Korenbrot, J.I., Mehta, M., Tserentsoodol, N., Postlethwait, J.H., and Rebrik, T.I. (2013) EML1 (CNG-Modulin) Controls Light Sensitivity in Darkness and under Continuous Illumination in Zebrafish Retinal Cone Photoreceptors. The Journal of neuroscience : the official journal of the Society for Neuroscience. 33(45):17763-17776.
The ligand sensitivity of cGMP-gated (CNG) ion channels in cone photoreceptors is modulated by CNG-modulin, a Ca2+-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.