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An Efficient Sieving Method to Isolate Intact Glomeruli from Adult Rat Kidney
Published on: November 1, 2018
Podocyte-specific Crb2 knockout mice develop focal segmental glomerulosclerosis
Akiko Tanoue1, Kan Katayama2,3, Yugo Ito4,5
1Department of Cardiology and Nephrology, Mie University Graduate School of Medicine, 2-174 Edobashi, Tsu, Mie, 514-8507, Japan.
Abstract:
Crb2 is a cell polarity-related type I transmembrane protein expressed in the apical membrane of podocytes. Knockdown of crb2 causes glomerular permeability defects in zebrafish, and its complete knockout causes embryonic lethality in mice. There are also reports of Crb2 mutations in patients with steroid-resistant nephrotic syndrome, although the precise mechanism is unclear. The present study demonstrated that podocyte-specific Crb2 knockout mice develop massive albuminuria and microhematuria 2-month after birth and focal segmental glomerulosclerosis and tubulointerstitial fibrosis with hemosiderin-laden macrophages at 6-month of age. Transmission and scanning electron microscopic studies demonstrated injury and foot process effacement of podocytes in 6-month aged podocyte-specific Crb2 knockout mice. The number of glomerular Wt1-positive cells and the expressions of Nphs2, Podxl, and Nphs1 were reduced in podocyte-specific Crb2 knockout mice compared to negative control mice. Human podocytes lacking CRB2 had significantly decreased F-actin positive area and were more susceptible to apoptosis than their wild-type counterparts. Overall, this study's results suggest that the specific deprivation of Crb2 in podocytes induces altered actin cytoskeleton reorganization associated with dysfunction and accelerated apoptosis of podocytes that ultimately cause focal segmental glomerulosclerosis.
Insights
Loss of cell polarity protein Crb2 in kidney podocytes causes focal segmental glomerulosclerosis. This protein deficiency leads to podocyte injury, apoptosis, and impaired kidney function, highlighting its critical role in glomerular health.
Area of Science:
- Nephrology
- Cell Biology
- Molecular Medicine
Background:
- Crumbs homologue 2 (Crb2) is a cell polarity protein crucial for kidney podocyte function.
- Mutations in CRB2 are linked to steroid-resistant nephrotic syndrome, but the underlying mechanisms remain unclear.
Purpose of the Study:
- To investigate the role of podocyte-specific Crb2 in the development of kidney disease.
- To elucidate the cellular and molecular mechanisms by which Crb2 deficiency leads to podocyte dysfunction and glomerulosclerosis.
Main Methods:
- Generation and analysis of podocyte-specific Crb2 knockout mice.
- Assessment of kidney function through urinalysis (albuminuria, microhematuria).
- Histopathological examination including electron microscopy and immunohistochemistry for podocyte markers (Wt1, Nphs2, Podxl, Nphs1).
- In vitro studies on human podocytes lacking CRB2 to assess F-actin organization and apoptosis.
Main Results:
- Podocyte-specific Crb2 knockout mice exhibited massive albuminuria and microhematuria by 2 months, progressing to focal segmental glomerulosclerosis and tubulointerstitial fibrosis by 6 months.
- Electron microscopy revealed podocyte injury and foot process effacement in knockout mice.
- Reduced glomerular Wt1-positive cells and decreased expression of key podocyte markers (Nphs2, Podxl, Nphs1) were observed.
- Human podocytes lacking CRB2 showed reduced F-actin area and increased susceptibility to apoptosis.
Conclusions:
- Podocyte-specific Crb2 deficiency induces significant alterations in the actin cytoskeleton, leading to podocyte dysfunction and apoptosis.
- These cellular changes ultimately result in the development of focal segmental glomerulosclerosis.
- Crb2 is essential for maintaining podocyte integrity and preventing glomerular disease.
