Nucleolar Protein 56 Deficiency in Zebrafish Leads to Developmental Abnormalities and Anemia via p53 and JAK2-STAT3 Signaling

SIMPLE SUMMARY: Ribosomopathies are a series of disorders caused by ribosomal dysfunction, usually causing tissue-specific defects such as anemia. Defects in several nucleolar proteins have been observed in human ribosomopathies. It remains to be determined whether any other ribosome proteins are involved in regulating erythropoiesis. We generated a nucleolar protein 56 (nop56)(−/−) zebrafish model using the CRISPR/Cas9 system and investigated its function. A nop56 deficiency induced severe morphological abnormalities and anemia. The erythroid lineage in definitive hematopoiesis and the maturation of erythroid cells were impaired in the nop56 mutants. Additionally, the p53 signaling pathway and the JAK2-STAT3 signaling pathway were abnormally activated in the mutants. The knockdown of p53 signaling using morpholino partially rescued the malformation, and the inhibition of JAK2 partially rescued the anemic phenotype. This study suggests that nop56 is a potential target for investigation in erythropoietic disorders, particularly those that may be associated with JAK-STAT activation. ABSTRACT: Ribosomes are the vital molecular machine for protein translation in a cell. Defects in several nucleolar proteins have been observed in human ribosomopathies. In zebrafish, a deficiency in these ribosomal proteins often results in an anemic phenotype. It remains to be determined whether any other ribosome proteins are involved in regulating erythropoiesis. Here, we generated a nucleolar protein 56 (nop56)(−/−) zebrafish model and investigated its function. A nop56 deficiency induced severe morphological abnormalities and anemia. WISH analysis showed that the specification of the erythroid lineage in definitive hematopoiesis and the maturation of erythroid cells were impaired in the nop56 mutants. Additionally, transcriptome analysis revealed that the p53 signaling pathway was abnormally activated, and the injection of a p53 morpholino partially rescued the malformation, but not the anemia. Moreover, qPCR analysis showed that the JAK2-STAT3 signaling pathway was activated in the mutants, and the inhibition of JAK2 partially rescued the anemic phenotype. This study suggests that nop56 is a potential target for investigation in erythropoietic disorders, particularly those that may be associated with JAK-STAT activation.