Diamond-Blackfan anemia

Establishment and characterization of CSCRi006-A: an induced pluripotent stem cell line generated from a patient with Diamond-Blackfan Anemia (DBA) carrying ribosomal protein S19 (RPS19) mutation

Diamond-Blackfan anemia (DBA) is a congenital hypoplastic anemia characterized by ineffective erythropoiesis. DBA is majorly caused by mutations in the ribosomal protein (RP) genes (Gadhiya and Wills in Diamond-Blackfan Anemia, https://www.statpearls.com/ ; 2023). A suitable disease model that yields a continuous supply of erythroid cells is required to study disease pathogenesis and drug discovery. Toward this, we reprogrammed dermal fibroblasts from a DBA patient with a heterozygous mutation c.22-23delAG in the RPS19 gene identified through exome sequencing. To generate induced pluripotent stem cells (iPSCs), we induced episomal expression of the reprogramming factors OTC3/4, L-MYC, LIN28, SOX2, and KLF4, and a p53 shRNA2. The DBA-iPSC line CSCRi006-A generated during this study was extensively characterized for its pluripotency and genome stability. The clone retained normal karyotype and showed high expression levels of pluripotency markers, OCT4, NANOG, SOX2, TRA-I-60, TRA-I-81, and SSEA4. It could differentiate into cells originating from all three germ cell layers, as identified by immunostaining for SOX17 (endoderm), Brachyury (mesoderm), and PAX6 (ectoderm). IPSCs provide a renewable source of cells for in vitro disease modeling. CSCRi006-A, a thoroughly characterized iPSC line carrying heterozygous RPS19 c.22-23delAG mutation, is a valuable cell line for the disease modeling of DBA. This iPSC line can be differentiated into different blood cell types to study the mechanisms of disease development and identify potential treatments.

Dental considerations in a paediatric patient with Diamond-Blackfan anaemia

Diamond-Blackfan anaemia (DBA) is a rare genetic disorder characterised by a decrease in the production of red blood cells due to bone marrow malfunction. The estimation of disease occurrence is approximately 1 in 100 000-2 00 000 live births. This paper presents the case of a 7-year-old male child diagnosed with DBA at the age of 4 months. The diagnosis was established with haematological findings, bone marrow biopsy and molecular testing. The case was managed successfully for dental symptoms without any complication.

A Novel Deletion in the RPL5 Gene in a Lebanese Child With Diamond Blackfan Anemia Unresponsive to Steroid Treatment

Diamond-Blackfan Anemia (DBA) is a rare inherited form of pure red cell aplasia that usually manifests in infancy or early childhood, and is characterized by normochromic macrocytic anemia and bone marrow erythroblastopenia. The majority of DBA cases are associated with mutations in ribosomal protein genes. Here, we describe a Lebanese girl with RPL5-mutated DBA unresponsive to steroid treatment who died from complications following late hematopoietic stem cell transplantation performed at the age of 15 years.

A new in-frame deletion in ribosomal protein S19 in a Chinese infant with Diamond-Blackfan anemia

Diamond-Blackfan anemia (DBA) is a congenital erythroid aplasia that usually presents as macrocytic anemia during infancy. Ribosomal protein S19 (RPS19) is identified as the first gene associated with DBA. RPS19 is mutated in 25% of DBA patients, but its role in DBA pathogenesis remains to be elucidated. We have identified a novel heterozygous frameshift mutation in RPS19 gene in a DBA child presenting with profound anemia after birth. A single nucleotide heterozygous deletion (C.251delG) results in frameshift in RPS19 gene in exon 4 at codon 84 with possible premature stop codon (p.Arg84LysfsX21). The mutant allele was not detected in her parents, indicating de novo mutation. Both alleles were expressed at the same level. Using an immunofluorescence technique, the mutated-type RPS19 expressions were mostly localized to entire nuclei with little staining for nucleoli and its intracellular localization significantly differed from the wild-type RPS19, which was localized to both nuclei and nucleoli. This type of a mutation could be very helpful in further understanding the role of the RPS19 protein in DBA pathogenesis.

Fanconi Syndrome Secondary to Deferasirox in Diamond-Blackfan Anemia: Case Series and Recommendations for Early Diagnosis

Deferasirox is an oral iron chelator used to treat patients with transfusion-related iron overload. We report, from two institutions, two children with Diamond-Blackfan anemia who developed Fanconi syndrome secondary to deferasirox administration, along with a review of the literature. The current recommendation for the laboratory monitoring of patients receiving deferasirox does not include serum electrolytes or urine analysis. Thus, despite routine clinic visits and bloodwork, these two patients presented with life-threatening electrolyte abnormalities requiring hospitalization. Hence, we propose the inclusion of serum electrolytes and urine analysis as part of routine monitoring to facilitate the early diagnosis of Fanconi syndrome in the context of high doses of deferasirox therapy.

