Speaker: Liz Ransey, assistant professor at Carnegie Mellon University

Title: "Cracking the Connexin Code: Rewriting gap junction proteins as novel tools for neuroscience and beyond"

Abstract: The coordination of activity between brain cells is a key determinant of neural circuit function in both normal physiology and disease states; nevertheless, methodologies capable of selectively regulating distinct circuits without affecting the surrounding context of brain activity remain sparce. Here, I discuss how I addressed this limitation by developing the components of a novel electrical synapse capable of synchronizing neurons by rationally engineering two gap junction proteins (connexins).

Specifically, I utilized protein mutagenesis, a novel in vitro assay of connexin docking, and computational modeling of connexin hemichannel interactions, to identify the structural motif that defines connexin docking specificity of Morone americana (white perch fish) connexin34.7 (Cx34.7) and connexin35 (Cx35). I then rationally designed this motif to generate Cx34.7 and Cx35 hemichannels that dock with each other, but not with themselves nor other major connexins expressed in the human central nervous system. The functionality of these hemichannels was validated in vivo within distinct neuronal circuits of two live animal models.  In Caenorhabditis elegans (worms), the expression of the engineered GJs was sufficient to recode a learned behavioral preference. Additionally, I demonstrated in vivo functionality in mice using two experimental paradigms: phase-amplitude coupling in a prelimbic microcircuit and the modulation of a stress adapted behavior via expression across a long-range monosynaptic projection. Thus, I established a genetically encoded, translational approach, ‘Long-term integration of Circuits using connexins’ (LinCx), for context-precise circuit-editing with unprecedented spatiotemporal specificity. Ultimately, I highlight how the strategies employed and methodologies developed to establish LinCx will contribute to the further development of next generation neural modulatory tools and novel therapeutics for Cx-associated pathologies.

Hosts: Clark Coffman, GDCB associate professor, and Stephanie Klein, GDCB postdoctoral research associate

Biography: As an interdisciplinary researcher, Liz Ransey employs biochemistry, cellular and structural biology to understand, dissect and reconfigure dynamic, multifunctional protein complexes involved in cell signaling. Specifically, her primary interests center on gap junctions – channels comprised of connexin (Cx) proteins that enable intercellular coordination and resource sharing, as well as metabolic exchange with the extracellular environment and rapid cellular adaptation to stress. 

Recently, as a postdoctoral fellow at Duke University, she utilized this expertise to evaluate Cx interactions and to engineer Cx docking specificity to generate novel, designer gap junctions (electrical synapses) as neuronal circuit modulators. As a new assistant professor in the Department of Biological Sciences at Carnegie Mellon University, she aims to investigate the complexation and assembly of gap junctions via systematic characterization and modification of the core features of Cxs (i.e., docking, oligomerization and selectivity) such that the complex interplay of numerous, unique gap junctions to global intercellular communication can be understood and manipulated. Such endeavors will contribute to the dissection of mechanisms of intercellular communication and the development of next generation genetic tools and therapeutics.

Originally from Toledo, Ohio, she completed her undergraduate degree in biochemistry at the Rochester Institute of Technology and received her Ph.D. in chemical biology from Harvard University. She is a first-generation college graduate and is passionate about providing education, mentorship, opportunities and representation for the next generations of diverse academic scholars. Her ultimate goal is to develop novel therapeutics for connexin-associated pathologies as well as connexin-based technologies for basic research applications, while contributing to an inclusive and positive scientific culture.