Quantitative Biosciences Thesis Proposal 
Luis Felipe Cedeño Pérez
School of Biological Sciences
Advisor: Dr. William C Ratcliff (School of Biological Sciences)
Open to the Community

Cellular Mechanisms Driving the Evolution and Stabilization of Multicellularity
April 15th, 2025 at 10 AM EDT
Room: S107 Howey Physics
Zoom link: https://gatech.zoom.us/j/91231002116?pwd=YySvm2Df1hxPsuUaJEnFTzP8DNLyM3…
Zoom meeting ID: 912 3100 2116
Passcode: 312409

Committee Members:
Dr G Ozan Bozdag (School of Biological Sciences)
Dr Peter J Yunker (School of Physics)
Dr Sam Brown (School of Biological Sciences)

Abstract:
The evolution of multicellularity represents one of life's major evolutionary transitions, transforming solitary cells into complex, integrated organisms. Despite its importance in shaping life on Earth, studying multicellularity presents unique challenges - the transitional forms connecting unicellular ancestors to modern multicellular organisms disappeared millions of years ago, leaving us with limited fossil evidence of how this process unfolded at the cellular level.
My research leverages the Multicellularity Long-Term Evolution Experiment (MuLTEE), which uses snowflake yeast to study multicellular evolution in real-time. Through directed evolution, we've created a system where simple clusters of cells evolve into macroscopic multicellular structures with novel properties. This experimental approach provides unprecedented insights into how multicellular adaptations emerge and stabilize, allowing us to witness unseen evolutionary processes in the laboratory.
In my thesis, I address three fundamental aspects of the origins of complex multicellularity. First, I investigate how changes in basic cellular properties, like cell division timing, manifest as adaptive multicellular traits. Second, I examine how unicellular fitness changes as complex multicellularity evolves, potentially leading to entrenchment in the multicellular state. Third, I explore the mechanistic basis of this entrenchment, particularly the trade-off between cellular elongation and time spent in mitosis. By studying these questions using an experimentally tractable model system, my work aims to illuminate the cellular foundations of one of life's most transformative evolutionary transitions.