Treatment-related toxicities in children with acute lymphoblastic leukaemia predisposition syndromes

Although most children with acute lymphoblastic leukaemia (ALL) do not harbor germline mutations that strongly predispose them to development of this malignancy, large syndrome registries and detailed mapping of exomes or whole genomes of familial leukaemia kindreds have revealed that 3-5% of all childhood ALL cases are due to such germline mutations, but the figure may be higher. Most of these syndromes are primarily characterized by their non-malignant phenotype, whereas ALL may be the dominating or even only striking manifestation of the syndrome in some families. Identification of such ALL patients is important in order to adjust therapy and offer genetic counseling and cancer surveillance to mutation carriers in the family. In the coming years large genomic screening projects are expected to reveal further hitherto unrecognised familial ALL syndromes. The treatment of ALL cases harboring cancer predisposing mutations can be challenging for both the physician and the patient due to their preexisting symptoms, their reduced tolerance to radio- and/or chemotherapy with enhanced risk of life-threatening organ toxicities, and the paucity of data from ALL patients with the same or similar syndromes being treated by contemporary protocols. Recent studies clearly indicate that many of these patients stand a good chance of cure, and that they should be offered chemotherapy with the intention to cure. Some of these syndromes are characterized by reduced tolerance to radiotherapy and/or specific anticancer agents, while others are not. This review summarises our current knowledge on the risk of acute toxicities for these ALL patients and provides guidance for treatment adjustments.

Anemia of Central Origin

Hypoproliferative anemia results from the inability of bone marrow to produce adequate numbers of red blood cells. The list of conditions that cause hypoproliferative anemia is long, starting from common etiologies as iron deficiency to rarer diagnoses of constitutional bone marrow failure syndromes. There is no perfect diagnostic algorithm, and clinical data may not always clearly distinguish "normal" from "abnormal", yet it is important for practicing clinicians to recognize each condition so that treatment can be initiated promptly. This review describes diagnostic approaches to hypoproliferative anemia, with particular emphasis on bone marrow failure syndromes.

Immunophenotypic Profiling of Erythroid Progenitor-Derived Extracellular Vesicles in Diamond-Blackfan Anaemia: A New Diagnostic Strategy

Diamond-Blackfan Anaemia (DBA) is a rare inherited anaemia caused by heterozygous mutations in one of 13 ribosomal protein genes. Erythroid progenitors (BFU-E and CFU-E) in bone marrow (BM) show a proapoptotic phenotype. Suspicion of DBA is reached after exclusion of other forms of BM failure syndromes. To improve DBA diagnosis, which is confirmed by mutation analysis, we tested a new approach based on the study of extracellular vesicles (EVs) isolated from plasma by differential centrifugations and analysed by flow cytometry. We chose CD34, CD71 and CD235a markers to study erythroid EVs. We characterised the EVs immunophentoypic profiles of 13 DBA patients, 22 healthy controls and 16 patients with other haematological diseases. Among the three EVs clusters we found, only the CD34+/CD71_low population showed statistically significant differences between DBA patients and controls (p< 0.05). The absence of this cluster is in agreement with the low levels of BFU-E found in DBA patients. The assessment of ROC curves demonstrated the potential diagnostic value of this population. We suggest that this assay may be useful to improve DBA diagnosis as a quicker and less invasive alternative to BM BFU-E culture analysis.

Pure red cell aplasia in a three-months-old infant possibly secondary to cytomegalo virus infection

We report a 3 months old child who presented with severe anemia due to pure red cell aplasia (PRCA). After ruling out other known causes of PRCA, congenital cytomegalovirus (CMV) infection was diagnosed to be the cause. The child responded to Ganciclovir and is doing well. CMV infection should be considered as differential diagnosis in PRCA during infancy.

Defects of protein production in erythroid cells revealed in a zebrafish Diamond-Blackfan anemia model for mutation in RPS19

Diamond–Blackfan anemia (DBA) is a rare congenital red cell aplasia that classically presents during early infancy in DBA patients. Approximately, 25% of patients carry a mutation in the ribosomal protein (RP) S19 gene; mutations in RPS24, RPS17, RPL35A, RPL11, and RPL5 have been reported. How ribosome protein deficiency causes defects specifically to red blood cells in DBA has not been well elucidated. To genetically model the predominant ribosome defect in DBA, we generated an rps19 null mutant through the use of TALEN-mediated gene targeting in zebrafish. Molecular characterization of this mutant line demonstrated that rps19 deficiency reproduced the erythroid defects of DBA, including a lack of mature red blood cells and p53 activation. Notably, we found that rps19 mutants' production of globin proteins was significantly inhibited; however, globin transcript level was either increased or unaffected in rps19 mutant embryos. This dissociation of RNA/protein levels of globin genes was confirmed in another zebrafish DBA model with defects in rpl11. Using transgenic zebrafish with specific expression of mCherry in erythroid cells, we showed that protein production in erythroid cells was decreased when either rps19 or rpl11 was mutated. L-Leucine treatment alleviated the defects of protein production in erythroid cells and partially rescued the anemic phenotype in both rps19 and rpl11 mutants. Analysis of this model suggests that the decreased protein production in erythroid cells likely contributes to the blood-specific phenotype of DBA. Furthermore, the newly generated rps19 zebrafish mutant should serve as a useful animal model to study DBA. Our in vivo findings may provide clues for the future therapy strategy for DBA.

The inherited bone marrow failure syndromes

Molecular pathogenesis may be elucidated for inherited bone marrow failure syndromes (IBMFS). The study and presentation of the details of their molecular biology and biochemistry is warranted for appropriate diagnosis and management of afflicted patients and to identify the physiology of the normal hematopoiesis and mechanisms of carcinogenesis. Several themes have emerged within each subsection of IBMFS, including the ribosomopathies, which include ribosome assembly and ribosomal RNA processing. The Fanconi anemia pathway has become interdigitated with the familial breast cancer syndromes. In this article, the diseases that account for most IBMFS diagnoses are analyzed.

