Microtubule networks in zebrafish hair cells facilitate presynapse transport and fusion during development

Sensory cells in the retina and inner ear rely on specialized ribbon synapses for neurotransmission. Disruption of these synapses is linked to visual and auditory dysfunction, but it is unclear how these unique synapses are formed. Ribbon synapses are defined by a presynaptic density called a ribbon. Using live-imaging approaches in zebrafish, we find that early in hair-cell development, many small ribbon precursors are present throughout the cell. Later in development, fewer and larger ribbons remain, and localize at the presynaptic active zone (AZ). Using tracking analyses, we show that ribbon precursors exhibit directed motion along an organized microtubule network towards the presynaptic AZ. In addition, we show that ribbon precursors can fuse together on microtubules to form larger ribbons. Using pharmacology, we find that microtubule disruption interferes with ribbon motion, fusion, and normal synapse formation. Overall, this work demonstrates a dynamic series of events that under..., Zebrafish animals
Zebrafish (Danio rerio) were bred and cared for at the National Institutes of Health (NIH) under animal study protocol #1362-13. Zebrafish larvae raised at 28°C in E3 embryo medium (5 mM NaCl, 0.17 mM KCl, 0.33 mM CaCl2, and 0.33 mM MgSO4, buffered in HEPES, pH 7.2). All experiments were performed on larvae aged 2-3 days post fertilization (dpf). Larvae were chosen at random at an age where sex determination is not possible. The previously described mutant and transgenic lines were used in this study: Tg(myo6b:ctbp2a-TagRFP)idc11Tg referred to as myo6b:riba-TagRFP; Tg(myo6b:YFP-Hsa.TUBA)idc16Tg referred to as myo6b:YFP-tubulin (Ohta et al., 2020; Wong et al., 2019). Tg(myo6b:ctbp2a-TagRFP)idc11Tg reliably labels mature ribbons, similar to a pan-CTBP immunolabel at 5 dpf (Figure 1-S2B). This transgenic line does not alter the number of hair cells or complete synapses per hair cell (Figure 1-S2A-D). In addition, myo6b:ctbp2a-TagRFP does not alter the size of ribbons (Fig..., # Microtubule networks in zebrafish hair cells facilitate presynapse transport and fusion during development

Dataset DOI: [10.5061/dryad.crjdfn3gg](10.5061/dryad.crjdfn3gg)

## Description of the data and file structure

Paper associated with dataset:

Elife (2024)

[https://doi.org/10.7554/eLife.98119.1](https://doi.org/10.7554/eLife.98119.1)

This dataset includes raw data collected at the NIH/NIDCD:

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Movies S1-S11

This dataset includes live imaging experiments that monitor microtubules or presynapse/ribbon movements in zebrafish posterior lateral-line hair cells (D1, M1I,L1-L5) in: wild type, *kif1aa* germline mutants, *kif1aa* crispant mutant animals and wild type animals treated with nocodazole or taxol (Figure 1,2,3,6,7,8 Figure 1-S2,2-S2,3-S1,6-S2,7-S1,8-S1 Movies S1-11). 

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