A Role for the DREAM Complex in the Regulation of Germline Apoptosis
Frances Compere, Lisa Petrella
Organisms exist in environments that are subject to changes and fluctuations that may incur stress upon them; thus, they have means to cope with or adapt to stress and ensure their survival and propagation. One means of dealing with stress that organisms have is to induce programmed cell death through apoptosis in cells that have been damaged by the stressful condition. We are studying apoptosis in response to stresses in the C. elegans germline.The germline is the only tissue in the adult animal that undergoes apoptosis. LIN-35, the single worm homolog of the Retinoblastoma (pRb) tumor suppressor has been shown to be important for the promotion of several of the apoptotic pathways in the germline. However, LIN-35 does not appear to work at the same point of the apoptotic pathways as other members of the E2F complex, EFL-1 and DPL-1. Another complex that LIN-35 interacts with is the conserved MuvB core of the the DREAM complex which made up of synMuv B proteins. We have found that DREAM complex mutants, like lin-35 mutants, have reduced germline apoptosis in response to DNA damage. It is of note that in embryonic tissues, the DREAM complex and LIN-35 bind at the promoter of ced-9/Bcl2 which is the anti-apoptotic regulator of the core apoptotic machinery. This could indicate that LIN-35 may be working with the DREAM complex to regulate germline apoptosis. We predict that DREAM complex mutants, like lin-35 mutants, will have increased levels of ced-9 expression but not that of ced-4 or ced-3 in the germline. We also predict that DREAM complex mutants will have an even more pronounced defect in germline apoptosis in an engulfment mutant background, like lin-35 mutants. Together these would indicate that the DREAM complex is a good candidate to be the complex with which LIN-35 is modulating germline apoptosis.
Compromised Mating Ability and Reduced Sperm Transfer Explain Reduced Fertility in C. elegans Males at High Temperature
Nicholas Sepulveda, Emily Nett, Lisa Petrella
Cuticle Morphology and Function in drd Mutants
Nate Fisher, Ed Blumenthal
The drop-dead (drd) gene is a gene of unknown function expressed in Drosophila melanogaster. After reaching adulthood, mutant flies lacking the gene die within two weeks and display a host of maladaptive and fatal phenotypes. While the exact nature of the role the gene plays in fly development is unknown, prior research has shown a unique expression pattern in the epidermal cells of larvae. Because of this, it was hypothesized that drd is involved in the synthesis of the cuticle—based also on the fact that the gene is involved in the formation of other similar barrier structures. The purpose of this project was to test for defects in cuticle function, measured by salt tolerance and survival in a wounding assay, and in cuticle appearance in drd mutant flies.
Elevational Differences in Climate are Associated With Changes in Density Dependence and Tree Species Diversity
Joseph LaManna, David Bell, Robert Pabst, David Shaw
Negative density dependence caused by host-pathogen interactions may explain differences in plant species diversity at landscape to global scales, but the mechanisms that affect changes in density dependence and species diversity remain unclear. We test the hypothesis that the strength of negative density dependence and plant species diversity both increase with temperature or precipitation along an elevational gradient. Higher temperatures were associated with stronger negative density dependence in young tree growth and survival. Higher temperatures were also associated with increased tree species diversity along the gradient. These results suggest that increases in temperature strengthen interactions between plant hosts and their pathogens, promoting higher species diversity in warmer environments.
Evolution of Antibiotic Resistance in Acinetobacter Baumannii
Identification and Functional Analysis of microRNAs in Male Gonads of C. Elegans
Lu Lu, Allison Abbott
microRNAs are short non-coding RNAs with a length of ~ 22 nucleotides that regulate gene expression at the post-transcriptional level. Disruption of miRNA function is associated with a wide array of human diseases, including male factor infertility. While evidence suggests that miRNA function is needed for production of functional sperm, the specific regulatory roles of miRNAs in this process are largely unknown. To address this question in Caenorhabditis elegans, I used small RNA sequencing on isolated gonad tissues to identify microRNA profile, which revealed a differential expression pattern of microRNAs between hermaphrodite and male gonads. Specifically, 27 miRNAs were found to be lower and 25 miRNAs were found to be higher in the hermaphrodite gonad compared with the male gonad. Functional analysis is being carried out on existing microRNA deletion mutants or microRNA mutants built with CRISPR genome editing tool. Specifically, mating assays are being used to screen potential miRNAs for regulation of male fertility and fecundity. This study will provide important clues for our understanding of microRNA regulatory roles in sperm formation and function.
