Molecular and cellular pathogenesis of the erythroid defect and the therapeutic effect of glucocorticoids in Diamond-Blackfan anaemia

Diamond-Blackfan Anaemia (DBA) is a rare inherited bone marrow (BM) failure syndrome characterised by selective anaemia, congenital anomalies and predisposition to malignancy. DBA is caused by monoallelic, loss-of-function mutations in ribosomal protein (RP) genes. Delineation of the precise erythroid defect underpinning anaemia in DBA has been hampered by a lack of markers that define cells giving rise to burst- and colony-forming unit-erythroid (BFU-E and CFU-E) colonies, i.e., the clonogenic assays that quantify early and late erythroid progenitor (EP) potential respectively. By combining flow-cytometry, cell-sorting and single cell clonogenic assays, I identify Lin-CD34+CD38+CD45RA-CD123-CD71+CD41a-CD105-CD36- BM cells as early EP (EEP) and Lin-CD34+/-CD38+CD45RA-CD123-CD71+CD41a-CD105+CD36+ cells as late EP (LEP) giving rise to BFU-E and CFU-E respectively. By applying these definitions to DBA, I reveal, for the first time, that both quantitative and qualitative defects in EEP and LEP contribute to defective erythropoiesis in DBA and its restoration by corticosteroids (CS). I also demonstrate that, while an EP defect associated with profound loss of erythroblasts (EB) is present in transfusion-dependent (TD) patients with RPS gene-associated DBA, EP/EB are relatively preserved in TD patients with RPL gene variants. Transcriptome profiling by RNA-sequencing of FACS-purified EB from RPL genotype patients compared with age-matched controls, provides a unique dataset showing a distinct DBA molecular signature, characterised by p53 and inflammatory signalling pathways. Remarkably, the cellular differences between RPL and RPS gene-associated DBA correlate with divergent clinical phenotypes: patients with RPL rather than RPS gene pathogenic variants are more likely to present with anaemia at an older age, and to respond to CS. Finally, although DBA is rare, I demonstrate its wider utility as a paradigm of disordered erythroid commitment, providing insight into normal haematopoiesis. The strategies described for prospective isolation of EP/EB constitute an original contribution to knowledge that will facilitate more incisive study of normal and aberrant erythropoiesis.Open Acces

Turning up the HEAT(R3) in Diamond-Blackfan anemia.

In this issue of Blood, O’Donohue et al1 identify biallelic mutations in HEATR3 as the underpinning cause of Diamond-Blackfan anemia (DBA) in 4 unrelated pedigrees. By using primary human cells, cell lines, and yeast models with HEATR3 deficiency, they delineate a mechanism by which reduced HEATR3 leads to erythroid failure. The mechanism includes impaired nuclear import of ribosomal protein uL18 (encoded by RPL5), defects in ribosomal RNA processing, and reduced production of the large (60S) ribosomal subunit, leading to p53-independent perturbation of erythroid development

Additional file 1: of Single-cell profiling of human megakaryocyte-erythroid progenitors identifies distinct megakaryocyte and erythroid differentiation pathways

Supplementary Figures S1 - S5. (PDF 10849 kb

Diagnosis, treatment, and surveillance of Diamond-Blackfan anaemia syndrome: international consensus statement

: Diamond-Blackfan anaemia (DBA), first described over 80 years ago, is a congenital disorder of erythropoiesis with a predilection for birth defects and cancer. Despite scientific advances, this chronic, debilitating, and life-limiting disorder continues to cause a substantial physical, psychological, and financial toll on patients and their families. The highly complex medical needs of affected patients require specialised expertise and multidisciplinary care. However, gaps remain in effectively bridging scientific discoveries to clinical practice and disseminating the latest knowledge and best practices to providers. Following the publication of the first international consensus in 2008, advances in our understanding of the genetics, natural history, and clinical management of DBA have strongly supported the need for new consensus recommendations. In 2014 in Freiburg, Germany, a panel of 53 experts including clinicians, diagnosticians, and researchers from 27 countries convened. With support from patient advocates, the panel met repeatedly over subsequent years, engaging in ongoing discussions. These meetings led to the development of new consensus recommendations in 2024, replacing the previous guidelines. To account for the diverse phenotypes including presentation without anaemia, the panel agreed to adopt the term DBA syndrome. We propose new simplified diagnostic criteria, describe the genetics of DBA syndrome and its phenocopies, and introduce major changes in therapeutic standards. These changes include lowering the prednisone maintenance dose to maximum 0·3 mg/kg per day, raising the pre-transfusion haemoglobin to 9-10 g/dL independent of age, recommending early aggressive chelation, broadening indications for haematopoietic stem-cell transplantation, and recommending systematic clinical surveillance including early colorectal cancer screening. In summary, the current practice guidelines standardise the diagnostics, treatment, and long-term surveillance of patients with DBA syndrome of all ages worldwide