Successful treatment of acquired pure red cell aplasia with oral corticosteroids in a patient with B-cell CLL

We present the case of a 57-year-old male patient diagnosed with chronic lymphoid leukaemia (CLL) B-cell type along with moderate anaemia. On follow-up investigations the aetiology of anaemia turned out to be pure red cell aplasia (PRCA) on trephine bone biopsy with an elevated serum erythropoietin level. The patient received blood transfusion support. He showed remarkable improvement on oral corticosteroids (prednisolone 60 mg/daily dose) with no further requirement of blood transfusion over next 3 months. However, when the dose of steroid was tapered down to 10 mg/day, the anaemia reappeared. An increase in the dose of steroid brought the haemoglobin level back to normal. Anaemia in CLL can be due to many reasons, of which PRCA is an uncommon association occurring in only around 1% of patients with CLL and usually refractory to the conventional treatment with steroids. This PRCA secondary to CLL is considered to be immune in origin and a response to combination of immunosuppressive therapy such as steroids, cyclosporine, rituximab is anticipated. Our case responded completely to oral steroids alone.

Cumulative haploinsufficiency and triplosensitivity drive aneuploidy patterns and shape the cancer genome

Aneuploidy has been recognized as a hallmark of cancer for more than 100 years, yet no general theory to explain the recurring patterns of aneuploidy in cancer has emerged. Here, we develop Tumor Suppressor and Oncogene (TUSON) Explorer, a computational method that analyzes the patterns of mutational signatures in tumors and predicts the likelihood that any individual gene functions as a tumor suppressor (TSG) or oncogene (OG). By analyzing >8,200 tumor-normal pairs, we provide statistical evidence suggesting that many more genes possess cancer driver properties than anticipated, forming a continuum of oncogenic potential. Integrating our driver predictions with information on somatic copy number alterations, we find that the distribution and potency of TSGs (STOP genes), OGs, and essential genes (GO genes) on chromosomes can predict the complex patterns of aneuploidy and copy number variation characteristic of cancer genomes. We propose that the cancer genome is shaped through a process of cumulative haploinsufficiency and triplosensitivity.

Genetic predispositions to childhood leukemia

While the majority of leukemia cases occur in the absence of any known predisposing factor, there are germline mutations that significantly increase the risk of developing hematopoietic malignancies in childhood. In this review article, we describe a number of these mutations and their clinical features. These predispositions can be broadly classified as those leading to bone marrow failure, those involving tumor suppressor genes, DNA repair defects, immunodeficiencies or other congenital syndromes associated with transient myeloid disorders. While leukemia can develop as a secondary event in the aforementioned syndromes, there are also several syndromes that specifically lead to the development of leukemia as their primary phenotype. Many of the genes discussed in this review can also be somatically mutated in other cancers, highlighting the importance of understanding shared alterations and mechanisms underpinning syndromic and sporadic leukemia.

Diamond blackfan anemia: a tertiary care center experience

Diamond Blackfan Anemia (DBA) is a rare hypoplastic anemia that presents in infancy with macrocytic anemia and reticulocytopenia. It is a ribosomopathy with autosomal dominant inheritance.

In our series of 10 patients with DBA, congenital malformations were observed in 50% of the cases. Age at symptom onset ranged from 0–12 months. Age at diagnosis ranged from 4 months to 96 months. Male: female ratio was 9:1. Response to prednisolone was observed in 4 out of the 10 patients (either during initial treatment or during re-challenge). Response to cyclosporine was found to be poor. Bone marrow transplantation was successful in attaining remission in one patient. Malignancies were not reported in any patient possibly due to a short follow up period.

A transgenic mouse model demonstrates a dominant negative effect of a point mutation in the RPS19 gene associated with Diamond-Blackfan anemia

Diamond Blackfan anemia (DBA) is an inherited erythroblastopenia associated with mutations in at least 8 different ribosomal protein genes. Mutations in the gene encoding ribosomal protein S19 (RPS19) have been identified in approximately 25% of DBA families. Most of these mutations disrupt either the translation or stability of the RPS19 protein and are predicted to cause DBA by haploinsufficiency. However, approximately 30% of RPS19 mutations are missense mutations that do not alter the stability of the RPS19 protein and are hypothesized to act by a dominant negative mechanism. To formally test this hypothesis, we generated a transgenic mouse model expressing an RPS19 mutation in which an arginine residue is replaced with a tryptophan residue at codon 62 (RPS19R62W). Constitutive expression of RPS19R62W in developing mice was lethal. Conditional expression of RPS19R62W resulted in growth retardation, a mild anemia with reduced numbers of erythroid progenitors, and significant inhibition of terminal erythroid maturation, similar to DBA. RNA profiling demonstrated more than 700 dysregulated genes belonging to the same pathways that are disrupted in RNA profiles of DBA patient cells. We conclude that RPS19R62W is a dominant negative DBA mutation.

Bone marrow transplantation for inherited bone marrow failure syndromes

The inherited bone marrow failure (BMF) syndromes are characterized by impaired hematopoiesis and cancer predisposition. Most inherited BMF syndromes are also associated with a range of congenital anomalies. Progress in improving the outcomes for children with inherited BMF syndromes has been limited by the rarity of these disorders, as well as disease-specific genetic, molecular, cellular, and clinical characteristics that increase the risks of complications associated with hematopoietic stem cell transplantation (HSCT). As a result, the ability to develop innovative transplant approaches to circumvent these problems has been limited. Recent progress has been made, as best evidenced in studies adding fludarabine to the preparative regimen for children undergoing unrelated donor HSCT for Fanconi anemia. The rarity of these diseases coupled with the far more likely incremental improvements that will result from ongoing research will require prospective international clinical trials to improve the outcome for these children.

