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Proc Natl Acad Sci U S A 2016 May 24;11321:6053-8. doi: 10.1073/pnas.1515516113.
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Deep-brain photoreception links luminance detection to motor output in Xenopus frog tadpoles.

Currie SP , Doherty GH , Sillar KT .

Nonvisual photoreceptors are widely distributed in the retina and brain, but their roles in animal behavior remain poorly understood. Here we document a previously unidentified form of deep-brain photoreception in Xenopus laevis frog tadpoles. The isolated nervous system retains sensitivity to light even when devoid of input from classical eye and pineal photoreceptors. These preparations produce regular bouts of rhythmic swimming activity in ambient light but fall silent in the dark. This sensitivity is tuned to short-wavelength UV light; illumination at 400 nm initiates motor activity over a broad range of intensities, whereas longer wavelengths do not cause a response. The photosensitive tissue is located in a small region of caudal diencephalon-this region is necessary to retain responses to illumination, whereas its focal illumination is sufficient to drive them. We present evidence for photoreception via the light-sensitive proteins opsin (OPN)5 and/or cryptochrome 1, because populations of OPN5-positive and cryptochrome-positive cells reside within the caudal diencephalon. This discovery represents a hitherto undescribed vertebrate pathway that links luminance detection to motor output. The pathway provides a simple mechanism for light avoidance and/or may reinforce classical circadian systems.

PubMed ID: 27166423
PMC ID: PMC4889350
Article link: Proc Natl Acad Sci U S A
Grant support: [+]

Species referenced: Xenopus laevis
Genes referenced: cry1 cry2 opn5 th
Antibodies: Cry1 Ab1 Cry2 Ab1 Opn5 Ab1

Article Images: [+] show captions
References [+] :
Berson, Phototransduction by retinal ganglion cells that set the circadian clock. 2002, Pubmed