title: Light-driven calcium signals in mouse cone photoreceptors.
abstract: Calcium mediates various neuronal functions. The complexity of neuronal Ca²⁺ signaling is well exemplified by retinal cone photoreceptors, which, with their distinct compartmentalization, offer unique possibilities for studying the diversity of Ca²⁺ functions in a single cell. Measuring subcellular Ca²⁺ signals in cones under physiological conditions is not only fundamental for understanding cone function, it also bears important insights into pathophysiological processes governing retinal neurodegeneration. However, due to the proximity of light-sensitive outer segments to other cellular compartments, optical measurements of light-evoked Ca²⁺ responses in cones are challenging. We addressed this problem by generating a transgenic mouse (HR2.1:TN-XL) in which both short- and middle-wavelength-sensitive cones selectively express the genetically encoded ratiometric Ca²⁺ biosensor TN-XL. We show that HR2.1:TN-XL allows recording of light-evoked Ca²⁺ responses using two-photon imaging in individual cone photoreceptor terminals and to probe phototransduction and its diverse regulatory mechanisms with pharmacology at subcellular resolution. To further test this system, we asked whether the classical, nitric oxide (NO)-soluble guanylyl-cyclase (sGC)-cGMP pathway could modulate Ca²⁺ in cone terminals. Surprisingly, NO reduced Ca²⁺ resting levels in mouse cones, without evidence for direct sGC involvement. In conclusion, HR2.1:TN-XL mice offer unprecedented opportunities to elucidate light-driven Ca²⁺ dynamics and their (dys)regulation in cone photoreceptors.
authors.affiliation: Centre for Integrative Neuroscience, University of Tübingen, 72076 Tübingen, Germany.
authors.forename: Tao
authors.initials: T
authors.lastname: Wei
authors.forename: Timm
authors.initials: T
authors.lastname: Schubert
authors.forename: François
authors.initials: F
authors.lastname: Paquet-Durand
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Tanimoto
authors.forename: Le
authors.initials: L
authors.lastname: Chang
authors.forename: Katja
authors.initials: K
authors.lastname: Koeppen
authors.forename: Thomas
authors.initials: T
authors.lastname: Ott
authors.forename: Oliver
authors.initials: O
authors.lastname: Griesbeck
authors.forename: Mathias W
authors.initials: MW
authors.lastname: Seeliger
authors.forename: Thomas
authors.initials: T
authors.lastname: Euler
authors.forename: Bernd
authors.initials: B
authors.lastname: Wissinger
mesh_terms: D000818:Animals; D015374:Biosensing Techniques / Q000379:methods; D002118:Calcium / Q000378:metabolism*; D004596:Electroretinography / Q000187:drug effects / Q000379:methods; D055537:Light Signal Transduction / Q000187:drug effects / Q000502:physiology*; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D023421:Models, Animal; D010775:Photic Stimulation / Q000379:methods; D017949:Retinal Cone Photoreceptor Cells / Q000187:drug effects / Q000378:metabolism*; D026423:S-Nitroso-N-Acetylpenicillamine / Q000494:pharmacology; D015398:Signal Transduction / Q000502:physiology; D019209:Troponin C / Q000235:genetics / Q000378:metabolism*
chemical_list: D008164:Luminescent Proteins; D019209:Troponin C; D026423:S-Nitroso-N-Acetylpenicillamine; D002118:Calcium