Characterization of a regulatory mechanism for posttranscriptional Lin28a induction through microRNA processing machinery in neuronal growth
| dc.contributor.advisor | Sockanathan, Shanthini | |
| dc.contributor.committeeMember | Meffert, Mollie K | |
| dc.contributor.committeeMember | Kolodkin, Alex | |
| dc.contributor.committeeMember | Green, Rachel | |
| dc.creator | Amen, Alexandra Marie | |
| dc.creator.orcid | 0000-0002-2285-7609 | |
| dc.date.accessioned | 2019-04-15T03:57:44Z | |
| dc.date.created | 2016-12 | |
| dc.date.issued | 2016-09-14 | |
| dc.date.submitted | December 2016 | |
| dc.date.updated | 2019-04-15T03:57:44Z | |
| dc.description.abstract | Environmental cues produce rapid transitions in gene expression to support growth and cellular plasticity through incompletely understood mechanisms. Brain-derived neurotrophic factor (BDNF) is a signaling molecule involved in development and plasticity that is dysregulated in numerous neurologic diseases. Prior work from our laboratory demonstrated that BDNF signaling confers translational specificity by regulating microRNA biogenesis, in part through induction of Lin28a protein. Lin28 RNA-binding proteins have evolutionarily-conserved roles in posttranscriptional coordination of pro-growth gene expression, but Lin28 is traditionally considered to be absent from terminally-differentiated cells, and signaling pathways allowing stimulus-dependent induction of Lin28 remain uncharacterized. The first portion of my dissertation focuses on elucidating a novel mechanism allowing rapid Lin28a induction in mature neurons. We find that Lin28a protein undergoes rapid basal turnover in hippocampal neurons, and is stabilized by BDNF-dependent activation of mitogen-activated protein kinase (MAPK). MAPK-mediated phosphorylation of the miRNA-processing factor, HIV TAR-RNA-binding protein (TRBP), promotes binding and stabilization of Lin28a, but not Lin28b, with accompanying reduction in Lin28-targeted miRNAs (Let-7 miRNAs). Further, phospho-TRBP recapitulates BDNF-induced neuronal dendritic spine growth, in a Lin28a-dependent manner. Finally, we demonstrate MAPK-dependent induction of TRBP and Lin28a downstream of diverse growth factors in multiple primary cell types, supporting a broad role for this newly described pathway in cellular trophic responses. Our finding of Lin28a regulation by phospho-TRBP in neuronal cells leads to the second portion of my dissertation, investigating the possibility that TRBP and Lin28a are dysregulated in a human tumor disorder, Neurofibromatosis Type 2 (NF2). We demonstrate that loss of Merlin protein in NF2 results in elevated TRBP, phospho-TRBP, and Lin28a proteins, and reduced Let-7 miRNAs. Additionally, ongoing studies suggest that abnormal tumor cell growth in NF2 is related to Lin28a overexpression, paving the way for potential research regarding novel therapeutics for NF2. Collectively, the work presented in my dissertation uncovers a previously unrecognized mechanism for induction of Lin28a that is conserved in both acute (trophic) and chronic (tumor) settings. This molecular mechanism underlying Lin28a stabilization has implications for understanding regulation and misregulation of translational specificity in synaptic responses, and in tumor and stem cell biology, where Lin28a is constitutively elevated. Advisor: Mollie K. Meffert, M.D., Ph.D | |
| dc.format.mimetype | application/pdf | |
| dc.identifier.uri | http://jhir.library.jhu.edu/handle/1774.2/60716 | |
| dc.language.iso | en_US | |
| dc.publisher | Johns Hopkins University | |
| dc.publisher.country | USA | |
| dc.subject | Gene expression regulation | |
| dc.subject | BDNF | |
| dc.subject | Synaptic plasticity | |
| dc.subject | MicroRNA processing | |
| dc.title | Characterization of a regulatory mechanism for posttranscriptional Lin28a induction through microRNA processing machinery in neuronal growth | |
| dc.type | Thesis | |
| dc.type.material | text | |
| local.embargo.lift | 2020-12-01 | |
| local.embargo.terms | 2020-12-01 | |
| thesis.degree.department | Neuroscience | |
| thesis.degree.discipline | Neuroscience | |
| thesis.degree.grantor | Johns Hopkins University | |
| thesis.degree.grantor | School of Medicine | |
| thesis.degree.level | Doctoral | |
| thesis.degree.name | Ph.D. |