Molecular biology and nuclear medicine in pediatric hydronephrosis.

Pediatric hydronephrosis may correspond to very different clinical situations, ranging from fully benign reversible dilatation to severe obstructive nephropathy. The genetic research is difficult, mainly because the condition is probably polygenic and the embryology of the urinary system is very complex and depends on a multifaceted interaction of genetic and environmental factors. Molecular biology has gained new insights in the complicated urinary system and in the mechanisms of obstructive nephropathy. Some mediators (tumor growth factor, tumor necrosis factor, renin angiotensin system, etc.) could be considered molecular markers of obstruction and it has been proposed to introduce them in clinical decision making, in order to make an accurate selection of patients needing surgical correction. Scintigraphy has been a standard procedure in the management of pediatric hydronephrosis for decades and has been used in many clinical studies designed to evaluate the role of selected molecular markers in clinical settings. The relationships between scintigraphic parameters and molecular mediators seems promising, in particular for the evaluation of the Reanin Angiotensin System, which plays many roles in the natural history of pediatric hydronephrosis. Angiotensin up-regulation is a turning point in many pediatric hydronephrosis and can be unveiled by captopril scintigraphy, which allows a timely diagnosis of obstruction, before irreversible parenchymal injury and loss of renal functio

Renal hypoplasia without optic coloboma associated with PAX2 gene deletion

PAX2 gene encodes a transcription factor that belongs to the paired-box family of homeotic genes and is widely expressed during the development of both ductal and mesenchymal components of the urogenital system. Human PAX2 gene maps on chromosome 10q24-q25 and comprises 12 exons. Exons 1\u20134 encode the paired box domain, which is essential for DNA-binding activity. At early stages, the gene is expressed in neural tube cells. Later on, its expression is detected in the developing urogenital system as well as in the ear, eye and central nervous system (CNS). In the urogenital system, PAX2 is expressed in the induced nephrogenic mesenchyme, during the mesenchymal-to-epithelial transition that preludes to glomerulus formation. Its expression is also detected in the branching ureteric bud, in collecting duct epithelia and in uterus, oviduct, vas deferent and epidydimis. PAX2 is thought to orchestrate the pattern of gene expression, including that of other PAX family members, also during other organ development. In humans, PAX2 heterozygous mutations, arising de novo or inherited in an autosomal dominant fashion, have been associated with renal coloboma syndrome (RCS) (OMIM 120330). Phenotypic features of the syndrome have been related to PAX2 haploinsufficiency. Haploinsufficiency deals with the notion that level of protein is critical to its correct function. RCS hallmarks are bilateral optic nerve coloboma and renal hypoplasia. The term coloboma includes developmental abnormalities of the optic nerve (ranging from mild optic disc dysplasia to optic nerve aplasia), retina, choroid and iris [1]. Renal hypoplasia is the most common renal abnormality (60% of patients). Oligomeganephronia, renal dysplasia or multicystic dysplastic kidney have also been reported [2\u20134]. Additional congenital anomalies may \u202

mRNA sequencing of a novel NPHS2 intronic mutation in a child with focal and segmental glomerulosclerosis

The NPHS2 gene encodes podocin, a membrane protein that acts as the structural scaffold in podocyte foot processes. NPHS2 mutations are associated with steroid-resistant neph-rotic syndrome (SRNS), with the pathologic variant being focal and segmental glomerulosclerosis (FSGS), an emerging cause of end-stage renal disease in children. We describe a novel NPHS2 sequence variant in a girl with SRNS. Onset occurred at the age of seven years, with edema, hypo-proteinemia, hypoalbuminemia, hypercholesterolemia, hypertriglyceridemia and nephrotic protei-nuria. Renal function was normal and autoimmunity markers were negative. Proteinuria failed to decrease after standard steroid therapy. Renal biopsy showed FSGS. Cyclosporine therapy was instituted, but no remission of proteinuria was achieved and chronic renal failure developed. Mole-cular analysis of the NPHS2 gene revealed a homozygous nucleotide substitution in position c.451+3A>T in intron 3-4. This nucleotide substitution has not been reported in the literature till date. The effect of the detected substitution on podocin protein was demonstrated by renal biopsy RNA extraction and cDNA amplification analysis. This technique had never been applied to a NPHS2 mutation. Based on these results, immunosuppressive drugs were discontinued and conser-vative therapy was undertaken

PAX2 gene mutations in pediatric and young adult transplant recipients: kidney and urinary tract malformations without ocular anomalies.

