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Systematic analysis of a human renal transcript dataset

ABSTRACT: Glomerular diseases account for the majority of cases with chronic renal failure. Several genes have been identified with key relevance for glomerular function. Quite a few of these genes show a specific or preferential mRNA expression in the renal glomerulus. To identify additional candidate genes involved in glomerular function in humans we generated a human renal glomerulus-specific transcript dataset (GTD) by comparing gene expression profiles from human glomeruli and tubulointerstitium obtained from six transplant living donors using Affymetrix HG-U133A arrays. This analysis resulted in 677 genes with prominent overrepresentation in the glomerulus. Genes with ‘a prior’i established known prominent glomerular expression served for validation and were all found in the novel expression library (e.g. CDKN1, DAG1, DDN, EHD3, MYH9, NES, NPHS1, NPHS2, PDPN, PLA2R1, PLCE1, PODXL, PTPRO, SYNPO, TCF21, TJP1, WT1). The mRNA expression for several novel glomerulus-enriched genes identified in REGGEL was validated by qRT-PCR. Gene ontology and pathway analysis identified biological processes previously not reported to be of relevance in glomeruli including among others axon guidance. This finding was further validated by assessing the expression of the axon guidance molecules neuritin (NRN1) and roundabout receptor ROBO1 and -2. Glomerular disease associated differential mRNA regulation of ROBO2 was found in diabetic nephropathy. In summary, using a comparative strategy on microdissected nephrons novel transcripts with predominant expression in the human glomerulus could be identified. A systematic analysis of this glomerulus-specifc gene expression library allows the detection of target molecules and biological processes involved in glomerular biology and renal disease.

ORGANISM(S): Homo sapiens

PROVIDER: GSE21785 | GEO | 2010/07/19

SECONDARY ACCESSION(S): PRJNA127311

REPOSITORIES: GEO

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Project description:Glomerular diseases account for the majority of cases with chronic renal failure. Several genes have been identified with key relevance for glomerular function. Quite a few of these genes show a specific or preferential mRNA expression in the renal glomerulus. To identify additional candidate genes involved in glomerular function in humans we generated a human renal glomerulus-specific transcript dataset (GTD) by comparing gene expression profiles from human glomeruli and tubulointerstitium obtained from six transplant living donors using Affymetrix HG-U133A arrays. This analysis resulted in 677 genes with prominent overrepresentation in the glomerulus. Genes with ‘a prior’i established known prominent glomerular expression served for validation and were all found in the novel expression library (e.g. CDKN1, DAG1, DDN, EHD3, MYH9, NES, NPHS1, NPHS2, PDPN, PLA2R1, PLCE1, PODXL, PTPRO, SYNPO, TCF21, TJP1, WT1). The mRNA expression for several novel glomerulus-enriched genes identified in REGGEL was validated by qRT-PCR. Gene ontology and pathway analysis identified biological processes previously not reported to be of relevance in glomeruli including among others axon guidance. This finding was further validated by assessing the expression of the axon guidance molecules neuritin (NRN1) and roundabout receptor ROBO1 and -2. Glomerular disease associated differential mRNA regulation of ROBO2 was found in diabetic nephropathy. In summary, using a comparative strategy on microdissected nephrons novel transcripts with predominant expression in the human glomerulus could be identified. A systematic analysis of this glomerulus-specifc gene expression library allows the detection of target molecules and biological processes involved in glomerular biology and renal disease. Sample from kidney biopsies of 6 transplant Living Donors (LD) were microdissected into tubular and glomerular compartment and separately hybridized an Affymetrix HG-U133A microarrays. Background correction and quantile normalization was ferformed using RMAexpress Version 0.3 as part of a dataset of 88 samples for glomeruli and 84 samples for tubuli. All data are reported in log2 scale. A background filter cut-off was defined to lower the count of false positive calls using the highest signal value obtained from non-human Affymetrix control oligonucleotides multiplied by a factor of 1.2, following previous studies: Schmid H, Boucherot A, Yasuda Y, et al.: Modular activation of nuclear factor-kappaB transcriptional programs in human diabetic nephropathy. Diabetes 55:2993-3003, 2006 A linear model was fit to compensate differences in expression due to separate sample processing of the compartments. Subsequently, genes were selected based on foldchange.

