COQ6 mutations in human patients produce nephrotic syndrome with sensorineural deafness
Saskia F. Heeringa, et al.
Saskia F. Heeringa, et al.
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Research Article Nephrology

COQ6 mutations in human patients produce nephrotic syndrome with sensorineural deafness

Abstract

Steroid-resistant nephrotic syndrome (SRNS) is a frequent cause of end-stage renal failure. Identification of single-gene causes of SRNS has generated some insights into its pathogenesis; however, additional genes and disease mechanisms remain obscure, and SRNS continues to be treatment refractory. Here we have identified 6 different mutations in coenzyme Q10 biosynthesis monooxygenase 6 (COQ6) in 13 individuals from 7 families by homozygosity mapping. Each mutation was linked to early-onset SRNS with sensorineural deafness. The deleterious effects of these human COQ6 mutations were validated by their lack of complementation in coq6-deficient yeast. Furthermore, knockdown of Coq6 in podocyte cell lines and coq6 in zebrafish embryos caused apoptosis that was partially reversed by coenzyme Q10 treatment. In rats, COQ6 was located within cell processes and the Golgi apparatus of renal glomerular podocytes and in stria vascularis cells of the inner ear, consistent with an oto-renal disease phenotype. These data suggest that coenzyme Q10–related forms of SRNS and hearing loss can be molecularly identified and potentially treated.

Authors

Saskia F. Heeringa, Gil Chernin, Moumita Chaki, Weibin Zhou, Alexis J. Sloan, Ziming Ji, Letian X. Xie, Leonardo Salviati, Toby W. Hurd, Virginia Vega-Warner, Paul D. Killen, Yehoash Raphael, Shazia Ashraf, Bugsu Ovunc, Dominik S. Schoeb, Heather M. McLaughlin, Rannar Airik, Christopher N. Vlangos, Rasheed Gbadegesin, Bernward Hinkes, Pawaree Saisawat, Eva Trevisson, Mara Doimo, Alberto Casarin, Vanessa Pertegato, Gianpietro Giorgi, Holger Prokisch, Agnès Rötig, Gudrun Nürnberg, Christian Becker, Su Wang, Fatih Ozaltin, Rezan Topaloglu, Aysin Bakkaloglu, Sevcan A. Bakkaloglu, Dominik Müller, Antje Beissert, Sevgi Mir, Afig Berdeli, Seza ϖzen, Martin Zenker, Verena Matejas, Carlos Santos-Ocaña, Placido Navas, Takehiro Kusakabe, Andreas Kispert, Sema Akman, Neveen A. Soliman, Stefanie Krick, Peter Mundel, Jochen Reiser, Peter Nürnberg, Catherine F. Clarke, Roger C. Wiggins, Christian Faul, Friedhelm Hildebrandt

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Figure 5

COQ6 knockdown causes apoptosis in podocytes and zebrafish embryos.

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COQ6 knockdown causes apoptosis in podocytes and zebrafish embryos. ...
(A–C) Coq6 downregulation in cultured mouse podocytes induced apoptosis that was diminished by CoQ10 treatment. Data are mean ± SEM. (A) Growth curve analysis of Coq6 knockdown clones. 20,000 podocytes were seeded per 24-well plate, plated, detached, and counted (n = 4). (B and C) Caspase-9 (B) and caspase-3 (C) activity in undifferentiated Coq6 knockdown clones by FIENA before and after CoQ10 treatment. RFUs derived from cleaved capase-9 or caspase-3 substrate peptide were measured in lysates from 1 × 106 cells (n = 3). C, control clone; No Tx, no treatment. *P < 0.001, †P < 0.05 versus control; #P < 0.005, ‡P < 0.05 versus untreated. (D–F) coq6 knockdown in zebrafish embryos 28 hours after fertilization increases apoptosis. (D) coq6-MO4 directed against zebrafish coq6 intron 7 splice donor blocked proper splicing of coq6 mRNA (see Supplemental Figure 1N). Negative controls were injected with 0.1 mM coq6 mismatch MO. Note the gray appearance of zebrafish heads upon differential interference contrast (DIC) microscopy as a sign of increased cell death. (E and F) Zebrafish dorsal head and lateral trunk views. Embryos were injected as indicated with 0.1 mM coq6-MO4 splice targeting MO (E), MO targeting the AUG translation start site (dcoq6 MO1; F), coq6 mismatch (mm) MO negative controls, or left uninjected (WT). Cells were stained by an antibody against cleaved caspase-3, a specific marker for apoptotic cells. Lens (asterisk), yolk sac (ys), and cloaca (arrow) are indicated. Scale bars: 1 mm (D); 100 μm (E and F).