title: Tight junction proteins ZO-1, occludin, and claudins in developing and adult human perineurium.
abstract: In peripheral nerves, groups of Schwann cell-axon units are isolated from the adjacent tissues by the perineurium, which creates a diffusion barrier responsible for the maintenance of endoneurial homeostasis. The perineurium is formed by concentric layers of overlapping, polygonal perineurial cells that form tight junctions at their interdigitating cell borders. In this study, employing indirect immunofluorescence and immunoelectron microscopy, we demonstrate that claudin-1 and -3, ZO-1, and occludin, but not claudin-2, -4, and -5, are expressed in the perineurium of adult human peripheral nerve. We also describe the expression of occludin, ZO-1, claudin-1, -3, and -5 in the developing human perineurium, showing that the expressions of claudin-1 and -3, ZO-1, and occludin follow similar spatial developmental expression patterns but follow different timetables in achieving their respective adult distributions. Specifically, claudin-1 is already largely restricted to perineurium-derived structures at 11 fetal weeks, whereas claudin-3 and occludin are weakly expressed in the perineurial structures at this age and acquire a well-defined perineurial distribution only between 22 and 35 fetal weeks. ZO-1 appears to acquire its mature profile even later during the third trimester. The results of the present and previous studies show that the perineurial diffusion barrier matures relatively late during human peripheral nerve development.
authors.affiliation: Department of Medical Biochemistry and Molecular Biology, University of Turku, Kiinamyllynkatu 10, 20520 Turku, Finland.
authors.forename: Kati P
authors.initials: KP
authors.lastname: Pummi
authors.forename: Anthony M
authors.initials: AM
authors.lastname: Heape
authors.forename: Reidar A
authors.initials: RA
authors.lastname: Grénman
authors.forename: Juha T K
authors.initials: JT
authors.lastname: Peltonen
authors.forename: Sirkku A
authors.initials: SA
authors.lastname: Peltonen
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D062445:Claudin-1; D062465:Claudin-3; D062506:Claudin-4; D057167:Claudins; D005333:Fetus / Q000294:innervation; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D008565:Membrane Proteins / Q000096:biosynthesis*; D016253:Microscopy, Immunoelectron; D008875:Middle Aged; D062793:Occludin; D010525:Peripheral Nerves / Q000196:embryology / Q000254:growth & development / Q000378:metabolism*; D010750:Phosphoproteins / Q000096:biosynthesis*; D019108:Tight Junctions / Q000378:metabolism*; D062826:Zonula Occludens-1 Protein
chemical_list: C568108:CLDN1 protein, human; C491875:CLDN2 protein, human; C568122:CLDN3 protein, human; C568157:CLDN4 protein, human; D062445:Claudin-1; D062465:Claudin-3; D062506:Claudin-4; D057167:Claudins; D008565:Membrane Proteins; C568985:OCLN protein, human; D062793:Occludin; D010750:Phosphoproteins; C569042:TJP1 protein, human; D062826:Zonula Occludens-1 Protein