Genetics of Normal and Defective Color Vision
Hosted By: Color Technical Group
30 January 2020, 13:00 - 14:00
Two types of image forming photoreceptors in the human eye, rods and cones, serve different functions. Humans perform daily activities at light levels that exceed those where rods contribute significantly to vision, but where cones are active. The capacity to see color is a prominent feature of cone vision, and requires multiple classes of cone photoreceptor. Most humans have trichromatic color vision that is mediated by at least three well-separated spectral classes of cone. Cones are also responsible for high spatial acuity vision, and participate in regulating eye growth throughout adolescence.
The three types of cone photoreceptor that mediate human color vision are classed according to their relative spectral sensitivities as short- (S), middle- (M) and long- (L) wavelength sensitive. Color information is extracted from neural circuits that compare the outputs of the different cone classes, and confer the capacity to distinguish more than 100 different gradations of hue, which include the unique hues alone, or in combination, such as, yellow-green, purple (red-blue), and orange (red-yellow). The color palette is greatly reduced for individuals with inherited red-green color vision deficiencies and, in the most severe cases, they lack red and green hue sensations and all of the intermediate color combinations.
Inherited color vision deficiencies are commonly caused by rearrangements, deletions and mutations of genes that encode the protein component (opsin) of the light-absorbing photopigment molecules present in cone photoreceptors. Inherited color vision deficiencies are categorized according to the number of functional cone types present in the retina. Monochromacy, dichromacy and anomalous trichromacy correspond to the presence of one, two or three functional cone types, respectively. All are caused by mutations that alter the complement of functional cone opsins expressed. Here we give an overview of the role of genetic variation in the L, M and S-cone opsin genes as the primary cause of inherited color vision deficiency, and discuss recently identified combinations of normal polymorphisms in these genes that cause a variety of vision disorders including cone dysfunction, nearsightedness (myopia), cone dystrophy and color vision deficiencies.
After viewing the webinar, you will:
- Understand the terms used for the most common forms of color vision deficiency
- Understand the genetics underlying normal color vision and the most common inherited forms of color vision deficiency
- Understand the genetic basis for individual differences in color vision behavior among individuals with normal color vision
About the Presenter: Maureen Neitz, University of Washington
Maureen Neitz received a PhD in Biochemistry and Molecular Biology from the University of California in Santa Barbara (UCSB) in 1986. She did a post-doctoral fellowship in the laboratory of Jerry Jacobs, at UCSB. She was on faculty at the Medical College of Wisconsin from 1991 to 2008, and in 2009 she took a position as Professor in Ophthalmology at the University of Washington where she is the Ray H Hill endowed professor. Maureen has been collaborating in her work on color vision genetics with her husband, Jay Neitz, since 1986. Her claims to fame include: 1) being the first to elucidate the molecular genetics of spectral tuning in the human L and M cone photopigments, which was published in the journal Science in 1991 and 2) demonstrating the neuroplasticity of the adult visual system using gene therapy to alter the color vision behavior in dichromatic squirrel monkeys, work that was published in Nature in 2009 and was chosen by Time Magazine as #3 on the list of the top 10 scientific discoveries in 2009.