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Interactions between the tumor suppressor proteins Discs Large (Dlg) and various factors involved
in asymmetric cell divisions of neuronal stem cells in Drosophila melanogaster.
Presenter: Mimmi U. Sewerin
Mentor: Dr. Peter J. Bryant
Drosophila melanogaster develops in a series of steps, including three instars of larval development, and
it is during the second instar that neuronal stem cells asymmetrically divide to form one neuronal
progenitor cell and one additional stem cell. According to previous data, tumorous growths in
mutant genotypes of Drosophila melanogaster coincide with high rates of symmetric cell divisions where
only stem cells are formed. Progenitor cells normally stop dividing and develop into functional
neurons, and stem cells keep dividing. Thus, overgrowth of the brain is a symptom of tumorous
growth. Two tumor suppressor genes, Partner of Inscuteable (pins) and discs large (Dlg), are crucial
for the asymmetric divisions of neuronal stem cells, and direct the distribution of Numb, Miranda,
and Prospero. These are cell fate determinants located at the apical surface of the neuroblast, and
regulate the formation of neuronal progenitor cells. My hypothesis is that if over-expressed, pins will
out-compete these proteins at the membrane and thus, neuronal progenitor cells will not be formed
leading to tumor formation and brain overgrowth. My results show that Numb is affected by the
over-expression of pins and no neuronal progenitor cells are formed, leading to tumor formation. No
results were seen for Miranda and Prospero, which can be due to the higher level of complexity of
the Miranda and Prospero genes. A new experiment designed to test these more complex genes can
be performed to test the relationship between pins and these genes.