Directed neuronal migration is an essential feature of the developing nervous system, requiring the precise navigation of cells through a complex and dynamic molecular environment. Errors in this process can give rise to severe anatomical and cognitive disorders in human development. Although some of the genes affected in these defects are known, the molecular mechanisms that guide migration remain poorly understood, in part due to the complexity of vertebrate preparations. This issue can be addressed in the enteric nervous system (ENS) of the moth Manduca, in which an identified set of migratory neurons (the EP cells) and their pathways (visceral muscle bands) remain uniquely accessible throughout development. Despite obvious morphological differences, neuronal development in this system employs similar signaling processes as found in mammalian systems, permitting a mechanistic analysis of migration in living embryos. Specifically, fasciclin II (MFas II) has been identified as an essential guidance cue for the EP cells. Like its vertebrate counterpart NCAM, MFas Il is a member of the immunoglobulin related adhesion receptor family. MFas II is required for normal migration, and its two isoforms (transmembrane and GPI-linked) exhibit distinct patterns of expression in the migratory neurons and their pathways. Intracellular injections of isoform-specific RNA and plasmids will be used to induce ectopic MFas II expression in non-pathway muscles, while antisense oligonucleotides and RNAi probes will be injected to block endogenous MFas II expression to test whether this receptor is both necessary and sufficient to support migration. The migratory behavior of the neurons will also be tested in primary culture on MFas Il-transfected cells. Parallel experiments will be used to test how each isoform affects neuronal motility. One of the isoforms has been shown to associate with a tyrosine kinase, whose identity and function will be determined by co-immunoprecipitation, microsequencing, and manipulations in culture. Column-linked GST fusion proteins and 2-hybrid approaches will be used in function-independent screens of MFas Il-interacting proteins. These experiments should lend insight into the fundamental mechanisms by which this important class of guidance cues regulate neuronal migration in vivo.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
2R01NS034439-05
Application #
6545456
Study Section
Molecular, Cellular and Developmental Neurosciences 2 (MDCN)
Program Officer
Finkelstein, Robert
Project Start
1996-12-12
Project End
2006-04-30
Budget Start
2002-07-25
Budget End
2003-04-30
Support Year
5
Fiscal Year
2002
Total Cost
$283,024
Indirect Cost
Name
Oregon Health and Science University
Department
Anatomy/Cell Biology
Type
Schools of Medicine
DUNS #
009584210
City
Portland
State
OR
Country
United States
Zip Code
97239
Coate, Thomas M; Swanson, Tracy L; Proctor, Thomas M et al. (2007) Eph receptor expression defines midline boundaries for ephrin-positive migratory neurons in the enteric nervous system of Manduca sexta. J Comp Neurol 502:175-91
Copenhaver, Philip F (2007) How to innervate a simple gut: familiar themes and unique aspects in the formation of the insect enteric nervous system. Dev Dyn 236:1841-64
Swanson, T L; Knittel, L M; Coate, T M et al. (2005) The insect homologue of the amyloid precursor protein interacts with the heterotrimeric G protein Go alpha in an identified population of migratory neurons. Dev Biol 288:160-78
Higgins, M R; Gibson, N J; Eckholdt, P A et al. (2002) Different isoforms of fasciclin II are expressed by a subset of developing olfactory receptor neurons and by olfactory-nerve glial cells during formation of glomeruli in the moth Manduca sexta. Dev Biol 244:134-54
Knittel, L M; Copenhaver, P F; Kent, K S (2001) Remodeling of motor terminals during metamorphosis of the moth Manduca sexta: expression patterns of two distinct isoforms of Manduca fasciclin II. J Comp Neurol 434:69-85
Wright, J W; Copenhaver, P F (2001) Cell type-specific expression of fasciclin II isoforms reveals neuronal-glial interactions during peripheral nerve growth. Dev Biol 234:24-41
Wright, J W; Copenhaver, P F (2000) Different isoforms of fasciclin II play distinct roles in the guidance of neuronal migration during insect embryogenesis. Dev Biol 225:59-78
Wright, J W; Snyder, M A; Schwinof, K M et al. (1999) A role for fasciclin II in the guidance of neuronal migration. Development 126:3217-28
Wright, J W; Schwinof, K M; Snyder, M A et al. (1998) A delayed role for nitric oxide-sensitive guanylate cyclases in a migratory population of embryonic neurons. Dev Biol 204:15-33