For those included, only the most salient phenotypes are listed, please refer to the text for more complete description. List of major proteins involved in mouse rod and cone phototransductions that have been knocked out, overexpressed or mutated1 1) Due to space limitation, not all the genetically engineered mouse lines are listed. When combined with electrophysiology, mouse genetics provides unmatched power in elucidating the in vivo functions of key phototransduction proteins, most of which have been knocked out, overexpressed or mutated in rods, yielding a rich body of information on the mechanisms underlying the amplification, recovery and adaptation of rod/cone photoresponses (Table 1, Figures 2 & 3). The mouse, however, has become an increasingly popular animal model for study in the past decade through the advent of gene-targeting techniques. Bovine retina, on the other hand, has been a favorite preparation for studying phototransduction by biochemists because of the abundance of tissue available. Individual amphibian and mammalian (including primate) photoreceptors can be recorded from with this method. Great progress has been made in understanding rod phototransduction since the introduction of the suction-electrode recording technique in the late 1970s (Baylor et al., 1979a). Rods are responsible for dim light vision, cones for bright light vision. Phototransduction takes place in the outer segment, while the ellipsoid is densely packed with mitochondria. Brightfield images of living rod and cone photoreceptors isolated from a salamander retina. They also mediate color vision by several cone types with different pigment spectra sensitivity.įig. They are much less sensitive to light than rods, but have higher temporal resolution. Cones mediate daylight vision (Figure 1). They are extremely sensitive and can signal the absorption of single photons. Rods are specialized for low-light vision. Vertebrates rely on retinal rods and cones for the conventional, image-forming vision while non-image-forming vision is mediated by intrinsically photosensitive retinal ganglion cells (ipRGCs) (see Part II Chapter 7).
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