Heterozygous humans for PAX2 mutations show autosomal dominant papillorenal syndrome (PRS), consisting of ocular colobomas, renal hypo/dysplasia and progressive renal failure in childhood. PAX2 mutations have also been identified in patients with isolated renal hypo/dysplasia. Twenty unrelated children and young adults with kidney and urinary tract malformations and no ocular abnormalities were retrospectively recruited for PAX2 mutational analysis. All patients had undergone renal transplantation after end-stage renal disease. We identified two new sequence variations: (i) a deletion causing a frameshift (c.69delC) and (ii) a nucleotide substitution determining a splice site mutation (c.410+5 G/A) by predictive analysis. Therefore, we suggest PAX2 molecular analysis to be extended to all patients with congenital malformations of kidney and urinary tract (CAKUT)

The impact of eNOS, MTR and MTHFR polymorphisms on renal graft survival in children and young adults.

BACKGROUND: The main cause of reduced long-term graft survival is chronic allograft injury. Cardiovascular risk factors such as hyperhomocysteinaemia, accumulation of asymmetric dimethylarginine, increased oxidative stress and decreased production of nitric oxide seem to play an important role. Functional polymorphisms of the endothelial isoform of nitric oxide synthase (NOS) gene cause an alteration in nitric oxide production. Nitric oxide levels, and thus oxidative stress, are also influenced by hyperhomocysteinaemia. METHODS: We carried out a genetic analysis of endothelial nitric oxide synthase (eNOS) 894G>T, methionine synthase (MTR) 2756A>G and methylenetetrahydrofolate reductase (MTHFR) 677C>T/1298A>C in 268 renal allograft recipient/donor (D/R) matches, with respect to long-term graft survival. RESULTS: While MTHFR 677C>T/1298A>G and MTR 2756A>G polymorphism distribution in both recipients (R) and donors (D) showed no significant difference between matches with loss of graft function and those with long-term graft survival, the frequency of the eNOS 894TT genotype of donors was significantly increased (P = 0.040) in matches with better graft survival. The multivariate analysis identified the eNOS 894 genotype and clinically acute rejection episodes as independent risk factors for graft loss (P = 0.0406 and P = 0.0093, respectively). CONCLUSIONS: The association between eNOS 894G>T polymorphism of donors and graft survival seems to suggest a role for this gene in chronic allograft injury; however, further studies are needed to confirm this hypothesis

Interleukin-8 and CXCR1 receptor functional polymorphisms and susceptibility to acute pyelonephritis

PURPOSE: We performed a case-control study in children diagnosed by the first episode of upper urinary tract infection with or without vesicoureteral reflux to evaluate the association of functional polymorphism of interleukin-8 (-251A>T and +2767A>G), and its receptor CXCR1 (+2607G>C). MATERIALS AND METHODS: Genomic DNA was obtained from 265 children with a clinical and laboratory diagnosis of urinary tract infection who were recruited in northeast Italy. The children were subdivided as 173 who were dimercapto-succinic acid scan positive with positive static renal scintigraphy in acute conditions, consistent with the diagnosis of acute pyelonephritis, and 92 who were dimercapto-succinic acid scan negative. Genetic analysis for the same polymorphisms was also extended to a control population of 106 umbilical cord DNA samples. RESULTS: Statistical analysis of genotype data showed that 1) the tested populations were in Hardy-Weinberg equilibrium, 2) there were significant differences between the dimercapto-succinic acid scan positive and negative groups (p=0.049), and the dimercapto-succinic acid scan positive group vs controls (p=0.032) in terms of interleukin-8 -251A>T polymorphism frequency, 3) there was also a significant difference in the distribution of IL-8 -251A>T and +2767A>G polymorphisms between dimercapto-succinic acid scan positive and negative children in the subgroup without vesicoureteral reflux (p=0.03 and 0.02, respectively) and 4) no significant differences were found in the frequency of the distribution of CXCR1 +2607G>C polymorphism in all groups. CONCLUSIONS: These data suggest that the gene for the proinflammatory chemokine interleukin-8 is involved in susceptibility to acute pyelonephritis during upper urinary tract infection in children with or without vesicoureteral reflux

Upper Urinary Tract Infections Are Associated with RANTES Promoter Polymorphism

We evaluated the association between MCP-1, CCR2, RANTES, and CCR5 gene polymorphisms and upper urinary tract infection in 273 children recruited in Northeast Italy. Statistical analysis of RANTES-403 G>A genotype frequencies showed that children carrying the RANTES-403 G allele are at higher risk for urinary tract infection, irrespective of vesicoureteral reflux