Proper function of the nervous system requires specific interactions between neurons and glia, and yet the precise mechanisms by which these interactions occur remain incompletely understood. The Drosophila segmental nerve, which comprises a layer of motor and sensory axons surrounded by an inner (peripheral) and outer (perineural) glial layer, provides a genetic system for the analysis of this intercellular signaling. Mutations in push, a gene identified and cloned in the PI's lab, and Nf1, the Drosophila homolog of the gene responsible for neurofibromatosis in humans, each increase the thickness of the perineural glial layer. In addition, the effect of push and Nf1 mutations are strongly potentiated by mutations in ine which encodes a neurotransmitter transporter. The effect of push mutations in perineural glial growth is also enhanced by mutations in eag which encodes a potassium channel subunit. Both push and Nf1 encode intermediates in the receipt of intercellular signaling pathways mediated by the PACAP neuropeptide, or by the amn-encoded protein, which is PACAP-related. Thus their results are consistent with a model in which perineural growth in Drosophila is controlled by two interacting neurotransmitter-mediated signaling pathways, one controlled by Amn and acting through push and Nf1, and the second controlled by substrate neurotransmitter of ine and acting through eag. The PI proposes a further dissection of these intercellular signaling pathways. Three specific questions are asked. First, is the Amn signal released from peripheral glia and received by perineural glia or is the signal released from neurons, received by peripheral glia and then signaled by a relay mechanism to perineural glia? Second, does the Eag potassium channel act in the Amn signaling cell, or in the Amn receiving cell, to modulate the effect of Amn signaling on perineural growth? Third, in other PACAP or Amn signaling pathways described, additional intermediates have been implicated, including PKA, Ras and Raf. Which of these intermediates participate in Amn signaling in the Drosophila segmental nerve? These experiments will provide new molecular insights into the nature of neuron/glia signaling. In addition, it appears that defects in signaling with this pathway models, at least in part, the tumor formation that occurs in neurofibromatosis. Thus the studies proposed here are anticipated to enable the development of new models for the role of Nf1 in tumor formation, and perhaps enable the development of new pharmacological strategies.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS039984-02
Application #
6490968
Study Section
Special Emphasis Panel (ZRG1-MDCN-1 (01))
Program Officer
Jacobs, Tom P
Project Start
2001-02-08
Project End
2004-12-31
Budget Start
2002-01-01
Budget End
2002-12-31
Support Year
2
Fiscal Year
2002
Total Cost
$252,503
Indirect Cost
Name
Rice University
Department
Biochemistry
Type
Schools of Arts and Sciences
DUNS #
050299031
City
Houston
State
TX
Country
United States
Zip Code
77005
Cardnell, Robert J G; Nogare, Damian E Dalle; Ganetzky, Barry et al. (2006) In vivo analysis of a gain-of-function mutation in the Drosophila eag-encoded K+ channel. Genetics 172:2351-8
Caldwell, Philip E; Walkiewicz, Magdalena; Stern, Michael (2005) Ras activity in the Drosophila prothoracic gland regulates body size and developmental rate via ecdysone release. Curr Biol 15:1785-95
Yager, J; Richards, S; Hekmat-Scafe, D S et al. (2001) Control of Drosophila perineurial glial growth by interacting neurotransmitter-mediated signaling pathways. Proc Natl Acad Sci U S A 98:10445-50