title: Claudin-2 is selectively expressed in proximal nephron in mouse kidney.
abstract: The proximal nephron possesses a leaky epithelium with unique paracellular permeability properties that underlie its high rate of passive NaCl and water reabsorption, but the molecular basis is unknown. The claudins are a large family of transmembrane proteins that are part of the tight junction complex and likely form structural components of a paracellular pore. To localize claudin-2 in the mouse kidney, we performed in situ hybridization using an isoform-specific riboprobe and immunohistochemistry using a polyclonal antibody directed against a COOH-terminal peptide. Claudin-2 mRNA and protein were found throughout the proximal tubule and in the contiguous early segment of the thin descending limb of long-looped nephrons. The level of expression demonstrated an axial increase from proximal to distal segments. In confocal images, the subcellular localization of claudin-2 protein coincided with that of the tight junction protein ZO-1. Our findings suggest that claudin-2 is a component of the paracellular pathway of the most proximal segments of the nephron and that it may be responsible for their uniquely leaky permeability properties.
authors.affiliation: Renal Division and Membrane Biology Program, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA.
authors.forename: A H
authors.initials: AH
authors.lastname: Enck
authors.forename: U V
authors.initials: UV
authors.lastname: Berger
authors.forename: A S
authors.initials: AS
authors.lastname: Yu
mesh_terms: D000818:Animals; D057167:Claudins; D005455:Fluorescent Antibody Technique; D005982:Glutathione Transferase / Q000235:genetics; D015151:Immunoblotting; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D007687:Kidney Tubules, Proximal / Q000737:chemistry*; D008138:Loop of Henle / Q000737:chemistry; D008565:Membrane Proteins / Q000032:analysis* / Q000235:genetics; D051379:Mice; D009399:Nephrons / Q000737:chemistry*; D015347:RNA Probes; D016372:RNA, Antisense; D012333:RNA, Messenger / Q000032:analysis; D011993:Recombinant Fusion Proteins; D014018:Tissue Distribution
chemical_list: D057167:Claudins; C113371:Cldn2 protein, mouse; D008565:Membrane Proteins; D015347:RNA Probes; D016372:RNA, Antisense; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D005982:Glutathione Transferase