High-fat diet and FGF21 cooperatively promote aerobic thermogenesis in mtDNA mutator mice.

Mitochondria are highly adaptable organelles that can facilitate communication between tissues to meet the energetic demands of the organism. However, the mechanisms by which mitochondria can nonautonomously relay stress signals remain poorly understood. Here we report that mitochondrial mutations in the young, preprogeroid polymerase gamma mutator (POLG) mouse produce a metabolic state of starvation. As a result, these mice exhibit signs of metabolic imbalance including thermogenic defects in brown adipose tissue (BAT). An unexpected benefit of this adaptive response is the complete resistance to diet-induced obesity when POLG mice are placed on a high-fat diet (HFD). Paradoxically, HFD further increases oxygen consumption in part by inducing thermogenesis and mitochondrial biogenesis in BAT along with enhanced expression of fibroblast growth factor 21 (FGF21). Collectively, these findings identify a mechanistic link between FGF21, a long-known marker of mitochondrial disease, and systemic metabolic adaptation in response to mitochondrial stress.

Identification of pathogen genomic variants through an integrated pipeline.

BACKGROUND: Whole-genome sequencing represents a powerful experimental tool for pathogen research. We present methods for the analysis of small eukaryotic genomes, including a streamlined system (called Platypus) for finding single nucleotide and copy number variants as well as recombination events. RESULTS: We have validated our pipeline using four sets of Plasmodium falciparum drug resistant data containing 26 clones from 3D7 and Dd2 background strains, identifying an average of 11 single nucleotide variants per clone. We also identify 8 copy number variants with contributions to resistance, and report for the first time that all analyzed amplification events are in tandem. CONCLUSIONS: The Platypus pipeline provides malaria researchers with a powerful tool to analyze short read sequencing data. It provides an accurate way to detect SNVs using known software packages, and a novel methodology for detection of CNVs, though it does not currently support detection of small indels. We have validated that the pipeline detects known SNVs in a variety of samples while filtering out spurious data. We bundle the methods into a freely available package.

A high resolution case study of a patient with recurrent Plasmodium vivax infections shows that relapses were caused by meiotic siblings.

Plasmodium vivax infects a hundred million people annually and endangers 40% of the world's population. Unlike Plasmodium falciparum, P. vivax parasites can persist as a dormant stage in the liver, known as the hypnozoite, and these dormant forms can cause malaria relapses months or years after the initial mosquito bite. Here we analyze whole genome sequencing data from parasites in the blood of a patient who experienced consecutive P. vivax relapses over 33 months in a non-endemic country. By analyzing patterns of identity, read coverage, and the presence or absence of minor alleles in the initial polyclonal and subsequent monoclonal infections, we show that the parasites in the three infections are likely meiotic siblings. We infer that these siblings are descended from a single tetrad-like form that developed in the infecting mosquito midgut shortly after fertilization. In this natural cross we find the recombination rate for P. vivax to be 10 kb per centimorgan and we further observe areas of disequilibrium surrounding major drug resistance genes. Our data provide new strategies for studying multiclonal infections, which are common in all types of infectious diseases, and for distinguishing P. vivax relapses from reinfections in malaria endemic regions. This work provides a theoretical foundation for studies that aim to determine if new or existing drugs can provide a radical cure of P. vivax malaria.

A chemotherapy-associated senescence bystander effect in breast cancer cells.

A bystander effect typically refers to the death, altered growth or damage of cells that have not directly received chemotherapy or irradiation. Cancer cells derived from solid tumors readily undergo senescence in response to chemotherapeutic agents, prompting us to test for the existence of a senescence bystander effect. MCF-7 breast cancer cells were acutely exposed to Adriamycin to trigger senescence. Naïve MCF-7 cells, when cultured in conditioned media from senescent breast cancer cells, growth arrested despite mitogenic stimulation and exhibited SA-beta-galactosidase activity, an enlarged cell size and stable upregulation of p21(WAF1) protein, collectively indicating a senescent state. In contrast, HCT-116 colon cancer cells, which also undergo p53-mediated senescence in response to acute AdR, did not undergo growth inhibition or senescence when cultured with conditioned media from senescent HCT-116 cells. Reciprocal experiments indicated that naïve HCT-116 cells, like MCF-7 cells, are susceptible to the growth inhibitory effects of a breast cancer-derived mediator, which is independent of residual drug in conditioned media. Our study reveals a novel action of Adriamycin, which may contribute to its potent anti-breast cancer activity and lead to the discovery of additional therapeutic targets for the exploitation of a senescence bystander effect.