CCDC103 mutations cause primary ciliary dyskinesia by disrupting assembly of ciliary dynein arms

Cilia are essential for fertilization, respiratory clearance, cerebrospinal fluid circulation and establishing laterality. Cilia motility defects cause primary ciliary dyskinesia (PCD, MIM244400), a disorder affecting 1:15,000-30,000 births. Cilia motility requires the assembly of multisubunit dynein arms that drive ciliary bending. Despite progress in understanding the genetic basis of PCD, mutations remain to be identified for several PCD-linked loci. Here we show that the zebrafish cilia paralysis mutant schmalhans (smh(tn222)) encodes the coiled-coil domain containing 103 protein (Ccdc103), a foxj1a-regulated gene product. Screening 146 unrelated PCD families identified individuals in six families with reduced outer dynein arms who carried mutations in CCDC103. Dynein arm assembly in smh mutant zebrafish was rescued by wild-type but not mutant human CCDC103. Chlamydomonas Ccdc103/Pr46b functions as a tightly bound, axoneme-associated protein. These results identify Ccdc103 as a dynein arm attachment factor that causes primary ciliary dyskinesia when mutated.     

An elaborate pathway required for Ras-mediated epigenetic silencing

The conversion of a normal cell to a cancer cell occurs in several steps and typically involves the activation of oncogenes and the inactivation of tumour suppressor and pro-apoptotic genes. In many instances, inactivation of genes critical for cancer development occurs by epigenetic silencing, often involving hypermethylation of CpG-rich promoter regions. It remains to be determined whether silencing occurs by random acquisition of epigenetic marks that confer a selective growth advantage or through a specific pathway initiated by an oncogene. Here we perform a genome-wide RNA interference (RNAi) screen in K-ras-transformed NIH 3T3 cells and identify 28 genes required for Ras-mediated epigenetic silencing of the pro-apoptotic Fas gene. At least nine of these RESEs (Ras epigenetic silencing effectors), including the DNA methyltransferase DNMT1, are directly associated with specific regions of the Fas promoter in K-ras-transformed NIH 3T3 cells but not in untransformed NIH 3T3 cells. RNAi-mediated knockdown of any of the 28 RESEs results in failure to recruit DNMT1 to the Fas promoter, loss of Fas promoter hypermethylation, and derepression of Fas expression. Analysis of five other epigenetically repressed genes indicates that Ras directs the silencing of multiple unrelated genes through a largely common pathway. Last, we show that nine RESEs are required for anchorage-independent growth and tumorigenicity of K-ras-transformed NIH 3T3 cells; these nine genes have not previously been implicated in transformation by Ras. Our results show that Ras-mediated epigenetic silencing occurs through a specific, complex, pathway involving components that are required for maintenance of a fully transformed phenotype.     

Modelling how ribavirin improves interferon response rates in hepatitis C virus infection

Nearly 200 million individuals worldwide are currently infected with hepatitis C virus (HCV). Combination therapy with pegylated interferon and ribavirin, the latest treatment for HCV infection, elicits long-term responses in only about 50% of patients treated. No effective alternative treatments exist for non-responders. Consequently, significant efforts are continuing to maximize response to combination therapy. However, rational therapy optimization is precluded by the poor understanding of the mechanism(s) of ribavirin action against HCV. Ribavirin alone induces either a transient early decline or no decrease in HCV viral load, but in combination with interferon it significantly improves long-term response rates. Here we present a model of HCV dynamics in which, on the basis of growing evidence, we assume that ribavirin decreases HCV infectivity in an infected individual in a dose-dependent manner. The model quantitatively predicts long-term response rates to interferon monotherapy and combination therapy, fits observed patterns of HCV RNA decline in patients undergoing therapy, reconciles conflicting observations of the influence of ribavirin on HCV RNA decline, provides key insights into the mechanism of ribavirin action against HCV, and establishes a framework for rational therapy optimization.     

Abscisin II-kinetin interaction in leaf senescence

Zusammenfassung Abscisin II, eine natürlich vorkommende, die Abtrennung beschleunigende Substanz, erhöhte das Altern von Blattscheiben vonArabidopsis sehr. Dieser Effekt von Abscisin II blieb jedoch beinahe vollständig unterdrückt, wenn Kinetin gleichzeitig zugefügt wurde.