Subterranean Fishes of the World

3284

2017

AIM 2017

Opsins are proteins classically known for forming the key lightsensing molecules responsible for the function of binocular and pineal eyes. Recent studies, however, showed opsin expression in deep-brain and skin of fish, suggesting light-sensing function in these tissues. Interestingly, changes in light conditions induced activity shifts in the blind Astyanax cavefish--calmer in the dark and more active in the light--, suggesting extraocular opsin activity. In zebrafish 42 opsin genes in 20 classes (rh1, rh2, lws, exorh, etc.) have been identified and are expressed in many tissues including: brain, eye, gut, heart, liver, muscle, pineal, skin and testis. Functional roles for some extraocular photoreceptors have been demonstrated in zebrafish deep-brain (phototaxis in darkened environment) and tilapia skin (pigmentation shift in response to light); the pineal gland also plays a role in light-dependent behavior (shadow response) in cavefish larvae. Here, we aimed to determine the opsin profile of A. mexicanus and explore the expression differences between cave and surface morphs in different tissues: telencephalon, tectum, pineal, basal brain, eye, and skin. A bioinformatics survey of the A. mexicanus genome revealed 29 orthologs of the 42 zebrafish opsins, representing 16 opsin classes thus, majority of teleost opsin classes are covered in the current genebuild. Tissue samples from the retina, pineal, telencephalon, tectum, cerebellum, other deep-brain area and skin, were dissected from adult surface and cave fish. Using qPCR, we detected high expression levels of multiple opsins in the cavefish pineal, implicating the pineal as a key tissue in cavefish lightdependent activity. We plan to perform CRISPR/Cas9 and/or pinealectomy to test the involvement of opsin genes and pineal for the light-dependent activity observed in cavefish.

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