The fruitless (fru) gene in Drosophila melanogaster is a multifunctional
gene having sex-specific functions in the regulation of male sexual behavior and
sex-nonspecific functions affecting adult viability and external morphology. While
much attention has focused on fru's sex-specific roles, little is known about its sex-nonspecific
functions. The embryonic central nervous system (CNS) is a prime
model system in which to study the genetic control of axonal outgrowth and proper
CNS formation. I have examined fru's sex-nonspecific role in embryonic neural
development. fru transcripts and FRU proteins from sex-nonspecific promoters are
expressed beginning at the earliest stages of neurogenesis and subsequently in both
neurons and glia. In embryos that lack most or all fru function, Fasciclin II- and
BP102-positive axons appeared to defasciculate from their normal pathway and
fasciculate along aberrant neuronal pathways, suggesting that one of fru's sex-nonspecific
roles is to regulate axonal differentiation. I next examined whether the
loss of fru function in FRU-expressing neuronal precursors causes neuronal fate
change. Analysis of fru mutant embryos revealed a lack of Even-skipped (Eve)
staining in Eve-expressing neurons, ectopic Eve staining in non-Eve-expressing
neurons and mispositioned dorsal Eve-expressing neurons, which suggests that fru
functions to maintain neuronal identity rather than to specify neuronal fate. In fru
mutants these defects in axonal projections and in Eve staining were rescued by the
expression of specific fru transgenes.
To better understand fru's function in the formation of the embryonic CNS,
I dissected out fru's function in neuron and glia through a genetic interaction study.
fru genetically interacts in neurons with longitudinal lacking to make proper axonal
projections. In addition, fru might be in the same genetic pathway as roundabout
(robo), a repulsive guidance receptor, and commissureless, a downregulator of
Robo, to ensure proper axonal pathfinding. Surprisingly, fru interacts with
tramtrack and glial cells missing to repress neuronal differentiation in the lateral
glia and with single-minded for the development of midline glia. Taken together,
fru function is required for proper axonal pathfinding in neurons and for proper
development of lateral and midline glia. / Graduation date: 2002
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/32559 |
| Date | 16 August 2001 |
| Creators | Song, Ho-Juhn |
| Contributors | Taylor, Barbara J. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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