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Abstract: Sequence-specific transcription factors are crucial to generating the gene expression patterns that drive the specification, morphogenesis, and physiology of organs and tissues. In order to better understand how organ form and function are orchestrated by transcription factors, we must better understand the genetic inputs and outputs of these critical regulators. In this work, I have utilized C. elegans to characterize the genetic networks and organ functions of three post-embryonically functioning transcription factors. The Pax family of transcription factors is highly conserved across animal species, and controls the development of multiple tissues and organs during development. In C. elegans males, two sensory mating structures, the copulatory spicules and the post-cloacal sensilla, are formed from stereotyped divisions of the two post-embryonic blast cells, B.a and Y.p, respectively. A C. elegans pax-6 transcript, vab-3, is necessary for the development of these sensory structures. Using a green fluorescent protein (GFP)-based vab-3 transcriptional reporter, I found that expression is restricted to the sensory organ lineages of B.a and Y.p. Transcription of vab-3 in the tail region of the worm requires the Abdominal-B homeobox gene, egl-5. Opposing this activation, a transcription factor cascade and a Wnt signaling pathway each act to restrict vab-3 expression to the appropriate cell lineages. Another C. elegans Pax gene, egl-38, is required for the development of the egg-laying system and rectum. However, few EGL-38 target genes are known. Using gene expression microarrays, we cross-referenced microarray data from an inducible EGL-38 strain and two egl-38 mutants that disrupt protein function in a tissue-preferential manner to identify potential tissue-specific EGL-38 target genes. One set of genes from this analysis was validated using GFP reporter transgenes. Most of these genes are expressed in egl-38-dependent tissues, and many display egl-38 dependence. In addition to the identification of target genes, this work revealed enrichments in gene classes that play a role in innate immunity. Consistent with this, we discovered a novel immune function for egl-38. We found that the gene activities of egl-38 and three egl-38-responsive genes from our validation set are associated with increased infection by the pathogenic bacterium M. nematophilum. However, we also show that egl-38 does not impact infection by a different pathogen, S. marcescens. While Pax genes regulate spatial tissue/organ identity, some transcription factors regulate temporal identity. In C. elegans, heterochronic genes function to ensure the precise timing of stage-specific developmental events. I positionally cloned a novel missense allele of the heterochronic transcription factor LIN-14, and revealed a previously undiscovered ability of this protein to solely affect late larval development. lin-14(sa485) hermaphrodites exhibit asynchrony between vulval and gonadal morphogenesis and maturation. Further, lin-14(sa485) preferentially disrupts the timing of vulval cell morphogenesis, but not cell division. I also show that terminal differentiation of a uterine cell type is delayed in lin-14(sa485) mutants.
Defines the current status of research in the genetics, anatomy, and development of the nematode C. elegans, providing a detailed molecular explanation of how development is regulated and how the nervous system specifies varied aspects of behavior. Contains sections on the genome, development, neural networks and behavior, and life history and evolution. Appendices offer genetic nomenclature, a list of laboratory strain and allele designations, skeleton genetic maps, a list of characterized genes, a table of neurotransmitter assignments for specific neurons, and information on codon usage. Includes bandw photos. For researchers in worm studies, as well as the wider community of researchers in cell and molecular biology. Annotation copyrighted by Book News, Inc., Portland, OR
The Neurobiology of C. elegans assembles together a series of chapters describing the progress researchers have made toward solving some of the major problems in neurobiology with the use of this powerful model organism. The first chapter is an introduction to the anatomy of the C. elegans nervous system. This chapter provides a useful introduction to this system and will help the reader who is less familiar with this system understand the chapters that follow. The next two chapters on learning, conditioning and memory and neuronal specification and differentiation, summarize the current state of the C. elegans field in these two major areas of neurobiology. The remaining chapters describe studies in C. elegans that have provided particularly exciting insights into neurobiology.
The nervous system is highly complex both in its structural order and in its ability to perform the many functions required for survival and interaction with the environment; understanding how it develops has proven to be one of the greatest challenges in biology. Such precision demands that key events at every developmental stage are executed properly and are coordinated to produce the circuitry underlying each of the adult nervous system's functions. This volume describes the latest research on the cellular and molecular mechanisms of neural circuitry development, while providing researchers with a one-stop overview and synthesis of contemporary thought in the area. Reviews current research findings on the development of neural circuitry, providing researchers with an overview and synthesis of the latest contemporary thought in the cellular and molecular mechanisms that underlie the development of neural circuitry Includes chapters discussing topics such as the guidance of nerve growth and the formation of plasticity of synapses, helping researchers better understand underlying mechanisms of neural circuit development and maintenance that may play a role in such human diseases/conditions as depression, anxiety, and pain Chapters make use of a variety of human and animal models, allowing researchers to compare and contrast neural circuitry development across a wide spectrum of models
Instead, we found that the homeodomain transcription factor family is set apart from other families by their distinctly sparse expression across the nervous system at comparatively high levels. These expression patterns along with the numerous examples of functional homeodomain terminal selectors suggest that the family is an underlying theme in neuronal specification. We further extended this analysis to available scRNA-Seq datasets in the mouse nervous system and noted select commonalities in homeobox family expression across organisms. In all, this study shows yet again that analyzing homeodomain transcription factors leads to fruitful insights on organismal development. We found that the complexity of the C. elegans nervous system can be categorized and largely specified by a single family of transcription factors, building on previous studies of their importance in neuronal function.
Energy production is a biological process required for life by all living organisms. However, this process exerts a major effect on aging as metabolism of nutritive energy at the mitochondria inevitably generates reactive oxygen species (ROS). ROS are by-products of cellular metabolism and have important physiological roles in cell signaling and homeostasis but can also harbor harmful effects. Because ROS readily react with other macromolecules, if ROS formation exceeds a physiological level and antioxidants are unable to balance out the damaging effects of ROS, a dangerous condition known as oxidative stress occurs. This accumulation of cellular damage severely compromises cell health and contributes to the onset of age-associated diseases. Many organisms have complex antioxidant systems to protect themselves and in Caenorhabditis elegans, SKN-1/Nrf2 and DAF-16/FOXO, promote the expression of stress resistance genes that aid in detoxifying ROS. Our lab has previously shown that transcription factors can influence the expression of phase II detoxifying genes, through SKN-1 activation, while phase I genes can be activated through DAF-16 which confer stress resistance. An RNAi screen against transcription factor ZTF-17 revealed thatSKN-1 target, gst-4p::gfpexpression, was enhanced. This suggested that ZTF-17 possessed repressor like functions during oxidative stress responses. I confirmed that ZTF-17 significantly reduced the activity of SKN-1 and DAF-16 on the skn-1cp and sod-3p target promoters indicating that ZTF-17 may interact directly and/or indirectly with the DNA to modulate transcription through repression. Analysis through various experiments using ztf-17(tm963) deletion mutants showed that genes related to oxidative stress, lifespan and longevity were enhanced to promote short-term oxidative stress resistance, but interestingly, mutants also had compromised heat shock survival. The stress regulatory network is extremely complex, and although detoxification processes exist, the molecular players involved in maintaining proper function under oxidative stress remains unclear. Thus, my investigation of ZTF-17s function along with characterizing its role as a potential negative regulator will help elucidate the mechanism to achieve stress resistance and the implications this has on lifespan and longevity.