Highlights d The pupillary light reflex of many sub-primates has a mechanism intrinsic to the iris d The mouse iris sphincter muscle is photosensitive, independent of synaptic transmission d Deleting melanopsin in sphincter muscle removes its intrinsic photosensitivity d The components of the melanopsin photosignaling in sphincter muscle are revealed In Brief Wang et al. show that a subset of mouse iris sphincter muscle cells express the visual pigment, melanopsin, with its photoactivation leading to muscle contraction and pupillary constriction. Thus, mouse iris sphincter muscle cells are bona fide, albeit unconventional, photoreceptors.
Wang, Q., Wing, W., Yue, S., Jiang, Z., Mikoshiba, K., Offermanns, S., … Yau, K.-W. (2017). Synergistic Signaling by Light and Acetylcholine in Mouse Iris Sphincter Muscle. Current Biology, 27, 1791-1799.e5. https://doi.org/10.1016/j.cub.2017.05.022