Focal segmental glomerulosclerosis is induced by microRNA-193a and its downregulation of WT1

Abstract

Focal segmental glomerulosclerosis (FSGS) is a frequent and severe glomerular disease characterized by destabilization of podocyte foot processes. We report that transgenic expression of the microRNA miR-193a in mice rapidly induces FSGS with extensive podocyte foot process effacement. Mechanistically, miR-193a inhibits the expression of the Wilms' tumor protein (WT1), a transcription factor and master regulator of podocyte differentiation and homeostasis. Decreased expression levels of WT1 lead to downregulation of its target genes PODXL (podocalyxin) and NPHS1 (nephrin), as well as several other genes crucial for the architecture of podocytes, initiating a catastrophic collapse of the entire podocyte-stabilizing system. We found upregulation of miR-193a in isolated glomeruli from individuals with FSGS compared to normal kidneys or individuals with other glomerular diseases. Thus, upregulation of miR-193a provides a new pathogenic mechanism for FSGS and is a potential therapeutic target.

Integration of Cistromic and Transcriptomic Analyses Identifies Nphs2, Mafb, and Magi2 as Wilms’ Tumor 1 Target Genes in Podocyte Differentiation and Maintenance

“…Examination of the WT1-deleted mouse podocytes displayed widening and flattening of the foot processes as well as interruption of the slit diagram ( Figure 2D). 20 The glomerular basement membrane and its charge seemed unaffected by the podocyte-specific inactivation of WT1 as shown in electron microscopic analyses ( Figure 2D). These morphologic changes of WT1 mutant podocytes are, thus, consistent with WT1-controlling genes that are involved in pathways that regulate, for example, the cytoskeleton or cell-cell interaction as mentioned above.…”

“…We used quadruple transgenic mice (WT1 fl/fl ;Nphs2-rtTA;LC1), which allow us to delete WT1 in adult kidneys on doxycycline induction. 20 To minimize secondary or tertiary effects, we isolated glomeruli with a magnetic bead perfusion method after 6 days of induction of WT1 deletion. At this time point, the respective knockout mice display slight proteinuria (Supplemental Figure 2).…”

“…Podocytespecific knockout of WT1 in adult mice results in proteinuria, foot process effacement, and FSGS. 20 However, the molecular role of WT1 in podocyte differentiation and maintenance is largely unknown. Here, we have identified the WT1 direct targetome in podocytes as well as WT1 target genes that are required for podocyte differentiation and homeostasis.…”

Recent advances of animal model of focal segmental glomerulosclerosis

“…Myosin 1e (Myo1e) is one of the two Src homology 3 domain-containing "long-tailed" type I myosins in Actin filament cross-linking protein/Interacts with integrins and strengthens the podocyte-GBM interaction Atypical protein kinase C [68][69][70][71] Tight junctions/Formation of Par complex and interacts with slit diaphragm Rhophilin-1 [80] Rho GTPase activating protein 24 [80] Cytoplasm/Rho GTPase-interacting protein, integrity of glomerular filtration barrier Angiotensin II receptor [55][56][57] Angiotensin-converting enzyme [55][56][57] Membrane/pseudocyst formation at podocyte CD2-associated protein [65][66][67] CD2-associated protein [64] Insertion site of the slit diaphragm/Formation SD complex with podocin and nephrin Laminin subunit beta-2 [81][82][83][84] Laminin subunit beta-2 [81][82][83][84] Podocyte anchoring and differentiation in GBM microRNA 193α [74,75] Cytoplasm/Inhibition of expression of WT-1 Myosin 1e [49,50] Myosin 1e [49,50] Actin binding long-tailed motor protein/Regulation of actin cytoskeleton Nuclear factor of activated T cells [76,77] Transient receptor potential 6 [53,54] Membrane/the activation of calcineurin-NFAT/Wnt signaling via the increased calcium influx Podocin [46] Podocin [58,59] Insertion site of the SD/SD assembly and maintaining the signaling of nephrin Shroom family member 3 …”

“…Decreased expression levels of WT1 lead downregulation of its target genes, specifically PODXL (podocalyxin) and NPHS1 (nephrin), as well as several other genes crucial for podocyte architecture, initiating a catastrophic collapse of the entire podocytestabilizing system [74]. In mice, inhibition of miR-193a by complementary-locked nucleic acids resulted in the upregulation of the podocyte proteins synaptopodin and WT1.…”