Project description:The Wilms tumor-suppressor gene WT1, a key player in renal development, also has a crucial role in maintenance of the glomerulus in the mature kidney. However, molecular pathways orchestrated by WT1 in podocytes, where it is highly expressed, remain unknown. Their defects are thought to modify the cross-talk between podocytes and other glomerular cells and ultimately lead to glomerular sclerosis, as observed in diffuse mesangial sclerosis (DMS) a nephropathy associated with WT1 mutations. To identify podocyte WT1 targets, we generated a novel DMS mouse line, performed gene expression profiling in isolated glomeruli, and identified excellent candidates that may modify podocyte differentiation and growth factor signalling in glomeruli. Scel, encoding sciellin, a protein of the cornified envelope in the skin, and sulf1, encoding a 6-O endosulfatase, are shown to be expressed in wild type podocytes and to be strongly down-regulated in mutants. Co-expression of Wt1, Scel and Sulf1 was also found in a mesonephric cell line, and siRNA-mediated knockdown of WT1 decreased Scel and Sulf1 mRNAs and proteins. By ChIP we show that Scel and Sulf1 are direct WT1 targets. Cyp26a1, encoding an enzyme involved in the degradation of retinoic acid, is shown to be up-regulated in mutant podocytes. Cyp26a1 may play a role in the development of glomerular lesions but does not seem to be regulated by WT1. These results provide novel clues in our understanding of normal glomerular function and early events involved in glomerulosclerosis. Experiment Overall Design: Isolation of glomeruli from mutant (FVB-N4 Wt1+/R394W) and wild-type (FVB-N4 Wt1+/+) was performed after cardiac Dynabead perfusion. GeneChip analysis of glomeruli from 5 Wt1+/R394W mice and 5 Wt1+/+ littermates (N4-FVB) were performed independently. Animals were unweaned 27-day-old males. The Wt1+/R394W mice used were showing little albuminuria (<3 ug/ul on Coomassie blue stained SDS-PAGE gel) and no evidence of mesangial lesions by light microscopy.

Project description:To gain molecular insight into kidney function, we performed a high-resolution quantitative analysis of gene expression in glomeruli and nine different nephron seg-ments dissected from mouse kidney using the long-SAGE method. We also developed dedicated bioinformatics tools and databases to annotate mRNA tags as transcripts. Over 800,000 mRNA SAGE tags were sequenced corresponding to >20,000 different mRNA tags present at least twice in at least one library. Hierarchical clustering analysis of tags demonstrated similarities between the three anatomical sub-segments of the proximal tubule, between the cortical and medullary segments of the thick ascending limb of Henle’s loop, and between the three segments constituting the aldosterone sensitive distal nephron segments, whereas the glomerulus and distal convoluted tubule clusterized independently. We also identified highly specific mRNA markers of each subgroup of nephron segments and of most nephron segments. Tag annotation also identified numbers of putative antisense mRNAs. This database constitutes a reference resource in which the quantitative expression of a given gene can be compared with that of other genes in the same nephron segment, or between different segments of the nephron. To illustrate possible applications of this database, we performed a deeper analysis of the glomerulus transcriptome which unexpectedly revealed expression of several ion and water carriers; within the glomerulus, they were found to be preferentially expressed in the parietal sheet. It also revealed the major role of the zinc finger transcription factor Wt1 in the specificity of gene expression in the glomerulus. Finally, functional annotation of glomerulus-specific transcripts showed the high proliferation activity of glomerular cells. Immunolabelling with anti-PCNA antibodies confirmed a high percentage of proliferating glomerular parietal cells. Approximately 1000 tubules from each different nephron segments were microdissected from 6-8 male CD1 mice. Over 800,000 mRNA SAGE tags were sequenced corresponding to >20,000 different mRNA tags present at least twice in at least one library.

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Systematic analysis of a human renal transcript dataset

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