Gene expression patterns of novel visual and non-visual opsin families in immature and mature Japanese eel males

Abstract

This study was carried out to identify and estimate physiological function of a new type of opsin subfamily present in the retina and whole brain tissues of Japanese eel using RNA–Seq transcriptome method. A total of 18 opsin subfamilies were identified through RNA–seq. The visual opsin family included Rh2, SWS2, FWO, DSO, and Exo-Rhod. The non-visual opsin family included four types of melanopsin subfamily (Opn4x1, Opn4x2, Opn4m1, and Opn4m2), peropsin, two types of neuropsin subfamily (Opn5-like, Opn5), Opn3, three types of TMT opsin subfamily (TMT1, 2, 3), VA-opsin, and parapinopsin. In terms of changes in photoreceptor gene expression in the retina of sexually mature and immature male eels, DSO mRNA increased in the maturation group. Analysis of expression of opsin family gene in male eel brain before and after maturation revealed that DSO and SWS2 expression in terms of visual opsin mRNA increased in the sexually mature group. In terms of non-visual opsin mRNA, parapinopsin mRNA increased whereas that of TMT2 decreased in the fore-brain of the sexually mature group. The mRNA for parapinopsin increased in the mid-brain of the sexually mature group, whereas those of TMT1 and TMT3 increased in the hind-brain of the sexually mature group. DSO mRNA also increased in the retina after sexual maturation, and DSO and SWS2 mRNA increased in whole brain part, suggesting that DSO and SWS2 are closely related to sexual maturation.

An Expanding Role for Nonvisual Opsins in Extraocular Light Sensing Physiology

“…These include VA-opsin, rhodopsin, and toad pinopsin (Pérez et al 2019), as well as the nonvisual opsins. OPN4 (Byun et al 2020, Eilertsen et al 2021, Kang et al 2010, Ma et al 2022, Nakane et al 2019, Potter et al 2018, Provencio et al 1998, Sandbakken et al 2012, OPN3 (and TMT-type Opsin 3) (Byun et al 2020, Fischer et al 2013, Kato et al 2016, and OPN5 (Byun et al 2020, Kojima et al 2011, Nakane et al 2010, Ohuchi et al 2012) have been reported in amphibian, fish, and bird species. Studies in Japanese quail have implicated OPN5 in regulating neuroendocrine function via a thyroid-signaling pathway that responds to photoperiodic changes (Nakane et al 2019).…”

Visual gene expression reveals a cone to rod developmental progression in deep-sea fishes

“…Studies investigating the gene expression in the retina of deep-sea fishes are scarce and usually focus on a selected few species 13,14,15,16,17 . In adults, species with pure rod retinas tend to only express rod opsin(s) 14,16 , albeit two species of pearlsides (Maurolicus spp.)…”

“…Studies investigating the gene expression in the retina of deep-sea fishes are scarce and usually focus on a selected few species (Zhang et al 2000, Douglas et al 2016, de Busserolles et al 2017, Musilova et al 2019a, Byun et al 2020. In adults, species with pure rod retinas tend to only express rod opsin(s) (Douglas et al 2016, Musilova et al 2019a, albeit two species of pearlsides (Maurolicus spp.)…”