Ribosomal protein S19 deficiency in zebrafish leads to developmental abnormalities and defective erythropoiesis through activation of p53 protein family

Abstract

Mutations in several ribosomal proteins (RPs) lead to Diamond-Blackfan anemia (DBA), a syndrome characterized by defective erythropoiesis, congenital anomalies, and increased frequency of cancer. RPS19 is the most frequently mutated RP in DBA. RPS19 deficiency impairs ribosomal biogenesis, but how this leads to DBA or cancer remains unknown. We have found that rps19 deficiency in zebrafish results in hematopoietic and developmental abnormalities resembling DBA. Our data suggest that the rps19-deficient phenotype is mediated by dysregulation of deltaNp63 and p53. During gastrulation, deltaNp63 is required for specification of nonneural ectoderm and its up-regulation suppresses neural differentiation, thus contributing to brain/ craniofacial defects. In rps19-deficient embryos, deltaNp63 is induced in erythroid progenitors and may contribute to blood defects. We have shown that suppression of p53 and deltaNp63 alleviates the rps19-deficient phenotypes. Mutations in other ribosomal proteins, such as S8, S11, and S18, also lead to up-regulation of p53 pathway, suggesting it is a common response to ribosomal protein deficiency. Our finding provides new insights into pathogenesis of DBA. Ribosomal stress syndromes represent a broader spectrum of human congenital diseases caused by genotoxic stress; therefore, imbalance of p53 family members may become a new target for therapeutics. (Blood. 2008;112: 5228-5237) IntroductionThe precise control of ribosome biogenesis and translation is vital for cell survival. Cell growth and proliferation as well as responses to genotoxic stress depend on ribosomal activity. Defective ribosomal synthesis has been associated with bone marrow failure syndromes, such as Diamond-Blackfan anemia (DBA), dyskeratosis congenita, and Shwachman-BodianDiamond syndrome. 1 DBA is a congenital syndrome characterized by anemia, bone marrow erythroblastopenia, and increased incidence of cancer. [1][2][3] Anemia is often accompanied by growth retardation and various malformations. Ribosomal protein S19 (RPS19) is mutated in one fourth of patients 4 ; mutations of other ribosomal proteins can also lead to DBA. 5,6 Red blood cells of DBA patients manifest altered transcription, translation, and activated apoptotic pathways. 7-9 RPS19 is necessary for ribosome biosynthesis. Certain RPS19 mutations affect its structure and assembly into the ribosome. 10,11 In yeast and human, deficiency of RPS19 impairs the processing of 18S rRNA and aberrant pre-40S particles are retained in the nucleolus. [12][13][14] Nucleolar organization is distorted in skin fibroblasts in all DBA patients regardless of the presence of RPS19 mutations, 13 suggesting that defect in ribosome biogenesis is a general feature of DBA. The nucleolus can act as a stress sensor; its disruption mediated p53 up-regulation. 15 Mutations in other proteins participating in ribosome biogenesis lead to p53 up-regulation. [16][17][18] Haploinsufficiency of RPS6 and RPL22 also leads to activation of p53. 19,20 Hence, we hypothesized that up-regulation o...

PIM1 kinase is destabilized by ribosomal stress causing inhibition of cell cycle progression

“…It is now well documented that ribosomal stress, defined as an alteration of ribosome synthesis, can induce the activation of the tumor suppressor p53 blocking cell proliferation and activating apoptosis (Pestov et al, 2001;Sulic et al, 2005;Anderson et al, 2007;Panic et al, 2007;Danilova et al, 2008;McGowan et al, 2008;Fumagalli et al, 2009). Here, we report the analysis of the effect of RPS19 deficiency on the metabolism of two erythroid cell lines.…”

“…It involves four ribosomal RNA molecules, about 80 RPs and nearly 200 non-ribosomal factors that are required for the synthesis, maturation and export of the two ribosomal subunits (Fatica and Tollervey, 2002). A number of reports suggest that perturbations of ribosome biogenesis, owing to a variety of causes (ribosomal stress), can activate a specific checkpoint and block cell proliferation mostly through a p53-dependent mechanism (Pestov et al, 2001;Rubbi and Milner, 2003;Anderson et al, 2007;Panic et al, 2007;Danilova et al, 2008;McGowan et al, 2008;Fumagalli et al, 2009). This occurs, for example, in the case of conditional deletion of RPS6 (Volarevic et al, 2000;Sulic et al, 2005) or in response to drugs that disrupt nucleolar structures (Rubbi and Milner, 2003).…”

Ribosome biogenesis surveillance: probing the ribosomal protein-Mdm2-p53 pathway

“…Although some RP imbalances predispose zebrafish to tumor development, other imbalances have, in fact, been reported to induce a p53-dependent phenotype. Deficiency in Rps19, a gene commonly mutated in Diamond-Blackfan anemia, as well as Rps8, Rps11 and Rps18, resulted in hematopoietic and developmental abnormalities that could be rescued by concomitant loss of p53 (Danilova et al, 2008). In addition, loss of Rpl11 also triggered developmental abnormalities and embryonic lethality because of p53-mediated apoptosis in morphant brains (Chakraborty et al, 2009).…”

Hematopoietic defects in rps29 mutant zebrafish depend upon p53 activation

“…Zebrafish embryos homozygous for ribosomal protein mutations can survive for several days, likely the result of maternal RNA and protein contribution. Morpholinos against rps19 and rpL11[15-17], as well as an rpL11 mutant[18], recapitulate many aspects of the DBA phenotype, including hematopoietic specific defects and p53 activation.…”