PhD Transfer Exam
Thursday, January 25th, 2018 at 1:10pm –University of Toronto at Mississauga – CCT2134
Nawar Alwash (Levine lab)
“The role of foraging gene (for) in Drosophila melanogaster social interaction networks (SINs)”
Drosophila melanogaster display social behaviours such as courtship, mating, aggression and foraging in groups. Recent studies have shown that different strains of D. melanogaster form social interaction networks (SINs) with different properties, suggesting that genes influence network phenotypes. The foraging gene (for) regulates food-related behaviours in several species including D. melanogaster. There are two naturally occurring alleles of the for gene: rover and sitter, where the rover flies are characterized with higher mobility in the presence of food. However, the role of the two variants in the formation of social networks remains unknown and that will be the focus of my research. I hypothesize that the for gene influences the formation of SINs and thus manipulating the for gene would lead to formation of networks with different SIN properties. I have shown that SINs formed by rover females have different properties than those formed by sitter females. I have also shown an effect of for copy number that is reflected in SIN phenotypes. To investigate this further, I aim to characterize the role of the for gene on social structure by investigating the effect of for on the formation of SINs during different developmental stages. I will also examine the allelic dominance pattern of the rover/sitter variant of for in the formation of SINs. Furthermore, I will explore the effect of external factors, such as stress and social experience, on SIN formation of the rover/sitter variants. This research will be the first to identify a specific gene influencing social network structure in D. melanogaster. In addition, understanding the role of for in the formation of SINs could potentially provide an insight into understanding the role of this gene in SIN formation of other organisms.
PhD Transfer Exam
Thursday July 20th, 2017 at 1:10 pm – Ramsay Wright Building, RW 432
Xiao Yu (Takehara-Nishiuchi Lab)
” Prefrontal long-range projection facilitating the formation of temporal association”
The ability to form associations between related events separated in time is important as it allows us to adapt to similar events in the future based on past experiences. I recently found that chemogenetic enhancement of neuron activity in the medial prefrontal cortex (mPFC) enables rats to form stimulus associations over a temporal gap that was prohibitively long for untreated rats to learn. Accompanying this improved learning were ramping increases of theta and beta oscillations in the mPFC during the temporal gap. These findings suggest that mPFC network activity during the gap determines whether two stimuli are associated across the gap. My recent and future work extend this finding in two directions. First, I show that enhancing mPFC activity after learning had no effect on memory formation, suggesting that elevated mPFC activity during learning is critical for memory enhancement. Second, to determine long-range projections through which mPFC activity enhances memory formation, I traced mPFC efferent projections and identified sub regions and cortical layers at which mPFC projections terminate. This, along with past behavioral literature, led me to hypothesize that mPFC projections to the lateral entorhinal cortex (LEC), nucleus reuniens (RE), and mediodorsal thalamus (MD) may be involved in memory enhancement. To test this idea, I will examine the impact of selective chemogenetic activation of the mPFC projections to one of these efferent regions on the formation of temporal associative memories. I will also monitor the activity of mPFC axon terminals in these efferent regions while rats form temporal stimulus associations while learning to ignore irrelevant stimuli. Through these two complementary experiments, I will be able to uncover how the mPFC routes the information on the behavioral relevance of stimuli to specific downstream targets, thereby uncovering a circuit basis on memory regulation by the mPFC.
PhD Transfer Exam
Tuesday June 13th, 2017 at 1:10 pm – Earth Science Building, Room 3087
Artyom Gritsunov (Christendat Lab)
” Structural analysis, kinetic characterization and in vivo investigation of plant quinate dehydrogenases and chlorogenic acid esterases“
The shikimate pathway leads to synthesis of aromatic compounds including lignin, pigments, hormones, and amino acids. Dehydroquinate is an intermediate of the shikimate pathway which can be diverted to other anabolic processes by enzymatic conversion to quinate. In plants, quinate is utilized for biosynthesis of Chlorogenic Acids (CGA). CGAs serve as lignin precursors, antifungal agents, solubility enhancers and UV light protectors. The anabolic aspect of CGA biosynthesis is very well studied, however enzymes involved in the catabolic metabolism of CGAs are poorly characterized. Additionally, the source of quinate remained unknown. To date, we have characterized a family of Quinate Dehydrogenases (QDHs) and identified a family of CGA esterases in a variety of land plants including Solanacea and Brassicaceae species. We hypothesize and aim to test that QDHs in combination with CGA esterases are responsible for regulating the quinate and CGA levels in Solanum species.