Defective Ribosomal RNA Maturation in Patients with Diamond Blackfan Anemia.

Diamond Blackfan Anemia (DBA) is a rare congenital red cell aplasia due to a selective defect of erythroid progenitor cell maturation. DBA patients exhibit a wide array of developmental abnormalities and can be predisposed to cancer. Heterozygous mutations in the gene encoding Rps19, a ribosomal protein of the small subunit, have been identified in 25% of DBA cases. By using human cell lines (TF-1) containing small interfering RNA (siRNA) designed to silence RPS19 we have shown that Rps19 deficient cells present an altered ribosomal profile which conveys a decrease in the 40S subunit population. This decrease is due to faulty maturation of the 21S precursor to functional 18S rRNA as illustrated by pulse chase and northern blot analysis of total RNA extracts from the cell lines. Analysis of these intermediates in CD34⁻ cells from the bone marrow of DBA patients harboring mutations in RPS19 revealed a pre-rRNA processing defect similar to that observed in TF-1 cells where RPS19 expression was reduced. This defect was observed to a lesser extent in CD34⁺ cells from DBA patients with mutations in RPS19. Thus, our data reveal that rRNA processing is disrupted in cells from DBA patients with mutated RPS19.