Diamond-Blackfan Anemia, a paradigm for ribosomal diseases – RiboCrash

A number of rare genetic diseases have been recently linked to mutations in genes encoding proteins involved in ribosome biogenesis or ribosome function. Most of these pathologies correspond to inherited bone marrow failure syndromes. These recent findings have led to the new concept of ribosomal disease. Diamond-Blackfan anemia (DBA), a rare congenital erythroblastopenia, has become a paradigm for ribosomal diseases. For the past three years, more than 10 ribosomal protein genes have been found to be haploinsufficient in DBA patients, which causes defects in ribosome biogenesis in patients.
This proposal is a joint effort of two groups with very complementary expertise in RNA biology and in hematology. It associates basic research with clinical practice. It comes as the follow-up of the RIBODBA project (ANR MRAR 2006-2009), which was designed to study the hypothesis that DBA was primarily linked to defects in ribosome biogenesis. Indeed, we showed that the diverse mutations affecting RPS19, the most frequently mutated ribosomal protein in DBA, prevent incorporation of the RPS19 into ribosomes, which affects ribosome biogenesis in patients. Such data have established DBA as a ribosomal disease and new questions are now emerging regarding the pathophysiological mechanism of DBA and the tissue specificity of the disease. One attractive possibility is that erythroid progenitors are highly sensitive to the stress caused by disorders in ribosome biogenesis (ribosomal stress). Alternatively, low amounts or defective quality of ribosomes could alter essential translation processes. We now want to test these hypotheses and understand why erythroid precursors are more sensitive to ribosomal protein haploinsufficiency. We will take advantage of the expertise of one of the partner in the culture of human erythroid progenitors to directly examine these hypotheses in cells from DBA patients. We will analyze the ribosomal stress response as well as the state of the translation machinery in DBA cells. In parallel, we propose to establish induced pluripotent stem (iPS) cells from DBA patients to study in vitro the molecular and cellular consequences on differentiation of mutations in ribosomal protein genes. In the long run, this technology could potentially offer a cure for DBA patients. Downstream of this mechanistic approach of DBA, we intend to find new biomarkers and improve DBA diagnosis based on our recent results on ribosome biogenesis alteration in this disease. In addition, the genes recently linked to DBA will be sequenced in patients of the French DBA registry in order to study genotype-phenotype correlations.
The experiments designed in this project will allow us to challenge various hypotheses to explain the effect of ribosomal protein haploinsufficiency in erythroid progenitors. We expect to determine the relative impact of ribosomal stress and translation impairment on differentiation of erythroid cells from DBA patients. This project should also yield important new tools for DBA study (induction of iPS cells, screening for RPS19 interacting drugs) and diagnosis (new biomarkers). From a broader perspective, we expect to get significant new insight on the mechanisms of ribosomal diseases. Beside rare diseases like Shwachman-Diamond syndrome, dyskeratosis congenita and cartilage-hair hypoplasia, these mechanisms could be involved in the 5q- syndrome, an aquired myelodysplasia, as well as in tumorogenesis.