Gene expression profiles of podocyte-associated molecules as diagnostic markers in acquired proteinuric diseases.
For identifying potential diagnostic markers of proteinuric glomerulopathies, glomerular mRNA levels of molecules relevant for podocyte function (alpha-actinin-4, glomerular epithelial protein 1, Wilms tumor antigen 1, synaptopodin, dystroglycan, nephrin, podoplanin, and podocin) were determined by quantitative real-time RT-PCR from microdissected glomeruli. Biopsies from 83 patients with acquired proteinuric diseases were analyzed (minimal change disease [MCD; n = 13], benign nephrosclerosis [n = 16], membranous glomerulopathy [n = 31], focal and segmental glomerulosclerosis [FSGS; n = 9], and controls [n = 14]). Gene expression levels normalized to two different housekeeping transcripts (glyceraldehyde-3-phosphate-dehydrogenase and 18 S rRNA) did not allow a separation between proteinuric disease categories. However, a significant positive correlation between alpha-actinin-4, glomerular epithelial protein 1, synaptopodin, dystroglycan, Wilms tumor antigen 1, and nephrin was found in all analyzed glomeruli, whereas podocin mRNA expression did not correlate. Because varying amounts of housekeeper cDNA per glomerulus can confound expression ratios relevant for a subpopulation of cells, an "in silico" microdissection was performed using a podocyte-specific cDNA as a reference gene. Expression ratio of podocin to synaptopodin, the two genes with the most disparate expression, allowed a robust separation of FSGS from MCD and nephrosclerosis. Segregation of FSGS from MCD via this ratio was confirmed in an independent population of formaldehyde-fixed archival biopsies (MCD, n = 5; FSGS, n = 4) after glomerular laser capture microdissection. In addition, the expression marker was able to predict steroid responsiveness in diagnostically challenging cases of MCD versus FSGS (n = 6). As the above approach can be performed as an add-on diagnostic tool, these molecular diagnostic parameters could give novel information for the management of proteinuric diseases.
Medizinische Poliklinik, Ludwig-Maximilians-University of Munich, Munich, Germany.
Holger
H
Schmid
Anna
A
Henger
Clemens D
CD
Cohen
Karin
K
Frach
Hermann-Josef
HJ
Gröne
Detlef
D
Schlöndorff
Matthias
M
Kretzler
D000185:Actinin / Q000235:genetics / Q000378:metabolism; D000328:Adult; D000368:Aged; D015415:Biomarkers; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism; D049030:Dystroglycans; D005260:Female; D005920:Glomerular Mesangium / Q000378:metabolism*; D015433:Glomerulonephritis, Membranous / Q000175:diagnosis* / Q000378:metabolism*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism; D008875:Middle Aged; D017027:Protein Tyrosine Phosphatases / Q000235:genetics / Q000378:metabolism; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D011507:Proteinuria / Q000175:diagnosis* / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D054631:Receptor-Like Protein Tyrosine Phosphatases, Class 3; D025721:WT1 Proteins / Q000235:genetics / Q000378:metabolism; D000098853:Podoplanin
D000185:Actinin; D015415:Biomarkers; D003598:Cytoskeletal Proteins; D049030:Dystroglycans; D047908:Intracellular Signaling Peptides and Proteins; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D008840:Microfilament Proteins; D017027:Protein Tyrosine Phosphatases; D011506:Proteins; D012333:RNA, Messenger; D054631:Receptor-Like Protein Tyrosine Phosphatases, Class 3; D025721:WT1 Proteins; C111453:ACTN4 protein, human; C483081:DAG1 protein, human; C407223:NPHS2 protein; C117468:PDPN protein, human; D000098853:Podoplanin; C503967:SYNPO protein, human; C113267:nephrin; C516888:PTPRO protein, human