Thesis Defense Announcement
To: the George Mason Community

Sarah Trunnell
Master of Science in Biology
Molecular Biology concentration

Date: Monday July 26, 2010
Time: 1:00 - 3:00 P.M.
Place: Occoquan Bldg., Room 312-G
Prince William campus

Thesis Chair: Dr. Daniel N. Cox, MMB Dept.

Disorders of the nervous system can often be attributed to developmental abnormalities occurring during neurogenesis, which affect the morphology, and ultimately functionality of neurons. In order to understand how the nervous system successfully matures, it is essential to uncover the molecular mechanisms governing neural development.   The peripheral nervous system (PNS) of Drosophila melanogaster, provides an excellent model system in which to elucidate the molecular mechanisms governing dendrite morphogenesis.  Spectraplakins are an evolutionarily conserved family of cytoskeletal cross-linking proteins that provide a link between the actin and microtubule cytoskeletons.  Given that cytoskeletal structure and organization are key mediators of neuronal shape, and by extension neuronal function, understanding the molecular mechanisms underlying the regulation of cytoskeletal dynamics in neurons is important to achieving insight into the process of class-specific neuronal dendrite morphogenesis.  To address the role of Spectraplakins in dendrite morphogenesis, this thesis focuses on investigating the sole known Spectraplakin gene in Drosophila referred to as short stop (shot).  This research demonstrates that shot exerts differential effects on class specific dendrite morphogenesis of Drosophila dendritic arborization (da) neurons of the PNS.  Comparative morphological analyses reveal shot is required to restrict dendritic complexity among the simpler class I and II da neurons, whereas shot is required to promote dendritic complexity among the more complex class III and IV da neurons.  Taken together, these results suggest dendrite morphogenesis is subject to context-dependent regulation mediated via shot.  Immunohistochemistry analyses further reveal that Shot protein is expressed in all da neurons.  Collectively, these studies provide novel insight into the role of Spectraplakins in dendrite development and suggest the importance of cross talk between the actin and microtubule cytoskeletons in mediating neuron-specific patterns of dendrite arborization.