A novel nicotinic acetylcholine receptor antagonist radioligand for PET studies

Using positron emission tomography (PET) with a specific and selective radioligand targeting nicotinic acetylcholine receptor (nAChR) would allow us to better understand various nAChR related CNS disorders. The use of radiolabeled nAChR antagonists would provide a much safer pharmacological profile, avoiding most peripheral side effects that might be generated from radiolabeled nAChR agonists even at the tracer level; thus, PET imaging with nAChR antagonists would facilitate clinical application. A potent and selective nAChR antagonist was labeled and characterized with PET in non-human primates. Its high brain uptake, high signal-to-noise ratio, and high specific binding strongly suggest a great potential to carry out imaging studies in humans. In addition, the use of a C-11 radiotracer would allow us to perform multiple PET studies in the same individual within a short time frame. The presence of an iodine atom in the molecule also allows the possibility to label with radioiodine for SPECT studies.     

2-Aminobenzimidazoles as potent Aurora kinase inhibitors

This Letter describes the discovery and key structure–activity relationship (SAR) of a series of 2-aminobenzimidazoles as potent Aurora kinase inhibitors. 2-Aminobenzimidazole serves as a bioisostere of the biaryl urea residue of SNS-314 (1c), which is a potent Aurora kinase inhibitor and entered clinical testing in patients with solid tumors. Compared to SNS-314, this series of compounds offers better aqueous solubility while retaining comparable in vitro potency in biochemical and cell-based assays; in particular, 6m has also demonstrated a comparable mouse iv PK profile to SNS-314.     

Split versions of Cleave and Rescue selfish genetic elements for measured self limiting gene drive

Gene drive elements promote the spread of linked traits, providing methods for changing the composition or fate of wild populations. Drive mechanisms that are self-limiting are attractive because they allow control over the duration and extent of trait spread in time and space, and are reversible through natural selection as drive wanes. Self-sustaining Cleave and Rescue (ClvR) elements include a DNA sequence-modifying enzyme such as Cas9/gRNAs that disrupts endogenous versions of an essential gene, a tightly linked recoded version of the essential gene resistant to cleavage (the Rescue), and a Cargo. ClvR spreads by creating loss-of-function (LOF) conditions in which those without ClvR die because they lack functional copies of the essential gene. We use modeling to show that when the Rescue-Cargo and one or both components required for LOF allele creation (Cas9 and gRNA) reside at different locations (split ClvR), drive of Rescue-Cargo is self-limiting due to a progressive decrease in Cas9 frequency, and thus opportunities for creation of LOF alleles, as spread occurs. Importantly, drive strength and duration can be extended in a measured manner—which is still self-limiting—by moving the two components close enough to each other that they experience some degree of linkage. With linkage, Cas9 transiently experiences drive by hitchhiking with Rescue-Cargo until linkage disequilibrium between the two disappears, a function of recombination frequency and number of generations, creating a novel point of control. We implement split ClvR in Drosophila, with key elements on different chromosomes. Cargo/Rescue/gRNAs spreads to high frequency in a Cas9-dependent manner, while the frequency of Cas9 decreases. These observations show that measured, transient drive, coupled with a loss of future drive potential, can be achieved using the simple toolkit that make up ClvR elements—Cas9 and gRNAs and a Rescue/Cargo.     

Dielectric behaviour and conformational stability of collagen on interaction with DNA

Collagen-DNA interaction studies will aid in improving the stability of DNA against nucleases. In the present study, the effect of DNA on different physico-chemical properties of collagen like viscosity, conformation and dielectric behaviour has been studied. Increase of DNA concentration leads to the increment of viscosity of collagen at the pH 4 and 5, but the trend is reversed at the pH of 6 and 7 due to the formation of collagen fibrils. The temperature dependent CD spectroscopic studies for collagen-DNA conjugate showed that thermal stability of collagen is modulated with increasing molar concentration of DNA. It also shows that DNA interactions with collagen did not result in change in the triple helical structure of collagen. Impedance measurements show that the strength of ion pairs for different molar concentrations of collagen-DNA conjugates has changed. Nyquist plot for collagen-DNA conjugate posses higher Y″ at DNA concentration of 1:25 and 1:50 whereas at 1:1 and 1:10 lower Y″ than the native collagen have been observed. An understanding of this nature of the collagen-DNA interactions is helpful for gene delivery applications.     

Inactivation of Retinoblastoma Protein (Rb1) in the Oocyte: Evidence That Dysregulated Follicle Growth Drives Ovarian Teratoma Formation in Mice

The origin of most ovarian tumors is undefined. Here, we report development of a novel mouse model in which conditional inactivation of the tumor suppressor gene Rb1 in oocytes leads to the formation of ovarian teratomas (OTs). While parthenogenetically activated ooctyes are a known source of OT in some mutant mouse models, enhanced parthenogenetic propensity in vitro was not observed for Rb1-deficient oocytes. Further analyses revealed that follicle recruitment and growth is disrupted in ovaries of mice with conditional inactivation of Rb1, leading to abnormal accumulation of secondary/preantral follicles. These findings underpin the concept that miscues between the germ cell and somatic compartments cause premature oocyte activation and the formation of OTs. Furthermore, these results suggest that defects in folliculogenesis and a permissive genetic background are sufficient to drive OT development, even in the absence of enhanced parthenogenetic activation. Thus, we have discovered a novel role of Rb1 in regulating the entry of primordial oocytes into the pool of growing follicles and signaling between the oocyte and granulosa cells during the protracted process of oocyte growth. Our findings, coupled with data from studies of other OT models, suggest that defects in the coordinated regulation between growth of the oocyte and somatic components in follicles are an underlying cause of OT formation.     

Initial licking responses of mice to sweeteners: effects of tas1r3 polymorphisms

Recent studies have established that the T1R3 receptor plays a central role in the taste-mediated ingestive response to sweeteners by mice. First, transgenic mice lacking the gene for T1R3, Tas1r3, show dramatically reduced lick responsiveness to most sweeteners. Second, strains with the taster allele of Tas1r3 (T strains) are more sensitive to low sweetener concentrations than strains with the nontaster allele (NT strains) and consume greater quantities of low- to midrange concentrations of sweeteners during 24-h tests. We asked how Tas1r3 polymorphisms influence the initial licking responses of four T strains (FVB/NJ, SWR/J, SM/J, and C57BL/6J) and four NT strains (BALB/cJ, 129P3/J, DBA/2J, and C3H/HeJ) to two sweeteners (sucrose and SC-45647, an artificial sweetener). We used the initial licking response as a measure of the taste-mediated ingestive response because its brief duration minimizes the potential contribution of nontaste factors (e.g., negative and positive postingestive feedback). Further, we used two complimentary short-term intake tests (the brief-access taste test and a novel 1-min preference test) to reduce the possibility that our findings were an epiphenomenon of a specific testing procedure. In both tests, the T strains were more responsive than the NT strains to low concentrations of each sweetener. At higher concentrations, however, there was considerable overlap between the T and NT strains. In fact, the initial licking response of several NT strains was more vigorous than (or equivalent to) that of several T strains. There was also considerable variation among strains with the same Tas1r3 allele. We conclude that Tas1r3 polymorphisms contribute to strain differences in initial lick responsiveness to low but not high concentrations of sweeteners.