Alfalfa Controls Nodulation during the Onset of Rhizobium-induced Cortical Cell Division

The formation of first nodules inhibits subsequent nodulation in younger regions of alfalfa (Medicago sativa L.) roots by a feedback regulatory mechanism that controls nodule number systemically (G Caetano-Anollés, WD Bauer [1988] Planta 175: 546-557). Following inoculation with wild-type Rhizobium meliloti, almost all infections associated with cortical cell division developed into mature nodules. While the distribution of Rhizobium- induced cell divisions closely paralleled the distribution of first emergent nodules, only 9 to 15% of total cell division foci failed to become functional nodules. Nodule formation was restricted to the primary root when plants were inoculated before lateral root emergence. Excision of these primary root nodules allowed nodules to reappear in lateral roots clustered around the location of the root tip at the time of nodule removal. Apparently, this region regained susceptibility to infection within the first hours after excision of primary nodules and suppression of nodulation was restored a day later probably due to the development of new infection foci. Our results suggest that alfalfa controls nodulation during the onset of cell division in the root cortex and not during infection development as in soybean.     

Dietary Regimens Modify Early Onset of Obesity in Mice Haploinsufficient for Rai1

Smith-Magenis syndrome is a complex genomic disorder in which a majority of individuals are obese by adolescence. While an interstitial deletion of chromosome 17p11.2 is the leading cause, mutation or deletion of the RAI1 gene alone results in most features of the disorder. Previous studies have shown that heterozygous knockout of Rai1 results in an obese phenotype in mice and that Smith-Magenis syndrome mouse models have a significantly reduced fecundity and an altered transmission pattern of the mutant Rai1 allele, complicating large, extended studies in these models. In this study, we show that breeding C57Bl/6J Rai1^+/− mice with FVB/NJ to create F1 Rai1^+/− offspring in a mixed genetic background ameliorates both fecundity and Rai1 allele transmission phenotypes. These findings suggest that the mixed background provides a more robust platform for breeding and larger phenotypic studies. We also characterized the effect of dietary intake on Rai1^+/− mouse growth during adolescent and early adulthood developmental stages. Animals fed a high carbohydrate or a high fat diet gained weight at a significantly faster rate than their wild type littermates. Both high fat and high carbohydrate fed Rai1^+/− mice also had an increase in body fat and altered fat distribution patterns. Interestingly, Rai1^+/− mice fed different diets did not display altered fasting blood glucose levels. These results suggest that dietary regimens are extremely important for individuals with Smith- Magenis syndrome and that food high in fat and carbohydrates may exacerbate obesity outcomes.     

Age-Related Onset of Obesity Corresponds with Metabolic Dysregulation and Altered Microglia Morphology in Mice Deficient for Ifitm Proteins

The IfitmDel mouse lacks all five of the Ifitm genes via LoxP deletion. This animal breeds normally with no obvious defect in development. The IfitmDel animals exhibit a steady and significantly enhanced weight gain relative to wild-type controls beginning about three months of age and under normal feeding conditions. The increased weight corresponds with elevated fat mass, and in tolerance tests they are hyporesponsive to insulin but respond normally to glucose. Both young (4 mo) and older (12 mo) IfitmDel mice have enhanced levels of serum leptin suggesting a defect in leptin/leptin receptor signaling. Analysis of the gene expression profiles in the hypothalamus of IfitmDel animals, compared to WT, demonstrated an altered ratio of Pomc and Npy neuropeptide expression, which likely impairs the satiation response of the IfitmDel animal leading to an increased eating behavior. Also elevated in hypothalamus of IfitmDel mice were pro-inflammatory cytokine expression and reduced IL-10. Anatomical analysis of the hypothalamus using immunohistochemistry revealed that microglia exhibit an abnormal morphology in IfitmDel animals and respond abnormally to Poly:IC challenge. These abnormalities extend the phenotype of the IfitmDel mouse beyond abnormal responses to viral challenge to include a metabolic phenotype and weight gain. Further, this novel phenotype for the IfitmDel mouse could be related to abnormal neuropeptide production, inflammatory status and microglia status in the hypothalamus.     

