definitive), generating erythroblasts with different functional characteristics. Human induced pluripotent stem cells (iPSCs) can be used as a model platform to study the development of red blood cells (RBCs) with many of the differentiation protocols after the primitive wave of hematopoiesis. Recent advances have established that definitive hematopoietic progenitors can be generated from iPSCs, creating a unique situation for comparing primitive and definitive erythrocytes derived from cell sources of identical genetic background. We generated iPSCs from healthy fetal liver (FL) cells and produced isogenic primitive or definitive RBCs which were compared directly to the FL-derived RBCs. Functional assays confirmed differences between the 2 programs, with primitive RBCs showing a reduced proliferation potential, larger cell size, lack of Duffy RBC antigen expression, and higher expression of embryonic globins. Transcriptome profiling by scRNA-seq demonstrated high similarity between FL- and iPSC-derived definitive RBCs along with very different gene expression and regulatory network patterns for primitive RBCs. In addition, iPSC lines harboring a known pathogenic mutation in the erythroid master regulator KLF1 demonstrated phenotypic changes specific to definitive RBCs. Our studies provide new insights into differences between primitive and definitive erythropoiesis and highlight the importance of ontology when using iPSCs to model genetic hematologic diseases. Beyond disease modeling, the similarity between FL- and iPSC-derived definitive RBCs expands potential applications of definitive RBCs for diagnostic and transfusion products.

[A child with persistent anaemia]

Background

Anemia in children is common and finding the underlying cause is often uncomplicated. However, in some cases, the underlying diagnosis is rare and difficult to diagnose.

Case presentation

A toddler presented with severe anemia with normal red cell indices and a low reticulocyte count. The remaining hematological parameters were normal, bar a slight thrombocytosis. At this point a diagnosis of transient erythroblastopenia of childhood (TEC) was made. The child continued to have slight anemia with intermittent macrocytosis and reticulocytopenia throughout childhood. Growth and development was normal, and there were no signs of congenital abnormalities in the heart or kidneys nor any craniofacial or phalangeal defects. Repeated bone marrow examinations showed no significant abnormal findings. As a teenager the patient was diagnosed with Diamond-Blackfan anemia through an exome-based gene panel which revealed a mutation in the RPL11 gene.

Interpretation

Congenital bone marrow failure syndromes do not always present in the classical way, leading to a delayed diagnosis. The increasing availability of different gene panels for patients with persistent abnormal hematological laboratory parameters offers the possibility of a more accurate diagnostic pathway, which is important for adequate follow-up and genetic counselling.

Disruption of mitochondrial energy metabolism is a putative pathogenesis of Diamond-Blackfan anemia

Energy metabolism in the context of erythropoiesis and related diseases remains largely unexplored. Here, we developed a primary cell model by differentiating hematopoietic stem progenitor cells toward the erythroid lineage and suppressing the mitochondrial oxidative phosphorylation (OXPHOS) pathway. OXPHOS suppression led to differentiation failure of erythroid progenitors and defects in ribosome biogenesis. Ran GTPase-activating protein 1 (RanGAP1) was identified as a target of mitochondrial OXPHOS for ribosomal defects during erythropoiesis. Overexpression of RanGAP1 largely alleviated erythroid defects resulting from OXPHOS suppression. Coenzyme Q10, an activator of OXPHOS, largely rescued erythroid defects and increased RanGAP1 expression. Patients with Diamond-Blackfan anemia (DBA) exhibited OXPHOS suppression and a concomitant suppression of ribosome biogenesis. RNA-seq analysis implied that the substantial mutation (approximately 10%) in OXPHOS genes accounts for OXPHOS suppression in these patients. Conclusively, OXPHOS disruption and the associated disruptive mitochondrial energy metabolism are linked to the pathogenesis of DBA.

Hemolysis-driven IFNα production impairs erythropoiesis by negatively regulating EPO signaling in sickle cell disease

ABSTRACT

Disordered erythropoiesis is a feature of many hematologic diseases, including sickle cell disease (SCD). However, very little is known about erythropoiesis in SCD. Here, we show that although bone marrow (BM) erythroid progenitors and erythroblasts in Hbbth3/+ thalassemia mice were increased more than twofold, they were expanded by only ∼40% in Townes sickle mice (SS). We further show that the colony-forming ability of SS erythroid progenitors was decreased and erythropoietin (EPO)/EPO receptor (EPOR) signaling was impaired in SS erythroid cells. Furthermore, SS mice exhibited reduced responses to EPO. Injection of mice with red cell lysates or hemin, mimicking hemolysis in SCD, led to suppression of erythropoiesis and reduced EPO/EPOR signaling, indicating hemolysis, a hallmark of SCD, and could contribute to the impaired erythropoiesis in SCD. In vitro hemin treatment did not affect Stat5 phosphorylation, suggesting that hemin-induced erythropoiesis suppression in vivo is via an indirect mechanism. Treatment with interferon α (IFNα), which is upregulated by hemolysis and elevated in SCD, led to suppression of mouse BM erythropoiesis in vivo and human erythropoiesis in vitro, along with inhibition of Stat5 phosphorylation. Notably, in sickle erythroid cells, IFN-1 signaling was activated and the expression of cytokine inducible SH2-containing protein (CISH), a negative regulator of EPO/EPOR signaling, was increased. CISH deletion in human erythroblasts partially rescued IFNα-mediated impairment of cell growth and EPOR signaling. Knocking out Ifnar1 in SS mice rescued the defective BM erythropoiesis and improved EPO/EPOR signaling. Our findings identify an unexpected role of hemolysis on the impaired erythropoiesis in SCD through inhibition of EPO/EPOR signaling via a heme-IFNα-CISH axis.

Potentials of ribosomopathy gene as pharmaceutical targets for cancer treatment

Ribosomopathies encompass a spectrum of disorders arising from impaired ribosome biogenesis and reduced functionality. Mutation or dysexpression of the genes that disturb any finely regulated steps of ribosome biogenesis can result in different types of ribosomopathies in clinic, collectively known as ribosomopathy genes. Emerging data suggest that ribosomopathy patients exhibit a significantly heightened susceptibility to cancer. Abnormal ribosome biogenesis and dysregulation of some ribosomopathy genes have also been found to be intimately associated with cancer development. The correlation between ribosome biogenesis or ribosomopathy and the development of malignancies has been well established. This work aims to review the recent advances in the research of ribosomopathy genes among human cancers and meanwhile, to excavate the potential role of these genes, which have not or rarely been reported in cancer, in the disease development across cancers. We plan to establish a theoretical framework between the ribosomopathy gene and cancer development, to further facilitate the potential of these genes as diagnostic biomarker as well as pharmaceutical targets for cancer treatment.