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Kidney Week

Abstract: FR-PO994

A Bioinformatics Analysis of Gene Expression in Experimental Alport Syndrome Reveals an Fstl1 Signature in the Kidney

Session Information

Category: Genetic Diseases of the Kidney

  • 1002 Genetic Diseases of the Kidney: Non-Cystic

Authors

  • Maksimowski, Nicholas, University of Toronto, Toronto, Ontario, Canada
  • Song, Xuewen, University of Toronto, Toronto, Ontario, Canada
  • Bae, Eun Hui, Chonnam National University Hospital, Gwangju, Korea (the Republic of)
  • Pei, York P., University Health Network and University of Toronto, Toronto, Ontario, Canada
  • Scholey, James W., University of Toronto, Toronto, Ontario, Canada
Background

Alport syndrome (AS) is a rare inherited form of chronic kidney disease characterized by progressive nephropathy and the development of end stage renal disease. It is caused by mutations in the Col4a3, Col4a4, and Col4a5 genes. The goal of my studies is to better understand the pathogenesis of AS in the kidney.

Methods

We performed studies using a well-characterized experimental murine model of AS. Global gene expression profiling of renal cortical mRNA samples was performed in male Col4a3-/- mice and Col4a3+/+ control mice at 4 and 7 weeks of age to identify early differentially expressed genes. We performed a cluster analysis and constructed a heat map on the microarray studies at 4 and 7 weeks of age. Studies using HK2 cells were conducted to analyze inflammation and apoptosis related to a protein of interest and its cognate receptor. Finally, using a transgenic mouse model with a reduction in our protein of interest we performed UUO at 7 weeks of age.

Results

The microarray analysis revealed that only 5 genes were differentially expressed in the kidneys of male Col4a3-/- mice at 4 weeks of age compared to Col4a3+/+. Amongst these genes was Follistatin-related protein 1 (FSTL1). We used search tool for the retrieval of interacting genes/proteins to predict protein-protein interactions (PPIs) thereby identifying a functional protein association network for FSTL1. The network included 39 proteins. Cluster analysis of the cognate genes from the FSTL1 protein network showed marked upregulation of gene expression at 7 weeks of age. FSTL1 increased NFκB mediated luciferase activity, caspase 3 activation and PARP cleavage in HK2 cells. These effects were due, at least in part to TLR4 receptor activation. The RT-qPCR analysis of mice that were subjected to UUO surgery showed an increase in FSTL1 expression as well as an increase in the expression of FSTL1’s cognate receptors compared to sham controls.

Conclusion

Our microarray and bioinformatics analyses identified early upregulation of FSTL1 in the kidneys of Col4a3-/- mice. A FSTL1 gene signature, based on predicted PPIs, emerged in the kidneys by 7 weeks of age. FSTL1 elicited an inflammatory response and activated apoptosis in HK2 cells. These findings support the hypothesis that FSTL1 may be a novel determinant of kidney injury in mice with experimental AS.