Rapamycin extends murine lifespan but has limited effects on aging.

Aging is a major risk factor for a large number of disorders and functional impairments. Therapeutic targeting of the aging process may therefore represent an innovative strategy in the quest for novel and broadly effective treatments against age-related diseases. The recent report of lifespan extension in mice treated with the FDA-approved mTOR inhibitor rapamycin represented the first demonstration of pharmacological extension of maximal lifespan in mammals. Longevity effects of rapamycin may, however, be due to rapamycin's effects on specific life-limiting pathologies, such as cancers, and it remains unclear if this compound actually slows the rate of aging in mammals. Here, we present results from a comprehensive, large-scale assessment of a wide range of structural and functional aging phenotypes, which we performed to determine whether rapamycin slows the rate of aging in male C57BL/6J mice. While rapamycin did extend lifespan, it ameliorated few studied aging phenotypes. A subset of aging traits appeared to be rescued by rapamycin. Rapamycin, however, had similar effects on many of these traits in young animals, indicating that these effects were not due to a modulation of aging, but rather related to aging-independent drug effects. Therefore, our data largely dissociate rapamycin's longevity effects from effects on aging itself.

Toxicity modelling of Plk1-targeted therapies in genetically engineered mice and cultured primary mammalian cells.

High attrition rates of novel anti-cancer drugs highlight the need for improved models to predict toxicity. Although polo-like kinase 1 (Plk1) inhibitors are attractive candidates for drug development, the role of Plk1 in primary cells remains widely unexplored. Therefore, we evaluated the utility of an RNA interference-based model to assess responses to an inducible knockdown (iKD) of Plk1 in adult mice. Here we show that Plk1 silencing can be achieved in several organs, although adverse events are rare. We compared responses in Plk1-iKD mice with those in primary cells kept under controlled culture conditions. In contrast to the addiction of many cancer cell lines to the non-oncogene Plk1, the primary cells' proliferation, spindle assembly and apoptosis exhibit only a low dependency on Plk1. Responses to Plk1-depletion, both in cultured primary cells and in our iKD-mouse model, correspond well and thus provide the basis for using validated iKD mice in predicting responses to therapeutic interventions.

A novel N-ethyl-N-nitrosourea-induced mutation in phospholipase Cγ2 causes inflammatory arthritis, metabolic defects, and male infertility in vitro in a murine model.

OBJECTIVE: It is difficult to identify a single causative factor for inflammatory arthritis because of the multifactorial nature of the disease. This study was undertaken to dissect the molecular complexity of systemic inflammatory disease, utilizing a combined approach of mutagenesis and systematic phenotype screening in a murine model. METHODS: In a large-scale N-ethyl-N-nitrosourea mutagenesis project, the Ali14 mutant mouse strain was established because of dominant inheritance of spontaneous swelling and inflammation of the hind paws. Genetic mapping and subsequent candidate gene sequencing were conducted to find the causative gene, and systematic phenotyping of Ali14/+ mice was performed in the German Mouse Clinic. RESULTS: A novel missense mutation in the phospholipase Cγ2 gene (Plcg2) was identified in Ali14/+ mice. Because of the hyperreactive external entry of calcium observed in cultured B cells and other in vitro experiments, the Ali14 mutation is thought to be a novel gain-of-function allele of Plcg2. Findings from systematic screening of Ali14/+ mice demonstrated various phenotypic changes: an abnormally high T cell:B cell ratio, up-regulation of Ig, alterations in body composition, and a reduction in cholesterol and triglyceride levels in peripheral blood. In addition, spermatozoa from Ali14/+ mice failed to fertilize eggs in vitro, despite the normal fertility of the Ali14/+ male mice in vivo. CONCLUSION: These results suggest that the Plcg2-mediated pathways play a crucial role in various metabolic and sperm functions, in addition to initiating and maintaining the immune system. These findings may indicate the importance of the Ali14/+ mouse strain as a model for systemic inflammatory diseases and inflammation-related metabolic changes in humans.