Institute of Developmental Biology and Regenerative Medicine, Southwest University, Beibei, Chongqing, China.
University of Chinese Academy of Sciences (Chongqing), Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Beibei, Chongqing, China.
Hepatology. 2023 Jul 1;78(1):167-178. doi: 10.1097/HEP.0000000000000186. Epub 2023 Jan 3.
In cases of end-stage liver diseases, the proliferation of existing hepatocytes is compromised, a feature of human chronic liver disease, in which most hepatocytes are dysfunctional. So far, liver transplantation represents the only curative therapeutic solution for advanced liver diseases, and the shortage of donor organs leads to high morbidity and mortality worldwide. The promising treatment is to prompt the biliary epithelial cells (BECs) transdifferentiation. However, the critical factors governing the initiation of BEC-derived liver regeneration are largely unknown. The zebrafish has advantages in large-scale genetic screens to identify the critical factors involved in liver regeneration. Here, we combined N-ethyl-N-nitrosourea screen, positional cloning, transgenic lines, antibody staining, and in situ hybridization methods and identified a liver regeneration defect mutant ( lrd ) using the zebrafish extensive liver injury model. Through positional cloning and genomic sequencing, we mapped the mutation site to rngtt . Loss of rngtt leads to the defects of BEC dedifferentiation, bipotential progenitor cell activation, and cell proliferation in the initiation stage of liver regeneration. The transdifferentiation from BECs to hepatocytes did not occur even at the late stage of liver regeneration. Mechanically, Rngtt transcriptionally regulates the attachment of mRNA cap to mTOR complex 1 (mTORC1) components and dnmt1 to maintain the activation of mTORC1 and DNA methylation in BECs after severe liver injury and prompt BEC to hepatocyte conversion. Furthermore, rptor and dnmt1 mutants displayed the same liver regeneration defects as rngtt mutation. In conclusion, our results suggest Rngtt is a new factor that initiates BEC-derived liver regeneration.
在终末期肝脏疾病中，现有肝细胞的增殖受到损害，这是人类慢性肝病的一个特征，其中大多数肝细胞功能失调。迄今为止，肝移植是治疗晚期肝病的唯一有效治疗方法，而供体器官的短缺导致全球发病率和死亡率居高不下。有前途的治疗方法是促使胆管上皮细胞（BEC）转分化。然而，控制 BEC 衍生的肝再生起始的关键因素在很大程度上尚不清楚。斑马鱼在大规模基因筛选中具有优势，可以鉴定参与肝再生的关键因素。在这里，我们结合 N-乙基-N-亚硝基脲筛选、定位克隆、转基因系、抗体染色和原位杂交方法，使用斑马鱼广泛的肝损伤模型鉴定了一个肝再生缺陷突变体（lrd）。通过定位克隆和基因组测序，我们将突变位点映射到 rngtt。rngtt 的缺失导致 BEC 去分化、双潜能祖细胞激活和肝再生起始阶段细胞增殖的缺陷。即使在肝再生的晚期，BEC 也不会向肝细胞转化。在机制上，Rngtt 转录调节 mRNA 帽与 mTOR 复合物 1（mTORC1）成分和 dnmt1 的结合，以维持严重肝损伤后 BEC 中 mTORC1 和 DNA 甲基化的激活，并促使 BEC 向肝细胞转化。此外，rptor 和 dnmt1 突变体表现出与 rngtt 突变相同的肝再生缺陷。总之，我们的结果表明 Rngtt 是启动 BEC 衍生的肝再生的一个新因素。
