Communicated by Maria Rita Passos-BuenoDiamond-Blackfan anemia (DBA) is an inherited disease characterized by pure erythroid aplasia. Thirty percent (30%) of patients display malformations, especially of the hands, face, heart, and urogenital tract. DBA has an autosomal dominant pattern of inheritance. De novo mutations are common and familial cases display wide clinical heterogeneity. Twenty-five percent (25%) of patients carry a mutation in the ribosomal protein (RP) S19 gene, whereas mutations in RPS24, RPS17, RPL35A, RPL11, and RPL5 are rare. These genes encode for structural proteins of the ribosome. A link between ribosomal functions and erythroid aplasia is apparent in DBA, but its etiology is not clear. Most authors agree that a defect in protein synthesis in a rapidly proliferating tissue, such as the erythroid bone marrow, may explain the defective erythropoiesis. A total of 77 RPS19 mutations have been described. Most are whole gene deletions, translocations, or truncating mutations (nonsense or frameshift), suggesting that haploinsufficiency is the basis of DBA pathology. A total of 22 missense mutations have also been described and several works have provided in vitro functional data for the mutant proteins. This review looks at the data on all these mutations, proposes a functional classification, and describes six new mutations. It is shown that patients with RPS19 mutations display a poorer response to steroids and a worse long-term prognosis compared to other DBA patients. Hum Mutat 29(7), [911][912][913][914][915][916][917][918][919][920] 2008.

Mutations in ribosomal proteins RPS19, RPS24 and RPS17 have been reported in DiamondBlackfan Anemia (DBA), an autosomal dominant disease characterised by pure red cell aplasia. DBA is the prototype of ribosomapathies: a protein synthesis defect in a tissue with a high cellular turnover is considered the cause of the erythroid progenitor failure. We have created the Diamond-Blackfan Anemia mutation database to curate and record DBA gene mutations, together with their functional consequences and clinical phenotypes. This locusspecific resource is open to future submissions and is available online (http://www.dbagenes.unito.it). It is founded on the Leiden Open (source) Variation Database (LOVD) system and includes data from sequence and structure analysis tools, genomic database resources and published reports. It lists all identified variants and background genomic information. Phenotypic data are accessed by selecting a particular mutation. The database includes 219 unique variants of which 86 are disease-causing mutations. The database will be supplemented with other DBA genes as soon as they are reported and their mutations are identified and it should be of assistance to clinicians and investigators involved in DBA research and care.© 2008 Wiley-Liss, Inc.KEY WORDS: Diamond-Blackfan Anemia, ribosomal protein, erythropoiesis, ribosome biogenesis. INTRODUCTIONDiamond-Blackfan anemia (DBA; MIM# 105650) is a pure red cell aplasia of childhood with an incidence ranging from 5 to 10 cases per million live births in Europe [Campagnoli et al., 2004]. Its main clinical features are normochromic and macrocytic anemia, reticulocytopenia and hypoplasia of erythroid progenitors in the bone marrow, whereas other hematopoietic lineages are usually normal [Campagnoli et al., 2004]. About 30% of patients display somatic abnormalities, involving the upper limbs, head, neck, the urogenital and cardiovascular systems, along with growth retardation. Patients have an increased risk of malignancies [Campagnoli et al., 2004;Lipton et al., 2001]. Management begins with corticosteroids, though the response is variable. Non-responders require multiple blood transfusions. Allogeneic bone marrow or stem cells transplantation is the only curative treatment at present [Roy et al., 2005;Lipton et al., 2006].Ribosomal protein (RP) S19 was the only gene associated with DBA for several years. It is mutated in 25% of patients with either sporadic or familial DBA, always in heterozygosity [Draptchinskaia et al., 1999;Campagnoli et al., 2008]. Mutations in RPS24 have been identified in 3/215 (~2%) DBA probands [Gazda et al., 2006] RPS17 mutation was reported in 1/24 [Cmejla et al., 2007]. Mutations in RPL35A [Farrar et al., 2007], RPL11 and RPL5 have been described, but not yet published in extenso. DBA is thus the only known human disease caused by an RP deficiency and is the prototype of ribosomapathies [Luzzatto and Karadimitris, 1998].The RPS19 gene (MIM# 603474) maps on locus 19q13.2, comprises six exons and spans 11 kb. The first exon (3...

Defects in genes encoding ribosomal proteins cause Diamond Blackfan Anemia (DBA), a red cell aplasia often associated with physical abnormalities. Other bone marrow failure syndromes have been attributed to defects in ribosomal components but the link between erythropoiesis and the ribosome remains to be fully defined. Several lines of evidence suggest that defects in ribosome synthesis lead to “ribosomal stress” with p53 activation and either cell cycle arrest or induction of apoptosis. Pathways independent of p53 have also been proposed to play a role in DBA pathogenesis.We took an unbiased approach to identify p53-independent pathways activated by defects in ribosome synthesis by analyzing global gene expression in various cellular models of DBA. Ranking-Principal Component Analysis (Ranking-PCA) was applied to the identified datasets to determine whether there are common sets of genes whose expression is altered in these different cellular models. We observed consistent changes in the expression of genes involved in cellular amino acid metabolic process, negative regulation of cell proliferation and cell redox homeostasis.These data indicate that cells respond to defects in ribosome synthesis by changing the level of expression of a limited subset of genes involved in critical cellular processes. Moreover, our data support a role for p53-independent pathways in the pathophysiology of DBA.

Background: Diamond-Blackfan anaemia (DBA) is a rare inherited red cell hypoplasia characterised by a defect in the maturation of erythroid progenitors and in some cases associated with malformations. Patients have an increased risk of solid tumors. Mutations have been found in several ribosomal protein (RP) genes, i.e RPS19, RPS24, RPS17, RPL5, RPL11, RPL35A. Studies in haematopoietic progenitors from patients show that haplo-insufficiency of an RP impairs rRNA processing and ribosome biogenesis. DBA lymphocytes show reduced protein synthesis and fibroblasts display abnormal rRNA processing and impaired proliferation.

The qPCR method for telomere length evaluation is an easy alternative to other methods and may thus be valuable in a clinical hematological laboratory setting. Telomere maintenance does not seem to be involved in the pathogenesis of DBA unlike in other BMFSs.