Deficiency of ribosomal protein (RPs) is associated with Diamond Blackfan Anemia, a congenital syndrome with bone marrow failure and variable malformations. Recent studies have demonstrated that deficiency of several RPs leads to activation of p53 and related family members, ΔNp53 and ΔNp63. In addition, P53 inhibition rescues hematopoiesis in RP-deficient mice and zebrafish. p53 activation, however, results in the alteration of many pathways and specific mechanisms leading to bone marrow failure and other defects in DBA remain unidentified. To understand the global changes in gene expression downstream of RP insufficiency, we took a system biology approach to characterize the molecular pathways involving p53. We studied pathways downstream of p53 that contribute to the RPL mutant phenotype in zebrafish. Changes in p53-dependent pathways in RPL11 mutants included dysregulation of cell cycle and apoptosis, shift in energy production from glycolysis to aerobic respiration, suppression of biosynthesis of structurally important proteins, downregulation of detoxifying enzymes, and upregulation of factors leading to activation of adrenal-pituitary axis and inflammation. Among multiple metabolic changes were those that led to increased levels of insulin and glucose. Both differentiation and production of blood were affected. Expression of genes that regulate the development and function of neural system were notably decreased, in particular, those involved in the development of anterior brain structures and eyes. The production and migration of neural crest cells were disrupted suggesting possible explanation for craniofacial and other defects observed in patients with DBA. The RPL11 mutants also had abnormal development of hematopoietic stem cells and shortened life span of mature red blood cells. Dexamethasone treatment led to downregulation of p53 expression; suppression of p53 targets mediating cell cycle arrest and apoptosis; and rescue of expression of HSC markers such as runx1. The life span of erythroid cells was also increased in response to dexamethasone treatment. These data contribute to our understanding of the molecular pathophysiology of DBA and suggest new potential targets for therapeutic intervention.
Sakamoto: Abbott Laboratories, Inc.: Research Funding; Genentech, Inc.: Research Funding.
Asterisk with author names denotes non-ASH members.