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Heather A. Van Epps, Chong M. Yim, James B. Hurley, Susan E. Brockerhoff; Investigations of Photoreceptor Synaptic Transmission and Light Adaptation in the Zebrafish Visual Mutant nrc. Invest. Ophthalmol. Vis. Sci. 2001;42(3):868-874.
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© ARVO (1962-2015); The Authors (2016-present)
purpose. To characterize the retinal physiology of the zebrafish visual mutant no optokinetic response c (nrc)
and to identify the genetic map position of the nrc mutation.
methods. Electroretinograms were recorded from wild-type and nrc zebrafish larvae between 5 to 6 days postfertilization. Responses to
flash stimuli, On and Off responses to prolonged light stimuli, and
responses to flash stimuli with constant background illumination were
characterized. The glutamate agonist, 2-amino-4-phosphonobutyric acid
(APB) was used to examine the photoreceptor specific a-wave component of the electroretinogram. Amplified
fragment length polymorphism methodology was used to place the nrc mutation on the zebrafish genomic map.
results. nrc and wild-type zebrafish larvae 5 to 6 days
postfertilization have similar threshold responses to light, but the b-wave of the nrc electroretinogram is
significantly delayed and reduced in amplitude. On and Off responses of nrc larvae to prolonged light have multiple oscillations
that do not occur in normal zebrafish larvae after 5 days
postfertilization. Analysis of the b-wave demonstrated a
light adaptation defect in nrc that causes saturation at
background light levels approximately 1 order of magnitude less than
those with wild-type larvae. Application of the glutamate analog, APB,
uncovered the photoreceptor component of the electroretinogram and
revealed a light adaptation defect in nrc photoreceptors. The nrc mutation was placed
approximately 0.2 cM from sequence length polymorphism marker Z7504 on
linkage group 10.
conclusions. The zebrafish mutant nrc is a possible model for human
retinal disease. nrc has defects in photoreceptor
synaptic transmission and light adaptation. The nrc mutant phenotype shows striking similarities with phenotypes of
dystrophin glycoprotein complex mutants, including patients with
Duchenne/Becker muscular dystrophy. Localization of the nrc mutation now makes it possible to evaluate candidate
genes and clone the nrc gene.
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