Student Theses and Dissertations
Date of Award
2015
Document Type
Thesis
Degree Name
Doctor of Philosophy (PhD)
Thesis Advisor
A. James Hudspeth
Keywords
synapse formation, zebrafish lateral line, hair-cell polarity, afferent innervation, neuronal projections, gene expression analysis
Abstract
Although much is known about how axons and dendrites are guided to a target tissue, little is understood regarding how pre- and postsynaptic partners are matched for synapse formation. The zebrafish lateral line offers the opportunity for greater insight into this process. Hair cells in the lateral-line neuromast exist as two intermingled subpopulations, anteriorly and posteriorly polarized cells. Afferent neurons form synapses with hair cells of only one subpopulation, and this polarity-specific innervation arises independently of synaptic activity. The research presented in my thesis deepens the understanding of synapse formation in the zebrafish lateral line. First, I examine the neuronal architecture of the neuromast at nanometer-scale resolution by imaging the tissue by serial block-face electron microscopy. The data demonstrate that afferent neurons show a polarity preference at the earliest stages of hair-cell innervation, and additionally that the synaptic arrangement appears to arise from interactions among neurons for access to synaptic ribbons rather than being mediated by an accessory cell. I next describe a novel phenomenon, the extension of transient, dynamic projections from the base of nascent hair cells beginning shortly after mitosis. The projections extend toward nearby mature hair-cell synapses and filopodia arising from afferent terminals extend directly along them toward unoccupied synaptic ribbons. Hair-cell projections lacking stable association of afferent neurons are larger than those that are stably innervated. The appearance of hair-cell projections is contemporaneous with the initiation of contact between afferent neurons and nascent hair cells, and the disappearance of projections coincides with the appearance of pre- and postsynaptic markers proteins. I propose a model in which hair-cell projections act as cellular scaffolds for the guidance of neurons to available synaptic sites. Finally, I describe a novel method for collecting subpopulations of cells for gene expression analysis, which I employ to compare the transcriptomes of anteriorly and posteriorly polarized hair cells. I identified a number of differentially expressed candidate genes that might mediate polarity-specific afferent innervation. This work expands the repertoire of tools available for investigations of the neuromast and enhances the understanding of synapse formation in the zebrafish lateral line.
DOI
10.48496/ndev-2157
License and Reuse Information
This work is licensed under a Creative Commons Attribution-NonCommercial-Share Alike 4.0 International License.
Recommended Citation
Dow, Eliot, "Synapse Formation in the Zebrafish Lateral Line" (2015). Student Theses and Dissertations. 277.
https://doi.org/10.48496/ndev-2157
Comments
A thesis presented to the faculty of The Rockefeller University in partial fulfillment of the requirements for the degree of Doctor of Philosophy