Abstract
Podocin (NPHS2) is a component of the glomerular slit membrane with major regulatory functions in the renal permeability of proteins. A loss of podocin and a decrease in its resynthesis can influence the outcome of renal diseases with nephrotic syndrome, such as minimal change glomerulonephritis, focal segmental glomerulosclerosis (FSGS) and membranous nephropathy. The transcriptional regulation of podocin may play a major role in these processes. We defined the transcriptional regulation of the human podocin gene and the influence of single nucleotide polymorphisms (SNPs) within its promoter region in the podocytes using reporter gene constructs and gel shift analysis. In addition, we took genomic DNA from healthy Caucasian blood donors and from biopsies of kidneys with defined renal diseases and screened it for podocin promoter SNPs. Our data shows that the transcription of podocin is mainly regulated by the transcription factor Lmx1b, which binds to a FLAT-F element and displays enhancer function. With the SNP variant −116T, there was a significant reduction in luciferase activity, and nuclear protein binding was observed, while the SNP −670C/T did not display functionality. The allelic distribution of −116C/T in patients with kidney diseases leading to nephrotic syndrome was not significantly different from that in the control group. Our data indicates that among other factors, podocin is specifically regulated by the transcription factor Lmx1b and by the functional polymorphism -116C/T. However, there is no association between −116C/T and susceptibility to minimal change glomerulonephritis, focal segmental glomerulosclerosis or membranous nephropathy.
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