Congenital anomalies of the kidney and urinary tract (CAKUT) account for 40–50 % of chronic kidney disease that manifests in the first two decades of life. Thus far, 31 monogenic causes of isolated CAKUT have been described, explaining ~12 % of cases. To identify additional CAKUT-causing genes, we performed whole-exome sequencing followed by a genetic burden analysis in 26 genetically unsolved families with CAKUT. We identified two heterozygous mutations in SRGAP1 in 2 unrelated families. SRGAP1 is a small GTPase-activating protein in the SLIT2–ROBO2 signaling pathway, which is essential for development of the metanephric kidney. We then examined the pathway-derived candidate gene SLIT2 for mutations in cohort of 749 individuals with CAKUT and we identified 3 unrelated individuals with heterozygous mutations. The clinical phenotypes of individuals with mutations in SLIT2 or SRGAP1 were cystic dysplastic kidneys, unilateral renal agenesis, and duplicated collecting system. We show that SRGAP1 is expressed in early mouse nephrogenic mesenchyme and that it is coexpressed with ROBO2 in SIX2-positive nephron progenitor cells of the cap mesenchyme in developing rat kidney. We demonstrate that the newly identified mutations in SRGAP1 lead to an augmented inhibition of RAC1 in cultured human embryonic kidney cells and that the SLIT2 mutations compromise the ability of the SLIT2 ligand to inhibit cell migration. Thus, we report on two novel candidate genes for causing monogenic isolated CAKUT in humans.
Bibliographical noteFunding Information:
We thank the physicians and the participating families, Anna Pisarek-Horowitz for assistance with early mouse embryonic kidney dissection, and Nine V. A. M. Knoers for mutation analysis of SRGAP1 in additional affected individuals. F.H. is an Investigator of the Howard Hughes Medical Institute, and the Warren E. Grupe Professor of Pediatrics. This research was supported by grants from the National Institutes of Health (R01DK088767 to FH; R01DK078226 to WL), by the March of Dimes Foundation (6-FY11-241 to FH; 1-FY12-426 to WL), by the Excellence Initiative of the German Federal and State Governments (EXC 294 to TBH), by the Excellence Initiative of the German Research Foundation (GSC-4, Spemann Graduate School to CS), by grants from the Dutch Kidney Foundation (KSTP12_010 to AMvE; CP11.18 to KYR), by Fonds NutsOhra (1303-070 to AMvE), and by the European Community’s Seventh Framework Program FP7/2009 (305608, EURenOmics to GvdH and KYR).
© 2015, Springer-Verlag Berlin Heidelberg.
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