Combined NGS Approaches Identify Mutations in the Intraflagellar Transport Gene IFT140 in Skeletal Ciliopathies with Early Progressive Kidney Disease

Ciliopathies are genetically heterogeneous disorders characterized by variable expressivity and overlaps between different disease entities. This is exemplified by the short rib‐polydactyly syndromes, Jeune, Sensenbrenner, and Mainzer‐Saldino chondrodysplasia syndromes. These three syndromes are frequently caused by mutations in intraflagellar transport (IFT) genes affecting the primary cilia, which play a crucial role in skeletal and chondral development. Here, we identified mutations in IFT140, an IFT complex A gene, in five Jeune asphyxiating thoracic dystrophy (JATD) and two Mainzer‐Saldino syndrome (MSS) families, by screening a cohort of 66 JATD/MSS patients using whole exome sequencing and targeted resequencing of a customized ciliopathy gene panel. We also found an enrichment of rare IFT140 alleles in JATD compared with nonciliopathy diseases, implying putative modifier effects for certain alleles. IFT140 patients presented with mild chest narrowing, but all had end‐stage renal failure under 13 years of age and retinal dystrophy when examined for ocular dysfunction. This is consistent with the severe cystic phenotype of Ift140 conditional knockout mice, and the higher level of Ift140 expression in kidney and retina compared with the skeleton at E15.5 in the mouse. IFT140 is therefore a major cause of cono‐renal syndromes (JATD and MSS). The present study strengthens the rationale for IFT140 screening in skeletal ciliopathy spectrum patients that have kidney disease and/or retinal dystrophy.     

Rapid Response to Cyclosporin A and Favorable Renal Outcome in Nongenetic Versus Genetic Steroid–Resistant Nephrotic Syndrome

Background and objectives

Treatment of congenital nephrotic syndrome (CNS) and steroid–resistant nephrotic syndrome (SRNS) is demanding, and renal prognosis is poor. Numerous causative gene mutations have been identified in SRNS that affect the renal podocyte. In the era of high–throughput sequencing techniques, patients with nongenetic SRNS frequently escape the scientific interest. We here present the long-term data of the German CNS/SRNS Follow-Up Study, focusing on the response to cyclosporin A (CsA) in patients with nongenetic versus genetic disease.

Design, setting, participants, & measurements

Cross–sectional and longitudinal clinical data were collected from 231 patients with CNS/SRNS treated at eight university pediatric nephrology units with a median observation time of 113 months (interquartile range, 50–178). Genotyping was performed systematically in all patients.

Results

The overall mutation detection rate was high at 57% (97% in CNS and 41% in SRNS); 85% of all mutations were identified by the analysis of three single genes only (NPHS1, NPHS2, and WT1), accounting for 92% of all mutations in patients with CNS and 79% of all mutations in patients with SRNS. Remission of the disease in nongenetic SRNS was observed in 78% of patients after a median treatment period of 2.5 months; 82% of nongenetic patients responded within 6 months of therapy, and 98% of patients with nongenetic SRNS and CsA–induced complete remission (normalbuminemia and no proteinuria) maintained a normal renal function. Genetic SRNS, on the contrary, is associated with a high rate of ESRD in 66% of patients. Only 3% of patients with genetic SRNS experienced a complete remission and 16% of patients with genetic SRNS experienced a partial remission after CsA therapy.

Conclusions

The efficacy of CsA is high in nonhereditary SRNS, with an excellent prognosis of renal function in the large majority of patients. CsA should be given for a minimum period of 6 months in these patients with nongenetic SRNS. In genetic SRNS, response to CsA was low and restricted to exceptional patients.     

Do we need pacemakers resistant to magnetic resonance imaging?

AIMS: Manufacturers of pacemakers (PM) and of magnetic resonance imaging (MRI) devices state that MRI scanning of PM wearers is contraindicated. This paper tries to summarise which effects can interfere with PM, what can be hazardous, and how treatment of PM in MRI can be modified to guarantee compatibility. MATERIAL AND METHODS: All PM tested were from deceased patients. Reed contact thresholds and reactions were investigated in low magnetostatic fields and compared with those in strong magnetostatic fields. Influence of gradient fields on PM and heating due to radiofrequency (RF) pulses were estimated. Thirty Legal Medicine Departments were questioned whether deaths of PM patients during MRI are known. RESULTS: Reed contacts are influenced above 0.7 mT. In MRI fields only 28% of the PM in magnet mode remained so in all orientations. Of synchronous PM, 76% remained synchronous in all orientations. Gradient fields can influence sensing but cannot stimulate. Power density and temperature rise produced by RF fall rapidly with distance. Our question revealed six deaths. All suffered from sick-sinus-syndrome and all were not PM dependent. In three cases ventricular fibrillation was proven as the cause of death. DISCUSSION: Asynchronous pacing due to magnetostatic and gradient fields may be problematic in patients with spontaneous rhythm. To avoid them, PM triggered MRI scan restricted to refractory period is proposed. Neither inhibition of PM nor heating of the electrode poses real risks. So far, we have examined eight patients 12 times in MRI triggered mode without problems.     

Decarbonylation: A metabolic pathway of cannabidiol in humans

Cannabidiol (CBD) is a non‐psychoactive cannabinoid, which is of growing medical interest. Previous studies on the metabolism of CBD showed mainly the formation of hydroxylated or oxidized derivatives, the formation of carboxylic acids or modifications of the aliphatic side chain. Using incubation of CBD with hepatic microsomes of mice, the formation of carbon monoxide was reported. We investigated the phase I metabolism of CBD and cannabidivarin (CBDV) using in vitro experiments with human liver microsomes in order to discover so far not considered metabolites. Identification of metabolites was done by liquid chromatography coupled with quadrupole time of flight mass spectrometry (LC?QToF?MS). Within these experiments, we came across decarbonylation of CBD and CBDV. Further investigations were focused on observed decarbonylated CBD (DCBD). To confirm this metabolite in humans in vivo, plasma samples containing large amounts of cannabinoids as well as serum and urine samples, collected after a voluntary intake of a CBD‐containing food supplement, were analyzed by LC coupled to triple quadrupole mass spectrometry (LC?QQQ?MS). DCBD was detected in in vitro incubation mixtures, serum samples, and urine samples (after alkaline or enzymatic hydrolysis) collected after the voluntary intake, as well as in plasma samples of cannabis users. DCBD appears to be an important supplementary human metabolite that might be helpful for the analytical confirmation of a CBD uptake and might improve the interpretation of the consumption of CBD‐containing products. Results of this study indicate a prolonged detectability of DCBD (in serum) in comparison to CBD after oral CBD ingestion.