Pathogenic pathways are activated in each major cell type of the glomerulus in the Cd2ap mutant mouse model of focal segmental glomerulosclerosis.

Eric W Brunskill,S Steven Potter

doi:10.1186/s12882-015-0063-z

Abstract

BackgroundMutations in several genes expressed in podocytes, including Cd2ap, have been associated with focal segmental glomerulosclerosis in humans. Mutant mouse models provide an opportunity to better understand the molecular pathology that drives these diseases.MethodsIn this report we use a battery of transgenic-GFP mice to facilitate the purification of all three major cell types of the glomerulus from Cd2ap mutant mice. Both microarrays and RNA-seq were used to characterize the gene expression profiles of the podocytes, mesangial cells and endothelial cells, providing a global dual platform cross-validating dataset.ResultsThe mesangial cells showed increased expression of profibrotic factors, including thrombospondin, Tgfb2 and Tgfb3, as well as the angiogenesis factor Vegf. They also showed upregulation of protective genes, including Aldh1a2, involved in retinoic acid synthesis and Decorin, a Tgfb antagonist. Of interest, the mesangial cells also showed significant expression of Wt1, which has generally been considered podocyte specific. The Cd2ap mutant podocytes showed upregulation of proteases as well as genes involved in muscle and vasculature development and showed a very strong gene expression signature indicating programmed cell death. Endothelial cells showed increased expression of the leukocyte adhesion associated factors Vcam1 and Sele, as well as Midkine (promoting angiogenesis), endothelin and many genes responsive to cytokines and interferons.ConclusionsThis study provides a comprehensive analysis of the changing properties of the three cell types of the glomerulus in Cd2ap mutants, identifying activated and repressed pathways and responsible genes, thereby delivering a deeper molecular understanding of this genetic disease.Electronic supplementary materialThe online version of this article (doi:10.1186/s12882-015-0063-z) contains supplementary material, which is available to authorized users.

Highlights

Mutations in several genes expressed in podocytes, including Cd2ap, have been associated with focal segmental glomerulosclerosis in humans
In the kidney CD2-associated protein (CD2AP) is found in podocytes at the slit diaphragm where it interacts with nephrin and podocin [1, 2]
Mesangial expansion is a hallmark of many glomerulopathies, with increased mesangial cell proliferation and matrix production resulting in altered gomerular basement membrane permeability and blood flow

Summary

Introduction

Mutations in several genes expressed in podocytes, including Cd2ap, have been associated with focal segmental glomerulosclerosis in humans. The CD2-associated protein (CD2AP) is a widely expressed adapter protein. Mutations in Cd2ap have been associated with focal segmental glomerulosclerosis (FSGS) in humans [3,4,5]. Mice with homozygous mutation of Cd2ap develop severe nephrotic syndrome, with mesangial cell proliferation, extracellular matrix deposition, glomerulosclerosis, extensive foot process effacement and die within weeks of birth [1]. Transgene driven podocyte specific expression of Cd2ap can rescue the Cd2ap homozygous mutant lethality, showing that the podocyte is the primary site of essential Cd2ap function in the kidney [6]. The Cd2ap mutant mouse is an excellent model system for the study of podocyte dysfunction driven glomerulosclerosis

Methods

Results

Conclusion