Please use this identifier to cite or link to this item: https://doi.org/10.1371/journal.pone.0051276
Title: Evolution and Functional Characterisation of Melanopsins in a Deep-Sea Chimaera (Elephant Shark, Callorhinchus milii)
Authors: Davies W.I.L.
Tay B.-H.
Zheng L.
Danks J.A.
Brenner S. 
Foster R.G.
Collin S.P.
Hankins M.W.
Venkatesh B. 
Hunt D.M.
Keywords: complementary DNA
melanopsin
article
Callorhincus milii
controlled study
deep sea chimaera
gene
gene duplication
gene expression
gene sequence
Holocephali
mammalian genetics
nonhuman
nucleotide sequence
opn4m1 gene
opn4m2 gene
opn4x gene
photoreceptor
photosensitivity
phylogeny
retina ganglion cell
reverse transcription polymerase chain reaction
RNA extraction
sensory system
sensory system electrophysiology
shark
Amino Acid Sequence
Animals
Base Sequence
Biological Evolution
Chimera
DNA Primers
Molecular Sequence Data
Phylogeny
Reverse Transcriptase Polymerase Chain Reaction
Rod Opsins
Sequence Homology, Amino Acid
Sharks
Callorhinchus milii
Chimaeridae
Chondrichthyes
Gnathostomata (vertebrate)
Invertebrata
Mammalia
Vertebrata
Issue Date: 2012
Citation: Davies W.I.L., Tay B.-H., Zheng L., Danks J.A., Brenner S., Foster R.G., Collin S.P., Hankins M.W., Venkatesh B., Hunt D.M. (2012). Evolution and Functional Characterisation of Melanopsins in a Deep-Sea Chimaera (Elephant Shark, Callorhinchus milii). PLoS ONE 7 (12) : e51276. ScholarBank@NUS Repository. https://doi.org/10.1371/journal.pone.0051276
Abstract: Non-visual photoreception in mammals is primarily mediated by two splice variants that derive from a single melanopsin (OPN4M) gene, whose expression is restricted to a subset of retinal ganglion cells. Physiologically, this sensory system regulates the photoentrainment of many biological rhythms, such as sleep via the melatonin endocrine system and pupil constriction. By contrast, melanopsin exists as two distinct lineages in non-mammals, opn4m and opn4x, and is broadly expressed in a wide range of tissue types, including the eye, brain, pineal gland and skin. Despite these findings, the evolution and function of melanopsin in early vertebrates are largely unknown. We, therefore, investigated the complement of opn4 classes present in the genome of a model deep-sea cartilaginous species, the elephant shark (Callorhinchus milii), as a representative vertebrate that resides at the base of the gnathostome (jawed vertebrate) lineage. We reveal that three melanopsin genes, opn4m1, opn4m2 and opn4x, are expressed in multiple tissues of the elephant shark. The two opn4m genes are likely to have arisen as a result of a lineage-specific duplication, whereas "long" and "short" splice variants are generated from a single opn4x gene. By using a heterologous expression system, we suggest that these genes encode functional photopigments that exhibit both "invertebrate-like" bistable and classical "vertebrate-like" monostable biochemical characteristics. We discuss the evolution and function of these melanopsin pigments within the context of the diverse photic and ecological environments inhabited by this chimaerid holocephalan, as well as the origin of non-visual sensory systems in early vertebrates. © 2012 Davies et al.
Source Title: PLoS ONE
URI: https://scholarbank.nus.edu.sg/handle/10635/161359
ISSN: 19326203
DOI: 10.1371/journal.pone.0051276
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