Stander Symposium abstract book - University of Dayton

POSTER SESSION 1
Hippo signaling controls Dronc activity to regulate organ size in Drosophila.
Presenter(s): Aidan Fenix, Shilpi Verghese
Advisor(s): Shimpi Bedi, Madhuri Kango-Singh
Biology - Graduate Research
The Hippo signaling pathway regulates organ size by simultaneously inhibiting cell proliferation and promoting apoptosis. The Hippo pathway is
composed of a highly conserved core kinase cascade that is regulated by multiple upstream inputs and has multiple transcriptional outputs. Hippo
signaling is required for cells to stop proliferation when organs have reached their proper size and hippo mutant animals produce severely overgrown
structures. In contrast, over-expression of Hippo (or loss of yki) results in formation of smaller organs due to induction of apoptosis. Hippo
pathway regulates apoptosis through its apoptotic target genes e.g., Hid, DIAP1 and the microRNA bantam. We found that cell death induced
by Hippo over-expression cannot be rescued by co-expression of pan caspase inhibitor p35 or DIAP1. Hence, we investigated the role of Dronc in
Hippo mediated cell death, as Dronc activity is resistant to p35 and not affected by changes in DIAP1 levels. We found that Hippo genetically interacts
with Dronc and requires dronc to induce cell death. Our data suggests Hippo pathway can regulate cell death through the RHG proteins and via
Dronc. Dronc along with its binding partner Dark can suppress the over-growth induced by over-expression of Yki, suggesting that normally Hippo
pathway needs to restrict Dronc activity to maintain tissue homeostasis. Consistent with this idea, we found the Hippo pathway transcriptionally
regulates dronc. Loss of dronc results in cell survival and dronc mutant cells proliferate faster than their wild-type twin spots. Here we present
dronc (a gene required for cell competition and for caspase-mediated cell death) as a novel target of Hippo signaling.
Identifying cis-regulatory element changes that underlie gene expression and phenotypic
evolution between species
Presenter(s): William A Rogers, Joseph R Salomone
Advisor(s): Thomas M Williams
Biology - Independent Research
Contributing substantially to the diversity of animal life on Earth are differences in regulatory DNA, particularly in cis-regulatory elements (CREs)
that contain information about where, when, and to what level genes are expressed. The variation in abdominal pigmentation in fruit fly species
provides a model to study both the evolution of CREs and the gene expression patterns they control. The bric-a-brac (bab) locus codes for the Bab1
and Bab2 proteins that are repressors of abdominal pigmentation development. In the species Drosophila melanogaster, pigmentation and Bab
expression are sexually dimorphic due to the activity of a CRE called the dimorphic element. As abdominal pigmentation patterns vary between
related species, our overarching hypothesis is that these phenotypic differences stem from changes in Bab expression via modifications to the
dimorphic element. To test this hypothesis we are studying 4 related species with different abdominal pigmentation by evaluating for each their
Bab1 and Bab2 expression and (2) testing the regulatory capability of their dimorphic element. Moreover, to understand how modern dimorphic
element activities evolved we used a sequence comparisons and the parsimony principle to derive the ancestral dimorphic element sequences,
which we have resurrected to evaluate their gene regulatory capability. Future studies will evaluate chimeric CREs of ancestral and extant dimorphic
elements to find the mutations responsible for the evolved Bab expression patterns.
Induction of Chromatin Remodeling using Histone Deacetylase Inhibitors to Study Role of
Oct4 in Notophthalmus viridescens (Newt) Eye Regeneration.
Presenter(s): Rital B Bhavsar
Advisor(s): Panagiotis A Tsonis
Biology - Graduate Research
Notophthalmus viridescens (Newts) are capable of regenerating many of its body parts and organs. They are the only salamander species that
exhibit regeneration of lens during adulthood. The lost lens is regenerated by transdifferentiation of the pigmented epithelial cells to lens cells.
This kind of cell type conversion is thus a natural potency of this organism. Whereas, in vitro cell type conversion studies are observed during
direct reprogramming where one cell type is converted to another cell type using a cell type specific transcription factor along with histone
deacetylase inhibitors. In this study, we proposed to compare the mechanisms of transdifferentiation during Newt lens differentiation and in vitro
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