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.