RESEARCH ARTICLE Human Mutation Mutations in SOX17 are Associated with Congenital Anomalies of the Kidney and the Urinary Tract Stefania Gimelli,1,2 Gianluca Caridi,3 Silvana Beri,4 Kyle McCracken,5 Renata Bocciardi,6 Paola Zordan,7 Monica Dagnino,3 Patrizia Fiorio,8 Luisa Murer,9 Elisa Benetti,9 Orsetta Zuffardi,1,10 Roberto Giorda,4 James M. Wells,5 Giorgio Gimelli,8 and Gian Marco Ghiggeri3,11 1Biologia Generale e Genetica Medica, Universita` di Pavia, Pavia, Italy; 2Service of Genetic Medicine, University Hospitals of Geneva, Geneva, Switzerland; 3Laboratorio di Fisiopatologia dell’Uremia, Istituto G. Gaslini, Genova, Italy; 4IRCCS E. Medea, 23842 Bosisio Parini (LC), Italy; 5Division of Developmental Biology, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio; 6Laboratorio di Genetica Molecolare, Istituto G. Gaslini, Genova, Italy; 7Division of Regenerative Medicine, Stem Cells and Gene Therapy, S. Raffaele Scientific Institute, Milan, Italy; 8Laboratorio di Citogenetica, Istituto G. Gaslini, Genova, Italy; 9Unita` di Nefrologia, Dialisi e Trapianto, Dipartimento di Pediatria, Azienda Ospedaliera, Universita` di Padova, Padova, Italy; 10IRCCS Fondazione C. Mondino, Pavia, Italy; 11Divisione di Nefrologia, Istituto G. Gaslini, Genova, Italy Communicated by Maria Rita Passos-Bueno Received 30 April 2010; accepted revised manuscript 15 September 2010. Published online 19 October 2010 in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/humu.21378 OFFICIAL JOURNAL www.hgvs.org ABSTRACT: Congenital anomalies of the kidney and the urinary tract (CAKUT) represent a major source of morbidity and mortality in children. Several factors (PAX, SOX,WNT, RET, GDFN, and others) play critical roles during the differentiation process that leads to the formation of nephron epithelia. We have identified mutations in SOX17, an HMG-box transcription factor and Wnt signaling antagonist, in eight patients with CAKUT (seven vesico-ureteric reflux, one pelvic obstruction). One mutation, c.775T4A (p.Y259N), recurred in six patients. Four cases derived from two small families; renal scars with urinary infection represented the main symptom at presentation in all but two patients. Transfection studies indicated a 5–10-fold increase in the levels of the mutant protein relative to wild-type SOX17 in transfected kidney cells. Moreover we observed a corresponding increase in the ability of SOX17 p.Y259N to inhibit Wnt/b-catenin transcriptional activity, which is known to regulate multiple stages of kidney and urinary tract development. In conclusion, SOX17 p.Y259N mutation is recurrent in patients with CAKUT. Our data shows that this mutation correlates with an inappropriate accumulation of SOX17-p.Y259N protein and inhibition of the b-catenin/Wnt signaling pathway. These data indicate a role of SOX17 in human kidney and urinary tract development and implicate the SOX17–p.Y259N mutation as a causative factor in CAKUT. Hum Mutat 31:1352–1359, 2010. & 2010 Wiley-Liss, Inc. KEY WORDS: congenital anomalies of the kidney; CA- KUT; SOX17; Wnt Additional Supporting Information may be found in the online version of this article. Correspondence to: Giorgio Gimelli, Laboratorio di Citogenetica, Istituto G. Gaslini, Genova, Italy. E-mail: giorgiogimelli@ospedale-gaslini.ge.it Contract grant sponsor: The Italian Telethon Foundation; Contract grant number: GGP08050 (to G.M.G. and G.C.). Introduction Mammalian kidneys derive from two tissue compartments of the embryonic mesoderm, that is, the ureteric bud (UB), derived from the Wolffian duct, and the metanephric mesenchyme (MM), whose interaction induces the metanephric mesenchyme to trans- differentiate into nephron epithelia [Vainio and Lin, 2002; Woolf et al., 2004]. Failure of this mechanism, such as in ectopic or supernumerary ureters [Kume et al., 2000; Miyazaki et al., 2000; Nishimura et al., 1999], is considered an underlying cause of a wide variety of renal malformation [Mackie and Stephens, 1975; Pope et al., 1999]. Gene targeting experiments in mice have led to the characterization of specific regulators of both the conversion of epithelial into mesenchymal cells and the branching of the ureteric bud. The Wingless-related signaling pathway (Wnt), for example, is critical at several stages of the process including initiation of metanephric development [Carroll et al., 2005], branching [Majumdar et al., 2003], and development of the nephron [Stark et al., 1994]. Several Wnt ligands and receptors are expressed during kidney development and activation of the Wnt pathway results in the translocation of b-catenin into the nucleus [Karihaloo et al., 2005]. b-Catenin is a key transcriptional effector of the Wnt pathway, and it was recently demonstrated that loss of b-catenin/Wnt signaling in the developing Wolffian duct causes defects including ectopic ureters and renal aplasia [Marose et al., 2008]. Tight control of the Wnt pathway is critical for normal development, and several Wnt antagonists are expressed during kidney and urinary tract development. One example is the HMG- box transcription factor SOX17, which is known to inhibit canonical Wnt signaling by forming a complex with b-catenin and TCF/LEF family members and targeting them for degradation in a GSK3b-independent manner [Sinner et al., 2007]. Analysis of the Genito-Urinary Development database (http://www.gudmap. org) [McMahon et al., 2008] shows in situ hybridization and microarray expression data demonstrating that Sox17 is expressed at several key stages during kidney and urinary development. Specifically, Sox17 is expressed in the ureteric bud and metanephric mesenchyme of the developing kidney and urinary tract between Theiler Stage 19–23 (E11.5–15.5 days after fertilization). Here we observe a young girl with congenital defects of the urinary tract, chronic constipation, and mild mental retardation, & 2010 WILEY-LISS, INC.