SBDS expression and localization at the mitotic spindle in human myeloid progenitors

Background

Shwachman-Diamond Syndrome (SDS) is a hereditary disease caused by mutations in the SBDS gene. SDS is clinically characterized by pancreatic insufficiency, skeletal abnormalities and bone marrow dysfunction. The hematologic abnormalities include neutropenia, neutrophil chemotaxis defects, and an increased risk of developing Acute Myeloid Leukemia (AML). Although several studies have suggested that SBDS as a protein plays a role in ribosome processing/maturation, its impact on human neutrophil development and function remains to be clarified.

Methodology/Principal Findings

We observed that SBDS RNA and protein are expressed in the human myeloid leukemia PLB-985 cell line and in human hematopoietic progenitor cells by quantitative RT-PCR and Western blot analysis. SBDS expression is downregulated during neutrophil differentiation. Additionally, we observed that the differentiation and proliferation capacity of SDS-patient bone marrow hematopoietic progenitor cells in a liquid differentiation system was reduced as compared to control cultures. Immunofluorescence analysis showed that SBDS co-localizes with the mitotic spindle and in vitro binding studies reveal a direct interaction of SBDS with microtubules. In interphase cells a perinuclear enrichment of SBDS protein which co-localized with the microtubule organizing center (MTOC) was observed. Also, we observed that transiently expressed SDS patient-derived SBDS-K62 or SBDS-C84 mutant proteins could co-localize with the MTOC and mitotic spindle.

Conclusions/Significance

SBDS co-localizes with the mitotic spindle, suggesting a role for SBDS in the cell division process, which corresponds to the decreased proliferation capacity of SDS-patient bone marrow CD34⁺ hematopoietic progenitor cells in our culture system and also to the neutropenia in SDS patients. A role in chromosome missegregation has not been clarified, since similar spatial and time-dependent localization is observed when patient-derived SBDS mutant proteins are studied. Thus, the increased risk of myeloid malignancy in SDS remains unexplained.

Thrombocytopenia and anemia in infants and children

Thrombocytopenia and anemia are the two most common hematologic conditions seen in the pediatric emergency department. Providers of emergency pediatric care must have an understanding of the causes and therapies for the various conditions that result from thrombocytopenia and anemia. This article reviews the common causes of isolated thrombocytopenia and anemia in infancy and childhood.

[Diamond-Blackfan anemia reveals the dark side of ribosome biogenesis]

Diamond-Blackfan anemia (DBA), a rare congenital erythroblastopenia, has recently become a paradigm for a growing set of genetic diseases linked to mutations in genes encoding ribosomal proteins or factors involved in ribosome biogenesis. Recent studies of the structure and the function of ribosomal proteins affected in DBA indicate that their mutation in DBA primarily impacts ribosome biogenesis. Accordingly, cells from DBA patients display anomalies in the maturation of ribosomal RNAs. The explanation of this unexpected link between ribosome biogenesis, a ubiquitous process, and a disease mostly affecting erythroid differentiation may stem in part from the emerging concept of ribosomal stress response, a signaling pathway triggering cell cycle arrest in response to a defect in ribosome synthesis. Future studies of DBA and other diseases related to defects in ribosome biogenesis are likely to rapidly provide important insights into the regulatory mechanisms linking cell cycle progression to this major metabolic pathway.

Many ribosomal protein mutations are associated with growth impairment and tumor predisposition in zebrafish

We have characterized 28 zebrafish lines with heterozygous mutations in ribosomal protein (rp) genes, and found that 17 of these are prone to develop zebrafish malignant peripheral nerve sheath tumors (zMPNST). Heterozygotes from the vast majority of tumor-prone rp lines were found to be growth-impaired, though not all growth-impaired rp lines were tumor-prone. Significantly, however, the rp lines with the greatest incidence of zMPNSTs all displayed a growth impairment. Furthermore, heterozygous cells from one tumor-prone rp line were out-competed by wild-type cells in chimeric embryos. The growth impairment resulting from heterozygosity for many rp genes suggests that a global defect in protein translation exists in these lines, raising the possibility that a translation defect that precedes tumor development is predictive of tumorigenesis.

Congenital cytopenias and bone marrow failure syndromes

Congenital bone marrow failure syndromes (CBMFS) are extremely uncommon diseases that can present in the neonate. The objective of this article is to review the presentation, diagnosis, pathophysiology, and management of CBMFS in relation to neonatology. CBMFS should be considered when a single or multiple blood cell lineages are low secondary to failure of production. Diagnosis in the neonatal period requires a high index of suspicion. In this particular age group, CBMFS should be considered when the neonate has a family history of CBMFS, is small for gestational age, or has other physical abnormalities. History and physical examination can lead to the diagnosis. CBMFS are often associated with a predisposition to cancer later in life.

