title: Bardet-Biedl syndrome highlights the major role of the primary cilium in efficient water reabsorption.
abstract: Studies of the primary cilium, now known to be present in all cells, have undergone a revolution, in part, because mutation of many of its proteins causes a large number of diseases, including cystic kidney disease. Bardet-Biedl syndrome (BBS) is an inherited ciliopathy characterized, among other dysfunctions, by renal defects for which the precise role of the cilia in kidney function remains unclear. We studied a cohort of patients with BBS where we found that these patients had a urinary concentration defect even when kidney function was near normal and in the absence of major cyst formation. Subsequent in vitro analysis showed that renal cells in which a BBS gene was knocked down were unciliated, but did not exhibit cell cycle defects. As the vasopressin receptor 2 is located in the primary cilium, we studied BBS-derived unciliated renal epithelial cells and found that they were unable to respond to luminal arginine vasopressin treatment and activate their luminal aquaporin 2. The ability to reabsorb water was restored by treating these unciliated renal epithelial cells with forskolin, a receptor-independent adenylate cyclase activator, showing that the intracellular machinery for water absorption was present but not activated. These findings suggest that the luminal receptor located on the primary cilium may be important for efficient transepithelial water absorption.
authors.affiliation: Laboratoire de Physiopathologie des syndromes rares héréditaires, AVENIR-Inserm, EA3949, Faculté de médecine de Strasbourg, Université de Strasbourg, Strasbourg, France. vincent.marion@unistra.fr
authors.forename: Vincent
authors.initials: V
authors.lastname: Marion
authors.forename: Dominique
authors.initials: D
authors.lastname: Schlicht
authors.forename: Anaïs
authors.initials: A
authors.lastname: Mockel
authors.forename: Sophie
authors.initials: S
authors.lastname: Caillard
authors.forename: Olivier
authors.initials: O
authors.lastname: Imhoff
authors.forename: Corinne
authors.initials: C
authors.lastname: Stoetzel
authors.forename: Paul
authors.initials: P
authors.lastname: van Dijk
authors.forename: Christian
authors.initials: C
authors.lastname: Brandt
authors.forename: Bruno
authors.initials: B
authors.lastname: Moulin
authors.forename: Hélène
authors.initials: H
authors.lastname: Dollfus
mesh_terms: D000042:Absorption; D000328:Adult; D000818:Animals; D051399:Aquaporin 2 / Q000502:physiology; D001127:Arginine Vasopressin / Q000502:physiology; D020788:Bardet-Biedl Syndrome / Q000378:metabolism*; D001834:Body Water / Q000378:metabolism*; D002478:Cells, Cultured; D018833:Chaperonins; D002923:Cilia / Q000502:physiology*; D005576:Colforsin / Q000494:pharmacology; D004847:Epithelial Cells / Q000378:metabolism; D056385:Group II Chaperonins / Q000502:physiology; D006801:Humans; D007668:Kidney / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D010641:Phenotype; D017483:Receptors, Vasopressin / Q000502:physiology
chemical_list: D051399:Aquaporin 2; C512111:BBS10 protein, human; C517002:BBS12 protein, human; C414726:MKKS protein, human; D017483:Receptors, Vasopressin; D001127:Arginine Vasopressin; D005576:Colforsin; D018833:Chaperonins; D056385:Group II Chaperonins