JNK Controls the Onset of Mitosis in Planarian Stem Cells and Triggers Apoptotic Cell Death Required for Regeneration and Remodeling

Regeneration of lost tissues depends on the precise interpretation of molecular signals that control and coordinate the onset of proliferation, cellular differentiation and cell death. However, the nature of those molecular signals and the mechanisms that integrate the cellular responses remain largely unknown. The planarian flatworm is a unique model in which regeneration and tissue renewal can be comprehensively studied in vivo. The presence of a population of adult pluripotent stem cells combined with the ability to decode signaling after wounding enable planarians to regenerate a complete, correctly proportioned animal within a few days after any kind of amputation, and to adapt their size to nutritional changes without compromising functionality. Here, we demonstrate that the stress-activated c-jun–NH₂–kinase (JNK) links wound-induced apoptosis to the stem cell response during planarian regeneration. We show that JNK modulates the expression of wound-related genes, triggers apoptosis and attenuates the onset of mitosis in stem cells specifically after tissue loss. Furthermore, in pre-existing body regions, JNK activity is required to establish a positive balance between cell death and stem cell proliferation to enable tissue renewal, remodeling and the maintenance of proportionality. During homeostatic degrowth, JNK RNAi blocks apoptosis, resulting in impaired organ remodeling and rescaling. Our findings indicate that JNK-dependent apoptotic cell death is crucial to coordinate tissue renewal and remodeling required to regenerate and to maintain a correctly proportioned animal. Hence, JNK might act as a hub, translating wound signals into apoptotic cell death, controlled stem cell proliferation and differentiation, all of which are required to coordinate regeneration and tissue renewal.     

Transcription Factor GATA1 Is Dispensable for Mast Cell Differentiation in Adult Mice

Although previous studies have shown that GATA1 is required for mast cell differentiation, the effects of the complete ablation of GATA1 in mast cells have not been examined. Using conditional Gata1 knockout mice (Gata1^−/y), we demonstrate here that the complete ablation of GATA1 has a minimal effect on the number and distribution of peripheral tissue mast cells in adult mice. The Gata1^−/y bone marrow cells were capable of differentiating into mast cells ex vivo. Microarray analyses showed that the repression of GATA1 in bone marrow mast cells (BMMCs) has a small impact on the mast cell-specific gene expression in most cases. Interestingly, however, the expression levels of mast cell tryptases in the mouse chromosome 17A3.3 were uniformly reduced in the GATA1 knockdown cells, and GATA1 was found to bind to a 500-bp region at the 5′ end of this locus. Revealing a sharp contrast to that observed in the Gata1-null BMMCs, GATA2 deficiency resulted in a significant loss of the c-Kit⁺ FcεRIα⁺ mast cell fraction and a reduced expression of several mast cell-specific genes. Collectively, GATA2 plays a more important role than GATA1 in the regulation of most mast cell-specific genes, while GATA1 might play specific roles in mast cell functions.     

Cell Kinetic Studies Fail to Identify Sequentially Proliferating Progenitors as the Major Source of Epithelial Renewal in the Adult Murine Prostate

There is evidence that stem cells and their progeny play a role in the development of the prostate. Although stem cells are also considered to give rise to differentiated progeny in the adult prostate epithelium ex vivo, the cohort of adult prostate stem cells in vivo as well as the mechanisms by which the adult prostate epithelium is maintained and regenerated remain highly controversial. We have attempted to resolve this conundrum by performing in vivo tracing of serially replicating cells after the sequential administration of two thymidine analogues to mice. Our results show that, during normal prostate homeostasis, sequentially proliferating cells are detected at a rate that is consistent with a stochastic process. These findings indicate that in vivo, under steady-state conditions, most adult prostate epithelial cells do not represent the progeny of a small number of specialized progenitors that generate sequentially replicating transit-amplifying (TA) cells but are formed by stochastic cell division. Similarly, no rapidly cycling TA cells were detected during regeneration following one cycle of androgen-mediated involution/regeneration of the prostate epithelium. These findings greatly enhance our understanding of the mechanisms regulating prostate epithelial cell renewal and may have significant implications in defining the cell of origin of proliferative prostatic diseases.     

Trachea-Derived Dpp Controls Adult Midgut Homeostasis in Drosophila

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Highlights? Trachea-derived Dpp/Bmp is required for midgut homeostasis ? Dpp expressed in tracheal cells reach intestinal cells through visceral muscles ? Dpp signaling is activated in enterocytes (ECs) in the Drosophila adult midgut ? Dpp signaling stabilizes ECs to restrict intestinal stem cell proliferation     

Voluntary Running in Young Adult Mice Reduces Anxiety-Like Behavior and Increases the Accumulation of Bioactive Lipids in the Cerebral Cortex

