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Science 329 (5990): 403-404

Copyright © 2010 by the American Association for the Advancement of Science


Seeing the Light of Day

Constance Cepko

Human beings are highly dependent on vision. It is our most well-developed and cherished sense, giving us color vision with high acuity during the day as well as excellent sensitivity at night. Vision begins with light reception by specialized cells in the retina, a thin sheet of neural tissue that lines the inside of the eyeball (1). Rod photoreceptors provide for sensitivity in dim light, whereas cone photoreceptors provide for color vision in bright light. Unfortunately, photoreceptors are very sensitive to genetic insults. Mutations in more than 200 genes can lead to blindness, more than 40 of which lead to the disease retinitis pigmentosa (2, 3). This disorder typically is due to a mutation in a gene expressed only in rods, and thus individuals with retinitis pigmentosa mutations are often born night-blind. Between ages 20 and 60, cone-mediated vision deteriorates (4), leading to total blindness. The poorly functioning cones in retinitis pigmentosa are the target of a potential gene therapy approach reported by Busskamp et al. on page 413 of this issue (5).

Department of Genetics and Department of Ophthalmology, Howard Hughes Medical Institute, Harvard Medical Schoo, Boston, MA 02115, USA.

E-mail: cepko{at}

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