Three-dimensional structural analysis reveals a Cdk5-mediated kinase cascade regulating hepatic biliary network branching in zebrafish

• DOI: 10.1242/dev.147397
• Publication Date: 2017-07-18T11:25:26Z
• Authors: Manali Dimri; Cassandra Bilogan; Lain X. Pierce; Gregory Naegele; Amit Vasanji; Isabel Gibson; Allyson McClendon; Kevin Tae; Takuya F. Sakaguchi
• Keywords: Models, Anatomic; 0301 basic medicine; Lim Kinases; Cyclin-Dependent Kinase 5; Zebrafish Proteins; 3. Good health; Animals, Genetically Modified; Gene Knockout Techniques; 03 medical and health sciences; Bile Ducts, Intrahepatic; Imaging, Three-Dimensional; Actin Depolymerizing Factors; p21-Activated Kinases; Larva; Mutation; Morphogenesis; Animals; Computer Simulation; Protein Kinase Inhibitors; Algorithms; Zebrafish; Signal Transduction

The intrahepatic biliary network is a highly branched three-dimensional network lined by biliary epithelial cells, but how its branching patterns are precisely established is not clear. We designed a new computer-based algorithm that quantitatively computes the structural differences of the three-dimensional networks. Utilizing the algorithm, we showed that inhibition of Cyclin-dependent kinase 5 (Cdk5) led to reduced branching in the intrahepatic biliary network in zebrafish. Further, we identified a previously unappreciated downstream kinase cascade regulated by Cdk5. Pharmacological manipulations of this downstream kinase cascade produced a crowded branching defect in the intrahepatic biliary network and influenced actin dynamics in biliary epithelial cells. We generated larvae carrying a mutation in cdk5 regulatory subunit 1a (cdk5r1a), an essential activator of Cdk5. cdk5r1a mutant larvae show similar branching defects as those observed in Cdk5 inhibitor-treated larvae. A small-molecule compound that interferes with the downstream kinase cascade rescued the mutant phenotype. These results provide new insights into branching morphogenesis of the intrahepatic biliary network.