Date of Award

Spring 2021

Document Type

Restricted Thesis

Terms of Use

© 2021 Cameron R. Tumey. All rights reserved. Access to this work is restricted to users within the Swarthmore College network and may only be used for non-commercial, educational, and research purposes. Sharing with users outside of the Swarthmore College network is expressly prohibited. For all other uses, including reproduction and distribution, please contact the copyright holder.

Degree Name

Bachelor of Arts


Biology Department

First Advisor

Bradley Justin Davidson


In bilateral organisms, the development of the left- right axis follows a conserved model. Although the steps of LR axial patterning are well established many mechanisms facilitating LR patterning remain poorly characterized. It is known that Nodal and ion flux signaling are necessary for the establishment of the LR asymmetric morphogenesis yet, it is unknown how these initial signaling pathways impact laterally asymmetric gene expression. Here we show how the model organism Ciona robusta can be utilized to visualize asymmetric gene expression as well as how gene expression is affected by early symmetry breaking mechanisms, Nodal and ion flux. In our research, asymmetric gene expression within Ciona, previously established by TOMOseq, was visualized with in situ hybridization. To explore the impact of Nodal and ion flux on asymmetric gene expression embryos were treated with Nodal and ion flux inhibitors and underwent in situ hybridization using genes previously identified as asymmetrically enriched. Through this process we found that our data was highly variable due to dechorionization. This being said, the research demonstrated that asymmetric gene expression is primarily localized in the mesenchyme, and trunk lateral cell lineages. I also observed interesting changes in the expression patterns of Crkl, Klhl4, FoxC, and Mef2 following inhibitor treatments.