Intermittent Hypoxia Causes Cardiometabolic Dysfunction in Obese, ob/ob Mice
Sarah Framnes-DeBoer, Aaron Jones, Deanna Arble
Obstructive sleep apnea (OSA) is a common sleep disorder characterized by repeated bouts of intermittent hypoxia (IH). Approximately, 40-70% of the obese population exhibit OSA and are at higher risk for developing hypertension, heart failure, and other cardiometabolic diseases. Leptin, a hormone increased with obesity, is also associated with cardiometabolic disease. It is unclear if it is leptin insensitivity or other aspects of obesity that make individuals more susceptible to cardiometabolic diseases when experiencing IH in the form of OSA. To determine the relative involvement of leptin and/or obesity in the cardiometabolic outcomes of IH, we exposed lean C57Bl/6J WT mice, leptin-deficient ob/ob mice, and weight-restricted ob/ob mice to 6 days of IH (a 30-second, 5% O2 desaturation event occurring every 6 minutes for 9 hours/day). We found that IH led to a negative energy balance in WT mice, resulting in both a decrease in food intake and weight loss. Interestingly, while leptin-deficient ob/ob mice also lost weight, these mice exhibited an increase in feeding with the IH exposure. These data suggest that leptin signaling during IH serves to reduce food intake. We further found that the obese, leptin-deficient ob/ob mice exhibited an IH-induced impairment in cardiac function as indicated by an increase in left ventricle internal diameter diastole and an increase in cardiac output. These cardiac impairments were not observed in either the WT or the weight-restricted ob/ob group. Taken together, we find that a 6-day exposure of IH is associated with a negative energy balance in mice and that both impaired leptin signaling and obesity are necessary for IH-induced cardiac impairments. Further research will focus on food intake and how that may mitigate cardiometabolic disease in OSA patients.
Investigating Serial Homology of the Adhesive Structures of Diplodactylid Lizards
Aaron Griffing, Thomas Sanger, Timothy Higham, Tony Gamble
One goal of evolutionary developmental biology (evo-devo) is to understand the role of development in the origin of phenotypic novelty and convergent evolution. Geckos are an ideal system to study this topic as they are species-rich and exhibit a suite of diverse morphologies many of which have independently evolved multiple times within geckos. Classic examples of such morphologies are adhesive toepads, which have been gained and lost at least 12 and seven times, respectively, through gecko evolutionary history. Crested geckos (Correlophus ciliatus) not only exhibit impressive adhesive toepads, but also an adhesive pad located at the tip of their prehensile tails. Although C. ciliatus was presumed extinct before being rediscovered in 1994, this species is now abundant in the pet trade, providing the ideal opportunity to study the development of these remarkable structures. Due to the overall differences in adult morphology between C. ciliatus toepads and tailpads, we hypothesized that the adhesive tailpads of C. ciliatus are not serial homologs of toepads; therefore, we predicted that tailpads would exhibit different morphological and temporal developmental patterns to those of toepads. To test this hypothesis, generated embryonic series of C. ciliatus and Lepidodactylus lugubris, a non-adhesive-tailed gecko. We visualized tail and toepad development using scanning electron microscopy (SEM). Early development of C. ciliatus tailpads is similar to that of toepads but rapidly diverges from this pattern through the formation of granular scales. Here, we discuss evidence for the serial homology and novel scale formation of adhesive tailpads and discuss development of adhesive structures in a phylogenetic context.
Microbial Community, Antibiotic Resistance Gene, and Pathogen Dynamics in River Bed Sediment Adjacent to Concentrated Livestock Farms
Rachelle Beattie, A. Bandla, S. Swarup, K. Hristova
Microorganisms present within freshwater benthic sediment contribute to a variety of ecosystem processes including primary production, decomposition, and nutrient cycling. Due to their functional importance, freshwater microorganisms are routinely used as biomarkers for the health of surface water ecosystems; thus, changes in microbial community composition and functional potential likely reflect anthropogenic contamination in surface waters. Using Next Generation Sequencing and multivariate statistical analyses, we measured the impact of manure contamination from concentrated dairy farms on the microbial communities of freshwater sediments. Results indicated that sediment microbial community composition and function were strongly impacted by manure fertilization with significant differences in community composition within the highly impacted watershed. Sediment microbial community composition was resilient to manure fertilization 5 months post application, but did not return to the original steady state.
Patterns and Mechanisms of Diversity Maintenance in Understory Layers of Old-growth Forests
Ethan Torres, Joseph LaManna
Over the summer, the authors of the poster and six other crew members established 321 1-meter square plots across several larger Long Term Ecological Research (LTER) plots in the H. J. Andrews Experimental Forest. These plots tagged and measured the abundance and height of every plant within the plot under 1 meter in height. With this data, we sought to analyze the mechanisms of biodiversity maintenance in these understory plants through several environmental variables - mainly local biotic interactions and climate effects. It was found that climate effects (mainly precipitation) is the variable most strongly correlated with understory abundance and species richness. This finding is of particular interest in that it varies from the known mechanisms of biodiversity maintenance found in larger trees of the same forests, as well as warns that changing climate patterns can have previously unknown effects on understory biodiversity.
