title: Complexity and developmental changes in the expression pattern of claudins at the blood-CSF barrier.
abstract: The choroid plexus epithelium controls the movement of solutes between the blood and the cerebrospinal fluid. It has been considered as a functionally more immature interface during brain development than in adult. The anatomical basis of this barrier is the interepithelial choroidal junction whose tightness has been attributed to the presence of claudins. We used quantitative real-time polymerase chain reaction, Western blot and immunohistochemistry to identify different claudins in the choroid plexuses of developing and adult rats. Claudin-1, -2, and -3 were highly and selectively expressed in the choroid plexus as compared to brain or parenchyma microvessels and were localized at epithelial junctions. Claudin-6, -9, -19, and -22 also displayed a previously undescribed choroidal selectivity, while claudin-4, -5, and -16 were enriched in the cerebral microvessels. The choroidal pattern of tight junction protein expression in prenatal brains was already complex and included occludin and zonula occludens proteins. It differed from the adult pattern in that the pore-forming claudin-2, claudin-9, and claudin-22 increased during development, while claudin-3 and claudin-6 decreased. Claudin-2 and claudin-11 presented a mirror image of abundance between lateral ventricle and fourth ventricle choroid plexuses. Imunohistochemical analysis of human fetal and postnatal brains for claudin-1, -2, and -3 demonstrated their early presence and localization at the apico-lateral border of the choroid plexus epithelial cells. Overall, choroidal epithelial tight junctions are already complex in developing brain. The observed differences in claudin expression between developing and adult choroid plexuses may indicate developmental differences in selective blood-cerebrospinal fluid transport functions.
authors.affiliation: Inserm U1028, CNRS UMR 5292, Lyon Neuroscience Research Center, Lyon-1 University, 69008 Lyon, France.
authors.forename: Ingrid
authors.initials: I
authors.lastname: Kratzer
authors.forename: Alexandre
authors.initials: A
authors.lastname: Vasiljevic
authors.forename: Catherine
authors.initials: C
authors.lastname: Rey
authors.forename: Michelle
authors.initials: M
authors.lastname: Fevre-Montange
authors.forename: Norman
authors.initials: N
authors.lastname: Saunders
authors.forename: Nathalie
authors.initials: N
authors.lastname: Strazielle
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Ghersi-Egea
mesh_terms: D000818:Animals; D001812:Blood-Brain Barrier / Q000378:metabolism*; D015153:Blotting, Western; D002831:Choroid Plexus / Q000378:metabolism; D057167:Claudins / Q000032:analysis* / Q000235:genetics*; D005260:Female; D020869:Gene Expression Profiling; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019108:Tight Junctions / Q000378:metabolism
chemical_list: D057167:Claudins