The Wt1^+/R394W Mouse Displays Glomerulosclerosis and Early-Onset Renal Failure Characteristic of Human Denys-Drash Syndrome

Abstract

Renal failure is a frequent and costly complication of many chronic diseases, including diabetes and hypertension. One common feature of renal failure is glomerulosclerosis, the pathobiology of which is unclear. To help elucidate this, we generated a mouse strain carrying the missense mutation Wt1 R394W, which predisposes humans to glomerulosclerosis and early-onset renal failure (Denys-Drash syndrome [DDS]). Kidney development was normal in Wt1؉/R394W heterozygotes. However, by 4 months of age 100% of male heterozygotes displayed proteinuria and glomerulosclerosis characteristic of DDS patients. This phenotype was observed in an MF1 background but not in a mixed B6/129 background, suggestive of the action of a strain-specific modifying gene(s). WT1 encodes a nuclear transcription factor, and the R394W mutation is known to impair this function. Therefore, to investigate the mechanism of Wt1 R394W-induced renal failure, the expression of genes whose deletion leads to glomerulosclerosis (NPHS1, NPHS2, and CD2AP) was quantitated. In mutant kidneys, NPHS1 and NPHS2 were only moderately downregulated (25 to 30%) at birth but not at 2 or 4 months. Expression of CD2AP was not changed at birth but was significantly upregulated at 2 and 4 months. Podocalyxin was downregulated by 20% in newborn kidneys but not in kidneys at later ages. Two other genes implicated in glomerulosclerosis, TGFB1 and IGF1, were upregulated at 2 months and at 2 and 4 months, respectively. It is not clear whether the significant alterations in gene expression are a cause or a consequence of the disease process. However, the data do suggest that Wt1 R394W-induced glomerulosclerosis may be independent of downregulation of the genes for NPHS1, NPHS2, CD2AP, and podocalyxin and may involve other genes yet to be implicated in renal failure. The Wt1 R394W mouse recapitulates the pathology and disease progression observed in patients carrying the same mutation, and the mutation is completely penetrant in male animals. Thus, it will be a powerful and biologically relevant model for investigating the pathobiology of the earliest events in glomerulosclerosis.Glomerulosclerosis, whether primary or secondary to other disease processes, is a key and common feature of progressive renal failure, which is a major cause of morbidity and mortality in the United States. Although several genetic and environmental insults are known to cause primary glomerulosclerosis, the cellular mechanism by which they initiate this process is still largely unknown. A knowledge of these mechanisms would greatly aid in identifying strategies to prevent or slow the development of glomerulosclerosis, regardless of its etiology.Glomeruli are complex and specialized structures responsible for blood filtration in the kidney and are targets of injury in a number of human diseases. The major functional features of the glomerulus are capillary loops lined with fenestrated endothelial cells, supporting mesangial cells, the glomerular basement membrane (GBM), and podocytes. The "octopuslike" ...

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