DBA-MULTIGENES: identification and characterization of candidate genes to gain new mechanistic insight into Diamond-Blackfan anemia pathophysiology. – DBA-MULTIGENES

Diamond-Blackfan anemia (DBA) is a rare congenital erythroblastopenia (7-12 per million live births), characterized by between 0-5% of the normal number of erythroid precursors in an otherwise unaffected bone marrow. In around 40% of DBA cases, patients are also affected by various congenital malformations. DBA is diagnosed early in infancy (median age at 2 month-old), and highlighted by an aregenerative, usually macrocytic anemia, the persistence of the fetal erythropoiesis, and elevated levels of erythrocyte adenosine deaminase (eADA). The intrinsic defect in erythropoiesis is characterized by a blockade of erythroid progenitor proliferation and differentiation between the erythropoietin (EPO)-independent (BFU-e) and EPO-dependent (CFU-e) stages.
To date, our knowledge of the underlying molecular determinants of DBA is fragmentary. The first gene defect identified was described in 1999 and, surprisingly for a disease with an erythroid tropism, concerned the ribosomal protein (RP) gene RPS19. Since the discovery of the RPS19 gene, 13 other defective RP genes have been associated with DBA: RPS7, RPS10, RPS17, RPS24, RPS26, RPS27a, RPS28, RPS29, RPL5, RPL11, RPL15, RPL26, RPL35a, including large deletions. As such, DBA is the first of a growing number of ribosome-related disease, or “ribosomopathies”. At a mechanistic level, DBA mutatins correlated with defects in pre-rRNA maturation. Ribosome protein haploinsufficiency also results in translation defects that are likely to affect genes crucial for erythroid differentiation. Hence, the GATA-1 gene was identified as the first non-RP gene involved in DBA. Despite these advances, however, genotyping of DBA patients revealed that 30% of sufferers do not display GATA-1 or RP mutations, indicating that other candidate genes remain to be identified.
In the present project, we propose to identify new candidate gene(s) in the French DBA patient cohort by targeted NGS, CGH/SNp array, and whole exome sequencing, and to further characterize two new candidate genes, which we have recently identified among DBA patient French registry. The allelic variations of the new candidate genes, identified by CGH/SNP array and whole exome sequencing, will be functionally validated using different approaches including erythroid culture, analyses of ribosome processing and function, nucleolus structure and the development of zebrafish models. Identification of new candidate genes in DBA is of worldwide importance and can thus be considered to be of high strategic value. It constitutes a prerequisite to improve DBA diagnosis and discover new therapeutic targets, which could ultimately lead to the development of new treatments.