(A) Phylogenetic tree of the human, mouse, and zebrafish ABCB11 proteins. (B) ABCB11 protein sequence identity for zebrafish, mouse, and human. (C,D) Expression of the abcb11a and abcb11b transcripts in wild-type (WT) larvae at 118 hours post fertilization (hpf) by whole mount in situ hybridization. Lateral views, anterior to the left. (E-G) Confocal single-plane images showing expression of Abcb11 protein (E) and Tg(EPV.Tp1-Mmu.Hbb:EGFP)/Tg(Tp1:GFP) transgene that labels the intrahepatic biliary cells (F) in WT larva. (G) is a merged image of (E) and (F). Ventral views, anterior to the top. (H) Confocal image showing sagittal section of a WT larva at 10 days post fertilization (dpf): Abcb11 protein (red) is detected in the liver, but not in the intestine (marked by the dashed line). (I) TEM image of a bile canaliculus connecting a hepatocyte (Hep) and an intrahepatic biliary epithelial cell (IBEC) in a WT larva. TJ, tight junction. (J) Confocal three-dimensional projection image showing punctate expression of Abcb11 protein (white) along the bile canaliculi in a WT larva. The canaliculi can be recognized by bright phalloidin staining (red) due to its enrichment of F-actin cytoskeleton. Tg(Tp1:GFP) transgene expression (green) marks the intrahepatic biliary cells. (K) Diagram showing the organization of liver cells in zebrafish. Scale bars: (C,D) 1 mm; (E-H) 20 μm; (I,J) 1 μm.