Mol Bio Colloquium

Mol Bio Colloquium

Graduate Student Colloquium

Event Date/Location

November 4, 2022 - 4:00 pm
Thomas Laboratory 003


  • Harsha Shan Photo

    Harsha Sen

    Graduate Student
    Mallorino Lab

    Harsha is a graduate student in the Department of Molecular Biology. He received his B.A. in Biology and Economics from Swarthmore College where he worked on modeling speciation dynamics during the Cambrian explosion, and on investigating the conservation of pericentric satellite repeats in great apes. He also studied paralogy in the dual genomes of the ciliate Oxytricha trifallax. After graduation, he worked in Steve McCarroll’s lab on developing single-cell, single-virion approaches for high-throughput inference of synaptic connectivity. Harsha is broadly interested in understanding biological systems from evolutionary and genomic perspectives by developing and using computational and molecular tools. Harsha plans to investigate the functional evolution of gliding and flying membranes in mammals using computational and high-throughput molecular approaches.

  • Celeste Rodriguez Photo

    Celeste Rodriguez

    Graduate Student
    Cohen Lab

    is a second-year Ph.D. student in Molecular biology. She grew up in the wonderful desert city of Reno, Nevada where she completed her undergraduate degree in Biochemistry and Molecular biology at the University of Nevada, Reno. There she studied plant cell walls, root hairs, and post-translational modifications. She then did a post-baccalaureate at Brown University looking at how phosphatases play a role in plant development. Now, at Princeton, she is interested in looking at the transcriptional changes in electrotaxing cells under various electrical fields and conditions.

    In the lab, you can find her in the TC hood, overly caffeinated and talking to her cells ... again. Outside of the lab, she can be found reading books, exploring new Mexican restaurants to try, hanging out with friends, and playing board games.

  • Emily K. Ho Photo

    Emily Kolenbrander Ho

    Postdoctoral Fellow
    Toettcher Lab


Mol Bio Graduate Colloquium


November 4, 2022







Cohen Lab


Characterizing the transcriptional landscape in electrically stimulated cells


Directed collective cell migration is critical in biological processes such as morphogenesis, cancer cell invasion and wound healing. Specifically, human skin generates an endogenous electrical field that is maintained and upon injury, this transepithelial potential is ‘short circuited’, initiating a current that the cells can sense and electrical fields of ~1V/cm . Cells follow this field in a process called ‘electrotaxis’. There is increasingly promising data that shows application of direct current stimulation to skin wounds can accelerate cell migration by activation of PI3K/PTEN pathway and also mediate the electrotactic response of neutrophils and dermal fibroblasts, both crucial for the healing process. Additionally, our group has shown accelerated in vitro wound closure using converging electric. Because of this potential, there is a plethora research covering the various conditions of electrotaxing cells across different parameters of electrical stimulation, types of electrodes uses and time course However, the exact molecular mechanisms and transcriptional changes that allow for this mode of migration remains elusive as there is no standardization of cells or devices in the literature. Existing research shows that electrotaxis does result in a transcriptional response; however, the exact correlation between migratory response and changes in gene expression is not unified across different stimulation parameters. Elucidating the coupling between transcriptional changes to cell migratory speed will generate an integrated atlas to understand how electrotaxis differs from other migratory responses and identify novel genes to further investigate its interaction with other signaling and metabolic pathways. Using my experimental experience and my lab’s unique expertise for electrotaxis, I plan to: (1) Characterize the biophysical changes across varying stimulation parameters and (2) Map the transcriptional landscape in electrotaxing cells.




Mallarino Lab


Molecular evolution and development of the mammalian gliding membrane


Understanding how genomic changes over evolutionary time lead to phenotypic changes is a central question in evolutionary biology. While many loci responsible for evolutionary trait loss (e.g. flightlessness in birds, loss of limbs in snakes, and pelvic reduction in sticklebacks) have been identified, little is known about gene regulatory network (GRN) changes that lead to the evolution of new traits. Furthermore, the degree of molecular and genomic convergence underlying instances of convergent trait gain is unclear. To address these questions, my dissertation will focus on studying the development and evolution of the mammalian gliding membrane, or patagium, a specialized tissue that has independently evolved in multiple groups of mammals.  First, using single-cell RNA and ATACseq, I will identify the cell-type specific GRNs that regulate the formation of the sugar glider patagium, and functionally test components of these GRNs using in vivo transgenic tools. Second, using a combination of comparative genomics, histology, epigenomics, and in vitro assays, I will determine whether bat lateral patagia evolved through shared or distinct molecular mechanisms. Taken together, this study will help dissect the GRNs involved in driving the development of a novel trait in sugar gliders, and help better understand how this trait has convergently evolved in different mammalian lineages.






Toettcher Lab


Put a (brachyenteron) ring on it: Erk signal interpretation and pattern formation in the early embryo


How do stripes of gene expression form at particular positions in the embryo? Classically, morphogen gradients induce distinct target genes at different embryonic positions that work in combination to establish specific stripes of downstream genes. For example, the posterior gradient of Torso activity in the early Drosophila embryo produces distinct domains of two target genes – tailless (tll) and huckebein (hkb) – that are required to produce a stripe of brachyenteron (byn), a gene involved in gut specification. However, recent live imaging and optogenetic experiments have revealed mysteries about byn patterning that cannot be explained by the classic gradient model. First, byn expression is dynamic, beginning as a cap that later refines into a stripe. Second, even simple, uniform optogenetic inputs are sufficient to rescue normal development, suggesting that the Torso gradient may not be absolutely required for the formation of a byn stripe. Using precision optogenetic control over Erk signaling in live embryos, we identify differential dynamics of byn’s regulators tailless and huckebein that explain the dynamic patterns of byn expression. Further, we find that intracellular diffusion of signaling components produces gradients of Erk activity, even from all-or-none optogenetic inputs. Altogether, this work reveals that formation of the byn stripe is remarkably robust to severe disruption of the signaling gradient.




Free and open to the university community and the public.


Department of Molecular Biology