Loss of p53 synthesis in zebrafish tumors with ribosomal protein gene mutations

Zebrafish carrying heterozygous mutations for 17 different ribosomal protein (rp) genes are prone to developing malignant peripheral nerve sheath tumors (MPNSTs), a tumor type that is seldom seen in laboratory strains of zebrafish. Interestingly, the same rare tumor type arises in zebrafish that are homozygous for a loss-of-function point mutation in the tumor suppressor gene p53. For these reasons, and because p53 is widely known to be mutated in the majority of human cancers, we investigated the status of p53 in the rp(+/-) MPNSTs. Using monoclonal antibodies that we raised to zebrafish p53, we found that cells derived from rp(+/-) MPNSTs are significantly impaired in their ability to produce p53 protein even in the presence of a proteasome inhibitor and gamma-irradiation. Although the coding regions of the p53 gene remain wild type, the gene is transcribed, and overall protein production rates appear normal in rp(+/-) MPNST cells, p53 protein does not get synthesized. This defect is observed in all MPNSTs we examined that were derived from our 17 zebrafish lines with rp gene mutations. To date, studies of p53 in malignancies have focused predominantly on either p53 gene mutations or the aberrant posttranslational regulation of the p53 protein. Our results show that the appropriate amount of numerous ribosomal proteins is required for p53 protein production in vivo and that disruption of this regulation most likely contributes to tumorigenesis.

Deficient RPS19 protein production induces cell cycle arrest in erythroid progenitor cells

The gene encoding ribosomal protein S19 (RPS19) is one of the responsible genes for Diamond-Blackfan anaemia (DBA), a congenital erythroblastopenia. Although haplo-insufficiency of RPS19 has been suggested to be the onset mechanism underlying the pathogenesis of DBA, the sequential mechanism has not been elucidated. In order to analyse the consequences of the missense mutation of RPS19 specific for DBA patients, we made mutated RPS19 expression vectors. Twelve C-terminally Flag-tagged missense mutants were exogenously expressed from retroviral vectors and analysed by Western blot analysis and flow cytometry. When these 12 mutants were expressed in the erythro-leukaemic cell lines K562 and human bone marrow CD34(+) cells, almost all of the mutant proteins (except for G120R) were unstable, and the levels of mutated RPS19 protein were significantly low. To address the effect of deficient RPS19 expression on cell proliferation, RPS19 was downregulated by siRNA. Repressive expression of RPS19 in human CD34(+) cells produced an elevated number of cells at G0 and induced erythroid progenitor-specific defects in BM cells. These results suggest that abnormal ribosomal biogenesis causes inadequate cell cycle arrest in haematopoietic progenitors, and that, subsequently, erythroid progenitors are specifically hampered. These in vitro phenotypes of genetically manipulated CD34(+) cells mimic DBA pathogenesis.

Molecular basis of Diamond-Blackfan anemia: structure and function analysis of RPS19

Diamond–Blackfan anemia (DBA) is a rare congenital disease linked to mutations in the ribosomal protein genes rps19, rps24 and rps17. It belongs to the emerging class of ribosomal disorders. To understand the impact of DBA mutations on RPS19 function, we have solved the crystal structure of RPS19 from Pyrococcus abyssi. The protein forms a five α-helix bundle organized around a central amphipathic α-helix, which corresponds to the DBA mutation hot spot. From the structure, we classify DBA mutations relative to their respective impact on protein folding (class I) or on surface properties (class II). Class II mutations cluster into two conserved basic patches. In vivo analysis in yeast demonstrates an essential role for class II residues in the incorporation into pre-40S ribosomal particles. This data indicate that missense mutations in DBA primarily affect the capacity of the protein to be incorporated into pre-ribosomes, thus blocking maturation of the pre-40S particles.

The functions of RPS19 and their relationship to Diamond-Blackfan anemia: a review

The relatively new study of ribosomal proteins has allowed for greater understanding of protein synthesis; however the connection between ribosomal proteins' roles and that of disease pathophysiology has not yet been established. RPS19 is a ribosomal protein linked to Diamond-Blackfan anemia whose functions have begun to be elucidated. We review here the known roles of RPS19 in both ribosome construction and other extra-ribosomal functions and discuss their relationship to Diamond-Blackfan anemia.

Diamond-Blackfan anemia: erythropoiesis lost in translation

Diamond-Blackfan anemia (DBA) is a congenital erythroid aplasia that usually presents as macrocytic anemia during infancy. Linkage analysis suggests that at least 4 genes are associated with DBA of which 2 have been identified so far. The known DBA genes encode the ribosomal proteins S19 and S24 accounting for 25% and 2% of the patients, respectively. Herein, we review possible links between ribosomal proteins and erythropoiesis that might explain DBA pathogenesis. Recent studies and emerging findings suggest that a malfunctioning translational machinery may be a cause of anemia in patients with DBA.

Impaired ribosome biogenesis in Diamond-Blackfan anemia

The gene encoding the ribosomal protein S19 (RPS19) is frequently mutated in Diamond-Blackfan anemia (DBA), a congenital erythroblastopenia. The consequence of these mutations on the onset of the disease remains obscure. Here, we show that RPS19 plays an essential role in biogenesis of the 40S small ribosomal subunit in human cells. Knockdown of RPS19 expression by siRNAs impairs 18S rRNA synthesis and formation of 40S subunits and induces apoptosis in HeLa cells. Pre-rRNA processing is altered, which leads to an arrest in the maturation of precursors to the 18S rRNA. Under these conditions, pre-40S particles are not exported to the cytoplasm and accumulate in the nucleoplasm of the cells in perinuclear dots. Consistently, we find that ribosome biogenesis and nucleolar organization is altered in skin fibroblasts from DBA patients bearing mutations in the RPS19 gene. In addition, maturation of the 18S rRNA is also perturbed in cells from a patient bearing no RPS19-related mutation. These results support the hypothesis that DBA is directly related to a defect in ribosome biogenesis and indicate that yet to be discovered DBA-related genes may be involved in the synthesis of the ribosomal subunits.

