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Deep Brain Photoreceptors Control Light-Seeking Behavior in Zebrafish Larvae

2012; Elsevier BV; Volume: 22; Issue: 21 Linguagem: Inglês

10.1016/j.cub.2012.08.016

1879-0445

António M. Fernandes, Kandice Fero, Aristides B. Arrenberg, Sadie A. Bergeron, Wolfgang Driever, Harold A. Burgess,

Zebrafish Biomedical Research Applications

Most vertebrates process visual information using elaborately structured photosensory tissues, including the eyes and pineal. However, there is strong evidence that other tissues can detect and respond to photic stimuli [1von Frisch K. Beitrage zur Physiologie der Pigmentzellen in der Fischhaut.Pflugers Arch. Gesamte Physiol. Menschen Tiere. 1911; 138: 319-387Crossref Scopus (172) Google Scholar, 2Adler K. Extraocular photoreception in amphibians.Photophysiology. 1976; 23: 275-298PubMed Google Scholar, 3Yokoyama K. Oksche A. Darden T.R. Farner D.S. The sites of encephalic photoreception in phosoperiodic induction of the growth of the testes in the white-crowned sparrow, Zonotrichia leucophrys gambelii.Cell Tissue Res. 1978; 189: 441-467Crossref PubMed Scopus (67) Google Scholar]. Many reports suggest that photosensitive elements exist within the brain itself and influence physiology and behavior; however, a long-standing puzzle has been the identity of the neurons and photoreceptor molecules involved [4Groos G. The comparative physiology of extraocular photoreception.Experientia. 1982; 38: 989-991Crossref PubMed Scopus (24) Google Scholar, 5Silver R. Witkovsky P. Horvath P. Alones V. Barnstable C.J. Lehman M.N. Coexpression of opsin- and VIP-like-immunoreactivity in CSF-contacting neurons of the avian brain.Cell Tissue Res. 1988; 253: 189-198Crossref PubMed Scopus (189) Google Scholar]. We tested whether light cues influence behavior in zebrafish larvae through deep brain photosensors. We found that larvae lacking eyes and pineal perform a simple light-seeking behavior triggered by loss of illumination (“dark photokinesis”). Neuroanatomical considerations prompted us to test orthopedia (otpa)-deficient fish, which show a profound reduction in dark photokinesis. Using targeted genetic ablations, we narrowed the photosensitive region to neurons in the preoptic area. Neurons in this region express several photoreceptive molecules, but expression of the melanopsin opn4a is selectively lost in otpa mutants, suggesting that opn4a mediates dark photokinesis. Our findings shed light on the identity and function of deep brain photoreceptors and suggest that otpa specifies an ancient population of sensory neurons that mediate behavioral responses to light.