Persistence of a Geographically-stable Hybrid Zone in Puerto Rican Dwarf Geckos
Brendan Pinto, James Titus-McQuillan, Juan Daza, Tony Gamble
Determining the mechanisms that create and maintain biodiversity is a central question in ecology and evolution. Speciation is the process that creates biodiversity. Speciation is mediated by incompatibilities that lead to reproductive isolation between divergent populations and these incompatibilities can be observed in hybrid zones. Gecko lizards are a speciose clade possessing an impressive diversity of behavioral and morphological traits. In geckos, however, our understanding of the speciation process is negligible. To address this gap, we used genetic sequence data (both mitochondrial and nuclear markers) to describe a putative hybrid zone between Sphaerodactylus nicholsi and Sphaerodactylus townsendi in Puerto Rico. We find strong support for the species-level status of each species and no evidence of movement, or unique climatic variables near the hybrid zone. We suggest that this narrow hybrid zone is geographically-stable and is maintained by a combination of dispersal and selection. Thus, this work has identified an extant model system within geckos that that can be used for future investigations detailing genetic mechanisms of reproductive isolation in an understudied vertebrate group.
Photoperiod Modulates Ventilatory Drive in the C57BI/6J Mouse
Aaron Jones, Nakia Chappelle, Deanna Arble
Obstructive Sleep Apnea (OSA) is commonly characterized by a reduction or cessation of breathing during sleep and significantly increases one’s risk for heart disease and mortality. Symptoms of OSA are exacerbated in the winter months, suggesting a role of seasonal photoperiod in disordered breathing. However, photoperiodic modulation of breathing is an unexplored topic open to novel therapeutic findings. Photoperiod plays a role in many physiological processes including alterations in leptin sensitivity. Given that our lab has previously shown leptin-mediated modulation of breathing in mice, we investigated the effect of photoperiod on leptin sensitivity and ventilatory drive in a mouse model. Male and female C57Bl/6J mice were housed in one of three photoperiods, long-day (20L:4D), short-day (4L:20D), or a standard 12L:12D day for 3 weeks prior to testing. Leptin sensitivity was assessed by reductions in body mass and food intake during 5 days of daily leptin treatment (i.p. 1¼g/g/day). Breathing and ventilatory drive were quantified using a whole-body plethysmograph. We found that mice housed in long-day photoperiods exhibited a greater reduction in body mass and food intake than those in 12L:12D or short-day photoperiods, indicative of increased leptin sensitivity. Ventilatory drive was also significantly reduced in mice housed on long-day photoperiods. Additionally, mice lacking the melanocortin-4 receptor, an important mediator of leptin signaling and body weight homeostasis, do not exhibit photoperiod-dependent changes in breathing. Taken together, these results suggest that a photoperiod-dependent increase in leptin sensitivity decreases ventilatory drive through a leptin-melanocortin pathway. Overall, these findings represent the first step in understanding the broader implications of light-mediated changes in breathing. Future studies will elucidate the underlying neuronal mechanisms and may prove useful for understanding and treating sleep-disordered breathing in humans.
Physiological Functional Traits May Explain Liana Performance During Seasonal Drought
Felipe Mello, Yuriani Cozzarelli, Maria Muriel Garcia-Leon, Christine Scoffoni, Stefan Schnitzer
Resource-based explanations for species abundance and distribution remain challenging in high diversity systems such as tropical forests. Trees and lianas, two important components of tropical forests, apparently compete strongly for resources. Lianas may compete particularly well with trees during seasonal drought, since recent studies show that lianas grow most in high-light, low rainfall conditions. However, few studies have examined whether differences in resource competition between trees and lianas can be quantified using different physiological functional traits. Here, we test the hypothesis that lianas have physiological functional traits that confer greater competitive ability than those of trees, and that differences between these traits are magnified during the dry season. We measured leaf hydraulic conductance, stomatal conductance and turgor loss point in six species of trees and six species of lianas growing in multiple plots in a common garden in Panama. All trees and lianas were planted at the same time and were allowed to grow for six years in full sun. We used the evaporative flux method (EFM) for maximum hydraulic conductance and stomatal conductance measurements, and osmometry to measure turgor loss point.
