1. The hypothalamic photoreceptors regulating seasonal reproduction in birds: A prime role for VA opsin
- Author
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Mark W. Hankins, Russell G. Foster, Wayne I. L. Davies, Jessica Rodgers, Stephanie Halford, José M. García-Fernández, Michael Turton, Steven Hughes, Rafael Cernuda-Cernuda, Brian K. Follett, and Stuart N. Peirson
- Subjects
Melanopsin ,medicine.medical_specialty ,Opsin ,endocrine system ,OPN5 ,genetic structures ,media_common.quotation_subject ,Hypothalamus ,Avian Proteins ,Birds ,Gonadotropin-Releasing Hormone ,03 medical and health sciences ,Sexual Behavior, Animal ,0302 clinical medicine ,Vasotocin ,biology.animal ,Internal medicine ,Neurosecretory ,medicine ,Animals ,Photopigment ,VA opsin ,Seasonal reproduction ,030304 developmental biology ,media_common ,0303 health sciences ,Gonadotropin-releasing hormone (GnRH) ,biology ,Opsins ,Endocrine and Autonomic Systems ,Vertebrate ,Endocrinology ,Evolutionary biology ,Photoperiodism ,Arginine-vasotocin (AVT) ,Seasons ,sense organs ,Reproduction ,030217 neurology & neurosurgery ,hormones, hormone substitutes, and hormone antagonists ,Photoreceptor Cells, Vertebrate - Abstract
Extraretinal photoreceptors located within the medio-basal hypothalamus regulate the photoperiodic control of seasonal reproduction in birds. An action spectrum for this response describes an opsin photopigment with a λmax of ∼492nm. Beyond this however, the specific identity of the photopigment remains unresolved. Several candidates have emerged including rod-opsin; melanopsin (OPN4); neuropsin (OPN5); and vertebrate ancient (VA) opsin. These contenders are evaluated against key criteria used routinely in photobiology to link orphan photopigments to specific biological responses. To date, only VA opsin can easily satisfy all criteria and we propose that this photopigment represents the prime candidate for encoding daylength and driving seasonal breeding in birds. We also show that VA opsin is co-expressed with both gonadotropin-releasing hormone (GnRH) and arginine-vasotocin (AVT) neurons. These new data suggest that GnRH and AVT neurosecretory pathways are endogenously photosensitive and that our current understanding of how these systems are regulated will require substantial revision.
- Published
- 2015