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A more recent version of this article appeared on May 1, 2008
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Submitted on October 24, 2007
Revised on February 29, 2008
Accepted on March 3, 2008
*Department of Cell Biology, University of Alabama at Birmingham Medical Center, Birmingham, AL 35294;
Department of Internal Medicine/Nephrology, Yale University School of Medicine, New Haven, CT 06520;
Department of Surgery, Vanderbilt University School of Medicine, Nashville, TN 37232;
Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831
Monitoring Editor: Keith Mostov
Meckel-Gruber Syndrome (MKS), Nephronophthisis (NPHP), and Joubert Syndrome (JBTS) are a group of heterogeneous cystic kidney disorders with partially overlapping loci. Many of the proteins associated with these diseases interact and localize to cilia and/or basal bodies. One of these proteins is MKS1, which is disrupted in some MKS patients and contains a B9 motif of unknown function that is found in two other mammalian proteins, B9D2 and B9D1. Caenorhabditis elegans also has three B9 proteins: XBX-7 (MKS1), TZA-1 (B9D2), and TZA-2 (B9D1). Herein, we report that the C. elegans B9 proteins form a complex that localizes to the base of cilia. Mutations in the B9 genes do not overtly affect cilia formation unless they are in combination with a mutation in nph-1 or nph-4, the homologues of human genes (NPHP1 and NPHP4, respectively) that are mutated in some NPHP patients. Our data indicate that the B9 proteins function redundantly with the nephrocystins to regulate the formation and/or maintenance of cilia and dendrites in the amphid and phasmid ciliated sensory neurons. Together, these data suggest that the human homologues of the novel B9 genes B9D2 and B9D1 will be strong candidate loci for pathologies in human MKS, NPHP, and JBTS.