http://jasn.asnjournals.org Journal of the American Society of Nephrology RSS feed -- recent Frontiers in Nephrology articles 1533-3450 Journal of the American Society of Nephrology 1046-6673 http://jasn.asnjournals.org/icons/banner/title.gif http://jasn.asnjournals.org http://jasn.asnjournals.org/cgi/content/short/18/5/1371?rss=1 2007-04-25 info:doi/10.1681/ASN.2007030299 American Society of Nephrology 5 18 1373 2007-05-01 1371 Frontiers in Nephrology http://jasn.asnjournals.org/cgi/content/short/18/5/1374?rss=1 The phenotypes that are associated with the common forms of polycystic kidney disease (PKD)—autosomal dominant (ADPKD) and autosomal recessive (ARPKD)—are highly variable in penetrance. This is in terms of severity of renal disease, which can range from neonatal death to adequate function into old age, characteristics of the liver disease, and other extrarenal manifestations in ADPKD. Influences of the germline mutation are at the genic and allelic levels, but intrafamilial variability indicates that genetic background and environmental factors are also key. In ADPKD, the gene involved, PKD1 or PKD2, is a major factor, with ESRD occurring 20 yr later in PKD2. Mutation position may also be significant, especially in terms of the likelihood of vascular events, with 5' mutations most detrimental. Variance component analysis in ADPKD populations indicates that genetic modifiers are important, but few such factors (beyond co-inheritance of a TSC2 mutation) have been identified. Hormonal influences, especially associated with more severe liver disease in female individuals, indicate a role for nongenetic factors. In ARPKD, the combination of mutations is critical to the phenotypic outcome. Patients with two truncating mutations have a lethal phenotype, whereas the presence of at least one missense change can be compatible with life, indicating that many missense changes are hypomorphic alleles that generate partially functional protein. Clues from animal models and other forms of PKD highlight potential modifiers. The information that is now available on both genes is of considerable prognostic value with the prospects from the ongoing genetic revolution that additional risk factors will be revealed.

]]> 2007-04-25 info:doi/10.1681/ASN.2007010125 American Society of Nephrology 5 18 1380 2007-05-01 1374 Frontiers in Nephrology http://jasn.asnjournals.org/cgi/content/short/18/5/1381?rss=1 Cysts in the kidney are among the most common inherited human pathologies, and recent research has uncovered that a defect in cilia-mediated signaling activity is a key factor that leads to cyst formation. The cilium is a microtubule-based organelle that is found on most cells in the mammalian body. Multiple proteins whose functions are disrupted in cystic diseases have now been localized to the cilium or at the basal body at the base of the cilium. Current data indicate that the cilium can function as a mechanosensor to detect fluid flow through the lumen of renal tubules. Flow-mediated deflection of the cilia axoneme induces an increase in intracellular calcium and alters gene expression. Alternatively, a recent finding has revealed that the intraflagellar transport 88/polaris protein, which is required for cilia assembly, has an additional role in regulating cell-cycle progression independent of its function in ciliogenesis. Further research directed at understanding the relationship between the cilium, cell-cycle, and cilia-mediated mechanosensation and signaling activity will hopefully provide important insights into the mechanisms of renal cyst pathogenesis and lead to better approaches for therapeutic intervention.

]]> 2007-04-25 info:doi/10.1681/ASN.2006111215 American Society of Nephrology 5 18 1388 2007-05-01 1381 Frontiers in Nephrology http://jasn.asnjournals.org/cgi/content/short/18/5/1389?rss=1 Wnt signaling cascades activate morphogenetic programs that range from cell migration and proliferation to cell fate determination and stem cell renewal. These pathways enable cells to translate environmental cues into the complex cellular programs that are needed to organize tissues and build organs. Wnt signaling is essential for renal development; however, the specific molecular underpinnings involved are poorly understood. Recent research has revealed an unexpected intersection between Wnt signaling and polycystic kidney disease. Some polycystic kidney disease proteins, such as Inversin and Bardet-Biedl syndrome family members, were found to use components of the Wnt signaling cascade to orient cells along a secondary polarity axis within the plane of the epithelium. These spatial cues may be needed to position nascent tubules with a defined geometry.

]]> 2007-04-25 info:doi/10.1681/ASN.2006121355 American Society of Nephrology 5 18 1398 2007-05-01 1389 Frontiers in Nephrology http://jasn.asnjournals.org/cgi/content/short/18/5/1399?rss=1 Diagnosis and treatment of autosomal dominant polycystic kidney disease (ADPKD) is rapidly changing. Cellular pathways that involve the polycystins are being mapped and involve the primary cilium, intracellular calcium and cAMP regulation, and the mammalian target of rapamycin (mTOR) pathway. With the use of new imaging approaches, earlier diagnosis of hepatic cystic disease is possible, and measurement of kidney and cystic growth as well as kidney blood flow is possible over relatively short periods. PKD gene type, gender, proteinuria, and the presence of hypertension relate to the rate of kidney growth in ADPKD. On the basis of risk factors for progression to ESRD and the pathogenic roles that intracellular cAMP and mTOR play in cystogenesis, novel therapies are now being tested, including maximal inhibition of the renin-angiotensin system, inhibition of renal intracellular cAMP using vasopressin V2 receptor antagonists, and somatostatin analogues, as well as inhibitors of mTOR. This review addresses the current understanding of the pathogenesis and the natural history of ADPKD; accuracy and reliability of diagnostic approaches in utero, childhood, and adulthood; the value of reliable magnetic resonance imaging to measure disease progression early in the course of ADPKD; and novel therapeutic approaches that are being evaluated in ADPKD.

]]> 2007-04-25 info:doi/10.1681/ASN.2007020155 American Society of Nephrology 5 18 1407 2007-05-01 1399 Frontiers in Nephrology