Role of Nephrin in Cell Junction Formation in Human Nephrogenesis

Abstract

Nephrin is a cell adhesion protein located at the slit diaphragm area of glomerular podocytes. Mutations in nephrin-coding gene (NPHS1) cause congenital nephrotic syndrome (NPHS1). We studied the developmental expression of nephrin, ZO-1 and P-cadherin in normal fetal kidneys and in NPHS1 kidneys. We used in situ hybridization and immunohistochemistry at light and electron microscopic levels. Nephrin and zonula occludens-1 (ZO-1) were first expressed in late S-shaped bodies. During capillary loop stage, nephrin and ZO-1 localized at the basal margin and in the cell-cell adhesion sites between developing podocytes, especially in junctions with ladder-like structures. In mature glomeruli, nephrin and ZO-1 concentrated at the slit diaphragm area. P-cadherin was first detected in ureteric buds, tubules, and vesicle stage glomeruli. Later, P-cadherin was seen at the basal margin of developing podocytes. Fetal NPHS1 kidneys with Fin-major/Fin-major genotype did not express nephrin, whereas the expression of ZO-1 and P-cadherin was comparable to that of control kidneys. Although early junctional complexes proved structurally normal, junctions with ladder-like structures and slit diaphragms were completely missing. The results indicate that nephrin is dispensable for early development of podocyte junctional complexes. However, nephrin appears to be essential for formation of junctions with ladder-like structures and slit diaphragms.

Nephrin Forms a Complex with Adherens Junction Proteins and CASK in Podocytes and in Madin-Darby Canine Kidney Cells Expressing Nephrin

“…17,18 To confirm the presence of P-cadherin in podocytes, we performed immunofluorescence labeling of kidney cryostat sections with P-cadherin-specific antibodies and confirmed previous work that P-cadherin is localized in podocytes (Figure 10A).…”

“…Two classes of cell adhesion molecules, those of the Ig superfamily, nephrin [3][4][5] and Neph1, 9,10 and those of the cadherin superfamily, P-cadherin 17,18 and FAT, 19 have previously been shown to be localized in part to the slit diaphragm region of podocytes. In this study we set out to determine whether nephrin interacts with adherens junction components and to identify additional binding partners of nephrin.…”

Cell junction-associated proteins IQGAP1, MAGI-2, CASK, spectrins, and α-actinin are components of the nephrin multiprotein complex

“…Junctional migration and foot process interdigitation can be followed by staining for the tight junction protein ZO-1, which localizes to the migrating junctional complex (6). Nephrin is first detected at the approximate time that junctional migration begins, when it colocalizes with ZO-1 in the junctional complex (11). P-cadherin is expressed in the renal vesicle before expression of podocalyxin and nephrin (11).…”

“…Nephrin (7) and its homologue Neph1 (8) are members of the Ig superfamily, and nephrin has been suggested to form the framework of the slit diaphragm by means of homophilic interactions between podocytes (9,10). The classical cadherin P-cadherin (2,11), another nonclassical cadherin superfamily member FAT (12), and the tight junction protein ZO-1 (6,13,14) are also localized at the slit diaphragm.…”

MAGI-1 is a component of the glomerular slit diaphragm that is tightly associated with nephrin

“…On the other hand, nephrin is a mainly localized and interacts with MAGI-1 at the level of slit diaphragm. 55 PAN treatment triggers the displacement of the slit diaphragm and highlights its roles to separate the apical and basolateral membranes. In PAN nephritic kidney, podocalyxin was found exclusively apical to the displaced slit membrane.…”