Zebrafish ultraviolet visual pigment: absorption spectrum, sequence, and localization.

Abstract

In many vertebrates, UV-sensitive photoreceptors have been identified by microspectrophotometry and UV-visual sensitivity has been identified by behavioral studies, but as yet no vertebrate UV-sensitive pigment gene has been isolated. We have sequenced a cDNA clone that hybridizes to short single cone cells in the zebrafish (Brachydanio rerio). These cells, which make up 25% of the cone population in zebrafish retinae, are UV-sensitive (lambda max approximately 360 nm). The visual pigment encoded by this gene is unusual in that its amino acid sequence is more homologous to the rod pigment rhodopsin (up to 89%) than to other cone pigments (35-83%). Like all other vertebrate visual pigments, it contains a lysine residue at position 296, the presumptive retinal binding site, and a glutamate residue at position 113. However, it is unique in possessing a lysine residue at position 126, which may account for the UV-sensitivity of the pigment.

Zebrafish: A model system for the study of eye genetics

“…The cones are subdivided into four classes based upon spectral sensitivity and morphology (Raymond et al, 1993;Robinson et al, 1993). The cone photoreceptors are tiered within the outer nuclear layer with the red-and green-sensitive cones paired as distinct long double cones ( Figure 1E).…”

“…Gaps in the distribution of cells or random clustering would result in under-representation or over-sampling of information in those regions of the visual field. In the fish retina, this arrangement is most evident in the outer nuclear layer where the position of each cone subtype is precisely arranged relative to the others (Fadool, 2003;Robinson et al, 1993) resulting in a highly ordered crystalline-like mosaic. In adult zebrafish, the mosaic is composed of columns of alternating blue-and UV-sensitive single cones that alternate in turn with columns of red-and greensensitive double cones.…”

Behavioral genetic approaches to visual system development and function in zebrafish

“…The zebrafish retina has five different visual pigments, including a UV sensitive pigment, supporting tetrachromatic vision (Robinson et al, 1993(Robinson et al, , 1995Vihtelic et al, 1999). The retina, including the inner retina, is now mature enough to support a number of behaviors that require form vision, including the optokinetic (OKR) and the optomotor response (OMR).…”

Zebrafish mutants as models for congenital ocular disorders in humans

“…Zebrafish possess one-rod photoreceptor and fourcone photoreceptor subtypes, which absorb light maximally in the red (570 nm), green (480 nm), blue (415 nm), and ultraviolet (362 nm) regions of the spectrum (Robinson et al, 1993). Each of these cone subtypes can be distinguished morphologically; the short single cones absorbing in the ultraviolet, the long single cones responding to blue light, and the red and green sensitive cones forming a double-cone pair.…”