Nephronophthisis-related ciliopathies (NPHP-RCs) are a group of inherited diseases that are associated with defects in primary cilium structure and function. To identify genes mutated in NPHP-RC, we performed homozygosity mapping and whole-exome sequencing for >100 individuals, some of whom were single affected individuals born to consanguineous parents and some of whom were siblings of indexes who were also affected by NPHP-RC. We then performed high-throughput exon sequencing in a worldwide cohort of 800 additional families affected by NPHP-RC. We identified two ADAMTS9 mutations (c.4575_4576del [p.Gln1525Hisfs∗60] and c.194C>G [p.Thr65Arg]) that appear to cause NPHP-RC. Although ADAMTS9 is known to be a secreted extracellular metalloproteinase, we found that ADAMTS9 localized near the basal bodies of primary cilia in the cytoplasm. Heterologously expressed wild-type ADAMTS9, in contrast to mutant proteins detected in individuals with NPHP-RC, localized to the vicinity of the basal body. Loss of ADAMTS9 resulted in shortened cilia and defective sonic hedgehog signaling. Knockout of Adamts9 in IMCD3 cells, followed by spheroid induction, resulted in defective lumen formation, which was rescued by an overexpression of wild-type, but not of mutant, ADAMTS9. Knockdown of adamts9 in zebrafish recapitulated NPHP-RC phenotypes, including renal cysts and hydrocephalus. These findings suggest that the identified mutations in ADAMTS9 cause NPHP-RC and that ADAMTS9 is required for the formation and function of primary cilia.
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The authors thank the families who contributed to this study. F.H. is the Warren E. Grupe professor. F.H. was supported by grants from the National Institutes of Health ( DK076683 , DK068306 ). H.Y.G. was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF), funded by the Korean government (MSIT 2018R1A2A3074572 and 2018R1A5A2025079 ). S.S.A. is supported by the Allen Distinguished Investigator Program , The Paul G. Allen Frontiers Group , the American Heart Association , and the NIH-NHLBI Program of Excellence in Glycoscience HL107147 . S.N. is supported by the Mark Lauer Pediatric Research Grant . E.W. was supported by the Leopoldina Fellowship Program , German National Academy of Sciences Leopoldina ( LPDS 2015-07 ). We thank Yonsei Advanced Imaging Center in cooperation with Carl Zeiss Microscopy and Electron Microscopy Core. We also thank Dr. Seok Jun Moon (Yonsei University College of Dentistry) for sharing the SMO-GFP RPE1 cells, and we thank Drs. Shyam Bihari Bansal and Vijay Kher (Kidney Institute, Medanta, the Medicity, India).
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