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Updated: May 6, 2026
Electroretinogram Analysis of the Visual Response in Zebrafish Larvae
Published on: March 16, 2015
EML1 (CNG-modulin) controls light sensitivity in darkness and under continuous illumination in zebrafish retinal cone
Juan I Korenbrot1, Milap Mehta, Nomingerel Tserentsoodol
1Departments of Ophthalmology and Physiology, School of Medicine, University of California, San Francisco, San Francisco, California 94143, Albert Eye Research Institute, Duke University Medical Center, Durham, North Carolina 27710, and Department of Biology, University of Oregon, Eugene, Oregon 97403.
Abstract:
The ligand sensitivity of cGMP-gated (CNG) ion channels in cone photoreceptors is modulated by CNG-modulin, a Ca(2+)-binding protein. We investigated the functional role of CNG-modulin in phototransduction in vivo in morpholino-mediated gene knockdown zebrafish. Through comparative genomic analysis, we identified the orthologue gene of CNG-modulin in zebrafish, eml1, an ancient gene present in the genome of all vertebrates sequenced to date. We compare the photoresponses of wild-type cones with those of cones that do not express the EML1 protein. In the absence of EML1, dark-adapted cones are ∼5.3-fold more light sensitive than wild-type cones. Previous qualitative studies in several nonmammalian species have shown that immediately after the onset of continuous illumination, cones are less light sensitive than in darkness, but sensitivity then recovers over the following 15-20 s. We characterize light sensitivity recovery in continuously illuminated wild-type zebrafish cones and demonstrate that sensitivity recovery does not occur in the absence of EML1.
