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1.  Hereditary Causes of Kidney Stones and Chronic Kidney Disease 
Pediatric nephrology (Berlin, Germany)  2013;28(10):1923-1942.
Adenine phosphoribosyltransferase (APRT) deficiency, cystinuria, Dent disease, familial hypomagnesemia with hypercalciuria and nephrocalcinosis (FHHNC) and primary hyperoxaluria (PH) are rare but important causes of severe kidney stone disease and/or chronic kidney disease in children. Recurrent kidney stone disease and nephrocalcinosis, particularly in pre-pubertal children, should alert the physician to the possibility of an inborn error of metabolism as the underlying cause. Unfortunately, the lack of recognition and knowledge of the five disorders has frequently resulted in an unacceptable delay in diagnosis and treatment, sometimes with grave consequences. A high index of suspicion coupled with early diagnosis may reduce or even prevent the serious long-term complications of these diseases. In this paper, we review the epidemiology, clinical features, diagnosis, treatment and outcome of patients with APRT deficiency, cystinuria, Dent disease, FHHNC and PH with emphasis on childhood manifestations.
PMCID: PMC4138059  PMID: 23334384
Nephrolithiasis; nephrocalcinosis; kidney failure; crystalline nephropathy; hereditary disorders; adenine phosphoribosyltransferase deficiency; 2,8-dihydroxyadeninuria; cystinuria; Dent disease; familial hypomagnesemia with hypercalciuria and nephrocalcinosis; primary hyperoxaluria
2.  Complexity of the 5′UTR region of the CLCN5 gene: eleven 5′UTR ends are differentially expressed in the human kidney 
BMC Medical Genomics  2014;7:41.
Dent disease 1 represents a hereditary disorder of renal tubular epithelial function associated with mutations in the CLCN5 gene that encoded the ClC-5 Cl-/H+ antiporter. All of the reported disease-causing mutations are localized in the coding region except for one recently identified in the 5’UTR region of a single patient. This finding highlighted the possible role for genetic variability in this region in the pathogenesis of Dent disease 1.
The structural complexity of the CLCN5 5’UTR region has not yet been fully characterized. To date 6 different 5’ alternatively used exons - 1a, 1b, 1b1 and I-IV with an alternatively spliced exon II (IIa, IIb) - have been described, but their significance and differential expression in the human kidney have not been investigated. Therefore our aim was to better characterize the CLCN5 5’UTR region in the human kidney and other tissues.
To clone more of the 5’ end portion of the human CLCN5 cDNA, total human kidney RNA was utilized as template and RNA ligase-mediated rapid amplification of cDNA 5’ ends was applied.
The expression of the different CLCN5 isoforms was studied in the kidney, leucocytes and in different tissues by quantitative comparative RT/PCR and Real -Time RT/PCR.
Eleven transcripts initiating at 3 different nucleotide positions having 3 distinct promoters of varying strength were identified. Previously identified 5’UTR isoforms were confirmed, but their ends were extended. Six additional 5’UTR ends characterized by the presence of new untranslated exons (c, V and VI) were also identified. Exon c originates exon c.1 by alternative splicing. The kidney uniquely expresses all isoforms, and the isoform containing exon c appears kidney specific. The most abundant isoforms contain exon 1a, exon IIa and exons 1b1 and c. ORF analysis predicts that all isoforms except 3 encode for the canonical 746 amino acid ClC-5 protein.
Our results confirm the structural complexity of the CLCN5 5’UTR region. Characterization of this crucial region could allow a clear genetic classification of a greater number of Dent disease patients, but also provide the basis for highlighting some as yet unexplored functions of the ClC-5 proton exchanger.
PMCID: PMC4105828  PMID: 25001568
Dent disease; CLCN5 gene; 5’UTR isoforms; mRNA variant; Gene expression
3.  An atypical Dent's disease phenotype caused by co-inheritance of mutations at CLCN5 and OCRL genes 
Dent's disease is an X-linked renal tubulopathy caused by mutations mainly affecting the CLCN5 gene. Defects in the OCRL gene, which is usually mutated in patients with Lowe syndrome, have been shown to lead to a Dent-like phenotype called Dent disease 2. However, about 20% of patients with Dent's disease carry no CLCN5/OCRL mutations. The disease's genetic heterogeneity is accompanied by interfamilial and intrafamilial phenotypic heterogeneity. We report on a case of Dent's disease with a very unusual phenotype (dysmorphic features, ocular abnormalities, growth delay, rickets, mild mental retardation) in which a digenic inheritance was discovered. Two different, novel disease-causing mutations were detected, both inherited from the patient's healthy mother, that is a truncating mutation in the CLCN5 gene (A249fs*20) and a donor splice-site alteration in the OCRL gene (c.388+3A>G). The mRNA analysis of the patient's leukocytes revealed an aberrantly spliced OCRL mRNA caused by in-frame exon 6 skipping, leading to a shorter protein, but keeping intact the central inositol 5-phosphatase domain and the C-terminal side of the ASH-RhoGAP domain. Only wild-type mRNA was observed in the mother's leukocytes due to a completely skewed X inactivation. Our results are the first to reveal the effect of an epistatic second modifier in Dent's disease too, which can modulate its expressivity. We surmise that the severe Dent disease 2 phenotype of our patient might be due to an addictive interaction of the mutations at two different genes.