Hodgkin lymphoma in a child with Diamond Blackfan anemia

Diamond Blackfan anemia (DBA) is a rare disease characterized by aplasia or hypoplasia of erythroid lineage. Normochromic, usually macrocytic, but occasionally normocytic anemia and reticulocytopenia are characteristic findings of DBA. DBA is associated with an increased risk of malignancy. Most of the reported malignancies are acute myeloid leukemia. Solid tumors including hepatocellular carcinoma and osteosarcoma have also been identified. We could find 29 reported cases with DBA and malignancy. Two of them were diagnosed as Hodgkin lymphoma at 15 and 23 years, respectively. Here we report a 7-year-old boy with DBA who developed Hodgkin disease.

Identification of a new in-frame deletion of six amino acids in ribosomal protein S19 in a patient with Diamond-Blackfan anemia

Ribosomal protein S19 (RPS19) is currently the only gene associated with Diamond-Blackfan anemia (DBA), a rare congenital pure red cell aplasia characterized by normochromic macrocytic anemia, reticulocytopenia, and normocellular bone marrow with a selective deficiency of erythroid precursors. RPS19 is mutated in 25% of DBA patients, but its role in DBA pathogenesis remains elusive. We have identified a novel heterozygous microdeletion in RPS19 in a DBA patient presenting with profound anemia after birth. The deletion of 18 nucleotides (233-250; A in start codon is +1) in exon 4 leads to the elimination of 6 amino acids 78IYGGRQ83, affecting the most conserved stretch of three amino acids (YGG) in RPS19. The mutated allele was not detected in the patient's family members, indicating de novo mutation. Both alleles were expressed at the same level. Using an immunofluorescence technique, the mutated RPS19 protein localized to nucleoli, and its intracellular distribution did not differ from the wild-type RPS19. The deletion of only a few amino acids of this protein with a preserved reading frame is rare, and this type of a mutation could be very helpful in further experiments to define the role of the RPS19 protein in DBA pathogenesis.

Investigation of a putative role for FLVCR, a cytoplasmic heme exporter, in Diamond-Blackfan anemia

Diamond-Blackfan anemia (DBA) is a rare congenital pure red cell aplasia. Previous studies indicate that mutations of a gene on chromosome 19q13.2, which encodes a ribosomal protein, are responsible for 25% of cases. Recent investigations suggest both the presence of a second candidate region on chromosome 8p and non-19q, non-8p disease. In linkage analysis studies of 28 multiplex DBA families, we identified 8 families with disease linkage to chromosome 1q31. In 4 families, the disease linked exclusively to 1q31. Here, we report that the FLVCR gene on 1q31, which encodes a cytoplasmic heme exporter associated with red cell aplasia in cats, is not involved in DBA in these families.

Diamond Blackfan anemia: A paradigm for a ribosome-based disease

Diamond Blackfan anemia is characterized by a severe hypoplastic anemia and a heterogeneous collection of other clinical features. Approximately 25% of Diamond Blackfan anemia cases are associated with mutations in the gene encoding ribosomal protein S19. The hypothesis presented here ties together molecular and clinical features of the disease, and establishes a conceptual framework for understanding many of the unusual characteristics of a growing number of diseases linked to factors involved in ribosome synthesis. The hypothesis states that ribosomal proteins are expressed in amounts that differ relative to one another in a tissue-specific manner, and that haploinsufficiency for a particular protein may make that protein limiting for ribosome assembly in some tissues, while other tissues remain unaffected. Further, polymorphisms in factors controlling the expression of a particular ribosomal protein gene may alter its expression and expand or contract the number of tissues affected from individual to individual. Support for the hypothesis comes from the observation that promoters in ribosomal protein genes exhibit little conservation and transcription profiling indicates that the absolute amounts of mRNAs for individual ribosomal proteins can vary dramatically relative to one another. Balanced expression of ribosomal proteins is achieved post-translationally, where excess proteins not assembled into ribosomal subunits are often rapidly degraded. The number of ribosomes per cell is therefore determined by the factors that limit assembly. In principle, any essential ribosomal protein could become limiting for assembly if its level of expression falls below a critical threshold. Whether an inactivating mutation in ribosomal protein gene would affect protein synthetic capacity of a tissue would depend on the ratio of the ribosomal protein relative to other ribosomal proteins in that tissue. If the ratio were high, the tissue may not be affected as the level of functional protein may not fall to a point where it becomes limiting for subunit assembly. In contrast, if the ratio were low, an inactivating mutation could make the protein limiting for subunit assembly resulting in a clinical phenotype. Polymorphisms in the myriad of cis- and trans-acting factors, which govern the expression of ribosomal proteins in response to developmental and physiological signals, could act to increase or decrease ribosomal protein expression and thereby impact the profile and severity of clinical phenotypes. Therefore, these factors represent targets for the development of new therapies to treat Diamond Blackfan anemia and other ribosome based diseases.

Development of cellular models for ribosomal protein S19 (RPS19)-deficient diamond–blackfan anemia using inducible expression of siRNA against RPS19

Diamond-Blackfan anemia (DBA) is a congenital red cell aplasia in which 25% of the patients have a mutation in the ribosomal protein S19 (RPS19) gene. No models exist for RPS19-deficient DBA and the molecular pathogenesis is unknown. To establish an in vitro inducible model for DBA, human erythroid leukemic cell lines, TF-1 and UT-7 cells, were cotransduced with a lentiviral vector expressing the green fluorescent protein (GFP) gene and small interfering RNA (siRNA) against RPS19 controlled by a tet operator regulatory element and another transactivator vector containing the red fluorescent protein (RFP) gene and the cDNA encoding a tetracycline-controllable transcriptional repressor. Following transduction, the RFP-positive and GFP-negative cell population was sorted by flow cytometry. Upon incubation with doxycycline (0.5 mug/ml), more than 98% of cells expressed GFP and the siRNA. Significant suppression of erythroid differentiation, cell growth, and colony formation was observed in cells treated with siRNA against RPS19 but not in cells treated with a control vector. These findings show that RPS19 plays an important role in the regulation of hematopoietic cell proliferation and erythroid differentiation. These novel cell lines represent models for RPS19-deficient DBA and can be used to identify the molecular mechanisms in RPS19-deficient DBA.