Leaf hydraulic conductance (Kleaf) in lianas was significantly higher during both dry and wet seasons compared to trees (Mean Kleaf dry season: Lianas=8.184 ± 2.14, Trees=3.384 ± 0.722; Wet season: Lianas=8.475 ± 1.815, Trees= 3.524 ± 0.923 mmol H20 m-2 s-1). Lianas had higher stomatal conductance (gs) than trees during both seasons with a decline in gs during the dry season (Mean gs dry season: Lianas=60.79 ± 9.502, Trees=41.906 ± 6.65; Wet season: Lianas= 82.945 ± 13.36, Trees=48.276 ± 7.615 mol H2O m-2 s-1). Seasonal differences indicate that plants adjust their leaf hydraulic physiology and stomatal conductance in the dry season due to water limitation. Leaf hydraulic conductance did not differ between lianas and trees within seasons. However, we found significant differences in stomatal conductance and turgor loss point between seasons for lianas. Therefore, we did find evidence that turgor loss point and stomata conductance may be driving the higher performance of lianas during the dry season compared to trees. The decrease in leaf turgor loss point and stomata conductance during the dry season compared to the wet season could indicate that leaf turgor could mediate stomata aperture and conductance.
Regulation of Oxidative Phosphorylation by the Mitochondrial Ribosome
Jessica Anderson, Rosemary Stuart
Synthetic Effects of H+, Na+, and Illuniation on Microtubule Dynamics in Light Responsive Chlamydomonas
Olivia Potter, Pinfen Yang
The versatile microtubule system plays crucial roles in cells. Some cellular processes harness its signature dynamic instability, whereas others rely on stabilized microtubules. Its various properties are controlled by numerous proteins. A recent study using fluorescent plus end binding EB1-NeonGreen (NG) as a reporter shows that microtubules in flagellated green alga, chlamydomonas, are highly sensitive to H+, Na+ and the illumination exciting NG. Light opens cation-permeant channelrhodopsins and modulates flagellar motility. To dissect individual effects, we investigated a-tubulin mutant, tub-2, which was refractory to H+- triggered rapid microtubule resorption, allowing revelations of the other changes. In tub-2, H+ had imperfect biphasic effects. Both low and high H+ decreased EB-NG plus end-binding comets, increased lattice binding and decelerated microtubule dynamics, albeit with distinct kinetics. In contrast, medium H+ drastically increased comets numbers and piggyback incidences, at the expense of comet sizes and lattice binding. Low Na+ had a similar effect as low H+. However, when present together, their influences became muted. Notably, NG-exciting illumination accentuate ion-elicited changes. These results demonstrate how acidification, salination and the activity of channels and transporters could jointly shape this crucial cytoskeletal system and thus diverse organisms.
The "Heart" of Green Algae
Pinfen Yang, Yi Liu, Brandon Wills, Xiaoyan Zhu
The Actin Cytoskeleton Network Plays a Role in Yeast Prion Transmission and Contributions to Prion Stability
Jacob Reilly, Anita Manogaran, Jane Dorweiler
The overarching project is for a new prion variant discovered by my PI and another researcher in the lab that will be getting published soon. My part of the project, and the part which I am presenting at both poster sessions, will be my contribution to the work of running the confirmatory protein assays, sucrose gradients followed by western blot analysis, to provide the final evidence for this new finding.
The Effect of intermittent Hypoxia on Body Weight Regulation in Diet Induced and Genetically Obese Mice
Kate Propsom, Sarah Frames-DeBoer, Deanna Arble
Obstructive Sleep Apnea (OSA) is characterized by periodic breathing cessation which results in blood oxygen desaturation. These drops in blood oxygen can be mirrored in animal models using an intermittent hypoxia (IH) protocol. As OSA affects over 50% of the overweight and obese populations, it is hypothesized that IH leads to further impairment of body weight regulation. To determine if insensitivity to leptin, which occurs with obesity, can exacerbate obesity in the context of IH, we utilized lean wild type, diet-induced obese (DIO) wild type, and leptin deficient ob/ob mice. All mice were exposed to 7 days of IH. Preliminary data demonstrate that IH leads to a negative energy balance in WT mice. IH does not alter the food intake of WT lean mice but reduces caloric intake in DIO mice, resulting in weight loss. Interestingly, ob/ob mice increase their food intake in response to IH. These results suggest that severe leptin insensitivity combined with IH may increase body weight and food intake homeostatic set points in mice. Clinically, these results help elucidate why an already overweight individual may be at a high risk for becoming obese after developing OSA.
The Effects of acute and Chronic Intermittent Hypoxia on Sympathetic TOne and Body Weight Regulation in Mice
Numerous studies have described a relationship between obstructive sleep apnea, characterized by intermittent hypoxia (IH), and an increase in sympathetic activation. The relative timeframe of this increase remains unknown, along with the metabolic consequences of that intermittent oxygen restriction. We tested norepinephrine, glucose tolerance, and body weight to determine possible correlations with these variables and intermittent hypoxia.