Qin Wei, Chen Zelin, Zhang Yihan, Yan Ruibin, Yan Guanrong, Li Song, Zhong Hanbing, Lin Shuo
Laboratory of Chemical Genomics, School of Chemical Biology and Biotechnology, Peking University Shenzhen Graduate School, Shenzhen, China.
Department of Biology, South University of Science and Technology of China, Shenzhen, Guangdong, China.
PLoS One. 2014 Jun 26;9(6):e100796. doi: 10.1371/journal.pone.0100796. eCollection 2014.
Ribosome biogenesis is an important biological process for proper cellular function and development. Defects leading to improper ribosome biogenesis can cause diseases such as Diamond-Blackfan anemia and Shwachman-Bodian-Diamond syndrome. Nucleolar proteins are a large family of proteins and are involved in many cellular processes, including the regulation of ribosome biogenesis. Through a forward genetic screen and positional cloning, we identified and characterized a zebrafish line carrying mutation in nucleolar protein with MIF4G domain 1 (nom1), which encodes a conserved nulceolar protein with a role in pre-rRNA processing. Zebrafish nom1 mutants exhibit major defects in endoderm development, especially in exocrine pancreas. Further studies revealed that impaired proliferation of ptf1a-expressing pancreatic progenitor cells mainly contributed to the phenotype. RNA-seq and molecular analysis showed that ribosome biogenesis and pre-mRNA splicing were both affected in the mutant embryos. Several defects of ribosome assembly have been shown to have a p53-dependent mechanism. In the nom1 mutant, loss of p53 did not rescue the pancreatic defect, suggesting a p53-independent role. Further studies indicate that protein phosphatase 1 alpha, an interacting protein to Nom1, could partially rescue the pancreatic defect in nom1 morphants if a human nucleolar localization signal sequence was artificially added. This suggests that targeting Pp1α into the nucleolus by Nom1 is important for pancreatic proliferation. Altogether, our studies revealed a new mechanism involving Nom1 in controlling vertebrate exocrine pancreas formation.
核糖体生物合成是细胞正常功能和发育的重要生物学过程。导致核糖体生物合成异常的缺陷可引发诸如先天性纯红细胞再生障碍性贫血和施-戴二氏综合征等疾病。核仁蛋白是一大类蛋白质，参与包括核糖体生物合成调控在内的许多细胞过程。通过正向遗传筛选和定位克隆，我们鉴定并表征了一条携带核仁蛋白MIF4G结构域1（nom1）突变的斑马鱼品系，该基因编码一种在rRNA前体加工中起作用的保守核仁蛋白。斑马鱼nom1突变体在内胚层发育中表现出主要缺陷，尤其是在外分泌胰腺方面。进一步研究表明，表达ptf1a的胰腺祖细胞增殖受损是造成该表型的主要原因。RNA测序和分子分析表明，突变胚胎中的核糖体生物合成和前体mRNA剪接均受到影响。已证明核糖体组装的几个缺陷具有p53依赖性机制。在nom1突变体中，p53缺失并不能挽救胰腺缺陷，这表明存在p53非依赖性作用。进一步研究表明，如果人工添加人核仁定位信号序列，与Nom1相互作用的蛋白磷酸酶1α可部分挽救nom1 morphants中的胰腺缺陷。这表明Nom1将Pp1α靶向核仁对胰腺增殖很重要。总之，我们的研究揭示了一种涉及Nom1控制脊椎动物外分泌胰腺形成的新机制。
