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Distinct synaptic transfer functions in same-type photoreceptors

Citation

Schröder, Cornelius et al. (2021), Distinct synaptic transfer functions in same-type photoreceptors, Dryad, Dataset, https://doi.org/10.5061/dryad.7wm37pvt0

Abstract

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.

Funding

Wellcome Trust, Award: 220277/Z/20/Z

European Research Council, Award: 677687

Biotechnology and Biological Sciences Research Council, Award: BB/R014817/1

German Ministry for Education and Research, Award: 01GQ1601

German Research Foundation, Award: BE5601/4-1

Leverhulme Trust, Award: PLP-2017-005

Lister Institute for Preventive Medicine, Award: Fellowship

Marie Curie Sklodowska Actions individual fellowship, Award: 748716

German Ministry for Education and Research

German Ministry for Education and Research, Award: 01IS18052C

German Ministry for Education and Research, Award: 01IS18039A

German Research Foundation, Award: EXC 2064 - 390727645

German Research Foundation, Award: BE5601/4-1

Marie Curie Sklodowska Actions individual fellowship, Award: 748716