Drosophila is a model system for studying how steroid hormones regulate neuronal development. The steroid hormones, the ecdysones, cause pruning of larval dendrites followed by sprouting of the adult arbor. Ecdysone acts through 3 isoforms of the ecdysone receptor (EcR) and isoform blends shape the neuronal response. Remodeling sensory neurons that can be viewed through the transparent cuticle provide an unparalleled opportunity to follow remodeling of complex dendritic trees in a living animal. Two-photon imaging used with molecular genetics will make it possible to link isoform specific patterns of gene activation to discrete cytodynamic modules and finally to the overall shape of the mature arbor.
The specific aims are to: 1) Use 2-photon imaging of membrane and cytoskeleton dynamics to define events underlying dendritic arbor collapse during stereotyped pruning. Studies focus on filopodial dynamics, how they relate to sites of arbor destabilization, and whether destabilization propagates within an arbor. Loss and gain of function studies will define the role of different EcR isoforms in these processes. 2) Determine the role of the epidermis in dendritic collapse. Dominant negative EcRs targeted to the neuron and/or the epidermis will block responses to steroid and the impact on distal retraction and arbor collapse will be determined. The role of filopodia in receiving epidermal cues will be examined. 3) Assess the role of phagocytes in dendrite removal. We will use time-lapse analysis of phagocyte responses to destabilized dendritic arbor, and determine the impact of blocking phagocytic activity on arbor removal. 4) Test the hypothesis that branch lability underlies growth plasticity and that the degree of plasticity is imposed by the levels of EcR-B. Loss and gain of function approaches will alter EcR isoform ratios and 2-photon microscopy will follow the cytodynamics of outgrowth. 5) Use EcR dominant-negative mutations to selectively suppress cytodynamic modules to establish the role of each on growth dynamics and on the final form of the arbor.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS029971-15
Application #
7157603
Study Section
Neurogenesis and Cell Fate Study Section (NCF)
Program Officer
Gwinn, Katrina
Project Start
1991-09-30
Project End
2008-11-30
Budget Start
2006-12-01
Budget End
2007-11-30
Support Year
15
Fiscal Year
2007
Total Cost
$292,295
Indirect Cost
Name
University of Washington
Department
Zoology
Type
Schools of Arts and Sciences
DUNS #
605799469
City
Seattle
State
WA
Country
United States
Zip Code
98195
Brown, Heather L D; Truman, James W (2009) Fine-tuning of secondary arbor development: the effects of the ecdysone receptor on the adult neuronal lineages of the Drosophila thoracic CNS. Development 136:3247-56
Williams, Darren W; Kondo, Shu; Krzyzanowska, Agnieszka et al. (2006) Local caspase activity directs engulfment of dendrites during pruning. Nat Neurosci 9:1234-6
Brown, Heather L D; Cherbas, Lucy; Cherbas, Peter et al. (2006) Use of time-lapse imaging and dominant negative receptors to dissect the steroid receptor control of neuronal remodeling in Drosophila. Development 133:275-85
MacWhinnie, Steven G B; Allee, J Paul; Nelson, Charles A et al. (2005) The role of nutrition in creation of the eye imaginal disc and initiation of metamorphosis in Manduca sexta. Dev Biol 285:285-97
Schubiger, Margrit; Carre, Clement; Antoniewski, Christophe et al. (2005) Ligand-dependent de-repression via EcR/USP acts as a gate to coordinate the differentiation of sensory neurons in the Drosophila wing. Development 132:5239-48
Zhou, Xiaofeng; Zhou, Baohua; Truman, James W et al. (2004) Overexpression of broad: a new insight into its role in the Drosophila prothoracic gland cells. J Exp Biol 207:1151-61
Schubiger, Margrit; Tomita, Shuichiro; Sung, Carl et al. (2003) Isoform specific control of gene activity in vivo by the Drosophila ecdysone receptor. Mech Dev 120:909-18
Stilwell, Geoffrey E; Nelson, Charles A; Weller, John et al. (2003) E74 exhibits stage-specific hormonal regulation in the epidermis of the tobacco hornworm, manduca sexta. Dev Biol 258:76-90
Grueber, Wesley B; Jan, Lily Y; Jan, Yuh Nung (2002) Tiling of the Drosophila epidermis by multidendritic sensory neurons. Development 129:2867-78
Riddiford, L M; Cherbas, P; Truman, J W (2000) Ecdysone receptors and their biological actions. Vitam Horm 60:Jan-73

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