The hippocampus (HPC) and the medial prefrontal cortex (mPFC) are two structures crucial for effective decision-making, and it has been shown that these two structure communicate when spatial working memory (WM) recall is necessary in rats. The hippocampal system is critical for episodic memory, and is especially important in the acquisition and retrieval of spatial information, while the mPFC’s major function is to form and store representations of events and contexts, so that in the future, the most appropriate behavioral response is used in a given context. We will be investigating the correlation between a rat’s behavior and neural activity in the mPFC and the HPC simultaneously to better understand the detailed interaction between these two structures. Rats are trained on a task where they must switch between two types of spatial learning strategies while on the maze to obtain a food reward. While the rat performs the task, we will monitor neural activity in the HPC and mPFC as well as the rat’s behavior. Past research has shown that identification of a certain deliberative behavior can be determined by looking at hippocampal oscillatory data. We predict there will be a correlation between this deliberative behavior made by the rat and an identifiable pattern in hippocampal-prefrontal engagement. We also expect to observe the two structures align their activity as the rat learns to switch from one strategy to the other, giving insight into the involvement of the hippocampal-prefrontal network in learning and decision-making. Understanding the neural mechanism employed in memory-guided decision-making has tremendous implications for the field of medicine, as disadvantageous decision-making and impaired volitional control are characteristic of many mental health disorders, such as addiction, eating disorders, depression, and anxiety disorders.

Enzymes have recently been incorporated into multiple high-value industrial syntheses, demonstrating the utility of enzymes as highly selective catalysts for practical industrial processes. However, the current scope of non-biological enzymatic reactions is narrow and new reactions and reaction pathways need to be engineered. The goal of our work in the Zalatan lab is engineering enzymes as catalysts in carbon-hydrogen bond functionalization reactions, a transformation critical for practical industrial synthesis where selective catalysis is still a major challenge. Importantly, we are interested in exploring more efficient and informed engineering approaches by establishing structure-function relationships with the enzymes that we work with. Our model system for this work is the non-heme iron(II) 2-oxoglutarate dependent oxygenase superfamily (Fe(II)-2OGs). We are using a high-throughput microfluidics based kinetic assay to determine key sites that we can target for mutagenesis and directed evolution in a candidate Fe(II)-2OG found to catalyze a new reaction. Overall, we expect that this work will enable new directions and principles for engineering Fe(II)-2OGs, and that lessons learned here can then be extended to additional industrially-relevant enzyme families.

The Wnt signaling pathway plays a critical role in mammalian cell development and regulates cell growth and differentiation. Two central proteins in this pathway are glycogen synthase kinase 3β (GSK3β) and β-catenin. Another protein, Axin, is responsible for holding these two proteins in close proximity in order to promote the reaction between them. The kinetic mechanism for the Axin-mediated reaction is well understood, but the relationship between this function and Axin’s structure is poorly characterized. I am currently generating a cryogenic electron microscopy (Cryo-EM) structure of Axin bound to GSK3β and β-catenin in order to investigate this mechanism. Cryo-EM is a technique for determining the structures of proteins that is especially suitable for large protein complexes, such as the one I have produced. Inital results indicate that the stoichiometry of the complex is much more complicated than initially assumed and does not follow the predicted 1:1:1 complex. Elucidating this structure will provide insight into how the structure of Axin promotes the reaction between GSK3β and β-catenin as well as how it provides Wnt signaling specificity. This structure will also be important for understanding and intervening in diseases such as cancer where Wnt signaling is dysregulated.