The renal segmental distribution of claudins changes with development.
BACKGROUND
Permeability properties of mammalian nephron are tuned during postnatal maturation. The transepithelial electrical resistance (TER) and complexity of tight junctions (TJs) vary along the different tubular segments, suggesting that the molecules constituting this structure change. We studied the differential expression of occludin and several claudins in isolated renal tubules from newborn and adult rabbits.


METHODS
Isolated renal tubules from newborn and adult rabbits were processed for occludin, claudin-1 and claudin-2 immunofluorescence, and Western blot detection of claudin-1 and -2. Claudin-5 was detected in whole kidney frozen sections. RT-PCR from isolated tubules was performed for claudins-1 to -8.


RESULTS
Immunofluorescence revealed that occludin, claudin-1 and -2 were present at the cell boundaries at the neonatal stage of development. Claudin-1 was detected in the tighter segments of the nephron (distal and collecting duct), while claudin-2 was found in the leaky portions (proximal). Claudin 5 was found in the kidney vasculature. PCR amplification revealed the presence of claudins-1 to -4 in tubules of newborns. In adults, claudins-1, -2 and -4 were present in proximal, Henle's loop and collecting segments; claudin-3 was in proximal and collecting tubules, while claudins-5 and -6 were absent from all tubular portions. Claudin-7 was restricted to proximal tubules, while claudin-8 was present in proximal and Henle's segments.


CONCLUSIONS
The pattern of occludin distribution is present from the neonatal age. Claudins-7 and -8 are up-regulated after birth. Each tubular segment expresses a peculiar set of claudins that might be responsible for the permeability properties of their TJs.
Center for Research and Advanced Studies (CINVESTAV), Department of Physiology, Biophysics and Neurosciences, México City, Mexico.
Jose Luis
JL
Reyes
Monica
M
Lamas
Dolores
D
Martin
Maria
M
del Carmen Namorado
Socorro
S
Islas
Jose
J
Luna
Michel
M
Tauc
Lorenza
L
González-Mariscal
D000818:Animals; D015153:Blotting, Western; D002458:Cell Fractionation; D062445:Claudin-1; D062465:Claudin-3; D062506:Claudin-4; D062507:Claudin-5; D057167:Claudins; D005455:Fluorescent Antibody Technique; D018507:Gene Expression Regulation, Developmental; D007684:Kidney Tubules / Q000737:chemistry / Q000254:growth & development / Q000502:physiology*; D008297:Male; D008565:Membrane Proteins / Q000032:analysis / Q000235:genetics*; D009399:Nephrons / Q000737:chemistry / Q000254:growth & development / Q000502:physiology*; D062793:Occludin; D011817:Rabbits; D019108:Tight Junctions / Q000737:chemistry
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; D062507:Claudin-5; D057167:Claudins; C568113:Cldn1 protein, mouse; C568123:Cldn3 protein, mouse; C568158:Cldn4 protein, mouse; C491511:Cldn5 protein, mouse; D008565:Membrane Proteins; C568985:OCLN protein, human; D062793:Occludin; C568986:Ocln protein, mouse; C502011:claudin 8; C122101:claudin 6