Emergence of Novel Color Vision in Mice Engineered to Express a Human Cone Photopigment

Neuroscience Research Institute and Department of Psychology, University of California, Santa Barbara, CA 93106, USA.
Science (Impact Factor: 33.61). 04/2007; 315(5819):1723-5. DOI: 10.1126/science.1138838
Source: PubMed


Changes in the genes encoding sensory receptor proteins are an essential step in the evolution of new sensory capacities. In primates, trichromatic color vision evolved after changes in X chromosome-linked photopigment genes. To model this process, we studied knock-in mice that expressed a human long-wavelength-sensitive (L) cone photopigment in the form of an X-linked polymorphism. Behavioral tests demonstrated that heterozygous females, whose retinas contained both native mouse pigments and human L pigment, showed enhanced long-wavelength sensitivity and acquired a new capacity for chromatic discrimination. An inherent plasticity in the mammalian visual system thus permits the emergence of a new dimension of sensory experience based solely on gene-driven changes in receptor organization.

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Available from: Gerald Jacobs
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    • "Such adaptability and plasticity of the brain will make the knock-in mice understand the world deeper than other mice. The above experiment in [5] inspires us a very interesting and challenging problem: can we exploit a computational model that is able to expand its cognitive dimension online freely? If this is achieved, the agent with such computational model will be able to expand its sensing capability during its lifetime. "
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    • "Although two distinct opsins is the norm in Pteropus (Wang et al. 2004; Müller et al. 2007; Zhao et al. 2009a), trichromatic vision is plausible in P. samoensis for two reasons: first, the visual system of Pteropodidae is strikingly similar to that of primates (Pettigrew 1986, 1995; Fig. 2), suggesting that P. samoensis has the neural preadaptations to support trichromatic vision. Such homoplasy is not strictly necessary, however, as the engineering of trichromatic mice demonstrates (Jacobs et al. 2007). Second, duplication of the long wavelength-sensitive (LWS) opsin gene is documented in at least one pteropodid species, Haplonycteris fischeri (Wang et al. 2004). "
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    ABSTRACT: A nocturnal bottleneck during mammalian evolution left a majority of species with two cone opsins, or dichromatic color vision. Primate trichromatic vision arose from the duplication and divergence of an X-linked opsin gene, and is long attributed to tandem shifts from nocturnality to diurnality and from insectivory to frugivory. Opsin gene variation and at least one duplication event exist in the order Chiroptera, suggesting that trichromatic vision could evolve under favorable ecological conditions. The natural history of the Samoan flying fox (Pteropus samoensis) meets these conditions-it is a large bat that consumes nectar and fruit and demonstrates strong diurnal proclivities. It also possesses a visual system that is strikingly similar to that of primates. To explore the potential for opsin gene duplication and divergence in this species, we sequenced the opsin genes of 11 individuals (19 X-chromosomes) from three South Pacific islands. Our results indicate the uniform presence of two opsins with predicted peak sensitivities of ca. 360 and 553 nm. This result fails to support a causal link between diurnal frugivory and trichromatic vision, although it remains plausible that the diurnal activities of P. samoensis have insufficient antiquity to favor opsin gene renovation.
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    • "keys, and some of the heterozygous mice gained red-green color vision capacities (Jacobs et al. 2007). Interestingly, red-green color vision in the mice was very weak compared with that shown by humans with normal trichromacy or by the monkeys treated with gene therapy; it was so weak, in fact, that it was not detected in two of the five mice tested. "
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