Claudin-1, claudin-2 and claudin-11 are present in tight junctions of choroid plexus epithelium of the mouse

The choroid plexus epithelium forms the blood-cerebrospinal fluid (CSF) bar rier and is responsible for the secretion of the CSF from the blood. The mo rphological correlate of the blood-CSF barrier are the tight junctions of c horoid plexus epithelium. By freeze-fracture electron microscopy it has bee n demonstrated that choroid plexus epithelial tight junctions form parallel strands resembling those of Sertoli cells building the blood-testis barrie r and those of the myelin sheaths of oligodendrocytes. As the oligodendrocy te specific protein/claudin-11 has been shown to be the central mediator of parallel-array tight junctions in Sertoli cells and myelin sheaths in mice , we asked whether claudin-11 is present in the tight junctions of choroid plexus epithelial cells of the mouse. Here, we present the first direct evi dence that claudin-11 besides claudin-1 and -2, occludin and the zonula occ ludens protein ZO-1 is present in choroid plexus epithelial tight junctions . During inflammation in the central nervous system such as experimental au toimmune encephalomyelitis, the molecular composition of choroid plexus epi thelial tight junctions does not change considerably. Their unique molecula r composition, with claudin-11 accompanied by claudin-1 and claudin-2 point s to a unique regulatory mechanism of the blood-CSF-barrier function. (C) 2 001 Published by Elsevier Science Ireland Ltd.