Identification of nephropathy candidate genes by comparing sclerosis-prone and sclerosis-resistant mouse strain kidney transcriptomes

Abstract

BackgroundThe genetic architecture responsible for chronic kidney disease (CKD) remains incompletely described. The Oligosyndactyly (Os) mouse models focal and segmental glomerulosclerosis (FSGS), which is associated with reduced nephron number caused by the Os mutation. The Os mutation leads to FSGS in multiple strains including the ROP-Os/+. However, on the C57Bl/6J background the mutation does not cause FSGS, although nephron number in these mice are equivalent to those in ROP-Os/+ mice. We exploited this phenotypic variation to identify genes that potentially contribute to glomerulosclerosis.MethodsTo identify such novel genes, which regulate susceptibility or resistance to renal disease progression, we generated and compared the renal transcriptomes using serial analysis of gene expression (SAGE) from the sclerosis-prone ROP-Os/+ and sclerosis resistant C57-Os/+ mouse kidneys. We confirmed the validity of the differential gene expression using multiple approaches. We also used an Ingenuity Pathway Analysis engine to assemble differentially regulated molecular networks. Cell culture techniques were employed to confirm functional relevance of selected genes.ResultsA comparative analysis of the kidney transcriptomes revealed multiple genes, with expression levels that were statistically different. These novel, candidate, renal disease susceptibility/resistance genes included neuropilin2 (Nrp2), glutathione-S-transferase theta (Gstt1) and itchy (Itch). Of 34 genes with the most robust statistical difference in expression levels between ROP-Os/+ and C57-Os/+ mice, 13 and 3 transcripts localized to glomerular and tubulointerstitial compartments, respectively, from micro-dissected human FSGS biopsies. Network analysis of all significantly differentially expressed genes identified 13 connectivity networks. The most highly scored network highlighted the roles for oxidative stress and mitochondrial dysfunction pathways. Functional analyses of these networks provided evidence for activation of transforming growth factor beta (TGFβ) signaling in ROP-Os/+ kidneys despite similar expression of the TGFβ ligand between the tested strains.ConclusionsThese data demonstrate the complex dysregulation of normal cellular functions in this animal model of FSGS and suggest that therapies directed at multiple levels will be needed to effectively treat human kidney diseases.

Pharmacologic control of oxidative stress and inflammation determines whether diabetic glomerulosclerosis progresses or decreases: A pilot study in sclerosis-prone mice

“…This study “highlighted the roles for oxidative stress” and “provided evidence for activation of the pro-fibrotic and pro-inflammatory transforming growth factor β1 (TGFβ1) signal” in the genetic susceptibility to GS. These data complemented other data suggesting that the pathogenesis of DKD includes both environmental [ 9 – 11 ] and genetic factors [ 5 , 12 ] in which inflammation and oxidative stress (OS/Infl) may play pivotal roles [ 6 , 13 – 17 ].…”

“…Diabetic nephropathy (DKD), the most common form of GS in adults, is restricted to a subset of diabetic patients (~20–40%) suggesting a role for a sclerosis-prone genetic background, similar to that described in animal models [ 1 – 3 ]. Factors in addition to hyperglycemia [ 4 ] and genetic susceptibility [ 5 ] that may influence the development of DKD include gender, age and dietary intake [ 6 – 8 ].…”

“…The first successful attempt to identify components of the sclerosis-prone phenotype was a comparison of young adult ROP Os+ (sclerosis-prone) and C57 Os/+ (sclerosis-resistant) mice by transcriptomes [ 6 ]. This study “highlighted the roles for oxidative stress” and “provided evidence for activation of the pro-fibrotic and pro-inflammatory transforming growth factor β1 (TGFβ1) signal” in the genetic susceptibility to GS.…”

Improving our resolution of kidney morphogenesis across time and space

“…Hence, the number of CM cells per tip at birth may be more important than final tip number in dictating final nephron complement. Evidence already exists for variation in nephron number between mouse strains, with a clear association between reduced nephron number and onset of chronic kidney disease in the inbred FVB/N strain [42 ] and oligosyndactyly (Os) [43] mice. The acquisition of quantitative whole organ datasets on these and other strains or genetic variants will ultimately facilitate mathematical modelling to predict how best to optimise final nephron number.…”

Development of a Model of Chronic Kidney Disease in the C57BL/6 Mouse with Properties of Progressive Human CKD

“…However, this mouse has proven to be resistant to the development of CKD. C57BL/6 mice have shown resistance to the induction of CKD by standard techniques such as streptozotocin-induced diabetes [ 3 ], bovine serum albumin overload proteinuria [ 4 ], and reduced renal mass [ 5 ]. Thus, developing a mouse model of CKD on the C57BL/6 background, that shares salient pathological features of human CKD, allows the use of preexisting knockout strains.…”