This study investigated the position, ultrastructure and life
history of glia in the midline of the Drosophila melanogaster Central
Nervous System (CNS) by using enhancer traps (AA142, X81,
argoswll, pointed1277) and reporter constructs (EEl, slilacZ 1.0,
slilacZ 4.5) as glial-specific markers. Previous work has established
that glia are necessary for proper formation and morphogenesis of
longitudinal and commissural axon tracts, and axon ensheathment
(Jacobs, 1993; Klambt et al., 1991; Jacobs and Goodman, 1989). By
the end of embryogenesis there are three midline glial (MG) cells
remaining in each segment (Sonnenfeld and jacobs, in press) which
this study verifies. In the third instar larval MG cells proliferate to
24 cells per segment as followed with the E. coli lacZ expressing
pointed1277 strain. These E. coli lacZ expressing pointed1277 MG
cells begin dividing 57 hours after hatching as seen with 5
-bromodeoxyuridine and hydroxyurea treatment. Some MG genes
cease midline expression before MG proliferation (seen with EEl,
X81), others (seen with AA142) continue to be expressed until the
beginning of MG proliferation. Only the argoswll, slilacZ 1.0, slilacZ
4.5, and pointed1277 expression strains continue E. coli lacZ
expression to the end of the larval stages. In the first larval stage a
few perineuropilar glia begin to express the E. coli lacZ gene and
increase to 400 cells per CNS in the third ins tar as seen in the
pointed1277 marker strain. pointed1277 EM micrographs show
that E. coli lacZ labeled cells have a glial-like ultrastructure. There
-
was no co-localization of the E. coli lacZ expression in pointed12 77
and an anti-RK2 (repo) antibody in third instar larvae. In
pointed1277 pupae the MG cell E. coli lacZ expression stops after 48-
72 hours and the prerineuropilar signal stops after 24 hours. In
newly hatched pointed1277 adults perineuropilar E. coli lacZ
expression is present with a cluster of 12 cells in the center of the
neuropil. To summarize, after embryogenesis, in the pointed1277
marker strain, the MG cells begin dividing after 57 hours and the E.
coli lacZ gene expression ends after the second day of the pupal
stage. In the first instar, perineuropilar glia begin to label for the E.
coli lacZ product and this expression ends by one day into the pupal
stage, with re-appearance in the adult CNS. / Thesis / Master of Science (MSc)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/22476 |
| Date | 12 1900 |
| Creators | Perz, Michael Jonathan |
| Contributors | Jacobs, J. Roger, Biology |
| Source Sets | McMaster University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis |
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