Mutations in sphingosine-1-phosphate lyase cause nephrosis with ichthyosis and adrenal insufficiency
Svjetlana Lovric, … , Julie D. Saba, Friedhelm Hildebrandt
Svjetlana Lovric, … , Julie D. Saba, Friedhelm Hildebrandt
Published February 6, 2017
Citation Information: J Clin Invest. 2017;127(3):912-928. https://doi.org/10.1172/JCI89626.
View: Text | PDF
Research Article Genetics Nephrology

Mutations in sphingosine-1-phosphate lyase cause nephrosis with ichthyosis and adrenal insufficiency

Abstract

Steroid-resistant nephrotic syndrome (SRNS) causes 15% of chronic kidney disease cases. A mutation in 1 of over 40 monogenic genes can be detected in approximately 30% of individuals with SRNS whose symptoms manifest before 25 years of age. However, in many patients, the genetic etiology remains unknown. Here, we have performed whole exome sequencing to identify recessive causes of SRNS. In 7 families with SRNS and facultative ichthyosis, adrenal insufficiency, immunodeficiency, and neurological defects, we identified 9 different recessive mutations in SGPL1, which encodes sphingosine-1-phosphate (S1P) lyase. All mutations resulted in reduced or absent SGPL1 protein and/or enzyme activity. Overexpression of cDNA representing SGPL1 mutations resulted in subcellular mislocalization of SGPL1. Furthermore, expression of WT human SGPL1 rescued growth of SGPL1-deficient dpl1Δ yeast strains, whereas expression of disease-associated variants did not. Immunofluorescence revealed SGPL1 expression in mouse podocytes and mesangial cells. Knockdown of Sgpl1 in rat mesangial cells inhibited cell migration, which was partially rescued by VPC23109, an S1P receptor antagonist. In Drosophila, Sply mutants, which lack SGPL1, displayed a phenotype reminiscent of nephrotic syndrome in nephrocytes. WT Sply, but not the disease-associated variants, rescued this phenotype. Together, these results indicate that SGPL1 mutations cause a syndromic form of SRNS.

Authors

Svjetlana Lovric, Sara Goncalves, Heon Yung Gee, Babak Oskouian, Honnappa Srinivas, Won-Il Choi, Shirlee Shril, Shazia Ashraf, Weizhen Tan, Jia Rao, Merlin Airik, David Schapiro, Daniela A. Braun, Carolin E. Sadowski, Eugen Widmeier, Tilman Jobst-Schwan, Johanna Magdalena Schmidt, Vladimir Girik, Guido Capitani, Jung H. Suh, Noëlle Lachaussée, Christelle Arrondel, Julie Patat, Olivier Gribouval, Monica Furlano, Olivia Boyer, Alain Schmitt, Vincent Vuiblet, Seema Hashmi, Rainer Wilcken, Francois P. Bernier, A. Micheil Innes, Jillian S. Parboosingh, Ryan E. Lamont, Julian P. Midgley, Nicola Wright, Jacek Majewski, Martin Zenker, Franz Schaefer, Navina Kuss, Johann Greil, Thomas Giese, Klaus Schwarz, Vilain Catheline, Denny Schanze, Ingolf Franke, Yves Sznajer, Anne S. Truant, Brigitte Adams, Julie Désir, Ronald Biemann, York Pei, Elisabet Ars, Nuria Lloberas, Alvaro Madrid, Vikas R. Dharnidharka, Anne M. Connolly, Marcia C. Willing, Megan A. Cooper, Richard P. Lifton, Matias Simons, Howard Riezman, Corinne Antignac, Julie D. Saba, Friedhelm Hildebrandt

×

Figure 2

Biological and biochemical consequences of recessive SGPL1 mutations.

Options: View larger image (or click on image) Download as PowerPoint
Biological and biochemical consequences of recessive SGPL1 mutations. (A...
(A–F) Kidney sections of Sgpl1–/– mice (A) and Sgpl1+/+ mice (B) were stained with anti-SGPL1 (red) and WT1 antibodies (green). (B–F) Coimmunofluorescence of SGPL1 with marker proteins (green) in Sgpl1+/+ kidney: podocyte (B, WT1), ER (C, BiP), podocyte foot processes (D, synaptopodin), mesangial cells (E, α–smooth muscle actin), and endothelial cells (F, CD31). Scale bars: 25 μm. (G and H) Structural modeling of SGPL1 mutations. The 2 monomers of the SGPL1 homodimer are shown in the drawing in blue and orange, respectively. (G) p.Arg222Gln; (H) p.Ser346Ile. (I) Coimmunoprecipitation to assess dimerization of WT vs. mutant SGPL1 proteins (see also Supplemental Figure 5). Coimmunoprecipitation is representative of 3 experiments. (J) Mislocalization of variant SGPL1 proteins upon overexpression in HEK293T cells. BiP (red), or Golgi marker GOLGB1 (red), and anti-Myc antibody (green). Scale bars: 10 μm. (K) SGPL1 enzyme activity levels in transformed HEK293T cells. HEK293T cells expressing a GFP indicate endogenous SGPL1 activity levels (a vs. b and a vs. d, P < 0.0025; c vs. d, P = 0.013; a vs. c, no significant difference). (L) SGPL1 protein expression and enzyme activity levels in fibroblasts from 2 control individuals (Ctrl 1 and 2), normal human foreskin fibroblasts (Fk), and 4 individuals with SGPL1 mutations. (a vs. b, P < 0.0001.) Results are from the averages of triplicates in K and L. (M) Immunofluorescence of SGPL1 in fibroblasts. BiP (green), Golgi marker GM130 (blue), and anti-SGPL1 antibody (red). Scale bars: 25 μm. (N) PHS toxicity test. Ability to complement dpl1Δ deletion on medium containing PHS was tested for human SGPL1 WT and mutants. (O) Synthetic lethality test. Human WT and p.Glu132Gly SGPL1 expressing RH4863 survived on 5-FOA plates. However, p.Arg222Gln and p.Ser346Ile mutants did not allow for survival of DPL1 (SGPL1) deficient strains.