目标:在发育中的肝脏,称为肝细胞的双潜能上皮祖细胞进行谱系分离,形成两种主要的上皮细胞类型,构成肝实质和胆管上皮细胞(胆管细胞)的大部分肝细胞,复杂的肾小管网络,对正常的肝功能至关重要。Notch和TGFβ信号促进胆管上皮细胞片的形成,组织成不连续管状结构的导管板。这些结构如何伸长和连接以形成连续管道仍未定义。我们旨在定义导管板从简单的上皮细胞片过渡到复杂且相连的胆管的机制。
方法:通过将来自胚胎小鼠肝脏的单细胞RNA测序与遗传工具和类器官模型相结合,我们在功能上解剖了平面细胞极性在导管图案化中的作用。
结果:我们显示平面细胞极性蛋白,VANGL2在肝内胆管发育中晚期表达,并在胆管细胞之间形成细胞-细胞接触。这些细胞接触的模式调节胆管细胞内肌动蛋白细胞骨架的正常极化,而Vangl2功能的丧失导致皮质肌动蛋白重塑的异常分布,导致胆管形成失败。
结论:平面细胞极性是胆管规范后雕刻的关键步骤,对于建立正常的组织结构至关重要。
■人类疾病和小鼠模型使我们能够定义在肝脏发育过程中如何指定哺乳动物的胆道谱系。一旦这种相对简单的上皮形成,它是如何经历形态发生,形成一个复杂的分支结构尚不清楚。与肝脏和肾脏等其他分支组织相似,胆管使用平面细胞极性信号来协调细胞运动;然而,这些生化信号如何与导管模式联系在一起仍不清楚。在这里,我们展示了核心平面细胞极性蛋白,VANGL2模式细胞-细胞接触如何在哺乳动物胆管中形成,以及导管细胞如何沿导管长度传递汇合的机械变化。这项工作揭示了生物管如何在哺乳动物组织(包括肝脏内)中分布,并且对于我们如何促进导管结构错误或形成不良的患者的导管生长至关重要。
OBJECTIVE: In the developing liver, bipotent epithelial progenitor cells undergo lineage segregation to form hepatocytes, which constitute the bulk of the liver parenchyma, and biliary epithelial cells (cholangiocytes), which comprise the bile
duct (a complex tubular network that is critical for normal liver function). Notch and TGFβ signalling promote the formation of a sheet of biliary epithelial cells, the ductal plate, that organises into discontinuous tubular structures. How these structures elongate and connect to form a continuous
duct remains undefined. We aimed to define the mechanisms by which the ductal plate transitions from a simple sheet of epithelial cells into a complex and connected bile
duct.
METHODS: By combining single-cell RNA sequencing of embryonic mouse livers with genetic tools and organoid models we functionally dissected the role of planar cell polarity in
duct patterning.
RESULTS: We show that the planar cell polarity protein VANGL2 is expressed late in intrahepatic bile duct development and patterns the formation of cell-cell contacts between biliary cells. The patterning of these cell contacts regulates the normal polarisation of the actin cytoskeleton within biliary cells and loss of Vangl2 function results in the abnormal distribution of cortical actin remodelling, leading to the failure of bile duct formation.
CONCLUSIONS: Planar cell polarity is a critical step in the post-specification sculpture of the bile duct and is essential for establishing normal tissue architecture.
UNASSIGNED: Like other branched tissues, such as the lung and kidney, the bile ducts use planar cell polarity signalling to coordinate cell movements; however, how these biochemical signals are linked to ductular patterning remains unclear. Here we show that the core planar cell polarity protein VANGL2 patterns how cell-cell contacts form in the mammalian bile duct and how ductular cells transmit confluent mechanical changes along the length of a
duct. This work sheds light on how biological tubes are patterned across mammalian tissues (including within the liver) and will be important in how we promote ductular growth in patients where the duct is mis-patterned or poorly formed.