Combinatorial therapies using voluntary exercise and diet supplementation with polyunsaturated fatty acids have synergistic effects benefiting brain function and behavior. Here, we assessed the effects of voluntary exercise on anxiety-like behavior and on total FA accumulation within three brain regions: cortex, hippocampus, and cerebellum of running versus sedentary young adult male C57/BL6J mice. The running group was subjected to one month of voluntary exercise in their home cages, while the sedentary group was kept in their home cages without access to a running wheel. Elevated plus maze (EPM), several behavioral postures and two risk assessment behaviors (RABs) were then measured in both animal groups followed immediately by blood samplings for assessment of corticosterone levels. Brains were then dissected for non-targeted lipidomic analysis of selected brain regions using gas chromatography coupled to mass spectrometry (GC/MS). Results showed that mice in the running group, when examined in the EPM, displayed significantly lower anxiety-like behavior, higher exploratory and risky behaviors, compared to sedentary mice. Notably, we found no differences in blood corticosterone levels between the two groups, suggesting that the different EPM and RAB behaviors were not related to reduced physiological stress in the running mice. Lipidomics analysis revealed a region-specific cortical decrease of the saturated FA: palmitate (C16:0) and a concomitant increase of polyunsaturated FA, arachidonic acid (AA, omega 6-C20: 4) and docosahexaenoic acid (DHA, omega 3-C22: 6), in running mice compared to sedentary controls. Finally, we found that running mice, as opposed to sedentary animals, showed significantly enhanced cortical expression of phospholipase A2 (PLA₂) protein, a signaling molecule required in the production of both AA and DHA. In summary, our data support the anxiolytic effects of exercise and provide insights into the molecular processes modulated by exercise that may lead to its beneficial effects on mood.     

Stathmin Is Dispensable for Tumor Onset in Mice

The microtubule-destabilizing protein stathmin is highly expressed in several types of tumor, thus deserving the name of oncoprotein 18. High levels of stathmin expression and/or activity favor the metastatic spreading and mark the most aggressive tumors, thus representing a realistic marker of poor prognosis. Stathmin is a downstream target of many signaling pathways, including Ras-MAPK, PI3K and p53, involved in both tumor onset and progression. We thus hypothesized that stathmin could also play a role during the early stages of tumorigenesis, an issue completely unexplored. In order to establish whether stathmin expression is necessary for tumor initiation, we challenged wild type (WT), stathmin heterozygous and stathmin knock-out (KO) mice with different carcinogens. Using well-defined mouse models of carcinogenesis of skin, bladder and muscle by the means of 7,12-dimethylbenz[α]antracene (DMBA)/12-O-tetradecanoylphorbol-13-acetate (TPA), N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN) and 3-methylcholanthrylene (3MC) treatments, respectively, we demonstrated that knock-out of stathmin has no impact on the onset of cancer in mice. No significant difference was noticed either when the Ras oncogene was mutated (skin carcinogenesis model) or when the p53 pathway was inactivated (bladder carcinomas and fibrosarcomas). Finally, we concomitantly impinged on p53 and Ras pathways, by generating WT and stathmin KO mouse embryo fibroblasts transformed with papilloma virus large T antigen (LgTAg) plus the K-Ras^G12V oncogene. In vivo growth of xenografts from these transformed fibroblasts did not highlight any significant difference depending on the presence or absence of stathmin. Overall, our work demonstrates that stathmin expression is dispensable for tumor onset, at least in mice, thus making stathmin a virtually exclusive marker of aggressive disease and a promising therapeutic target for advanced cancers.     

Redrawing the US Obesity Landscape: Bias-Corrected Estimates of State-Specific Adult Obesity Prevalence

Background

State-level estimates from the Centers for Disease Control and Prevention (CDC) underestimate the obesity epidemic because they use self-reported height and weight. We describe a novel bias-correction method and produce corrected state-level estimates of obesity and severe obesity.

Methods

Using non-parametric statistical matching, we adjusted self-reported data from the Behavioral Risk Factor Surveillance System (BRFSS) 2013 (n = 386,795) using measured data from the National Health and Nutrition Examination Survey (NHANES) (n = 16,924). We validated our national estimates against NHANES and estimated bias-corrected state-specific prevalence of obesity (BMI≥30) and severe obesity (BMI≥35). We compared these results with previous adjustment methods.

Results

Compared to NHANES, self-reported BRFSS data underestimated national prevalence of obesity by 16% (28.67% vs 34.01%), and severe obesity by 23% (11.03% vs 14.26%). Our method was not significantly different from NHANES for obesity or severe obesity, while previous methods underestimated both. Only four states had a corrected obesity prevalence below 30%, with four exceeding 40%–in contrast, most states were below 30% in CDC maps.

Conclusions

Twelve million adults with obesity (including 6.7 million with severe obesity) were misclassified by CDC state-level estimates. Previous bias-correction methods also resulted in underestimates. Accurate state-level estimates are necessary to plan for resources to address the obesity epidemic.