Identification and Characterization of MicroRNA Modulators in Caenorhabditis Elegans: A Dissertation
Authors
Ren, ZhijiFaculty Advisor
Victor Ambros, PhDAcademic Program
Interdisciplinary Graduate ProgramUMass Chan Affiliations
Program in Molecular MedicineDocument Type
Doctoral DissertationPublication Date
2016-02-26Keywords
Dissertations, UMMSCaenorhabditis Elegans
MicroRNAs
3' Untranslated Regions
RNA-Binding Proteins
RNA Interference
Caenorhabditis elegans Proteins
Caenorhabditis Elegans
MicroRNAs
3' Untranslated Regions
RNA-Binding Proteins
RNA Interference
Caenorhabditis elegans Proteins
Developmental Biology
Metadata
Show full item recordAbstract
MicroRNAs (miRNAs) are endogenous non-coding small RNAs that posttranscriptionally regulate gene expression primarily through binding to the 3’ untranslated region (3’UTR) of target mRNAs, and are known to play important roles in various developmental and physiological processes. The work presented in this thesis was centered on understanding how Caenorhabditis elegans miRNAs are modulated by genetic, environmental, or physiological factors and how these small RNAs function to maintain the robustness of developmental processes under stressful conditions. To identify modulators of the miRNA pathway, I developed sensitized genetic backgrounds that consist of a panel of miRNA gene mutants and miRNA biogenesis factor mutants with partially penetrant phenotypes. First, I found that upon infection of Caenorhabditis elegans with Pseudomonas aeruginosa, an opportunistic pathogen of diverse plants and animals, let-7 family miRNAs are engaged in reciprocal regulatory interactions with the p38 MAPK innate immune pathway to maintain robust developmental timing despite the stress of pathogen infection. These let-7 family miRNAs, along with other developmental timing regulators, are also integrated into innate immune regulatory networks to modulate immune responses. Next, I demonstrated that loss-of-function mutations of Staufen (stau-1), a double-stranded RNA-binding protein, increase miRNA activity for several miRNA families, and this negative modulation of Staufen on miRNA activity acts downstream of miRNA biogenesis, possibly by competing with miRNAs for binding to target mRNA 3’UTRs. In summary, these studies provide a better understanding on how miRNAs are modulated by various environmental and cellular components, and further support the role of the miRNA pathway in conferring robustness to developmental processes under these perturbations.DOI
10.13028/M22G6VPermanent Link to this Item
http://hdl.handle.net/20.500.14038/32207Rights
Copyright is held by the author, with all rights reserved.ae974a485f413a2113503eed53cd6c53
10.13028/M22G6V
Scopus Count
Related items
Showing items related by title, author, creator and subject.
-
Diet-responsive Gene Networks Rewire Metabolism in the Nematode Caenorhabditis elegans to Provide Robustness against Vitamin B12 Deficiency: A DissertationWatson, Emma (2015-09-17)Maintaining cellular homeostasis is a complex task, which involves monitoring energy states and essential nutrients, regulating metabolic fluxes to accommodate energy and biomass needs, and preventing buildup of potentially toxic metabolic intermediates and byproducts. Measures aimed at maintaining a healthy cellular economy inherently depend on the composition of nutrients available to the organism through its diet. We sought to delineate links between dietary composition, metabolic gene regulation, and physiological responses in the model organism C. elegans. As a soil-dwelling bacterivore, C. elegans encounters diverse bacterial diets. Compared to a diet of E. coli OP50, a diet of Comamonas aquatica accelerates C. elegans developmental rate, alters egg-laying dynamics and shortens lifespan. These physiological responses are accompanied by gene expression changes. Taking advantage of this natural, genetically tractable predator-prey system, we performed genetic screens i) in C. elegans to identify regulators of diet-responsive genes, and ii) in E. coli and Comamonas to determine dietary factors driving transcriptional responses in C. elegans. We identified a C. elegans transcriptional program that regulates metabolic genes in response to vitamin B12 content in the bacterial diet. Interestingly, several B12- repressed metabolic genes of unknown function are highly activated when B12- dependent propionyl-CoA breakdown is impaired, and inactivation of these genes renders animals sensitive to propionate-induced toxicity. We provide genetic and metabolomic evidence in support of the hypothesis that these genes form a parallel, B12-independent, β-oxidation-like propionate breakdown shunt in C. elegans, similar to the pathway utilized by organisms like yeast and plants that do not use vitamin B12.
-
Age-related Changes in the Neuronal Architecture of Caenorhabditis Elegans: A DissertationKhandekar, Anagha (2015-10-16)Though symptoms such as loss of vision, decline in cognition and memory are evident during aging, the underlying processes that affect neuronal function during aging are not well understood. Unlike changes in other tissues and organs, age-related changes in the nervous system affect the overall physical, mental as well as social state of human beings. To start elucidating the molecular mechanisms underlying normal age-dependent brain decline, we have characterized structural neuronal changes occurring during Caenorhabditis elegans aging. Our analysis reveals distinct neuronal alterations that arise with age and that the types of changes and their age of onset are neuronal-type specific, highlighting the differential susceptibility of neurons to the stresses of life. We also find that these age-dependent neuronal changes are largely uncoupled from lifespan. As a first step towards understanding the neuropathological conditions manifested during senescence, we have characterized the role of the neuronal maintenance gene sax-7/L1CAM in normal C. elegans aging. Our comparison of age-related structural changes in the wild-type nervous system with that of sax-7 mutants, indicates that loss of function of sax-7 results in accelerated neuronal deterioration that mimics alterations occurring during normal aging. Conversely, overexpressing wild-type copies of SAX-7 delays some of the neuronal changes that accompany normal aging, indicating that SAX-7 plays a neuroprotective role. Additionally we find that x mechanical stress from body movements impacts the neuronal changes during adulthood. Taken together, our results give an entry point into the mechanisms of age-related neuroanatomical changes and neuronal protection.
-
A cohort of Caenorhabditis species lacking the highly conserved let-7 microRNANelson, Charles J.; Ambros, Victor R. (2021-04-23)The let-7 gene encodes a highly conserved microRNA with critical functions integral to cell fate specification and developmental progression in diverse animals. In Caenorhabditis elegans, let-7 is a component of the heterochronic (developmental timing) gene regulatory network, and loss-of-function mutations of let-7 result in lethality during the larval to adult transition due to misregulation of the conserved let-7 target, lin-41. To date, no bilaterian animal lacking let-7 has been characterized. In this study, we identify a cohort of nematode species within the genus Caenorhabditis, closely related to C. elegans, that lack the let-7 microRNA, owing to absence of the let-7 gene. Using Caenorhabditis sulstoni as a representative let-7-lacking species to characterize normal larval development in the absence of let-7, we demonstrate that, except for the lack of let-7, the heterochronic gene network is otherwise functionally conserved. We also report that species lacking let-7 contain a group of divergent let-7 paralogs-also known as the let-7-family of microRNAs-that have apparently assumed the role of targeting the LIN-41 mRNA.