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Dissertation
Dynein-driven forces transport and configure microtubules and neurofilaments during axonal growth and retraction
Doctor of Philosophy (Ph.D.), Drexel University
Nov 2004
DOI:
https://doi.org/10.17918/00000967
Abstract
The morphological differentiation of developing neurons, from symmetric to highly polarized cellular design, depends on elaboration of the neuronal cytoskeleton, which consists of microtubules, actin filaments and neurofilaments. Microtubules provide architectural support and serve as tracks along which molecular motors transport various cellular cargos. In spite of their fundamental importance, the mechanisms that underlie the establishment of neuronal microtubule array are largely unknown. Highly controlled dynamic behavior of microtubules has long been recognized as an important regulatory mechanism. However, growing evidence has suggested that molecular motor proteins also contribute to the establishment and rearrangement of the microtubule array. My dissertation explores roles that motor proteins play in the differentiation of the neuronal cytoskeleton during axonal growth and retraction. There are two specific aims. (1) Investigate the role of cytoplasmic dynein-driven forces in transporting and configuring microtubules and neurofilaments during axonal growth. (2) Determine the nature of microtubule alteration, depolymerization versus dynein-driven reconfiguration, underlying physiological axonal retraction. For aim 1, we inhibited cytoplasmic dynein in cultured rat sympathetic neurons by two distinct strategies, dynamitin overexpression and dynein heavy chain RNAi. We performed live cell microtubule and neurofilament transport assays to investigate roles of dynein in transporting these polymers. We found that cytoplasmic dynein powers the anterograde microtubule transport and the retrograde neurofilament transport in axons. We also showed that together with dynamic regulations of microtubules, cytoplasmic dynein plays crucial roles in configuring the axonal microtubule array. For aim 2, cultured chicken DRG neurons were exposed to nitric oxide to elicit axonal retraction. The status of the microtubule array in retracted axons was studied by immunocytochemistry. We found that there is no detectable loss of microtubule polymer levels in retracting axons, but the microtubules retreat backward and reconfigured into a twisted array to accommodate the shortening of the axon. Our results support a microtubule "reconfiguration" model during physiological axonal retraction. In summary, my dissertation provides direct evidence for the essential role of dynein-driven forces in transporting and configuring the neuronal cytoskeleton during axonal growth and retraction.
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Details
- Title
- Dynein-driven forces transport and configure microtubules and neurofilaments during axonal growth and retraction
- Creators
- Yan He
- Contributors
- Peter W. Baas (Advisor)
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Number of pages
- x, 115 pages
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- Neurobiology and Anatomy; College of Medicine; Drexel University
- Other Identifier
- 991014970314504721