2002 — 2008 |
Hales, Karen |
N/AActivity Code Description: No activity code was retrieved: click on the grant title for more information |
Career: Genetic Dissection of Mitochondrial Morphogenesis During Drosophila Spermatogenesis
Mitochondria are the organelles in which the energy from food is harnessed into ATP. In many cell types, mitochondria undergo dynamic shape changes and regulated movement, events which are thought to coordinate delivery of ATP to subcellular regions with highest energy demand. Mechanisms by which mitochondria are moved and shaped have been partially characterized in single-celled eukaryotes, but not all of these mechanisms are conserved in more complex organisms. The scientific goal of this project is to elucidate molecular mechanisms of mitochondrial dynamics during spermatogenesis in Drosophila melanogaster. An undergraduate research program will be established, and students will identify and characterize genes associated with mitochondrial morphogenesis. The educational goal is to incorporate experimental questions from the research into a genetics laboratory course taught annually at Davidson College. Spermatogenesis in Drosophila is an ideal metazoan model system for genetic analysis of mitochondrial morphogenesis, since 1) mitochondria normally aggregate, fuse, and elongate beside the flagellar axoneme in spermatids, and 2) genetic defects in mitochondrial morphogenesis can lead to sterility, a phenotype for which many genetic screens have been performed. Students will take both forward and reverse genetic approaches to characterize gene products that are required for mitochondrial movement and shaping in Drosophila spermatids. These approaches interweave many classical and molecular genetic techniques, such as recombination mapping, transposon mobilization, complementation, polymerase chain reaction, DNA subcloning, blotting and hybridization, and immunolocalization. Sequence analysis using online tools and computer databases will be an essential component of the research. Students will benefit from the connections they observe between classroom learning and laboratory discoveries, especially as they see the integration of classical and molecular genetics. Undergraduates in independent projects and in the genetics laboratory course will be particularly motivated by the prospect of contributing original findings to the scientific literature. Sperm cells require a great deal of energy; the structures within each cell that generate and provide usable "fuel" are mitochondria. During sperm cell formation, mitochondria undergo shape changes essential for sperm cell motility. In this project, undergraduates will perform studies of sterile mutant fruit fly strains that show mitochondrial defects. Students will identify and characterize genes which control the movement and shaping of mitochondria. This project will expand knowledge of mechanisms of mitochondrial dynamics.
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0.915 |
2007 |
Hales, Karen G |
R15Activity Code Description: Supports small-scale research projects at educational institutions that provide baccalaureate or advanced degrees for a significant number of the Nation’s research scientists but that have not been major recipients of NIH support. The goals of the program are to (1) support meritorious research, (2) expose students to research, and (3) strengthen the research environment of the institution. Awards provide limited Direct Costs, plus applicable F&A costs, for periods not to exceed 36 months. This activity code uses multi-year funding authority; however, OER approval is NOT needed prior to an IC using this activity code. |
Genetic Control of Mitochondrial Aggregation in Drosophila Spermatogenesis
[unreadable] DESCRIPTION (provided by applicant): Mitochondria, the organelles in which energy is harnessed from food into usable ATP form, are moved and shaped within specialized cell types to fulfill different energy needs. The focus of this proposal is to use the model system spermatogenesis in Drosophila melanogaster to elucidate molecular mechanisms by which mitochondrial morphogenesis, specifically mitochondrial movement, occurs. Drosophila spermatogenesis is an ideal context for the analysis of mitochondrial morphogenesis, since mitochondria aggregate, fuse, interwrap, unfurl, and elongate during meiosis and spermatid development; defects in these processes often lead to male sterility, and male sterile mutants can be generated, maintained, and characterized easily. The majority of the proposal centers on the nmd gene, its paralog CG4701, and other members of the AAA+ ATPase family to which nmd and CG4701 belong. The nmd gene is required for mitochondrial aggregation during Drosophila spermatogenesis and encodes an AAA+ ATPase homologous to a