PT  - JOURNAL ARTICLE
AU  - Cornelius Schröder
AU  - Jonathan Oesterle
AU  - Philipp Berens
AU  - Takeshi Yoshimatsu
AU  - Tom Baden
TI  - Eye-Region Specific Ribbon Tuning Supports Distinct Modes of Synaptic Transmission in Same-Type Cone-Photoreceptors
AID  - 10.1101/2021.02.24.432674
DP  - 2021 Jan 01
TA  - bioRxiv
PG  - 2021.02.24.432674
4099  - http://biorxiv.org/content/early/2021/02/24/2021.02.24.432674.short
4100  - http://biorxiv.org/content/early/2021/02/24/2021.02.24.432674.full
AB  - Many sensory systems use ribbon-type synapses to transmit their signals to downstream circuits. The properties of this synaptic transfer fundamentally dictate which aspects in the original stimulus will be accentuated or suppressed, thereby partially defining the detection limits of the circuit. Accordingly, sensory neurons have evolved a wide variety of ribbon geometries and vesicle pool properties to best support their diverse functional requirements. However, the need for diverse synaptic functions does not only arise across neuron types, but also within. Here we show that UV-cones, a single type of photoreceptor of the larval zebrafish eye, exhibit striking differences in their synaptic ultrastructure and consequent calcium to glutamate transfer function depending on their location in the eye. We arrive at this conclusion by combining serial section electron microscopy and simultaneous “dual-colour” 2-photon imaging of calcium and glutamate signals from the same synapse in vivo. We further use the functional dataset to fit a cascade-like model of the ribbon synapse with different vesicle pool sizes, transfer rates and other synaptic properties. Exploiting recent developments in simulation-based inference, we obtain full posterior estimates for the parameters and compare these across different retinal regions. The model enables us to extrapolate to new stimuli and to systematically investigate different response behaviours of various ribbon configurations. We also provide an interactive, easy-to-use version of this model as an online tool. Overall, we show that already on the synaptic level of single neuron types there exist highly specialized mechanisms which are advantageous for the encoding of different visual features.Competing Interest StatementThe authors have declared no competing interest.