| Summary: | 博士 === 國立陽明大學 === 遺傳學研究所 === 92 === ABSTRACT
unpaired (upd) encodes a ligand for the Jak/STAT signaling pathway in
Drosophila. In the second instar and early third larval eye disc, upd is expressed in the
center of the posterior margin. upd loss-of-function mutations caused eye size
reduction and upd over-expression caused eye enlargement. Upd regulates eye size
through the Dome/Jak (Hop)/STAT92 signaling pathway to promote cell proliferation.
Interestingly the effect of Upd is only on cells located anterior to MF, but has no
effect on the second mitotic wave, which is posterior to MF. Overexpression of upd
behind MF can non-autonomously induce cell proliferation in the anterior region. The
G1 cyclin, cycD transcript level was also enhanced anterior to MF. Consistent with the
long-range effect, I found that the extracellular Upd protein can be detected over a
comparable long range up to 20 rows of cells anterior to MF, suggesting that Upd acts
directly over a long distance as a signaling molecule.
N and eyg regulate in the cell proliferation during eye development. I found that
N and eyg have genetic interaction with upd. Either N or eyg can induce upd
expression. Overexpression of upd can rescue the defect caused by eyg mutant or ey>
NDN. These suggest that upd is downstream to N and eyg to regulate eye development.
In the early 3rd instar, upd is expressed in the furrow initiation site of the eye disc.
Ectopic expression of upd at lateral margins can induce dpp expression which is
required for furrow initiation, and repress wg expression which antagonizes furrow
initiation. At dorsal lateral margin, expression of upd can induce ectopic eye field.
These indicate that upd can regulate pattern formation during eye development
besides its function on promoting cell proliferation.
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