Brain area‐specific diurnal and photic regulation of val‐opsinA and val‐opsinB genes in the zebrafish

Abstract

Zebrafish possess two isoforms of vertebrate ancient long (VAL)-opsin, val-opsinA (valopa) and val-opsinB (valopb), which probably mediate non-visual responses to light. To understand the diurnal and light-sensitive regulation of the valop genes in different cell groups, the current study used real-time quantitative PCR to examine the diurnal changes of valopa and b mRNA levels in different brain areas of adult male zebrafish. Furthermore, effects of the extended exposure to light or dark condition, luminous levels and the treatment with a melatonin receptor agonist or antagonist on valop transcription were examined. In the thalamus, valop mRNA levels showed significant diurnal changes; valopa peaked in the evening, while valopb peaked in the morning. The diurnal change of valopa mRNA levels occurred independent of light conditions, whereas that of valopb mRNA levels were regulated by light. A melatonin receptor agonist or antagonist did not affect the changes of valop mRNA levels. In contrast, the midbrain and hindbrain showed arrhythmic valop mRNA levels under light and dark cycles. The differential diurnal regulation of the valopa and b genes in the thalamus and the arrhythmic expression in the midbrain and hindbrain suggest involvement of deep brain VAL-opsin in time-and light-dependent physiology.

Organization of alpha‐transducin immunoreactive system in the brain and retina of larval and young adult Sea Lamprey (Petromyzon marinus), and their relationship with other neural systems

“…Non‐mammalian vertebrates possess a wide range of intrinsically photoreceptive sites expressing members of the non‐visual opsin family (see Hankins, Davies, & Foster, ). ISH studies in the brain of zebrafish and other teleosts have revealed different neuronal populations that express opsins (Philp et al, ; Matos‐Cruz et al, ; Fischer et al, ; Nakane et al, ; Eilertsen et al, ; Hang, Kitahashi, & Parhar, ; Sato et al, ). Some of the Opn5 (neuropsin)‐expressing forebrain populations of medaka and zebrafish (Sato et al, ) are located in regions similar to those containing the post‐optic/hypothalamic opsin and/or transducin‐expressing CSF‐c neuronal populations of lampreys (García‐Fernández & Foster, ; García‐Fernández et al, ; present results).…”

Diversification of non-visual photopigment parapinopsin in spectral sensitivity for diverse pineal functions

“…Most animals also possess multiple opsins that underlie non-visual functions such as circadian photoentrainment, suggesting their possible diverse and complicated involvement in varied types of non-visual photoreception [ 4 – 7 ]. However, the significance of the diversification of non-visual opsins remains uncertain, although comparative studies of duplicated non-visual opsins such as melanopsin and vertebrate ancient-long (VAL)-opsin have revealed differences in their expression patterns [ 8 – 12 ]. The pineal and related organs of non-mammalian vertebrates are a good model for examining this issue because they are photosensitive organs with diverse functions.…”

Deep Brain Photoreceptor (val-opsin) Gene Knockout Using CRISPR/Cas Affects Chorion Formation and Embryonic Hatching in the Zebrafish

“…In the zebrafish, the VAL-opsin isoforms are expressed in both the eyes and the brain [10, 11, 15], and the VAL-opsin photoreceptors in the eyes and the brain are thought to play distinct roles in zebrafish physiology [16]. Furthermore, VAL-opsinA and VAL-opsinB photoreceptors are expected to have distinct functions in the eyes [11].…”

“…In the current study, F0 valopa and valopb mutants exhibited a similar parental-effect phenotype in their eggs and resultant embryos. Our previous work determined the co-expression of valopa and valopb in the thalamic valop cell group within the brain, which may play a GABA-dependent modulatory role in light-dependent physiology [15, 16]. There is evidence of seasonal variation in the levels of GABA-synthesizing enzymes in the brain and GABA control on pituitary gonadotropin release in fish species [53–57].…”

“…Two isoforms of zebrafish VAL-opsin, encoded by the val-opsinA ( valopa ) and val-opsinB ( valopb ) genes [11], exist and might have separate functions. Indeed, our recent studies concluded that VAL-opsin isoforms are involved in different neurochemical systems in multiple brain regions and mediate the control of time- and light-dependent physiology and behaviours in adult zebrafish [15, 16]. However, no reverse genetic studies have been conducted to study the functions of deep brain opsins including VAL-opsin in non-mammalian models.…”