Mutations in INVS encoding inversin cause nephronophthisis type 2, linking renal cystic disease to the function of primary cilia and left-right axis determination.

Nephronophthisis (NPHP), an autosomal recessive cystic kidney disease, leads to chronic renal failure in children. The genes mutated in NPHP1 and NPHP4 have been identified, and a gene locus associated with infantile nephronophthisis (NPHP2) was mapped. The kidney phenotype of NPHP2 combines clinical features of NPHP and polycystic kidney disease (PKD). Here, we identify inversin (INVS) as the gene mutated in NPHP2 with and without situs inversus. We show molecular interaction of inversin with nephrocystin, the product of the gene mutated in NPHP1 and interaction of nephrocystin with beta-tubulin, a main component of primary cilia. We show that nephrocystin, inversin and beta-tubulin colocalize to primary cilia of renal tubular cells. Furthermore, we produce a PKD-like renal cystic phenotype and randomization of heart looping by knockdown of invs expression in zebrafish. The interaction and colocalization in cilia of inversin, nephrocystin and beta-tubulin connect pathogenetic aspects of NPHP to PKD, to primary cilia function and to left-right axis determination.

Causes and risk factors for death in systemic sclerosis: a study from the EULAR Scleroderma Trials and Research (EUSTAR) database.

OBJECTIVES: To determine the causes and predictors of mortality in systemic sclerosis (SSc). METHODS: Patients with SSc (n=5860) fulfilling the American College of Rheumatology criteria and prospectively followed in the EULAR Scleroderma Trials and Research (EUSTAR) cohort were analysed. EUSTAR centres completed a structured questionnaire on cause of death and comorbidities. Kaplan-Meier and Cox proportional hazards models were used to analyse survival in SSc subgroups and to identify predictors of mortality. RESULTS: Questionnaires were obtained on 234 of 284 fatalities. 55% of deaths were attributed directly to SSc and 41% to non-SSc causes; in 4% the cause of death was not assigned. Of the SSc-related deaths, 35% were attributed to pulmonary fibrosis, 26% to pulmonary arterial hypertension (PAH) and 26% to cardiac causes (mainly heart failure and arrhythmias). Among the non-SSc-related causes, infections (33%) and malignancies (31%) were followed by cardiovascular causes (29%). Of the non-SSc-related fatalities, 25% died of causes in which SSc-related complications may have participated (pneumonia, sepsis and gastrointestinal haemorrhage). Independent risk factors for mortality and their HR were: proteinuria (HR 3.34), the presence of PAH based on echocardiography (HR 2.02), pulmonary restriction (forced vital capacity below 80% of normal, HR 1.64), dyspnoea above New York Heart Association class II (HR 1.61), diffusing capacity of the lung (HR 1.20 per 10% decrease), patient age at onset of Raynaud's phenomenon (HR 1.30 per 10 years) and the modified Rodnan skin score (HR 1.20 per 10 score points). CONCLUSION: Disease-related causes, in particular pulmonary fibrosis, PAH and cardiac causes, accounted for the majority of deaths in SSc.

Renal perfusion in scleroderma patients assessed by microbubble-based contrast-enhanced ultrasound.

OBJECTIVES: Renal damage is common in scleroderma. It can occur acutely or chronically. Renal reserve might already be impaired before it can be detected by laboratory findings. Microbubble-based contrast-enhanced ultrasound has been demonstrated to improve blood perfusion imaging in organs. Therefore, we conducted a study to assess renal perfusion in scleroderma patients utilizing this novel technique. MATERIALS AND METHODOLOGY: Microbubble-based contrast agent was infused and destroyed by using high mechanical index by Siemens Sequoia (curved array, 4.5 MHz). Replenishment was recorded for 8 seconds. Regions of interests (ROI) were analyzed in renal parenchyma, interlobular artery and renal pyramid with quantitative contrast software (CUSQ 1.4, Siemens Acuson, Mountain View, California). Time to maximal Enhancement (TmE), maximal enhancement (mE) and maximal enhancement relative to maximal enhancement of the interlobular artery (mE%A) were calculated for different ROIs. RESULTS: There was a linear correlation between the time to maximal enhancement in the parenchyma and the glomerular filtration rate. However, the other parameters did not reveal significant differences between scleroderma patients and healthy controls. CONCLUSION: Renal perfusion of scleroderma patients including the glomerular filtration rate can be assessed using microbubble-based contrast media.

A gene mutated in nephronophthisis and retinitis pigmentosa encodes a novel protein, nephroretinin, conserved in evolution.

Nephronophthisis (NPHP) comprises a group of autosomal recessive cystic kidney diseases, which constitute the most frequent genetic cause for end-stage renal failure in children and young adults. The most prominent histologic feature of NPHP consists of development of renal fibrosis, which, in chronic renal failure of any origin, represents the pathogenic event correlated most strongly to loss of renal function. Four gene loci for NPHP have been mapped to chromosomes 2q13 (NPHP1), 9q22 (NPHP2), 3q22 (NPHP3), and 1p36 (NPHP4). At all four loci, linkage has also been demonstrated in families with the association of NPHP and retinitis pigmentosa, known as "Senior-Løken syndrome" (SLS). Identification of the gene for NPHP type 1 had revealed nephrocystin as a novel docking protein, providing new insights into mechanisms of cell-cell and cell-matrix signaling. We here report identification of the gene (NPHP4) causing NPHP type 4, by use of high-resolution haplotype analysis and by demonstration of nine likely loss-of-function mutations in six affected families. NPHP4 encodes a novel protein, nephroretinin, that is conserved in evolution--for example, in the nematode Caenorhabditis elegans. In addition, we demonstrate two loss-of-function mutations of NPHP4 in patients from two families with SLS. Thus, we have identified a novel gene with critical roles in renal tissue architecture and ophthalmic function.