Large-scale Identification of Chemically Induced Mutations in Drosophila melanogaster.

Forward genetic screens using chemical mutagens have been successful in defining the function of thousands of genes in eukaryotic model organisms. The main drawback of this strategy is the time-consuming identification of the molecular lesions causative of the phenotypes of interest. With whole-genome sequencing (WGS), it is now possible to sequence hundreds of strains, but determining which mutations are causative among thousands of polymorphisms remains challenging. We have sequenced 394 mutant strains, generated in a chemical mutagenesis screen, for essential genes on the Drosophila X chromosome and describe strategies to reduce the number of candidate mutations from an average of -3500 to 35 single-nucleotide variants per chromosome. By combining WGS with a rough mapping method based on large duplications, we were able to map 274 (-70%) mutations. We show that these mutations are causative, using small 80-kb duplications that rescue lethality. Hence, our findings demonstrate that combining rough mapping with WGS dramatically expands the toolkit necessary for assigning function to genes

Promoting help-seeking behavior for urinary incontinence

The authors evaluated the effectiveness of a combined primary care physician education and public awareness campaign about urinary incontinence. The campaign was designed to (a) trigger help-seeking behavior in older adults with urine leakage problems and (b) encourage primary care providers to offer appropriate treatment for urinary incontinence (UI). Outcome measures included data from helpline callers and physician surveys before and after the two interventions. Most callers who later sought care turned to their primary care physician. The median estimated number of patients presenting with UI in primary care doctor\u27s offices changed from 9 per month to 11 per month, a change that was not statistically significant. Physicians\u27 optimism for the potential gains from incontinence treatment increased

Antidiabetic actions of a non-agonist PPARγ ligand blocking Cdk5-mediated phosphorylation

PPARγ is the functioning receptor for the thiazolidinedione (TZD) class of antidiabetes drugs including rosiglitazone and pioglitazone. These drugs are full classical agonists for this nuclear receptor, but recent data have shown that many PPARγ-based drugs have a separate biochemical activity, blocking the obesity-linked phosphorylation of PPARγ by Cdk5. Here we describe novel synthetic compounds that have a unique mode of binding to PPARγ, completely lack classical transcriptional agonism and block the Cdk5-mediated phosphorylation in cultured adipocytes and in insulin-resistant mice. Moreover, one such compound, SR1664, has potent antidiabetic activity while not causing the fluid retention and weight gain that are serious side effects of many of the PPARγ drugs. Unlike TZDs, SR1664 also does not interfere with bone formation in culture. These data illustrate that new classes of antidiabetes drugs can be developed by specifically targeting the Cdk5-mediated phosphorylation of PPARγ

Partial agonists activate PPARgamma using a helix 12 independent mechanism

Binding to helix 12 of the ligand-binding domain of PPARgamma is required for full agonist activity. Previously, the degree of stabilization of the activation function 2 (AF-2) surface was thought to correlate with the degree of agonism and transactivation. To examine this mechanism, we probed structural dynamics of PPARgamma with agonists that induced graded transcriptional responses. Here we present crystal structures and amide H/D exchange (HDX) kinetics for six of these complexes. Amide HDX revealed each ligand induced unique changes to the dynamics of the ligand-binding domain (LBD). Full agonists stabilized helix 12, whereas intermediate and partial agonists did not at all, and rather differentially stabilized other regions of the binding pocket. The gradient of PPARgamma transactivation cannot be accounted for solely through changes to the dynamics of AF-2. Thus, our understanding of allosteric signaling must be extended beyond the idea of a dynamic helix 12 acting as a molecular switch.John B. Bruning, Michael J. Chalmers, Swati Prasad, Scott A. Busby, Theodore M. Kamenecka, Yuanjun He, Kendall W. Nettles, and Patrick R. Griffi

Design, Synthesis, and Biological Evaluation of Indole Biphenylcarboxylic Acids as PPARγ Antagonists

The thiazolidinediones (TZD) typified by rosiglitazone are the only approved therapeutics targeting PPARγ for the treatment of type-2 diabetes (T2DM). Unfortunately, despite robust insulin sensitizing properties, they are accompanied by a number of severe side effects including congestive heart failure, edema, weight gain, and osteoporosis. We recently identified PPARγ antagonists that bind reversibly with high affinity but do not induce transactivation of the receptor, yet they act as insulin sensitizers in mouse models of diabetes (SR1664). This Letter details our synthetic exploration around this novel series of PPARγ antagonists based on an <i>N</i>-biphenylmethylindole scaffold. Structure–activity relationship studies led to the identification of compound <b>46</b> as a high affinity PPARγ antagonist that exhibits antidiabetic properties following oral administration in diet-induced obese mice