The natural history of severe anemia in cartilage-hair hypoplasia

Anemia is seen in over 80% of patients with cartilage-hair hypoplasia (CHH). While this is usually mild and self-limited, some patients demonstrate a severe, persistent anemia resembling that seen in Diamond-Blackfan anemia (DBA). This paper examines the natural history of 12 patients with CHH and severe anemia. Phenotypic features and mutation data (where available) were reviewed, but no significant differences were found that predicted severe anemia. Severe anemia is estimated to occur in approximately 6% of CHH patients and is permanent in more than half of these patients. Thrombocytosis, though not previously reported in CHH, was noted in five patients, similar to that seen in DBA. The role of possible gene-gene and gene-environment interactions is discussed.

Diamond-Blackfan anemia in Japan: clinical outcomes of prednisolone therapy and hematopoietic stem cell transplantation

The epidemiology and treatment outcomes for Diamond-Blackfan anemia (DBA) were surveyed in a cohort of 54 children (M/F = 26:28) registered in Japan from 1988 to 1998. The annual incidence was 4.02 cases per million births, the median age at diagnosis was 60 days, and 59% of the cases presented by 3 months of age. Three patients had a familial occurrence. All patients received prednisolone (PSL), and cyclosporin A (CsA) was added to the therapy in 17 patients. Forty-seven patients received transfusions, and 13 underwent hematopoietic stem cell transplantation (HSCT). The cumulative probabilities of a medication-free or a transfusion-free state prior to HSCT were 36% and 69%, respectively, at more than 5 years after diagnosis. Thirteen patients were weaned from PSL therapy without HSCT, and CsA was not associated with weaning from therapy. Transfusion and medication were stopped at 249 days and 933 days after diagnosis in 34 and 13 patients, respectively, who achieved a state of independence. No initial findings predicted the treatment dependence. More than 20% of patients experienced sustained hemosiderosis and/or adverse effects of PSL. The ages and reticulocyte counts at diagnosis of the patients who underwent HSCT were lower than in the patients who did not. HSCT led to the highest success (85%) of all previous reports, even though 5 alternative donors were included in our study. Two cord blood transplants from unrelated donors failed. These findings suggest the need for developing an integral treatment strategy including selective HSCT for refractory DBA.

Comprehensive banking of sibling donor cord blood for children with malignant and nonmalignant disease

Banking of cord blood (CB) for unrelated hematopoietic stem cell (HSC) transplantation is well established. However, directed-donor banking of CB for siblings in a current good tissue practices (cGTP) environment has not previously been investigated. Families were eligible for the present study if they were caring for a child with a disorder treatable by HSC transplantation and expecting the birth of a full sibling. We devised standard operating procedures and policies to address eligibility, donor recruitment, donor and recipient evaluation, CB collection, shipping, graft characterization, storage, and release of CB from quarantine. Many of these policies are distinctly different from those established for unrelated-donor CB banks. We enrolled 540 families from 42 states. Collections occurred at several hundred different hospitals. No family was deferred on the basis of health history or infectious disease testing, but departures from standard donor suitability criteria were documented. Disease categories for sibling recipients included malignancy, sickle cell anemia, thalassemia major, nonmalignant hematological conditions, and metabolic errors. Mean CB volume (including anticoagulant) was 103.1 mL; mean nucleated cell count was 8.9 x 10(8). Cell dose exceeded 1.5 x 10(7) nucleated cells per kilogram for 90% of banked units. Seventeen units (3.4%) have been transplanted. Sixteen of the 17 CB allograft recipients had stable engraftment of donor cells. Remote-site collection of sibling donor CB can be accomplished with a high success rate and in a cGTP-guided environment. The cellular products have been used successfully for transplantation; their number and characteristics should be adequate to support the first prospective clinical investigations of sibling CB transplantation.

Response of Diamond-Blackfan anemia to metoclopramide: evidence for a role for prolactin in erythropoiesis

A 47-year-old woman with severe macrocytic anemia markedly improved during the second and third trimesters of 3 pregnancies and when breast-feeding her 2 children. Because the serum prolactin level is elevated at these times, we later treated her with metoclopramide (10 mg orally 3 times daily), a medication known to induce prolactin release. Her serum prolactin levels increased from 7 to 133 ng/mL (normal < 20 ng/mL) and hematocrit from 17% to 22% to 35%. With continued therapy (now 10 mg orally daily), her hematocrit has ranged from 30% to 40% for 6 years, although the macrocytosis persists (mean corpuscular volume, 100-112 fL). On the basis of this observation, a pilot study was undertaken of metoclopramide therapy in patients with Diamond-Blackfan anemia who were refractory to low doses of corticosteroids. Fifteen patients were enrolled and 9 completed the planned 16 weeks of therapy. Three individuals responded, suggesting that this therapeutic approach may benefit others. As with the index case, the anemia did not improve until 12 to 15 weeks of therapy had been completed.

