ARHGDIA mutations cause nephrotic syndrome via defective RHO GTPase signaling
Heon Yung Gee, … , Edgar A. Otto, Friedhelm Hildebrandt
Heon Yung Gee, … , Edgar A. Otto, Friedhelm Hildebrandt
Published August 1, 2013; First published July 8, 2013
Citation Information: J Clin Invest. 2013;123(8):3243-3253. https://doi.org/10.1172/JCI69134.
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Category: Research Article

ARHGDIA mutations cause nephrotic syndrome via defective RHO GTPase signaling

Abstract

Nephrotic syndrome (NS) is divided into steroid-sensitive (SSNS) and -resistant (SRNS) variants. SRNS causes end-stage kidney disease, which cannot be cured. While the disease mechanisms of NS are not well understood, genetic mapping studies suggest a multitude of unknown single-gene causes. We combined homozygosity mapping with whole-exome resequencing and identified an ARHGDIA mutation that causes SRNS. We demonstrated that ARHGDIA is in a complex with RHO GTPases and is prominently expressed in podocytes of rat glomeruli. ARHGDIA mutations (R120X and G173V) from individuals with SRNS abrogated interaction with RHO GTPases and increased active GTP-bound RAC1 and CDC42, but not RHOA, indicating that RAC1 and CDC42 are more relevant to the pathogenesis of this SRNS variant than RHOA. Moreover, the mutations enhanced migration of cultured human podocytes; however, enhanced migration was reversed by treatment with RAC1 inhibitors. The nephrotic phenotype was recapitulated in arhgdia-deficient zebrafish. RAC1 inhibitors were partially effective in ameliorating arhgdia-associated defects. These findings identify a single-gene cause of NS and reveal that RHO GTPase signaling is a pathogenic mediator of SRNS.

Authors

Heon Yung Gee, Pawaree Saisawat, Shazia Ashraf, Toby W. Hurd, Virginia Vega-Warner, Humphrey Fang, Bodo B. Beck, Olivier Gribouval, Weibin Zhou, Katrina A. Diaz, Sivakumar Natarajan, Roger C. Wiggins, Svjetlana Lovric, Gil Chernin, Dominik S. Schoeb, Bugsu Ovunc, Yaacov Frishberg, Neveen A. Soliman, Hanan M. Fathy, Heike Goebel, Julia Hoefele, Lutz T. Weber, Jeffrey W. Innis, Christian Faul, Zhe Han, Joseph Washburn, Corinne Antignac, Shawn Levy, Edgar A. Otto, Friedhelm Hildebrandt

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Figure 2

ARHGDIA, RAC1, CDC42, and RHOA colocalize and interact in rat glomeruli.

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ARHGDIA, RAC1, CDC42, and RHOA colocalize and interact in rat glomeruli....
(A) Coimmunofluorescence of ARHGDIA with podocyte marker proteins in rat glomeruli. ARHGDIA is highly expressed in podocytes, as identified by the expression of nuclear WT1. ARHGDIA partially colocalized with synaptopodin, but not with podocalyxin or GLEPP1. (B) ARHGDIA partially colocalized with the SRNS protein PLCε1 in proximal cell bodies and primary processes of podocytes. Direct fluorescent labeling of anti-PLCε1. (C) Coimmunofluorescence of ARHGDIA with the RHO GTPases RAC1, CDC42, and RHOA in adult rat glomeruli. ARHGDIA partially colocalized with RHOA, RAC1, and CDC42 in proximal cell bodies and primary processes, whereas RHOA, RAC1, and CDC42 exhibited a broad glomerular staining pattern in podocyte cell bodies and processes. Scale bars: 10 μm. (D) Coimmunoprecipitation of ARHGDIA in rat renal glomerular lysates. The protein complex precipitated by an anti-ARHDGIA antibody includes the RHO small GTPases RHOA, RAC1, and CDC42. The immunoprecipitation (IP) experiment is representative of more than 3 experiments.