Nephrin localizes to the slit pore of the glomerular epithelial cell.
BACKGROUND
Recognition that mutation of the protein nephrin, encoded by the NPHS1 gene, singly results in the cellular alterations that result in foot process effacement, and nephrotic range proteinuria emphasizes the pivotal role that this protein plays in regulating glomerular filter integrity. This article reports the development of reagents necessary to study the biology of nephrin in mouse, and describes the initial characterization of the nephrin protein.


METHODS
A cDNA including the full-length mouse nephrin open reading frame was cloned and sequenced. Immuno-affinity purified polyclonal antiserum directed against the cytoplasmic domain of mouse nephrin was developed.


RESULTS
Nephrin identified in mouse glomerular extract was found to be a glycoprotein with an apparent molecular mass of 185 kDa. As detected by indirect immunofluorescence microscopy and immunogold electron microscopy, nephrin was located only in visceral glomerular epithelial cells, where it was targeted to intercellular junctions of mature podocyte foot processes. In developing glomeruli of newborn mouse, antinephrin immunolocalized to the earliest slit pore regions between differentiating podocytes, sites where slit diaphragms first become visible.


CONCLUSIONS
As a putative cell adhesion molecule of the immunoglobulin superfamily, nephrin likely participates in cell-cell interactions between podocyte foot processes and may represent a component of the slit diaphragm.
Holzman
L B
LB
University of Michigan Medical School, 1560 Medical Science Research Building II, Ann Arbor 48109-0676, USA. lholzman@umich.edu
St John
P L
PL
Kovari
I A
IA
Verma
R
R
Holthofer
H
H
Abrahamson
D R
DR
D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn; D015152:Blotting, Northern; D002450:Cell Communication / Q000502:physiology; D003001:Cloning, Molecular; D018076:DNA, Complementary; D004847:Epithelial Cells / Q000737:chemistry* / Q000502:physiology / Q000648:ultrastructure; D005455:Fluorescent Antibody Technique; D015870:Gene Expression / Q000502:physiology; D007365:Intercellular Junctions / Q000737:chemistry*; D007678:Kidney Glomerulus / Q000166:cytology* / Q000254:growth & development; D008565:Membrane Proteins; D051379:Mice; D008810:Mice, Inbred C57BL; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D011506:Proteins / Q000032:analysis* / Q000235:genetics*; D012333:RNA, Messenger / Q000032:analysis; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic / Q000502:physiology
D018076:DNA, Complementary; D008565:Membrane Proteins; D011506:Proteins; D012333:RNA, Messenger; C113267:nephrin