S. cerevisiae mitochondrial outer membrane protein of unknown function. Nmd and its paralog CG4701 are related, though not orthologous, to the AAA+ ATPases spastin and katanin 60, which sever microtubules. The overall goals are to determine the mechanisms by which these gene products influence mitochondrial movement and aggregation. The subcellular localization of Nmd and CG4701 will be determined through epitope tagging and analysis of transgenic flies. The function of CG4701, whose expression pattern suggests testis specificity, will be determined by traditional as well as RNAi mutant analysis. The roles of Nmd and CG4701 in microtubule dynamics will be assessed through visualization of microtubule structure in mutants as well as through assessment of Nmd and CG4701 binding to microtubules (both in their wild type and permanently ATP-bound forms). The roles of spastin and katanin 60 in spermatogenesis will be tested via phenotypic analysis of spastin male sterile alleles as well as mutant alleles of a testis specific katanin 60 paralog. Finally, characterization and cloning of the mitoshell gene, required for proper aggregation of mitochondria in spermatids, will elucidate from another angle molecular mechanisms of mitochondrial aggregation. The long term objectives of this study are to learn basic molecular mechanisms of mitochondrial biology and to set the stage for analysis of human orthologs of the genes in question. Previously, identification of mitochondrial fusion mediators in Drosophila and Saccharomyces cerevisiae led to deepened understanding of the genetic diseases optic atrophy and Charcot Marie Tooth syndrome, each associated with an ortholog of a mitochondrial fusion gene identified in model systems. Since many neurodegenerative diseases result from mitochondrial defects, the proposed work may in the long term uncover mechanisms underlying other such disorders. Mitochondrial defects underlie many neurodegenerative diseases and may be associated with premature aging as well as infertility. Elucidation of molecular mechanisms by which mitochondria are moved and shaped in different cell types will enable deeper understanding of mitochondria-related disorders, setting the stage for the design of treatments. [unreadable] [unreadable] [unreadable]
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1 |
2012 |
Hales, Karen G |
R15Activity Code Description: Supports small-scale research projects at educational institutions that provide baccalaureate or advanced degrees for a significant number of the Nation’s research scientists but that have not been major recipients of NIH support. The goals of the program are to (1) support meritorious research, (2) expose students to research, and (3) strengthen the research environment of the institution. Awards provide limited Direct Costs, plus applicable F&A costs, for periods not to exceed 36 months. This activity code uses multi-year funding authority; however, OER approval is NOT needed prior to an IC using this activity code. |
Aaa Atpases Linking Mitochondria With Microtubule Processing in Flies and Yeast
DESCRIPTION (provided by applicant): Mitochondria, the organelles in which food energy is harnessed into usable ATP form, are moved and shaped to fulfill different energy needs within specialized cells. Many human genetic neurodegenerative disorders are associated with defects of mitochondrial dynamics. Drosophila melanogaster spermatogenesis is an ideal model system for genetic dissection of conserved mechanisms of mitochondrial morphogenesis, since mitochondria undergo dramatic shaping during sperm development. After meiosis, all mitochondria in a Drosophila spermatid normally fuse into two giant mitochondrial derivatives that interwrap precisely and intricately to form a spherical structure called the Nebenkern, which then unfurls and elongates along the growing sperm tail. The main focus is to elucidate molecular mechanisms underlying mitochondrial shaping, as a way to characterize genes whose human homologs might underlie mitochondrial dysfunction. We previously identified the Drosophila nmd gene (no mitochondrial derivative) as required for aggregation of mitochondria during spermatogenesis. The Nmd gene product is an AAA ATPase related to microtubule-severing proteins spastin and katanin, though unlike those relatives, Nmd is unique in its localization to both mitochondria and centrosomes/basal bodies. A paralog of Nmd, CG4701, is required for mitochondrial shaping later in spermatogenesis. Both paralogs seem to be required also for male meiotic cytokinesis, perhaps through effects on the meiotic spindle. A yeast ortholog exists but has not been well characterized. Since various observations initially suggest a conserved role for Nmd family members in both mitochondrial shaping and microtubule