Synapse Formation in the Zebrafish Lateral Line

<p>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.</p>

Name thesis:degree_name

Doctor of Philosophy (PhD)

Level thesis:degree_level

Thesis

Year

2015

Author dc:creator

• Dow, Eliot

Contributors dc:contributor

• A. James Hudspeth

• synapse formation
• zebrafish lateral line
• hair-cell polarity
• afferent innervation
• neuronal projections
• gene expression analysis
• Life Sciences

Repository record dc:identifier

https://digitalcommons.rockefeller.edu/student_theses_and_dissertations/277

OAI identifier oai:identifier

oai:digitalcommons.rockefeller.edu:student_theses_and_dissertations-1278