Figure 2. The two isoforms of Cldn15lb are differentially expressed during development.

a–b, In situ hybridization with transcript variant-specific probes. a, cldn15lb_tv1 is not expressed at the 2-cell stage. At 42 hpf, it is expressed mainly in the liver (arrow) with some expression in the head. Its expression in the liver intensifies through 60 and 72 hpf. Low level expression is observed in the pancreas at 72 hpf (arrowhead). a′, Detailed analysis at 72 hpf shows that expression in the liver is in a unique, tree-like pattern. b, cldn15lb_tv2 is detected at 2-cell stage indicating that it is maternally deposited. cldn15lb_tv2 transcripts can be found in the gut (arrowhead), head, and pectoral fins at 42 hpf. Minimal expression of cldn15lb_tv2 is found in the liver at 72 hpf (arrow). c, Left, in situ hybridization of cldn15lb in wildtype and cloche^m39mutant larvae. Probe used was against the 3′UTR of cldn15lb and thus labels both transcripts. Right, vibratome cross section of in situ hybridization with fluorescence microscopy. In situ hybridization signal does not co-localize with GFP-positive endothelial cells and is present in cloche^m39 mutants, which lack most endothelial cells, indicating that cldn15lb is not expressed in the intrahepatic vasculature.