Signaling Roles of Intermediate Filament Isoforms in Neural Development

University Of Virginia Main Campus, Charlottesville VA

Investigators

Abstract

This project aims to advance scientific knowledge by addressing an unanswered question in biology: what are the molecular principles that create different types of cells? The research focuses on a class of proteins which are expressed in strikingly cell-type specific patterns, the intermediate filament (IF) proteins. The project focuses on neurons in the brain which are known to switch IF subtype as they develop their mature shape, including extending long axons to the correct location in the brain. The research aims to determine why neurons switch from one IF subtype to another as they grow. The project will also broaden the impact by contributing to desired societal outcomes: 1) broadening education in STEM fields to support a better informed and more scientifically literate public, and 2) increasing the diversity and inclusivity of the STEM workforce. Especially, the lab aims for full participation of women, persons with disabilities, and underrepresented minorities in STEM at all levels. The project funds research experiences for undergraduates (REU) for one underrepresented minority student during each summer. The REU funded by this project provides hands-on experience in laboratory research by investigating the roles of diverse intermediate filaments in growing axons. In addition, the selected REU student will participate in the institutionally established SRIP (summer research internship program) at the University of Virginia which provides professional skill training and guidance for pursuing a career in STEM in individual and group settings. SRIP has a history of successfully placing participating undergraduate researchers into STEM careers. This project seeks to discover how developmental IF subtype switching from nestin to neurofilaments in neurons affects signaling to the microtubule cytoskeleton to regulate growth cone structure and motility. The PI’s lab recently discovered that the IF protein nestin regulates growth cone morphology. In addition, nestin changes the response of growth cones to the guidance cue Sema3a. It does so by binding the kinase Cdk5 and its substrate, the microtubule associated protein DCX, thereby increasing DCX phosphorylation. As neurons mature, they switch IF subtype from nestin to neurofilaments, which bind DCX but not Cdk5. The project will test the novel hypothesis that neuronal IFs regulate microtubule dynamics and bundling in axonal growth cones via DCX downstream of Sema3a signaling. Aim 1 will discover how experimental IF switching affects axonal microtubules and growth cone behavior. Aim 2 will discover how experimental IF switching affects Sema3a responses in cortical neurons. The project will use state-of-the-art imaging approaches in cultured cortical neurons in combination with downregulation and overexpression of different IF subtypes to uncover the mechanisms by which different IF subtypes modulate microtubule dynamics in growth cones during axon outgrowth. Responsiveness to extracellular cues by growth cones during development is influenced not only by the cue available, the receptors expressed on the surface, the intracellular substrates present, but also by the IF subtypes expressed. The PI proposes that neuronal IF subtypes can act as either amplifiers or dampeners of ubiquitous kinase cascades to provide local and cell-type specific regulation of effector responses. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.