Nucleolar Protein Nop2 Promotes Neural Differentiation by Regulating Ribosome Biogenesis-related Processes
The NOP2 nucleolar protein (NOP2) serves pivotal functions in ribosome biogenesis, cell cycle regulation and embryonic development, yet its spatiotemporal dynamics and mechanistic contributions to neural development remain elusive. Through CRISPR/Cas9-mediated knockout modeling in zebrafish, we demonstrated that NOP2 nucleolar protein homolog (yeast) (nop2) deficiency induced embryonic lethality within 3-5 days post-fertilization (dpf), accompanied by pathognomonic microcephaly and cerebral edema. Mechanistic analysis suggested that nop2 ablation triggered differentiation impairment in neural progenitors, which accumulated extensively in brain tissue and led to impaired generation of neurons and glial cells. In addition, nop2 deficiency activated p53-dependent apoptosis in neural cells. Biochemical characterization revealed compromised pre-ribosomal particle processing in mutants, establishing defective ribosome biogenesis as the primary molecular lesion. Ribosome profiling (Ribo-seq) uncovered aberrant regulation of nervous system processes and activation of p53-mediated apoptosis in neural cells. Genetic epistasis experiments demonstrated that tp53 mutation partially rescued neurogenic defects and reduced cerebral edema, but failed to rescue microcephaly. These findings provide evidence supporting the role of Nop2 as a significant regulator in neural development. Our results demonstrate that Nop2 promotes neural differentiation by regulating ribosome biogenesis-related processes, thereby extending our previous research on rRNA metabolism-related genes in neurodevelopment. Moreover, our study provides critical insights into developing early interventions against neurodevelopmental disorders associated with ribosomopathies. Overall design: For Ribo-seq: Brain tissues of siblilng and nop2 mutant zebrafish at 48 hpf were isolated in  1xPBS at 4°C, rapidly froze in liquid nitrogen, and sent to Gene Denovo for ribosome sequencing. Ribosomes were separated, and sequencing libraries were prepared. For RNA-BS-seq: We collected brain tissues of these two zebrafish groups mention above at 48 hpf in pre-cooling 1xPBS, rapidly frozen them in liquid nitrogen, and sent E-GENE for RNA bisulfite sequencing. mRNA was isolated, bisulfite-converted, and purified. Libraries were generated through cDNA synthesis and PCR amplification.