processing, the primary emphasis in the proposed research is to determine genetically and biochemically the interactions between these mitochondrial AAA ATPases (in both flies and yeast) and microtubules and other structures. These gene products are homologous to human protein ATAD1 which is important in neurons for internalization of receptors but about which little else is known. ATAD1 may be a good candidate for another version of spastic paraplegia that maps in the same region of the genome. Our work will allow for important insight into the molecular roles of this human gene in health and disease. As a final aim, the genes defective in two male sterile Drosophila strains with related phenotypes to nmd and CG4701 will be identified, allowing identification of further gene families that may ultimately be associated with human mitochondrial neuropathies, myopathies, and infertility syndromes. PUBLIC HEALTH RELEVANCE: Defects of mitochondrial shaping and movement underlie many neurodegenerative diseases and may be associated with premature aging as well as infertility. Elucidation of molecular mechanisms by which mitochondrial shaping is mediated by fly and yeast mitochondrial proteins related to those implicated in hereditary spastic paraplegia will enable characterization of related functions in humans. These efforts may provide a deeper understanding of mitochondria-related disorders and set the stage for the design of treatments.
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1 |
2012 — 2016 |
Hales, Karen |
N/AActivity Code Description: No activity code was retrieved: click on the grant title for more information |
Rui: Roles For Tissue-Specific Atp Synthase Subunits and Other Proteins in Mitochondrial Shaping During Drosophila Spermatogenesis
INTELLECTUAL MERIT Mitochondria, the structures inside cells where energy is harnessed from food, are moved and shaped in specialized cells such as neurons and sperm to fulfill different energy needs. Spermatogenesis (sperm cell formation) in the fruit fly Drosophila melanogaster is an ideal context for determining the molecular basis of mitochondrial shaping, since mitochondria undergo dramatic events during sperm development, and since the fruit fly is a well-characterized model organism. The project addresses two broad questions: 1) do tissue-specific ATP synthase subunits control tissue-specific mitochondrial shaping, and 2) how are distinct mitochondrial populations defined and maintained within the same cell? Both will be pursued through genetic and molecular analysis of Drosophila male sterile mutants showing defects in the Nebenkern, the structure in post-meiotic spermatids that consists of exactly two interwrapped giant mitochondrial derivatives. The hypothesis that a testis-expressed version of an ATP synthase subunit contributes to the dramatic internal structure of the Nebenkern will be tested through microscopy, molecular biology, fly husbandry, and transgenic techniques. Roles for testis-expressed paralogs of other ATP synthase subunits will also be explored. In addition, to determine how distinct mitochondrial populations are defined, the role of Parkin and PINK1 proteins in the segregation of the two mitochondrial derivatives in the Nebenkern will be assessed. The research could demonstrate how tissue-specific mitochondrial morphology is governed by specific ATP synthase isoforms, as well as how distinct viable mitochondrial populations are maintained.
BROADER IMPACTS The project will result in the research training of many undergraduate students including four to eight students each academic semester and three summer students. Additionally, one undergraduate student per summer from a historically black college or university (HBCU) will be involved in the research. Davidson students from underrepresented groups in science will also be encouraged to embark upon research in the laboratory. A laboratory technician (usually a recent college graduate aiming to attend graduate school) will also receive research training. For most students this will be their first research experience. All students will be mentored in scientific communication and data presentation, and they will present their work at the Davidson College research symposia that occur annually in May and September. A subset of these students will present their experimental results at the Annual Drosophila Research Conference. Outcomes will be tracked as these students embark upon careers in science. In addition, elements of the project will be integrated into the teaching of a Genetics course so that the entire class (approximately 32 undergraduate students per year) will carry out original research and will be challenged and stimulated to make publishable discoveries.
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0.915 |