Study of 22 Egyptian patients with Diamond-Blackfan anemia, corticosteroids, and cyclosporin therapy results

OBJECTIVE

Diamond-Blackfan anemia is a rare congenital hypoproliferative anemia of infancy and early childhood. Treatment with corticosteroids is commonly used, but with limited success. Trials with cyclosporin-A (CSA) are not frequently reported. Therefore, in this study we analyzed our results in the management of this rare disease by different medical treatments.

DESIGN

The results of 22 patients diagnosed at our Hematology Center in the New Cairo University Children's Hospital during the period 1991-2001 were retrospectively analyzed. Our patients first received prednisolone (2 mg/kg/d) for different courses according to their response. Since the year 2000, the steroid nonresponders received CSA (3-12 mg/kg/d) for 6 months unless treatment complications developed.

RESULTS

The age at the onset of the disease ranged from 1 to 24 months (median: 2.5 months). The mean values of the hemoglobin, the reticulocyte count, and the myeloid/erythroid ratio at the onset of the disease were 4.75 +/- 1.79 g/dL, 0.14 +/- 0.16, and 39.4 +/- 27.08, respectively. Patients received prednisolone from 0.25 to 10 years (median: 2 years). Ten patients were nonresponders (45.5%), and 5 patients (22.7%) responded to corticosteroid therapy. Two of 5 responders are off treatment with a hemoglobin level of >9 g/dL, and 3 of 5 are currently corticosteroid-dependent. Of 10 patients not responding to steroids, 8 received CSA for 6 months. Four patients (50%) responded to CSA therapy. A significant positive association was found between CSA dose and response.

CONCLUSION

CSA therapy should be tried in steroid-resistant Diamond-Blackfan anemia patients before blood transfusion or corticosteroid therapy complications are instituted.

Blackfan-Diamond anemia and dyserythropoietic anemia presenting with increased nuchal translucency at 12 weeks of gestation

Blackfan-Diamond anemia is a congenital hypoplastic anemia with a birth prevalence of about 1 in 200,000, usually presenting in the first few months of life and commonly associated with cardiac, urogenital and digital anomalies. Congenital dyserythropoietic anemias are a group of rare congenital anemias characterized by ineffective erythropoiesis. We report on two cases of congenital fetal anemia, one with Blackfan-Diamond anemia and one with dyserythropoietic anemia, presenting with increased nuchal translucency at 12 weeks of gestation.

High-dose methylprednisolone therapy in pure red cell aplasia

OBJECTIVE

To report our experience using high-dose methylprednisolone (HDMP) treatment in a patient with primary acquired pure red cell aplasia (PRCA) who failed to respond to conventional prednisone therapy.

CASE SUMMARY

A 29-year-old woman reported weakness, was easily fatigued, and had developed palpitations. On physical examination, pallor and splenomegaly were detected. On blood smear, mild macrocytic anemia was seen. Bone marrow aspiration and biopsy revealed normocellularity, erythroid hypoplasia (E/M: 1/10), reduction in erythroid precursors, and normal megakaryocytes and myeloid series. No disease associated with secondary PRCA was detected. Oral prednisone 1 mg/kg (total 60 mg/d) was started as conventional treatment. However, the patient's status deteriorated and the hemoglobin concentration fell from 6.5 to 5.5 g/dL within the first week of hospitalization. HDMP was then begun. Treatment protocol consisted of methylprednisolone 30 mg/kg for 4 days, 20 mg/kg for 3 days, 10 mg/kg for 3 days, 5 mg/kg for 4 days, and 1 mg/kg for 2 weeks. The patient's hemoglobin concentration increased from 5.5 to 14.2 g/dL over a period of 9 weeks. Transient hyperglycemia and cushingoid appearance were seen during prednisone treatment.

DISCUSSION

Exactly how steroids enhance erythropoiesis in PRCA is unknown. It seems likely that steroids render abnormal erythroid progenitors more sensitive to marrow growth factors, thereby permitting them to differentiate to functional precursors. HDMP treatment had been rarely used in patients with primary acquired PRCA. Limited studies using HDMP have shown variable results.

CONCLUSIONS

HDMP treatment may be considered safe and effective in patients with primary acquired PRCA who do not respond to conventional steroid therapy.

Current knowledge on the pathophysiology of Fanconi anemia: from genes to phenotypes

Fanconi anemia (FA) is an autosomal recessive disease characterized by congenital anomalies, bone marrow failure, and leukemia susceptibility. FA cells show chromosome instability and hypersensitivity to DNA cross-linking agents such as mitomycin C. Recent studies indicate that there are at least 8 genetically distinct FA groups (A, B, C, D1, D2, E, F, G). To date, 6 genes (for A, C, D2, E, F, and G) have been cloned. In this review, we describe the structures and functions of FA proteins. Increasing evidence indicates that the multiple FA proteins cooperate in a biochemical pathway and/or a multimer complex. FANCD2, a downstream component of the FA pathway, has recently been shown to be ubiquitinated in response to DNA damage and to translocate to nuclear foci containing BRCA1, a breast cancer susceptibility gene product, suggesting a role for this protein in DNA repair functions. We also describe 2 emerging issues: genotype-phenotype relationships and mosaicism. The FA pathway is likely to play a critical role as a caretaker of genomic integrity in hematopoietic stem cells. Clarifying the molecular basis of this disease may provide new insights into the pathogenesis of bone marrow failure syndromes and myeloid malignancies.