Bulkhead-like apical membrane structures between hepatocytes are required 1 for anisotropic lumen expansion and liver tissue morphogenesis 2

1 Max Planck Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany. 8 2 Present address: Zentrale Mikroskopie im Biologiezentrum der Christian-Albrechts-Universität zu Kiel, 24118 Kiel, 9 Germany. 10 3 Department of Computational Molecular Biology, Max Planck Institute for Molecular Genetics, 14195 Berlin, 11 Germany. 12 4 Skolkovo Institute of Science and Technology, Skolkovo, Russia. 13 5 Lomonosov Moscow State University, Department of Chemistry, Moscow, 119991, Russia. 14 6 Present address: Institute of Applied Optics and Biophysics, Friedrich-Schiller-University Jena, Max-Wien Platz 4, 15 07743 Jena, Germany. 16 7 Nelson Laboratories LLC, Salt Lake City, Utah 84123, United States. 17 8 Lead contact 18 * Correspondence: zerial@mpi-cbg.de 19 20