CLDN1, a protein which belongs to the group of claudins, helps create a barrier preventing substances from freely passing through paracellular space and prevents neonatal ichthyosis-sclerosing cholangitis syndrome.
Claudin-1 is a protein that in humans is encoded by the CLDN1 gene. It belongs to the group of claudins. Tight junctions represent one mode of cell-to-cell adhesion in epithelial or endothelial cell sheets, forming continuous seals around cells and serving as a physical barrier to prevent solutes and water from passing freely through the paracellular space. Loss of function mutations result in neonatal ichthyosis-sclerosing cholangitis syndrome. 
