Date of Award
2026
Document Type
Thesis
Degree Name
Doctor of Philosophy (PhD)
Thesis Advisor
A. James Hudspeth
Abstract
The development of complex tissues requires the coordination of cell-fate decisions and the spatial organization of cells. Mechanosensory organs, such as the mammalian inner ear, illustrate this principle: their function depends on the precise orientation and arrangement of specialized receptor cells known as hair cells. In the zebrafish lateral line, which is evolutionarily related to the mammalian inner ear, each sensory organ contains two oppositely polarized hair-cell types that detect water flows arriving from the head or tail of the fish. These cells arise as sisters from a symmetric cell division of a mother cell, and their opposite polarities are established by a Notch-Delta signaling event that determines the ultimate polarization of each sister. Although fate is specified early, the initial spatial arrangement of sisters is random, and roughly half of all pairs undergo a cell-pair rotation to achieve mirror-symmetric organization along the anteroposterior (AP) axis. The robustness of this behavior suggests that sister cells acquire both directional information relative to each other and an ability to interpret the organ’s AP axis. In this thesis, I investigate how Notch-mediated cell fate specification endows cells with the properties required for reliable positioning within the pair. I developed a semiautomated 3D image segmentation and tracking pipeline to analyze cell-pair behaviors. Loss of notch1a or constitutive expression of the Notch transcriptional effector NICD disrupted both cell-pair rotation and the directionality of pair movement. Notably, WT cell pairs did not drift directionally over time, because sisters moved in opposing directions as they separated. However, when both cells were Notch-, cell-pair centroids drifted anteriorly on average, replicating previous results, and drifted posteriorly when both cells were Notch+, indicating that Notch signaling flips the polarity of cell movement by approximately 180º. These results indicate that Notch transcriptionally establishes polarity-specific mechanical properties. Single-cell RNA sequencing revealed a polarityspecific transcriptome distinguishing Notch+ from Notch- cells, including the kinase stk32a, which was specific to Notch+ cells and has recently been implicated in hair-cell polarity in the mammalian vestibular system. Perturbing stk32a asymmetry in the neuromast impaired cell-pair behaviors, revealing an unexpected chiral rotation bias, and disrupted hair-bundle polarity, suggesting that Notch+ cells require stk32a to interpret and act upon global organ-axis cues. Together, these findings establish a mechanistic link between cell-fate specification, interpretation of polarity cues, individual and pair-level behaviors, and the emergence of tissue-wide organization in a developing sensory organ.
License and Reuse Information
This work is licensed under a Creative Commons Attribution-NonCommercial-Share Alike 4.0 International License.
Recommended Citation
Atlas, Emily, "From Cell fate to Cell Behavior: Mechanisms of Hair Cell Pair Organization in the Zebrafish Lateral Line" (2026). Student Theses and Dissertations. 853.
https://digitalcommons.rockefeller.edu/student_theses_and_dissertations/853
Comments
A Thesis Presented to the Faculty of The Rockefeller University in Partial Fulfillment of the Requirements for the degree of Doctor of Philosophy