PMCID: PMC3658198  PMID: 23047739
Dent's disease; Lowe syndrome; CLCN5 gene; OCRL1 gene; digenic inheritance; epistatic interaction
4.  Involvement of the Tubular ClC-Type Exchanger ClC-5 in Glomeruli of Human Proteinuric Nephropathies 
PLoS ONE  2012;7(9):e45605.
Glomerular protein handling mechanisms have received much attention in studies of nephrotic syndrome. Histopathological findings in renal biopsies from severely proteinuric patients support the likelihood of protein endocytosis by podocytes. ClC-5 is involved in the endocytosis of albumin in the proximal tubule.
To investigate whether ClC-5 is expressed in the glomerular compartment and whether it has a role in proteinuric nephropathies. ClC-5 expression was studied using Real-time PCR in manually- and laser-microdissected biopsies from patients with type 2 diabetes (n 37) and IgA nephropathy (n 10); in biopsies of membranous glomerulopathy (MG) (n 14) immunohistochemistry for ClC-5 (with morphometric analysis) and for WT1 was done. Controls: cortical tissue (n 23) obtained from unaffected parts of tumor-related nephrectomy specimens.
ClC-5 was expressed at glomerular level in all biopsies. Glomerular ClC-5 levels were significantly higher in diabetic nephropaty and MG at both mRNA and protein level (p<0.002; p<0.01). ClC-5 and WT1 double-staining analysis in MG showed that ClC-5 was localized in the podocytes. ClC-5 ultrastructural immunolocalization was demonstrated in podocytes foot processes. Our study is the first to demonstrate that ClC-5 is expressed in human podocytes. The ClC-5 overexpression found in biopsies of proteinuric patients suggests that proteinuria may play a part in its expression and that podocytes are likely to have a key role in albumin handling in proteinuric states.
PMCID: PMC3454393  PMID: 23029130
5.  Pathogenesis of nephrolithiasis: recent insight from cell biology and renal pathology 
Randall’s plaques are very common in idiopathic calcium-oxalate nephrolithiasis. These papillary plaques have an apatite mineral structure. While these calcium deposits are generally assumed to be secondary to a purely physico-chemical phenomenon, we advance the hypothesis that they form due to a truly ectopic biomineralization in the renal tissue, and that Henle’s loop epithelial cells, or pericyte-like interstitial cells, or papillary stem cells differentiating along a bone lineage might be involved.
PMCID: PMC2781203  PMID: 22460990
: CaOx renal stones, ectopic calcification, epithelial-mesenchymal transformation, papilla, Randall’s plaque
6.  Genes involved in TGFβ1-driven epithelial-mesenchymal transition of renal epithelial cells are topologically related in the human interactome map 
BMC Genomics  2007;8:383.
Understanding how mesenchymal cells arise from epithelial cells could have a strong impact in unveiling mechanisms of epithelial cell plasticity underlying kidney regeneration and repair.
In primary human tubular epithelial cells (HUTEC) under different TGFβ1 concentrations we had observed epithelial-to-mesenchymal transition (EMT) but not epithelial-myofibroblast transdifferentiation. We hypothesized that the process triggered by TGFβ1 could be a dedifferentiation event. The purpose of this study is to comprehensively delineate genetic programs associated with TGFβ1-driven EMT in our in vitro model using gene expression profile on large-scale oligonucleotide microarrays.
In HUTEC under TGFβ1 stimulus, 977 genes were found differentially expressed. Thirty genes were identified whose expression depended directly on TGFβ1 concentration. By mapping the differentially expressed genes in the Human Interactome Map using Cytoscape software, we identified a single scale-free network consisting of 2630 interacting proteins and containing 449 differentially expressed proteins. We identified 27 hub proteins in the interactome with more than 29 edges incident on them and encoded by differentially expressed genes. The Gene Ontology analysis showed an excess of up-regulated proteins involved in biological processes, such as "morphogenesis", "cell fate determination" and "regulation of development", and the most up-regulated genes belonged to these categories. In addition, 267 genes were mapped to the KEGG pathways and 14 pathways with more than nine differentially expressed genes were identified. In our model, Smad signaling was not the TGFβ1 action effector; instead, the engagement of RAS/MAPK signaling pathway seems mainly to regulate genes involved in the cell cycle and proliferation/apoptosis.
Our present findings support the hypothesis that context-dependent EMT generated in our model by TGFβ1 might be the outcome of a dedifferentiation. In fact: 1) the principal biological categories involved in the process concern morphogenesis and development; 2) the most up-regulated genes belong to these categories; and, finally, 3) some intracellular pathways are involved, whose engagement during kidney development and nephrogenesis is well known. These long-term effects of TGFβ1 in HUTEC involve genes that are highly interconnected, thereby generating a scale-free network that we named the "TGFβ1 interactome", whose hubs represent proteins that may have a crucial role for HUTEC in response to TGFβ1.
PMCID: PMC2174485  PMID: 17953753

Results 1-6 (6)